Previous changes

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.

November to December 2021 — reviewed. A literature search was conducted in December 2021 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to the recommendations have been made.

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

December 2016 — reviewed. A literature search was conducted in November 2016 to identify evidence-based guidelines, UK policy, systematic reviews, and key RCTs published since the last revision of the topic. There have been changes to clinical recommendations on referral for suspected cancer based on the 2015 National Institute for Health and Care Excellence guideline Suspected cancer: recognition and referral. There have also been minor changes and expansion to the section on oral hygiene measures and the use of systemic antibiotics and mouthwashes for people with plaque-related gingivitis and periodontitis. Structural changes have been made to the topic.

February 2013 — minor update. The 2013 QIPP options for local implementation have been added to this topic.

October 2012 — minor update. The 2012 QIPP options for local implementation have been added to this topic.

August 2012 — reviewed. A literature search was conducted in August 2012 to identify evidence-based guidelines, UK policy, systematic reviews, and key RCTs published since the last revision of the topic. No changes to clinical recommendations have been made.

June 2011 — minor update. The 2010/2011 QIPP options for local implementation have been added to this topic. 

February 2011 — topic structure revised to ensure consistency across CKS topics — no changes to clinical recommendations have been made.

January 2010 — Minor update to the referral criteria in Referral section. 

August to December 2007 — 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.

July 2004 — written. Validated in September 2004 and issued in November 2004.

New evidence

Evidence-based guidelines

No new evidence-based guidelines since 1 May 2026.

HTAs (Health Technology Assessments)

No new HTAs since 1 May 2026.

Economic appraisals

No new economic appraisals relevant to England since 1 May 2026.

Systematic reviews and meta-analyses

No new systematic reviews or meta-analysis which reach the CKS threshold for inclusion since 1 May 2026.

Primary evidence

No new primary evidence which reaches the CKS threshold for inclusion published since 1 May 2026.

New policies

No new national policies or guidelines since 1 May 2026.

New safety alerts

No new safety alerts since 1 May 2026.

Changes in product availability

No changes in product availability since 1 May 2026.

Basis for recommendation

The recommendations on the diagnosis of gingivitis and periodontitis are based on guidance from the British Medical Association Patients presenting with dental problems [BMA, 2024], the Scottish Dental Clinical Effectiveness Programme (SDCEP) Prevention and treatment of periodontal diseases in primary care [SDCEP, 2024] and Management of acute dental problems [SDCEP, 2026], and the British Society of Periodontology The good practitioner’s guide to periodontology [BSP, 2016], and expert opinion in review articles [Coventry, 2000; Jaramillo, 2005; Preshaw, 2015; Wadia and Ide, 2017; Herrera, 2018; Haas, 2025] and a textbook [Lehner, 2010].

Referral to a dentist

• The British Medical Association states that [BMA, 2024]:
  • GPs are not responsible for treating dental problems.
  • GPs should not attempt to manage a condition requiring dental skills unless they have appropriate training.
  • Before refusing to treat a patient asking for emergency dental treatment, the GP must ascertain that the condition requires only dental treatment.
  • Primary care teams must judge the nature of the patient’s condition by undertaking reasonable enquiries and, where appropriate, a clinical assessment.
  • Where an apparent dental problem is established, GPs should direct the patient to a dentist or local emergency service, or refer them to secondary care. If the person has no usual dentist or there is no response from the usual dentist, the patient should contact NHS 111 (England), NHS 24 (Scotland), NHS Direct or local dental helplines (Wales), or the Health and Social Care Board (Northern Ireland).
• CKS therefore recommends referral to a dentist to confirm the diagnosis of gingivitis or periodontitis because a full examination of gingival and periodontal tissues (beyond the scope of primary medical care) is required. This involves probing for depth and bleeding, an assessment of tooth mobility, and an assessment of severity, based on the amount of inflammation in gingivitis and the degree of attachment loss in chronic periodontitis. Radiographs may be required to assess bone loss in more severe periodontitis [Preshaw, 2015; BSP, 2016; SDCEP, 2024].

