close

Log in

Access to premium content is restricted to healthcare professionals / registered members. Login with your email address to continue.

Forgot Your Password?

Don't have an account? Sign up

By signing in or creating an account, you agree to our Terms and conditions and Privacy notice

This site is intended for Healthcare Professionals only
Back to CKS

Infections and infestations Men's health Sexual health Women's health

Trichomoniasis

Last revised in December 2024

Trichomoniasis is a sexually transmitted infection (STI) caused by the flagellated protozoan Trichomonas vaginalis.

Trichomoniasis: Summary

  • Trichomoniasis is a sexually transmitted infection (STI) caused by the flagellate protozoan Trichomonas vaginalis. It is the most common non-viral STI worldwide.
  • Complications include perinatal complications (preterm delivery and/or low birthweight infant), infertility, and enhanced HIV transmission.
  • Up to 50% of women with trichomoniasis have no symptoms. When present, common symptoms include vaginal discharge, vulval itching, dysuria, and offensive odour.
  • Of men with trichomoniasis, 15–50% are asymptomatic and usually present as sexual partners of infected women. The most common symptoms are urethral discharge and/or dysuria. 
  • The diagnosis of trichomoniasis should ideally be confirmed by a sexual health specialist. If referral is declined or not possible, the person can be tested in primary care.
    • For women, a high vaginal swab (from the posterior fornix) should be sent for laboratory testing.
      • If microscopy is not readily available, a urine sample or self-administered vaginal swab may be taken.
    • For men, a urethral swab and/or urine sample should be sent for laboratory testing.
    • The person should be offered tests for other STIs (chlamydia, gonorrhoea, HIV, and syphilis as a minimum).
  • Treatment for confirmed trichomoniasis should ideally be started by a sexual health specialist. If this is declined or not possible, the person can be managed in primary care.
    • Written information on trichomoniasis as well as advice on reducing the risk of further infection and exposure to other STIs should be given.
    • For men and women (not pregnant or breastfeeding), oral metronidazole 400–500 mg twice a day for 7 days should be prescribed. 
    • For breastfeeding and symptomatic pregnant women, oral metronidazole 400 mg twice a day should be prescribed for 7 days. 
    • For asymptomatic pregnant women, specialist advice should be sought.
    • For people with HIV, oral metronidazole 500 mg twice a day for 7 days is recommended.
    • Current partner(s) and any partner(s) from within the 4-week period prior to presentation should also be treated and screened for other STIs.
  • After completion of treatment, the person should be followed up to review symptoms, check contact tracing, and discuss results of the STI screen.
    • Sexual abstinence should be advised for at least 1 week and until the person and their partner(s) have completed treatment and follow up.
    • Tests to confirm cure should not be routinely done.
  • If symptoms persist or recur after treatment, the person should be referred to a sexual health specialist. If this is declined or not possible:
    • Compliance with the first-line treatment should be reviewed.
    • The possibility of reinfection should be considered.
    • The diagnosis should be reconsidered.
    • A repeat course of 7-day metronidazole treatment (400–500 mg twice a day) should be considered. In pregnant or breastfeeding women, specialist advice should be sought from a GUM specialist before any further treatment is prescribed.
  • Specialist advice should be sought from a GUM specialist:
    • If there are contraindications to the use of metronidazole.
    • If the second-line treatment course fails.
    • For people with failed first-line single-dose treatment.

Have I got the right topic?

From age 13 years onwards.

This CKS topic covers the diagnosis and management of trichomoniasis in men and women (including pregnant and breastfeeding women).

This CKS topic does not cover the management of other sexually transmitted infections.

There are separate CKS topics on Bacterial vaginosis, Candida - female genital, Chlamydia - uncomplicated genital, Gonorrhoea, Herpes simplex - genital, HIV infection and AIDS, Pelvic inflammatory disease, Pruritus vulvae, Syphilis, Urethritis - male, and Vaginal discharge.

The target audience for this CKS topic is healthcare professionals working within the NHS in the UK, and providing first contact or primary healthcare.

How up-to-date is this topic?

Changes

December 2024 — minor update. The recommendations for the dose of metronidazole and length of treatment for trichomoniasis have been updated in line with the most recent UK guidelines.

Previous changes

November 2024 — reviewed. A literature search was conducted in September 2024 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of the topic. There have been minor structural changes to the topic. Information on the risk factors, prognosis, and differential diagnosis have been added. There have been changes to the recommendation on the diagnosis of trichomoniasis to include information on sampling using nucleic acid amplification testing. There have been no major changes to recommendations on management.

November 2023 — minor update. Recommendations relating to tinidazole, and the prescribing information section for tinidazole have been removed from this topic as the product has been discontinued in the UK. 

July 2023 — minor update. The manufacturer's SPC for metronidazole has been updated to note that QT prolongation has been reported (unknown frequency), particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval.

May 2020 — minor update. Tinidazole contraindications and cautions for pregnant women updated in line with manufacturer's SPC.

November 2019 — reviewed. A literature search was conducted in October 2019 to identify evidence-based guidelines, UK policy systematic reviews and key randomized controlled trials published since the last review of this topic. No major changes to recommendations have been made.

