Previous changes

May 2024 — minor update. Information added stating that concomitant treatment with clarithromycin and ivabradine is now contra-indicated, as per the manufacturer's updated SPC.

December 2023 — minor update. Update to drug interactions section for erythromycin to include information on interactions with Lomitapide and Corticosteroids, as per the manufacturer's Summary of Product Characteristics (SPC).

November 2023 — minor update. Interactions section for flucloxacillin updated in line with updated manufacturer's summary of product characteristics.

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

November to December 2016 — reviewed. A literature search was conducted in November 2016 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of the topic. Aspiration and corticosteroid injection are no longer recommended as treatments for bursitis in primary care. Minor restructuring of the topic has been undertaken.

July 2015 — minor update. The prescribing information sections on clarithromycin and erythromycin have been re-written for clarity.

July 2013 — minor update. Update to the text to reflect recent advice from the Medicines and Healthcare products Regulatory Agency (MHRA) regarding diclofenac.

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.

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

December 2010 — minor update. Advice on use of pressure dressings after aspiration has been clarified. Issued in December 2010.

November 2010— minor update. Dose information for corticosteroid injections has been added. Issued in November 2010.

July to November 2010 — a new CKS topic. The evidence base has been reviewed in detail, and recommendations are clearly justified and transparently linked to the supporting evidence.

New evidence

Evidence-based guidelines

No new evidence-based guidelines since 1 July 2026.

HTAs (Health Technology Assessments)

No new HTAs since 1 July 2026.

Economic appraisals

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

Systematic reviews and meta-analyses

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

Primary evidence

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

New policies

No new national policies or guidelines since 1 July 2026.

New safety alerts

No new safety alerts since 1 July 2026.

Changes in product availability

No changes in product availability since 1 July 2026.

Aspiration of bursal fluid

• Aspiration of bursal fluid provides a sample for analysis to differentiate septic and non-septic pre-patellar bursitis. It may also relieve pain, reduce bacterial load, and increase range of movement.
• Bursal aspiration can be performed in primary care if the expertise and equipment are available.
• If septic bursitis is suspected, aspiration should ideally be carried out before antibiotics are started. See the section on Management in primary care.
• Bursal fluid should be sent to the laboratory in a sterile container for Gram staining, culture, and crystal analysis to provide a more definitive diagnosis. Differential white cell count and glucose levels may help with the diagnosis, especially in the absence of positive Gram stain or culture.
• The appearance of the fluid may be suggestive of the nature of the bursitis but is not specific:
  • If pus is aspirated — septic bursitis is likely (but many septic fluids are only slightly turbid in appearance, and other inflammatory non-infective conditions, such as rheumatoid arthritis, may also produce pus).
  • If straw-coloured fluid is aspirated — non-septic bursitis is more likely.
  • If blood-stained fluid is aspirated — septic bursitis, trauma, gout, or rheumatoid arthritis are all possible.
  • If milky fluid is aspirated — tophaceous gout or pseudogout is likely; rheumatoid arthritis is a rarer cause of milky fluid aspirate.
• The presence of urate crystals will provide a definitive diagnosis of gout, but sepsis and gout can coexist.

Basis for recommendation

History and examination 

• These recommendations and the clinical features of pre-patellar bursitis are based on expert opinion in review articles [Baumbach, 2014; Hong, 2014; Khodaee, 2017; Parker, 2018; Sato, 2020] and 2023 French national guidance [Darrieutort-Laffite, 2023].
  • The diagnosis of bursitis is primarily clinical. Routine investigations are unlikely to be beneficial but may be a useful adjunct to a thorough history and physical examination to help rule out differential diagnoses. 
  • People with chronic bursitis typically present with swelling over the involved bursa and may report associated occupations or activities, but often have minimal or no pain (because the bursa has had time to expand and to accommodate the increased fluid). However, those with acute traumatic/hemorrhagic bursitis or septic bursitis can present with significant pain, tenderness, and decreased range of motion [Khodaee, 2017]
  • Due to the superficial location of the bursa, any traumatic or dermatological skin lesion (such as eczema or psoriasis) can predispose to bacterial migration into the bursal sac increasing the risk of septic bursitis [Baumbach, 2014].
  • History and examination are not completely reliable in distinguishing between septic and non-septic bursitis, due to the overlap of clinical features. 

Investigations

The recommendations for blood tests and imaging are based on expert opinion in review articles [Baumbach, 2014; Hong, 2014; Khodaee, 2017]. Bursal swelling, redness, and tenderness are inadequate to differentiate between septic and non-septic bursitis [Baumbach, 2014].