Basis for recommendation

Recommendations on the differential diagnosis of gingivitis and periodontitis are based on National Institute for Health and Care Excellence (NICE) guidelines Suspected cancer: recognition and referral [NICE, 2026], expert opinion in review articles [Meraw, 1998; Coventry, 2000; Atout, 2013; Rotaru, 2025] and a textbook [Lehner, 2010]. 

How should I manage someone with suspected plaque-associated gingivitis/periodontitis?

• If there are any concerning features, such as:
  • Unexplained or atypical enlargement of the gingivae — consider the possibility of leukaemia and investigate and refer appropriately.
  • Periodontitis presenting in children or young adults, or progressing rapidly — consider the possibility of serious conditions such as aggressive periodontitis, immunosuppression, or malignancy.
  • Unexplained ulceration in the oral cavity lasting for more than 3 weeks — consider an urgent suspected cancer pathway referral for oral cancer.
  • Either a lump on the lip or in the oral cavity, or a red or red and white patch in the oral cavity consistent with erythroplakia or erythroleukoplakia — consider an urgent suspected cancer pathway referral or seek immediate advice from an oral medicine or oral and maxillofacial specialist. If there is not a strong suspicion of oral cancer, consider an urgent referral (for an appointment within 2 weeks) to a dentist.
    • If there is likely to be a delay in the person accessing a dentist, use clinical judgement and consider an urgent suspected cancer pathway referral or seek immediate advice from an oral medicine or oral and maxillofacial specialist.
  • For further information on the concerning features which may exist in people with oral cancer, particularly a persistent lump on the lip, in the oral cavity or a neck lump, please see the CKS topic Head and neck cancers - recognition and referral.
• Advise routine regular review by a dentist or hygienist.
  • Review interval will depend on the advice of the dentist.
  • People with predisposing risk factors may require frequent professional cleaning.
  • For people with diabetes, explain that they are at increased risk of periodontal (gum) disease and encourage them to make a dental appointment as soon as possible. 
• Give advice on oral hygiene. Advise the person to remove plaque by:
  • Brushing their teeth for 2 minutes twice a day (in the morning and last thing at night), preferably with a powered toothbrush.
    • Advise that toothbrushes should ideally have a small head with medium texture bristles and should be replaced when signs of wear appear (every 1–3 months).
    • Advise use of a fluoride-containing toothpaste and to 'spit, don't rinse' when cleaning teeth.
    • Refer people who are unable to use a toothbrush to a dentist. 
  • Daily interdental cleaning before brushing teeth.
    • Choice of interdental cleaning aid will depend on personal preference. However, advise that for most people with periodontitis, interdental brushes will be more effective than dental floss or tape because of the size of their interdental spaces. People with varying interdental gaps (common in periodontitis) will need several different sizes of interdental brushes. Brushes should fit into the interdental space without the wire rubbing the tooth. 
• Do not routinely recommend mouthwashes.
• Antibiotics are not usually necessary and should be prescribed only on the advice of a specialist.
• Offer smoking cessation advice if appropriate. For more information, see the CKS topic on Smoking cessation.

How should I manage someone with suspected necrotizing gingivitis?