October 2018 — minor update. Adverse effects for metronidazole updated within prescribing information. 

January to March 2015 — reviewed. A literature search was conducted in December 2014 to identify evidence-based guidelines, UK policy systematic reviews and key randomized controlled trials published since the last review of this topic. Advice from the Clinical Effectiveness Group, British Association for Sexual Health and HIV (BASHH), United Kingdom National Guideline on the Management of Trichomoniasis vaginalis has been added to this topic. No major changes to recommendations have been made.

August 2009 — minor update. Advice from the National Institute for Health and Care Excellence (NICE) guideline on when to suspect child maltreatment has been added to this topic. 

February to June 2009 — converted from CKS guidance to CKS topic structure. The evidence base has been reviewed in detail, and recommendations are more clearly justified and transparently linked to the supporting evidence. There are no major changes to recommendations.

February 2008 — minor update. Text changed in line with the National Guideline on the Management of Trichomonas vaginalis (2007) from BASHH. 

October–December 2005 — reviewed. Validated in March 2006 and issued in May 2006.

March 2002 — reviewed. Validated in June 2002 and issued in July 2002.

June 1999 — rewritten, replacing previous guidance called Trichomonas vaginalis infection. Validated in October 1999 and issued in January 2000.

Update

New evidence

Evidence-based guidelines

No new evidence-based guidelines since 1 September 2024.

HTAs (Health Technology Assessments)

No new HTAs since 1 September 2024.

Economic appraisals

No new economic appraisals relevant to England since 1 September 2024.

Systematic reviews and meta-analyses

No new systematic reviews published since 1 September 2024.

Primary evidence

No new primary evidence published since 1 September 2024.

New policies

No new national policies or guidelines since 1 September 2024.

New safety alerts

No new safety alerts since 1 September 2024.

Changes in product availability

No changes in product availability since 1 September 2024.

Goals and outcome measures

Goals

To support primary healthcare professionals to:

  • Recognise symptoms suggestive of trichomoniasis.
  • Where possible, refer to a genito-urinary medicine (GUM) clinic or other sexual health specialist. If specialist referral is declined or not possible:
    • Make a diagnosis in primary care.
    • Provide appropriate treatment to the person and current partner(s) and any partner from within the 4-week period prior to presentation.
    • Provide information and advice on trichomoniasis, and advise on measures to reduce the risks of further sexually transmitted infections (STIs).
    • Screen the person, current partner(s), and partner(s) from within the 4-week period prior to presentation for other STIs.
    • Arrange appropriate follow up.

Outcome measures

No outcome measures were found during the review of this topic.

Audit criteria

No audit criteria were found during the review of this topic.

QOF indicators

No QOF indicators were found during the review of this topic.

QIPP - Options for local implementation

No QIPP indicators were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

Background information

What is it?

  • Trichomoniasis is a sexually transmitted infection (STI) caused by the flagellate protozoan Trichomonas vaginalis.
  • In adults, transmission of T. Vaginalis is almost exclusively through sexual intercourse. Vertical transmission can occur from an infected mother to baby during vaginal delivery [Fürnkranz, 2021].
  • In women, the organism is found in the vagina, urethra, and paraurethral glands.
  • In men, the organism is usually located in the urethra but has also been isolated from the subpreputial sac and from lesions on the penis.

[BASHH, 2013; Sherrard, 2021]

How common is it?

  •  Trichomoniasis is the most common non-viral sexually transmitted infection (STI) in the world [Field, 2018; Van Gerwen, 2023]  
    • The World Health Organization (WHO) estimated that more than 156 million cases of trichomoniasis occurred in 2016, greater than for either chlamydia (127 million) or gonorrhoea (87 million). However, T. vaginalis diagnosis is relatively rare in the UK, with around 6000 cases reported each year, compared with over 200,000 chlamydia cases [Rowley, 2019; Field, 2018]. 
    • National STI surveillance data in England show that over 90% of diagnosed T. vaginalis cases occur in women, a gender difference attributed to more rapid spontaneous clearance of infection in men.
      • Between 2009 and 2011, just under 50% of T. vaginalis diagnoses were in women of white ethnicity (10.7 per 100,000 population), but the rate of T. vaginalis diagnoses was much higher in black Caribbean women (329.6 per 100,000) and women of other black ethnicities (498.4 per 100,000), and much lower in men (33.9 per 100,000 in black Caribbean men and 0.6 per 100,000 in white men) [Field, 2018].
    • Despite having the highest prevalence of any STI globally, there is a lack of data on the incidence and prevalence of trichomoniasis in the general population, possibly because asymptomatic people may not seek healthcare. Consequently, trichomoniasis is underdiagnosed and, therefore, undertreated [Field, 2018; Van Gerwen, 2023].
    • A cross-sectional study investigating the age-specific prevalence of trichomoniasis in sexually active people found that it is uncommon in the UK [Field, 2018].
      • Urine from 4386 participants aged 16–44 years reporting one or more lifetime sexual partner(s) was tested for T. vaginalis.
      • Urinary T. vaginalis was detected in seven women and no men, giving a weighted prevalence estimate of 0.3% (95% confidence interval [CI] 0.1% to 0.5%).
      • Of the seven women with T. vaginalis detected, four were of black or mixed ethnicity (prevalence 2.7% [95% CI 0.9% to 7.7%]) and 5 reported recent partners of black or mixed ethnicity. 
      • The prevalence of a self-reported history of T. vaginalis (past 5 years) was 0.1% (95% CI 0.0% to 0.2%) in women and 0.0% (95% CI 0.0% to 0.2%) in men.