• • Bursal aspiration is recommended to distinguish between septic and non-septic bursitis, as this is fundamental to successful management [Aaron, 2011; Baumbach, 2014; Khodaee, 2017].
  • An X-ray is indicated if there is recent trauma with concern for fracture, a foreign body, calcification, or bony abnormality [Khodaee, 2017].  
  • Blood tests can be considered to help distinguish septic from non-septic bursitis. The peripheral white blood count may not differ between infectious and non-infectious bursitis and may not even be elevated above the normal range. However, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) usually are elevated in septic bursitis [Khodaee, 2017].  
  • Because the presence of diabetes increases the chance of infection, blood glucose level should be measured to rule out the disease [Khodaee, 2017]. 

Bursal aspiration 

• The information on the appearance of the bursal fluid is based on expert opinion in review articles [Baumbach, 2014; Khodaee, 2017]. 
• The recommendation to request Gram stain, culture, and crystal examination is based on expert opinion in review articles [Baumbach, 2014; Khodaee, 2017].
• Bursal aspiration should be performed before antibiotics are administered, as they are likely to diminish the likelihood of isolating the causative organism [Khodaee, 2017].

Basis for recommendation

The information on differential diagnosis is based on expert opinion in review articles [Aaron, 2011; Hanrahan, 2013; Khodaee, 2017; Parker, 2018].

How should I manage pre-patellar bursitis in primary care?

• If clinically confident that the bursitis is non-septic:
  • Advise the person to use conservative measures until symptoms improve. These include rest, ice, activity modification, and simple analgesia.
    
    • Ice may be used to reduce swelling. It should be applied to the area for 10 minutes at a time, every few hours, but not directly onto the skin (a thin towel can be placed between the ice and the skin).
    • Activity modification will minimise mechanical stress on the inflamed bursa. This involves avoiding activities that worsen symptoms (for example, kneeling) and protecting the area where possible (for example, by using kneepads).
    • Simple analgesia, such as paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs), can be used for pain relief. Topical NSAIDs may be tried initially in preference to systemic NSAIDs if paracetamol is insufficient. See the CKS topics on Analgesia - mild-to-moderate pain and NSAIDs - prescribing issues for detailed prescribing information on paracetamol and NSAIDs.
    • Reassure the person that most people will respond to conservative treatment.
  • Advise the person to re-attend if there are worsening symptoms, such as increasing pain and spreading inflammation, which could be caused by infection.
  • Consider bursal aspiration (if the expertise and equipment are available) to improve function and comfort, particularly if the effusion is large.
  • If there is no response to conservative measures and/or aspiration, consider a corticosteroid injection into the bursa only if you are confident that bursitis is non-septic and there is expertise and experience in performing this procedure.
    
    •  If the requisite skills are not available and/or there is a risk of introducing or aggravating infection (signs of inflammation, a surgical scar, or abnormal skin at the injection site), refer to a specialist.
  • Refer to a specialist if there is no response to available treatments in primary care after 2 months. 
• If septic bursitis is suspected:
  • Aspirate bursal fluid using an aseptic technique, and treat empirically with an oral antibiotic which covers staphylococcal and streptococcal species (for an initial period of 7 days) until culture results are known. If aspiration is not possible, treat empirically with an oral antibiotic and refer for aspiration.
    
    • Flucloxacillin (500 mg four times daily) is the preferred antibiotic. For people over 70 kg, prescribe 1000 mg four times daily. 
    • Clarithromycin (500 mg twice daily) may be used if the person is allergic to penicillin. Erythromycin (500 mg four times daily) is the preferred macrolide in pregnancy and breastfeeding.
    • If the person is immunocompromised, seek specialist advice.
    • See the section on Prescribing information for the contraindications, cautions, adverse effects, and drug interactions of these antibiotics.
  • Provide advice on conservative management (rest, ice, activity modification, and simple analgesia). 
  • Review every few days to monitor the effectiveness of treatment.
    • Antibiotic treatment may be necessary for 1–4 weeks, depending on individual response.
    • Adjust antibiotic treatment according to sensitivities.
  • If swelling, tenderness, and erythema recur, consider repeating aspiration. The period between aspirations should be guided by clinical response.
  • Admit or refer (depending on the severity of symptoms) if the response is inadequate or complications are suspected.
• If bursitis is a result of overuse:
  • Advise the person to avoid repetitive activities that are likely to cause chronic stress on the bursa. Where this is not possible (for example, if bursitis has been precipitated by occupation), protective devices (such as thick foam cushions or kneepads) can be used to protect the knees.
• If the person has gout, rheumatoid arthritis, or associated cellulitis:
  • Ensure that these conditions are managed appropriately. See the CKS topics on Gout, Rheumatoid arthritis, and Cellulitis - acute for more information.
• Offer written information and advice on the management and prevention of bursitis.
  • The NHS website has patient information on bursitis.

When should I admit or refer a person with pre-patellar bursitis?