• If there are any concerning features, such as:
  • Unexplained or atypical enlargement of the gingivae — consider the possibility of leukaemia and investigate and refer appropriately.
  • Periodontitis presenting in children or young adults, or progressing rapidly — consider the possibility of serious conditions such as aggressive periodontitis, immunosuppression, and malignancy.
  • Unexplained ulceration in the oral cavity lasting for more than 3 weeks — consider a suspected cancer pathway referral (for an appointment within 2 weeks) for oral cancer. 
  • Either a lump on the lip or in the oral cavity, or a red or red and white patch in the oral cavity consistent with erythroplakia or erythroleukoplakia — consider an urgent suspected cancer pathway referral or seek immediate advice from an oral medicine or oral and maxillofacial specialist. If there is not a strong suspicion of oral cancer, consider an urgent referral (for an appointment within 2 weeks) to a dentist.
    • If there is likely to be a delay in the person accessing a dentist, use clinical judgement and consider an urgent suspected cancer pathway referral or seek immediate advice from an oral medicine or oral and maxillofacial specialist.
  • For further information on the concerning features which may exist in people with oral cancer, particularly a persistent lump on the lip, in the oral cavity or a neck lump, please see the CKS topic Head and neck cancers - recognition and referral.
• Advise a person with suspected necrotizing gingivitis to urgently see a dentist for assessment and management. 
• While the person is waiting to be seen by a dentist, prescribe:
  • Metronidazole 400 mg three times a day for 3 days for adults, or 200 mg to 250 mg three times a day for 10–17 year olds (or amoxicillin 500 mg three times a day for 3 days if metronidazole is inappropriate) if the person is immunocompromised or has systemic involvement, for example, fever, malaise, or lymphadenopathy. 
  • Paracetamol or ibuprofen for pain relief. For more information, see the CKS topics on Analgesia - mild-to-moderate pain and NSAIDs - prescribing issues.
  • Chlorhexidine (0.12% or 0.2%) or hydrogen peroxide 6% mouthwash.
• Advise routine regular review by a dentist or hygienist.
  • Review interval will depend on the advice of the dentist.
  • People with predisposing risk factors may require frequent professional cleaning.
• Give advice on oral hygiene. Once the acute pain has subsided, advise the person to remove plaque by:
  • Brushing their teeth for 2 minutes twice a day (in the morning and last thing at night), preferably with a powered toothbrush. During the acute phase, the person should, if possible, use a soft toothbrush to clean their teeth.
    • Advise that toothbrushes should have a small head with medium texture bristles and should be replaced when signs of wear appear (every 1–3 months).
    • Advise use of a fluoride-containing toothpaste and to 'spit, don't rinse' when cleaning teeth.
    • Refer people who are unable to use a toothbrush to a dentist. 
  • Daily interdental cleaning before brushing teeth.
    • Choice of interdental cleaning aid will depend on personal preference. However, advise that for most people with periodontitis, interdental brushes will be more effective than dental floss or tape because of the size of their interdental spaces. People with varying interdental gaps (common in periodontitis) will need several different sizes of interdental brushes. Brushes should fit into the interdental space without the wire rubbing the tooth.
• Offer smoking cessation advice if appropriate. For more information, see the CKS topic on Smoking cessation.

What contraindications and cautions are associated with amoxicillin?

• Do not prescribe amoxicillin to people with a true penicillin hypersensitivity or hypersensitivity to another beta-lactam agent (for example a cephalosporin).
  • Allergic reactions to penicillins occur in 1–10% of exposed individuals. Anaphylactic reactions occur in fewer than 0.05% of treated patients.
• Prescribe amoxicillin with caution in people with:
  • Hypersensitivity to cephalosporins.
  • Renal impairment — reduce the dose if the person's estimated glomerular filtration rate (eGFR) is less than 30 mL/minute/1.73 m².
    • eGFR 10 to 30 mL/minute/1.73 m² — maximum dose 500 mg twice daily.
    • eGFR less than 10 mL/minute/1.73 m² — maximum dose 500 mg daily.
  • Glandular fever (infective mononucleosis) — these people are especially susceptible to amoxicillin-induced skin rashes.
  • Acute or chronic lymphocytic leukaemia — these people are susceptible to amoxicillin-induced skin rashes.

[EMC, 2025a; BNF, 2026]

What are the adverse effects of amoxicillin?