What are the risk factors?

Risk factors for trichomoniasis infection include:

  • Current gonorrhoea or chlamydia infection (in women).
  • Having two or more sexual partners in the previous year.
  • Lack of consistent condom use.
  • Women with bacterial vaginosis.

[Kissinger, 2015; Sherrard, 2021]

What is the prognosis?

  • Between 10–50% of trichomoniasis infections are asymptomatic, with the most common symptoms being vaginal discharge, vulval itching, dysuria, and odour in women, and urethral discharge and/or dysuria in men. However, trichomoniasis infection is associated with more severe complications.
  • Untreated infection may persist or resolve spontaneously.
    • There is a spontaneous cure rate of 20–25%.
  • Recurrence is common, ranging from 5–37% of cases, most likely resulting from reinfection.

[Sherrard, 2021; Kissinger, 2022]

What are the complications?

  • Trichomoniasis may be associated with the following complications:
    • In women:
      • Perinatal complications (preterm delivery and/or low birthweight infant) [Van Gerwen, 2021].
      • Predisposition to maternal postpartum sepsis [Sherrard, 2021].
      • Facilitation of HIV transmission, and there is some evidence that there may be an increased risk of Trichomonas vaginalis infection in people who are HIV positive [Sherrard, 2021; Masha, 2019]. 
      • Pelvic inflammatory disease [Wiringa, 2020]. 
      • Alterations to the normal vaginal flora, increasing susceptibility to bacterial vaginosis [Kalia, 2020]. 
      • Increased risk of cervical cancer, including in women co-infected with human papillomavirus. One meta-analysis reported that women who were T. vaginalis positive were over 5 times more likely to develop cervical cancer (RR 5.23, 95% CI 3.03–9.04) [Hamar, 2023].
      • Infertility [Zhang, 2022].
    • In men:
      • Acute and chronic prostatitis. 
      • Facilitation of HIV transmission, and there is some evidence that there may be an increased risk of T. vaginalis infection in people who are HIV positive [Sherrard, 2021; Masha, 2019]. 
      • Increased risk of prostate cancer [Van Gerwen, 2023].
      • Infertility [Zhang, 2022]. 

Diagnosis

How should I diagnosis trichomoniasis in women?

When diagnosing women:

  • Take a history. 
    • Ask about the symptoms experienced (if any), including the duration, severity, and any exacerbating factors (such as after intercourse, or during menses). 
      • Up to 50% of women with trichomoniasis are asymptomatic.
      • When present, common symptoms include vaginal discharge (in up to 70% of women), vulval itching, dysuria, or offensive odour, but these are not specific to trichomoniasis. Vaginal discharge varies in consistency from thin and scanty to profuse and thick. The classic discharge is frothy and yellow-green, and occurs in 10–30% of infected women.
      • Other symptoms include vulvitis, vaginitis, vulval soreness, vulval ulceration, lower abdominal pain, and dysuria.
    • Ask about:
      • Any treatments tried (prescription or over-the-counter) and their effects.
      • Medical history (past and present).
      • Drug history, including the use of oral contraceptives.
      • Use of new soaps or detergents, and the use of feminine hygiene products such as wipes and sprays.
      • Sexual history, including information about new sexual partners, number of sexual partners in the last year, use of condoms, and history of previous STI. 

When diagnosing men:

  • Take a history. 
    • Ask about the symptoms experienced (if any), including the duration, severity, and any exacerbating factors (such as after intercourse). 
      • About 15–50% of men are asymptomatic and usually present as sexual partners of infected women.
      • When present, the most common symptoms are urethral discharge and/or dysuria. Urethral discharge is present in about 20–60% of men and is usually in small or moderate amounts.
      • Other symptoms include urinary frequency and urethral irritation. 
      • Rarely, the man may complain of a copious purulent urethral discharge or complications such as prostatitis. 
    • Ask about:
      • Any treatments tried (prescription or over-the-counter) and their effects.
      • Medical history (past and present).
      • Drug history.
      • Sexual history, including information about new sexual partners, number of sexual partners in the last year, use of condoms, and history of previous STI. 

Basis for recommendation

These recommendations are largely based on the Royal College of General Practitioners (RCGP) and British Association of Sexual Health and HIV (BASHH) guideline Sexually transmitted infections in primary care [BASHH, 2013], the BASHH United Kingdom national guidelines on the management of Trichomoniasis vaginalis [Sherrard, 2021], and the BASHH Standards for the management of sexually transmitted infections (STIs) [BASHH, 2019].