• Admit the person urgently if they have:
  • A suspected septic joint (which presents with a limited range of movement of the elbow joint, unlike septic bursitis).
  • Septic bursitis and severe infection or systemic toxicity, including high fever.
• Admit the person on the same day if they have septic bursitis and: 
  • Extensive cellulitis.
  • A pointing abscess requires incision and drainage if the expertise to perform this procedure is not available in primary care.
• Admission to the hospital may also be required if the person is immunocompromised or has other comorbid medical conditions, such as diabetes or rheumatoid arthritis.
• Refer urgently or seek specialist advice if there is no response, or an inadequate response, to an antibiotic in septic bursitis — a change in antibiotic, intravenous antibiotic, or incision and drainage may be required.
• Also refer if:
  • Aspiration is needed, but there is no expertise available in primary care.
  • The person experiences recurrent septic bursitis — surgical excision of the bursa may be required, but only after infection has cleared.
• Consider referral if a person with non-septic bursitis, in whom septic bursitis has been excluded, does not respond after 2 months of conservative measures (refer sooner if their symptoms are pronounced, for example, significant discomfort) — corticosteroid injection into the bursa or surgical management may be beneficial.

What are the contraindications and cautions for flucloxacillin?

• Do not prescribe flucloxacillin in people with:
  • A true penicillin allergy — allergic reactions to penicillins occur in 1–10% of exposed individuals; anaphylactic reactions occur in fewer than 0.05% of treated people.
    • People with a history of atopy (e.g. asthma, eczema, hay fever) are at a higher risk of anaphylactic reactions to penicillins — people with a history of anaphylaxis, urticaria, or rash immediately after penicillin administration are at risk of immediate hypersensitivity and should not receive a penicillin.
    • People with a history of a minor rash (non-confluent, non-pruritic rash restricted to a small area of the body) or a rash that occurs more than 72 hours after penicillin administration are probably not allergic to penicillin and it should not be withheld unnecessarily for serious infections — the possibility of an allergic reaction should, however, be borne in mind.
  • History of flucloxacillin-associated jaundice or hepatic dysfunction.
• Prescribe flucloxacillin with caution in people with:
  • Hepatic dysfunction (not flucloxacillin-related), aged over 50 years, or with a serious underlying medical condition — these people are at increased risk of hepatic reactions.
  • Severe renal impairment — reduce the dose if the person's estimated glomerular filtration rate (eGFR) is less than 10 mL/minute/1.73 m².
  • A history of allergy — these people are more likely to develop a sensitivity reaction.

[EMC, 2023; BNF, 2026]

What are the adverse effects of flucloxacillin?

• Gastrointestinal — diarrhoea, nausea and vomiting (common).
  • Very rarely: antibiotic-associated colitis.
• Nervous system — headache, dizziness (uncommon).
• Skin and subcutaneous tissue — skin rash, urticaria and purpura (uncommon).
  • Very rarely: erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalised exanthematous pustulosis.
• Other rare, or very rare adverse effects include:
  • Anaphylaxis.
  • Arthralgia and myalgia (very rare) — may sometimes develop more than 48 hours after the start of the treatment.
  • Hepatitis, cholestatic jaundice — this may occur up to several weeks after treatment with flucloxacillin has been stopped. Risk factors include treatment for more than 2 weeks, and increasing age.
  • Interstitial nephritis.
  • Neutropenia, thrombocytopenia, haemolytic anaemia.

 [EMC, 2023; BNF, 2026]

What are the drug interactions of flucloxacillin?

• Paracetamol — concomitant use of flucloxacillin and paracetamol has been associated with high anion gap metabolic acidosis (HAGMA), due to accumulation of 5-oxoproline. The risk is higher with prolonged use and in people who are older, female, malnourished, have vitamin B deficiency, diabetes, or severe illness. Be vigilant for signs of metabolic acidosis in these groups, particularly when treatment extends beyond 2–3 weeks. If HAGMA is suspected, discontinue paracetamol promptly.
• Methotrexate — methotrexate clearance may be reduced, causing an increased risk of toxicity, however, serious interactions are uncommon. 
  • Standard routine monitoring will identify any decreases in elimination in people on high-dose regimens. For people on low-dose regimens, consult local or national guidelines/protocols for monitoring and management.
• Coumarin and indanedione anticoagulants (warfarin, phenidione) — consider increased monitoring of international normalized ratio (INR) and adjust the dose accordingly.
• Posaconazole, voriconazole — concentrations of antifungal is greatly decreased. If concurrent use is unavoidable, monitor for decreased efficacy and consider increasing the dose of the azole (although this may not resolve the issue). 
• Probenecid — concomitant administration may result in increased levels of flucloxacillin.
• Live cholera vaccine — efficacy of vaccine may be reduced. Avoid flucloxacillin from 14 days before to 10 days after receiving live cholera vaccine.
• Live typhoid vaccine — immune response to vaccine may be reduced. Avoid flucloxacillin from 3 days before to 3 days after receiving live typhoid vaccine.