Adverse effects of amoxicillin include:

• Gastrointestinal — nausea and diarrhoea (common), vomiting (uncommon).
  • Very rarely: antibiotic associated colitis.
• Skin — skin rash (common), urticaria and pruritus (uncommon).
  • Very rarely: erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, mucocutaneous candidiasis, bullous and exfoliative dermatitis, acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), and symmetrical drug-related intertriginous and flexural exanthema (SDRIFE; also known as baboon syndrome).
• Other very rare adverse effects include:
  • Hepatitis, cholestatic jaundice, moderate rise in aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT).
  • Hyperkinesia, dizziness, convulsions.
  • Interstitial nephritis, crystalluria.
  • Leucopenia, thrombocytopenia, haemolytic anaemia.
  • Prolonged bleeding time and prothrombin time.
  • Severe allergic reactions, including angioneurotic oedema, anaphylaxis, serum sickness and hypersensitivity vasculitis.

[EMC, 2025a; BNF, 2026]

What drug interactions are important with amoxicillin?

Key drug interactions with amoxicillin include:

• Probenecid — concurrent use with amoxicillin is not recommended as it may cause increased and prolonged blood levels of amoxicillin.
• Allopurinol — be aware of the increased risk of rash when allopurinol is given with amoxicillin. 
• Anticoagulants (for example, warfarin) — monitor the international normalized ratio (INR) closely during concomitant use. Adjustment of the anticoagulant dose (according to the INR) may be necessary.
• Methotrexate — amoxicillin may reduce methotrexate excretion, causing an increased risk of toxicity, monitor methotrexate levels more closely. One recommendation is to carry out twice weekly platelet and white cell counts for 2 weeks initially, with the measurement of methotrexate levels if toxicity is suspected.
  • Penicillins may reduce the excretion of methotrexate, potentially increasing toxicity. The interaction is not usually serious and risk factors are unknown (even people on low doses of methotrexate have been affected).
• Tetracyclines — the bactericidal effects of amoxicillin may be antagonized.
• Oral hormonal contraception — additional contraceptive precautions are not required during or after courses of amoxicillin.
  • However, women should be advised about the importance of correct contraceptive practice if they experience vomiting or diarrhoea. For further information, see the sections on vomiting or diarrhoea in the CKS topics on Contraception - combined hormonal methods and Contraception - progestogen-only methods.

[CoSRH, 2022; EMC, 2025a; BNF, 2026; Preston, 2026]

Can amoxicillin be used in pregnancy and breastfeeding?

Pregnancy

• Amoxicillin is not known to be harmful in pregnancy [BNF, 2026].
• The UK Teratology Information Service (UKTIS) states that when penicillins are taken at therapeutic doses during pregnancy, the majority of a large amount of data shows no increased risk of congenital malformation, miscarriage, intrauterine death, low birth weight, preterm delivery, or neonatal complications [UKTIS, 2019].

Breastfeeding

• Trace amounts of amoxicillin are found in breastmilk, but it is appropriate to use in women who are breastfeeding [BNF, 2026].
• Amoxicillin is considered one of the preferred choice of penicillin antibiotics in breastfeeding, as there is more evidence and experience to support use [SPS, 2024].
  • Although there is a low risk of adverse effects in the infant, precautionary parental monitoring should quickly identify any complications. Symptoms to monitor for include gastro-intestinal disturbances, oral candida infection, hypersensitivity reactions (including rashes or breathing problems), nausea, irritability, and drowsiness .

What is the dose recommendation for oral chlorhexidine mouthwash?

• Thoroughly rinse the mouth for approximately 1 minute with 10 mL chlorhexidine twice daily.
  • Chlorhexidine may be incompatible with some ingredients in toothpaste — advise the person to leave an interval of at least 30 minutes between using the mouthwash and their toothpaste.

[EMC, 2023; BNF, 2026; SDCEP, 2026b]

What are the cautions and contraindications associated with chlorhexidine mouthwash?

• Do not prescribe chlorhexidine to people who have previously experienced a hypersensitivity reaction to it or its excipients.

[EMC, 2023; BNF, 2026]

What are the adverse effects of chlorhexidine?