Taking a detailed history

  • This recommendation is based on the RCGP/BASHH guideline, which states that appropriate medical and sexual history, examination, and tests should be taken when managing people with a suspected STI [BASHH, 2013].
  • The recommended questions to ask are based on expert opinion in the RCGP/BASHH guideline [BASHH, 2013] and in BMJ Best Practice guidelines [BMJ Best Practice, 2023] Urethritis [BMJ Best Practice, 2024].

How should I assess someone with a suspected trichomoniasis infection?

If a woman is suspected of having a trichomoniasis infection, refer the woman to a genito-urinary medicine (GUM) clinic or other local specialist sexual health service for confirmation of the diagnosis. If this is declined or not possible, perform the following examination and investigations (obtain consent and offer a chaperone). 

  • Palpate the abdomen (if appropriate) to assess for tenderness or a mass (which may indicate malignancy).
  • Inspect the vulva for lesions, discharge, vulvitis, ulcers, and any other changes.
  • Perform a speculum examination (except in a pregnant woman with a low-lying placenta) to visualize the cervix and vagina to look for characteristic signs of trichomoniasis.
    • Trichomoniasis, when symptomatic, is characterized by a yellow-green, frothy discharge with a fishy odour.
    • Inflammation of the vulva and vagina, or more rarely a strawberry appearance of the cervix (cervicitis), may be observed on pelvic examination. 
    • About 5–15% of women will have no abnormalities on examination.
  • Test the pH of the vaginal discharge to help distinguish between trichomoniasis and other causes for symptoms. 
    • Collect discharge from the lateral wall of the vagina with a swab, and transfer it onto narrow-range pH paper (pH 3.8–5.5).
    • Measure the pH by comparing the colour of the moist test section of pH paper against the graded standard.
    • The normal vaginal pH in a woman of childbearing age is 3.5–4.5.
    • A pH greater than 4.5 is suggestive of trichomoniasis.
  • Take a high vaginal swab from the posterior fornix for microscopy (if available) and nucleic acid amplification testing (NAAT), at the time of speculum examination.
    • Place all swabs for bacterial culture in Amies transport medium with charcoal. 
    • Mark the request as 'suspected trichomoniasis infection' if the local laboratory does not routinely perform Trichomonas vaginalis wet microscopy or culture.
    • Transport samples to the laboratory as soon as possible. If there is a delay in transportation, the swab should be refrigerated at 4°C for no longer than 48 hours.
      • If microscopy is not being performed, a self-administered vaginal swab is recommended for NAAT instead.
  • In women with vaginal symptoms, consider other causes of vaginal discharge. For more information, see the CKS topic on Vaginal discharge.

If a man is suspected of having a trichomoniasis infection, or they are a sexual partner of an infected woman, refer the man to a genito-urinary medicine (GUM) clinic or other local specialist sexual health service for confirmation of the diagnosis. If this is declined or not possible, it is reasonable to arrange tests in primary care, but the results may not be as reliable.

  •  Take a urethral swab sample or arrange a self-taken penile-meatal swab for a NAAT.
    • In most men, there may be no signs, even in the presence of symptoms suggesting urethritis. 
    • Rarely, the man may present with balanitis/balanoposthitis (inflammation of the glans penis and prepuce).
  • In men with urethral symptoms, consider other causes of urethritis. For more information, see the CKS topic on Urethritis - male.

For both men and women with a suspected trichomoniasis infection offer tests for:

Basis for recommendation

These recommendations are largely based on the Royal College of General Practitioners (RCGP) and British Association of Sexual Health and HIV (BASHH) guideline Sexually transmitted infections in primary care [BASHH, 2013], the BASHH United Kingdom national guidelines on the management of Trichomoniasis vaginalis 2021 [Sherrard, 2021], and the BASHH Standards for the management of sexually transmitted infections (STIs) [BASHH, 2019].

Choice of sample for NAAT

  • Self-administered vaginal swabs are likely to give equivalent results to clinician-taken swabs when using nucleic acid amplification tests (NAATs) [Sherrard, 2021].
  • First-catch urine samples may be used to diagnose women, based on local NAAT assay availability. Urine testing has been evaluated with some NAATs and has shown acceptable sensitivity in the range 88–90% [Sherrard, 2021].
  • Clinician-taken urethral swabs or self-taken penile-meatal swabs will diagnose approximately 80% of cases using NAATs and are the recommended sample [Sherrard, 2021]. First-catch urine samples may be used depending on the local availability of the NAAT assay. Urine is currently approved for only one NAAT.
  • Detection of T. vaginalis in specimens from men (urine, penile-meatal and urethral swabs) is currently outside of most commercial NAAT assay scope, therefore, local validation would be necessary [Sherrard, 2021].

What else might it be?

  • Other conditions that may cause vaginal discharge include:
  • For more information, see the CKS topic on Vaginal discharge.
  • Other conditions that may cause urethritis include:
  • For more information, see the CKS topic on Urethritis - male.

Basis for recommendation

The information on the differential diagnosis of trichomoniasis is based on the BMJ Best Practice guidelines Assessment of vaginal discharge [BMJ Best Practice, 2023] and Urethritis [BMJ Best Practice, 2024], and the Royal College of General Practitioners (RCGP) and British Association of Sexual Health and HIV (BASHH)  guideline Sexually transmitted infections in primary care [BASHH, 2013].

Management

Scenario: Management of trichomoniasis

From age 13 years onwards.

How should I manage a person with confirmed trichomoniasis?

Ideally, treatment of confirmed trichomoniasis should be provided by a genito-urinary medicine (GUM) clinic or other local specialist sexual health service. If this is declined or not possible, the person should be managed in primary care.

If a sexually transmitted infection (STI) is suspected or diagnosed in a child or young person, the healthcare professional should have a low threshold for discussing with a GUM specialist or paediatrician, and local child safeguarding procedures should be followed. Further information is available in the CKS topic on Child maltreatment - recognition and management.

  • Provide a detailed explanation of their condition with an emphasis on the long-term implications for their own health, and that of their sexual partners. Offer written information on trichomoniasis as an STI, including information on possible complications and measures to reduce the risk of further STIs. Patient information is available from:
  • Treat the infection.
    • For men and women (not pregnant or breastfeeding):
      • Prescribe oral metronidazole 400–500 mg twice a day for 7 days. 
        • Alternatively, prescribe metronidazole 2 g as a single oral dose.
      • Seek advice from a GUM specialist if the person has a confirmed metronidazole allergy.
    • For breastfeeding women and symptomatic pregnant women:
      • Prescribe oral metronidazole 400 mg twice a day for 7 days.
      • Where possible, inform other healthcare professionals involved in the woman's care (such as the woman's midwife and obstetrician) of the diagnosis and treatment.
      • Seek specialist advice from a GUM specialist if the woman is unable or unwilling to take metronidazole.
      • High-dose metronidazole (2 g single dose) is not recommended during pregnancy and breastfeeding.
    • For asymptomatic pregnant women: 
      • Seek specialist advice from a GUM specialist.
    • For people with HIV:
      • Prescribe oral metronidazole 500 mg twice a day for 7 days.
      • Seek advice from a GUM specialist if the person has a confirmed metronidazole allergy.
    • Treat current partner(s) simultaneously, and also treat any partner(s) from within the 4-week period prior to presentation.
  • Offer screening for other STIs (if not already done). See the sections on Diagnosis - women and Diagnosis - men for more information.
    • Also screen the person's current partner(s) and partner(s) from within the 4-week period prior to presentation. 
  • Arrange follow up after treatment to:
    • Review the person for persistent symptoms, which may indicate treatment failure.
    • Confirm that contact tracing has been carried out.
    • Discuss the results of the STI screen.
  • Advise sexual abstinence for at least 1 week after starting treatment and until the person and partner(s) have completed treatment and follow up.
  • Tests of cure are only recommended if the patient remains symptomatic following treatment, or if symptoms recur.

Basis for recommendation

These recommendations are largely based on the Royal College of General Practitioners (RCGP) and British Association of Sexual Health and HIV (BASHH) guideline Sexually Transmitted infections in Primary Care [BASHH, 2013], the BASHH United Kingdom national guidelines on the management of Trichomoniasis vaginalis [Sherrard, 2021], and the British National Formulary (BNF) [BNF, 2024].

Treating men and women (not pregnant or breastfeeding) 
  • Evidence from a meta-analysis [Howe, 2017] and an open-label, randomized controlled trial (RCT) [Kissinger, 2018] suggests that there is higher treatment failure for the single-dose metronidazole treatment regimen compared with the 7-day regimen, 7 day treatment is, therefore, the preferred treatment.
  • While it is recognised that 400 mg is the standard dose of metronidazole used in the UK, most of the recent evidence is based on 500 mg and this dose is also listed in the British National Formulary. It is therefore recommended to use 500 mg twice daily for 7 days where 500 mg tablets are available. 
Treating breastfeeding women and symptomatic pregnant women
  • This recommendation is based on the BASHH guideline [Sherrard, 2021].
  • The recommendation to inform other healthcare professionals (for example the midwife and obstetrician) is based on what CKS considers to be good medical practice.
  • Information regarding the safety of metronidazole in pregnancy and breastfeeding is summarized in the section on Pregnancy and breastfeeding in Prescribing information.
Treating asymptomatic pregnant women
  • CKS recommends seeking specialist advice in asymptomatic pregnant women due to the lack of consensus regarding optimal treatment of this group [Gulmezoglu, 2011].

How should I manage treatment failure?

  • ​​​​​​If symptoms persist or recur after the first-line treatment is completed, the person should ideally be treated by a genito-urinary medicine (GUM) clinic or other local specialist sexual health service. If this is declined or not possible:
    • Check adherence to the first-line treatment and exclude vomiting of metronidazole.
    • Exclude the possibility of reinfection. 
      • Check that current partner(s) have been treated appropriately and simultaneously.
    • Reconsider the diagnosis. 
      • Ensure that other causes of symptoms have been excluded. For more information on symptoms in women, see the CKS topic on Vaginal discharge. For more information on symptoms in men, see the CKS topic on Urethritis - male.
      • Offer repeat testing. For more information on the tests, see the sections on Diagnosis - women and Diagnosis - men. Leave 48 hours after the end of initial treatment before re-testing.
    • Manage the infection.
      • For men and women (not pregnant or breastfeeding), repeat the 7-day course of metronidazole treatment (400–500 mg twice a day).
      • For pregnant or breastfeeding women, discuss with a GUM specialist or the woman's obstetrician before prescribing any further treatment.
    • Seek advice from a GUM specialist:
      • If the second-line treatment regimen fails.
      • For people with failed first-line single-dose treatment.