• Adverse effects reported with the use of chlorhexidine 2% mouthwash include:
  • Superficial discolouration of the tongue and/or teeth (not permanent).
    • Advise the person to reduce their tea, coffee, and red wine intake.
    • Some people will require treatment by a dentist to remove staining.
  • Transient altered taste and burning sensation of the tongue — usually improves with continued use.
  • Mucosal irritation — if oral desquamation occurs, advise dilution of mouthwash with an equal volume of water before use.
  • Rarely, parotid gland swelling, irritative skin reactions, and allergic reactions (including anaphylaxis).

[EMC, 2023; BNF, 2026; SDCEP, 2026b]

What are the important interactions with chlorhexidine mouthwash?

• Chlorhexidine is incompatible with anionic agents, including those which are usually present in conventional toothpastes — advise the person to leave an interval of at least 30 minutes between using the mouthwash and their toothpaste.

[EMC, 2023; SDCEP, 2026b]

Can chlorhexidine mouthwash be used in pregnancy and breastfeeding?

• The manufacturer advises that no special precautions are required when chlorhexidine mouthwash is required by those who are pregnant or breastfeeding.

[EMC, 2023]

What cautions and contraindications are associated with metronidazole?

• Do not prescribe metronidazole to people with:
  • Known metronidazole or nitroimidazole hypersensitivity.
• Prescribe metronidazole with caution to:
  • People with active or chronic severe peripheral and central nervous system disease — risk of neurological aggravation.
  • 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 people with Cockayne syndrome) have been reported with systemic metronidazole.
    • Only prescribe metronidazole after careful benefit-risk assessment and only if no alternative treatment is available.
    • Perform liver function tests (LFTs) just prior to the start of treatment, during treatment, and at the end of treatment until liver function is within normal ranges, or until the baseline values are reached.
    • If the LFTs become markedly elevated during treatment with metronidazole, discontinue the treatment. 
    • Advise the person to immediately report any symptoms of potential liver injury and to stop taking metronidazole if these occur.
  • People with severe liver disease or hepatic encephalopathy — metronidazole is mainly metabolized by hepatic oxidation. Substantial impairment of metronidazole clearance may occur in the presence of advanced hepatic insufficiency. Significant cumulation may occur in people with hepatic encephalopathy, and the resulting high plasma concentrations of metronidazole may contribute to the symptoms of the encephalopathy. Prescribe one third of the recommended daily dose once daily.
  • People with alcohol dependency — there may be a disulfiram-like reaction (flushing, increased respiratory rate, increased pulse rate, nausea, headache, and dizziness) if taken with alcohol.
  • Pregnant or breastfeeding women.

[EMC, 2025b; BNF, 2026]

What are the adverse effects of metronidazole?

• Severe bullous skin reactions, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, or acute generalized exanthematous pustulosis, have been rarely reported with oral metronidazole. If symptoms/signs are present, treatment must be immediately discontinued.
• Warn people taking metronidazole about the potential for drowsiness, dizziness, confusion, hallucinations, convulsions, or transient visual disorders. Advise them not to drive or operate machinery if these symptoms occur. These symptoms are thought to be very rare.
• Other adverse effects of oral metronidazole include:
  • Rare — anaphylaxis.
  • Very rare — arthralgia, myalgia, ataxia, darkening of urine, dizziness, drowsiness, headache, pruritus, rash, erythema multiforme, hepatitis, jaundice, leucopenia (on prolonged or intensive therapy), pancytopenia, thrombocytopenia, pancreatitis, peripheral neuropathy (on prolonged or intensive treatment), psychotic disorders, and transient epileptiform seizures (on prolonged or intensive treatment).
  • Frequency not known — angioedema, anorexia, aseptic meningitis, depressed mood, hearing loss, fever, furred tongue, gastrointestinal disturbances, nausea, vomiting, oral mucositis, taste disturbances, urticaria, and optic neuropathy.

[EMC, 2025b; BNF, 2026]

What are the important drug interactions with metronidazole?