Basis for recommendation

These recommendations are largely based on the British Association of Sexual Health and HIV(BASHH) United Kingdom national guidelines on the management of Trichomoniasis vaginalis [Sherrard, 2021].

When to seek specialist advice
  • For people who do not respond to the second-line treatment, BASHH recommends higher dose treatment (metronidazole 2 g daily for 5–7 days, or metronidazole 800 mg three times daily for 7 days) based on evidence that 70% of people responded to higher doses of metronidazole.
  • However, CKS recommends seeking specialist advice as these are off-label doses.

Prescribing information

Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) or the British National Formulary (BNF).

Metronidazole

What are the contraindications and cautions for metronidazole?

  • Do not prescribe metronidazole in people with:
    • Known metronidazole or nitroimidazole hypersensitivity.
  • Prescribe metronidazole with caution in people with:
    • Cockayne syndrome — cases of severe hepatotoxicity/acute hepatic failure, including cases with a fatal outcome with very rapid onset after treatment initiation in patients with Cockayne syndrome have been reported with products containing metronidazole for systemic use.
      • Only prescribe after careful benefit-risk assessment and only if no alternative treatment is available. Liver function tests must be performed just prior to the start of therapy, throughout and at the end of treatment until liver function is within normal ranges, or until the baseline values are reached.
    • Active or chronic severe peripheral and central nervous system disease, as there is a risk of neurological aggravation.
    • Hepatic encephalopathy — prescribe one-third of the daily dosage once daily.

[EMC, 2023a; BNF, 2023]

What are the adverse effects of metronidazole?

  • Blood disorders — agranulocytosis, neutropenia, thrombocytopenia, pancytopenia (very rare).
  • Eye — transient diploplia, or myopia (very rare).
  • Gastrointestinal — nausea, vomiting, epigastric pain, taste disturbances, furred tongue, oral mucositis (unknown frequency).
  • Nervous system — drowsiness, dizziness, convulsions, headaches, encephalopathy (very rare)
  • Psychiatric — psychotic disorders, confusion, hallucinations (very rare).
  • Skin — rash, pruritus, flushing, erythema multiforme, Stevens-Johnson syndrome or toxic epidermal necrolysis, acute generalised exanthematous pustulosis, fixed drug eruption (very rare).
  • Other rare, or very rare adverse effects include:
    • Anaphylaxis.
    • Anorexia.
    • Darkening of urine.
    • Hearing impairment, tinnitus.
    • Liver enzyme increases, jaundice, pancreatitis.
    • Myalgia, arthralgia.

[EMC, 2023a; BNF, 2024]

What are the drug interactions of metronidazole?

  • Alcohol — some people taking metronidazole experience a disulfiram-like reaction with alcohol. Reactions of this kind are generally more unpleasant than serious. Warn the person that they might experience this reaction if they drink alcohol whilst on metronidazole and for at least 48 hours afterwards. 
  • Busulfan — plasma levels of busulfan may be increased leading to toxicity. Avoid high doses of busulfan. If conventional doses of busulfan are given, monitor blood count weekly.
  • Ciclosporin — levels of ciclosporin may be increased. Monitor serum creatinine and ciclosporin concentrations.
  • Ergometrine — metronidazole is predicted to increase the exposure to ergot derivatives, which might lead to ergotism. If concurrent use is unavoidable, be alert for symptoms of ergotism (such as coldness, numbness, or tingling of the hands and feet), and strongly advise patients not to take any further doses and to seek medical advice.
  • Fluorouracil — the toxicity of fluorouracil, but not its efficacy, is increased by metronidazole. Monitor the person for increased toxicity. 
  • Lithium — metronidazole may increase lithium levels. If concurrent use is unavoidable, taper lithium dose before administering metronidazole. Monitor lithium concentrations, creatinine, and electrolytes.
  • Phenobarbital, phenytoin — the metabolism of metronidazole is increased significantly. Monitor effects of concurrent use as the dose of metronidazole may need to be increased.
  • Warfarin — the anticoagulant effects of warfarin may be increased by metronidazole.  Monitor the international normalized ratio (INR) and adjust the warfarin dose accordingly. 
  • Live cholera vaccines — the efficacy of the live vaccine may be affected. Avoid concurrent use and for 14 days before, and for 10 days after, live cholera vaccines.
  • Live typhoid vaccines — the immune response to the vaccine may be reduced. Antibacterials should be stopped from 3 days before to 3 days after receiving live typhoid vaccines.

[Preston, 2024]

Pregnancy and breastfeeding

  • Pregnancy
    • Although there is inadequate evidence of the safety of metronidazole in pregnancy, it has been in wide use for many years without clinical issues. 
    • According to the United Kingdom Teratology Information Service (UKTIS):
      • Available data, which are almost exclusively based on oral exposure, do not indicate an increased risk of congenital malformation, low birth weight, intrauterine death, or neonatal complications with metronidazole use in human pregnancy.
      • Preterm delivery has been reported in women with bacterial vaginosis or trichomoniasis. However, the relative contribution of the underlying maternal infection and metronidazole exposure to pregnancy outcome is uncertain, and recent studies have not found an association between metronidazole use and preterm delivery.
      • Data on spontaneous abortion are conflicting: a cohort study found no significant increase in risk, whereas a nested case-control analysis suggests a possible association with metronidazole treatment in pregnancy.
    • The manufacturer states that metronidazole should not be given during pregnancy unless essential and that short, high-dose treatment courses are not recommended during pregnancy.
  • Breastfeeding
    • A significant amount of metronidazole enters breast milk and may give it a bitter taste.
    • The manufacturer states that metronidazole should not be used during breastfeeding unless essential and that short, high-dose treatment courses are not recommended during breastfeeding.

[Sherrard, 2021; UKTIS, 2022; EMC, 2023b; BNF, 2024]

Supporting evidence

The recommendations in this CKS topic are largely based on the Royal College of General Practitioners (RCGP) and British Association of Sexual Health and HIV (BASHH) guideline Sexually Transmitted infections in Primary Care [BASHH, 2013] and the BASHH United Kingdom National Guidelines on the Management of Trichomoniasis vaginalis [Sherrard, 2021].

How this topic was developed

This section briefly describes the processes used in developing and updating this topic. Further details on the full process can be found in the About Us section and on the Clarity Informatics website.

Search strategy

A literature search was conducted for guidelines and systematic reviews on primary care management of trichomoniasis.

Search dates

July 2019 - September 2024

Key search terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline.The terms listed below are the core search terms that were used for EBSCOhost MEDLINE (searched 29th July 2019). These were combined with filters to identify guidelines, systematic reviews and primary care relevant literature in EBSCOhost MEDLINE. The strategy was adapted for The Cochrane Library databases.

S4    S1 OR S2 OR S3 
S3    AB ( trichomoniasis* or trichomonas ) OR TI ( trichomoniasis* or trichomonas ) 
S2    (MH "Trichomonas vaginalis") 
S1    (MH "Trichomonas Infections+") 

Sources of guidelines

Sources of systematic reviews and meta-analyses

  • The Cochrane Library:
    • Systematic reviews
    • Protocols
    • Database of Abstracts of Reviews of Effects
  • Medline (with systematic review filter)
  • EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

Sources of randomized controlled trials

  • The Cochrane Library:
    • Central Register of Controlled Trials
  • Medline (with randomized controlled trial filter)
  • EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

Sources of national policy

Patient experiences

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

  • Clinical accuracy.
  • Consistency with other providers of clinical knowledge for primary care.
  • Accuracy of implementation of national guidance (in particular NICE guidelines).
  • Usability.

Principles of the consultation process

  • The process is inclusive and any individual may participate.
  • To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
  • Comments received after the deadline will be considered, but they may not be acted upon before the clinical topic is issued onto the website.
  • Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
  • External reviewers are not paid for commenting on the draft topics.
  • Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
  • All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
  • All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

  • Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
  • Stakeholders identified from the following groups are invited to review draft topics:
    • Experts in the topic area.
    • Professional organizations and societies (for example, Royal Colleges).
    • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
    • Guideline development groups where the topic is an implementation of a guideline.
    • The British National Formulary team.
    • The editorial team that develop MeReC Publications.
  • Reviewers are provided with clear instructions about what to review, what comments are particularly helpful, how to submit comments, and declaring interests.

Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

  • Topic selection
  • Scoping of topic
  • Selection of clinical scenarios
  • First draft internal review
  • Second draft internal review
  • External review
  • Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

  • Animal studies
  • Original research is not written in English

Possible exclusions for reviewed literature:

  • Sample size too small or study underpowered
  • Bias evident or promotional literature
  • Population not relevant
  • Intervention/treatment not relevant
  • Outcomes not relevant
  • Outcomes have no clear evidence of clinical effectiveness
  • Setting not relevant
  • Not relevant to UK
  • Incorrect study type
  • Review article
  • Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

  • Feasibility
    • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
  • Organizational and Financial Impact Analysis
  • Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
    • Eligible population
    • Current interventions
    • Likely uptake of new intervention or recommendation
    • Cost of the current or new intervention mix
    • Impact on other costs
    • Condition-related costs
    • In-direct costs and service impacts
    • Time dependencies
  • Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

  • Personal financial interests
  • Personal family interest
  • Personal non-financial interest
  • Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.