• Important drug interactions associated with metronidazole include: 
  • Alcohol — some people taking oral metronidazole experience a disulfiram-like reaction (flushing, increased respiratory rate, increased pulse rate, nausea, headache, and dizziness) with alcohol.
    • Although there is no conclusive evidence to support this interaction, warn the person that they might experience this reaction if they drink alcohol whilst taking metronidazole.
    • Advise that alcohol should be avoided during treatment with metronidazole and for at least 48 hours afterwards.
  • Anticoagulants — the anticoagulant effects of warfarin and acenocoumarol can be markedly increased by metronidazole. There is no interaction with heparin. 
    • Monitor the international normalized ratio (INR) if concurrent treatment is indicated, and adjust the anticoagulant dose accordingly.
    • Warn the person of the possible risk of increased bruising and bleeding, and advise them on when to seek medical help.
  • Busulfan — plasma levels may be increased when used concurrently with metronidazole, which may increase the risk of severe busulfan toxicity.
  • Capecitabine and 5-fluorouracil — metronidazole can reduce the clearance of 5-fluorouracil, concomitant use may therefore increase the risk of toxicity.
  • Ciclosporin — people receiving concurrent metronidazole and ciclosporin are at risk of elevated serum ciclosporin levels.
    • When co-administration of metronidazole and ciclosporin is necessary, monitor serum ciclosporin and creatinine levels closely.
  • Ergot derivatives — metronidazole is predicted to increase the exposure to the ergot derivatives, which might lead to ergotism.
  • Lithium — raised lithium levels accompanied by evidence of possible renal damage has been reported in people treated simultaneously with lithium and metronidazole.
    • Before starting metronidazole in a person taking lithium, seek specialist advice about tapering or stopping lithium treatment.
    • If concurrent treatment is unavoidable, closely monitor plasma concentrations of lithium, creatinine, and electrolytes.
  • Phenobarbital or phenytoin — people receiving phenobarbital or phenytoin metabolize metronidazole at a much greater rate than normal, thereby reducing the half-life to approximately 3 hours. In addition, both metronidazole and phenytoin can increase the risk of peripheral neuropathy.
  • The manufacturers SPC also notes that QT prolongation has been reported (unknown frequency), particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval.
  • Oral hormonal contraceptives — additional contraceptive precautions are not required during or after courses of metronidazole. However, advise women on the importance of correct contraceptive practice if they experience vomiting or diarrhoea.
    • For further information, see the section on vomiting or diarrhoea in the CKS topics on Contraception - combined hormonal methods and Contraception - progestogen-only methods.

[CoSRH, 2022; EMC, 2025b; BNF, 2026; Preston, 2026]

Can metronidazole be used in pregnancy and breastfeeding?

Pregnancy

• The manufacturer recommends that metronidazole should only be used in pregnancy where the benefits are considered to outweigh the risks [EMC, 2025b].
• The UK Teratology Information Service (UKTIS) states that the available human data do not, overall, indicate an increased risk of congenital malformation, preterm delivery, low infant birth weight, intrauterine death, or neonatal complications following metronidazole exposure in pregnancy. Metronidazole exposure in early pregnancy has been associated with miscarriage in some studies, but it is possible that the underlying maternal infection may have influenced these associations, meaning that a causal association with metronidazole exposure has not been established [UKTIS, 2022].

Breastfeeding

• The manufacturer recommends that metronidazole should only be used in breastfeeding where the benefits are considered to outweigh the risks [EMC, 2025b].
• The Specialist Pharmacy Service recommends that short oral courses of metronidazole are considered to be compatible with breastfeeding, but infant monitoring is recommended [SPS, 2023].
  • Metronidazole has a low molecular weight and very low protein binding (less than 20%), and passes into breast milk in moderate amounts.
  • As oral bioavailability is high, the infant will absorb most of the metronidazole present within breastmilk, but drug accumulation is unlikely given the short half-life of metronidazole and its active metabolite.
  • Although there is a low risk of adverse effects in the infant, precautionary parental monitoring for gastro-intestinal disturbances, oral candida infection, hypersensitivity reactions (including rashes), nausea, poor feeding and inadequate weight gain should quickly identify any complications.