References

  • BASHH, RCOG (2013) Sexually transmitted infections in primary care. Royal College of General Practitioners and British Association for Sexual Health and HIV. http://www.bashh.org [Free Full-text]
  • BASHH (2019) Standards for the management of sexually transmitted infections (STIs). British Association of Sexual Health and HIV. http://www.bashh.org [Free Full-text]
  • BMJ Best Practice (2023) Assessment of vaginal discharge. BMJ Publishing Group. https://bestpractice.bmj.com
  • BMJ Best Practice (2024) Urethritis. BMJ Publishing Group. https://bestpractice.bmj.com
  • BNF (2023) British National Formulary. National Institute for Health and Care Excellence. https://bnf.nice.org.uk
  • BNF (2024) British National Formulary. National Institute for Health and Care Excellence. https://bnf.nice.org.uk
  • EMC (2023a) SPC for Metronidazole 400 mg Tablets. Electronic Medicines Compendium. Datapharm Communications Ltd. https://www.medicines.org.uk/emc [Free Full-text]
  • EMC (2023b) SPC for flagyl 400mg tablets. Electronic Medicines Compendium. Datapharm Communications Ltd. https://www.medicines.org.uk [Free Full-text]
  • Field, N., Clifton, S., Alexander, S., et al. (2016) Trichomonas vaginalis infection is uncommon in the British general population: implications for clinical testing and public health screening. Sexually Transmitted Infections 94, 226-229. [Abstract]
  • Fürnkranz, U. and Walochnik, J. (2021) Nosocomial infections: do not forget the parasites! Pathogens 10(2), 238. [Abstract] [Free Full-text]
  • Gulmezoglu, A. and Azhar, M. (2011) Interventions for trichomoniasis in pregnancy (Cochrane Review). The Cochrane Library. John Wiley & Sons, Ltd. http://www.thecochranelibrary.com [Free Full-text]
  • Hamar, B., Teutsch, B., Hoffmann, E., et al. (2023) Trichomonas vaginalis infection is associated with increased risk of cervical carcinogenesis: A systematic review and meta-analysis of 470 000 patients. International Journal of Gynaecology and Obstetrics 163(1), 31-43. [Abstract] [Free Full-text]
  • Howe, K. and Kissinger, P.J. (2017) Single-dose compared with multidose metronidazole for the treatment of trichomoniasis in women: a meta-analysis. Sexually Transmitted Diseases 44(1), 29-34. [Free Full-text]
  • Kalia, N., Singh, J. and Kaur, M. (2020) Microbiota in vaginal health and pathogenesis of recurrent vulvovaginal infections: a critical review. Annals of Clinical Microbiology and Antimicrobials 19(1), 5. [Abstract] [Free Full-text]
  • Kissinger, P. (2015) Epidemiology and treatment of trichomoniasis. Current Infectious Disease Reports 17(6), 484. [Abstract] [Free Full-text]
  • Kissinger, P., Muzny, C.A., Mena, L.A., et al. (2018) Single-dose versus 7-day-dose metronidazole for the treatment of trichomoniasis in women: an open-label, randomised controlled trial. The Lancet Infectious Diseases 18(11), 1251-1259. [Abstract]
  • Kissinger, P.J., Gaydos, C.A., Seña, A.C., et al. (2022) Diagnosis and management of Trichomonas vaginalis: summary of evidence reviewed for the 2021 Centers for Disease Control and Prevention Sexually Transmitted Infections Treatment Guidelines. Clinical Infectious Disease 13(74), S152-S161. [Abstract] [Free Full-text]
  • Masha, S.C., Cools, P., Sanders, E.J., et al. (2019) Trichomonas vaginalis and HIV infection acquisition: a systematic review and meta-analysis. Sexually Transmitted Infections 95(1), 36-42. [Abstract] [Free Full-text]
  • Preston, C.L (2024) Stockley's Drug Interactions. Medicines Complete. Pharmaceutical Press. https://www.medicinescomplete.com
  • Rowley, J., Vander Hoorn, S., Korenromp, E., et al. (2019) Chlamydia, gonorrhoea, trichomoniasis and syphilis: global prevalence and incidence estimates, 2016. Bulletin of the World Health Organisation 97(8), 548-562. [Abstract] [Free Full-text]
  • Sherrard, J., Pitt, R., Hobbs, K.R., et al. (2021) British Association for Sexual Health and HIV (BASHH) United Kingdom national guideline on the management of Trichomonas vaginalis 2021. International Journal of STD & AIDS 33(8), 740-750. [Abstract] [Free Full-text]
  • UKTIS (2022) Use of metronidazole in pregnancy. UK Teratology Information Service. https://uktis.org [Free Full-text]
  • Van Gerwen, O.T., Craig-Kuhn, M.C., Jones, A.T., et al. (2021) Trichomoniasis and adverse birth outcomes: a systematic review and meta-analysis. BJOG 128(12), 1907-1915. [Abstract] [Free Full-text]
  • Van Gerwen, O.T., Opsteen, S.A., Graves, K.J. and Muzny, C.A. (2023) Trichomoniasis. Infectious Disease Clinics of North America 37(2), 245-265. [Abstract] [Free Full-text]
  • Wiringa, A.E., Ness, R.B., Darville, T., et al. (2020) Trichomonas vaginalis, endometritis and sequelae among women with clinically suspected pelvic inflammatory disease. Sexually Transmitted Infections 96(6), 436-438. [Abstract] [Free Full-text]
  • Zhang, Z., Li, Y., Lu, H., et al. (2022) A systematic review of the correlation between Trichomonas vaginalis infection and infertility. Actra Tropica 236, 106693. [Abstract] [Free Full-text]
Change privacy settings