For a complete list of possible drug interactions for flucloxacillin, see the electronic Medicines Compendium (eMC) or the British National Formulary (BNF).

[Preston, 2026]

Can flucloxacillin be used during pregnancy or breastfeeding?

Pregnancy

• Flucloxacillin is not known to be harmful in pregnancy.

Breastfeeding

• All penicillin antibiotics, including flucloxacillin, can be used during breastfeeding. Flucloxacillin is one of the preferred choices as there is more evidence and experience to support its use. Only negligible quantities pass into breastmilk.
• As a precaution, monitor the infant for gastrointestinal disturbances, oral candida infection, hypersensitivity reactions (including rashes or breathing problems), nausea, irritability, and drowsiness. These effects are generally mild and self-limiting.
• If the infant is unwell or premature, or multiple medicines are being taken, seek further specialist advice from the UK Drugs in Lactation Advisory Service
  • Penicillins (and cephalosporins) are the antibiotics of choice in women who are breastfeeding.

[SPS, 2024; EMC, 2023]

What are the contraindications and cautions for erythromycin?

• Do not prescribe erythromycin to people with: 
  • Acute porphyrias.
  • A history of QT interval prolongation (congenital or acquired) or ventricular cardiac arrhythmia, including Torsades de Pointes.
  • Electrolyte disturbances (such as hypokalaemia or hypomagnesaemia) — due to the risk of arrhythmia associated with QT interval prolongation.
• Prescribe erythromycin with caution to people with:
  
  • Cardiac disease or heart failure, conduction disturbances or clinically relevant bradycardia, or if taking concomitant medicines associated with QT interval prolongation.
  • Hepatic impairment.
  • Severe renal impairment — maximum dose 1500 mg daily due to the risk of ototoxicity.
  • Myasthenia gravis.

  [MHRA, 2020; BNF, 2026; EMC, 2025a]

What are the adverse effects of erythromycin?

• Gastrointestinal (GI) — diarrhoea, GI discomfort/disorders, nausea, vomiting, pancreatitis (common or very common); constipation (uncommon).
  • Rare or very rare: antibiotic-associated colitis.
• Cardiovascular — QTc interval prolongation, Torsades de Pointes, palpitations and cardiac rhythm disorders, including ventricular tachyarrhythmias (uncommon).
• Ear and labyrinth disorders — hearing impairment, tinnitus.
• Hepatobiliary — cholestatic hepatitis, jaundice, hepatic dysfunction, hepatomegaly, hepatic failure, hepatocellular hepatitis.
• Skin and subcutaneous tissues — skin reactions (common or very common); Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme (uncommon); acute generalized exanthematous pustulosis (AGEP) (frequency unknown).
• Other common adverse effects include:
  • Dizziness.
  • Headache.
  • Vasodilation.
  • Vision disorders.

 [EMC, 2025a; BNF, 2026]

What are the drug interactions of erythromycin?

• Drug interactions for erythromycin include:

  • Aminophylline, theophylline — aminophylline can cause hypokalaemia (potentially increasing the risk of Torsade de Pointes) when given with erythromycin. Theophylline clearance (from aminophylline) can be reduced if given concurrently with erythromycin. Oral erythromycin exposure may be reduced by theophylline. Monitor theophylline levels after 48 hours and adjust the dose accordingly. Monitor potassium concentrations closely and the effects of oral erythromycin to ensure they are adequate. Consider giving an alternative antibiotic. 
  • Calcium channel blockers (amlodipine, diltiazem) — erythromycin possibly inhibits the metabolism of calcium channel blockers, increasing the risk of adverse effects, such as hypotension. Monitor for adverse effects (for example, bradycardia, hypotension, headache, oedema) and reduce the calcium channel blocker dose as necessary.
  • Corticosteroids — levels of corticosteroids may be increased. Monitor for corticosteroid adverse effects (such as moon face, weight gain, hyperglycaemia), and adjust the corticosteroid dose or stop the macrolide as appropriate. 
  • Rifampicin — may induce the metabolism of erythromycin, resulting in sub-therapeutic levels.
    • If concurrent use is necessary, monitor erythromycin efficacy closely.
  • Carbamazepine — erythromycin can increase carbamazepine levels, causing carbamazepine toxicity (which may present as nausea and vomiting, ataxia, and drowsiness).
    • Avoid concurrent use, unless carbamazepine levels can be monitored closely. 
  • Ciclosporin — levels are greatly increased by erythromycin. Monitor concentrations and effects (for example, renal function) more frequently if erythromycin is started or stopped. Adjust the ciclosporin dose as required. 
  • Cisapride, domperidone — levels may be raised, increasing the risk of potentially life-threatening arrhythmias (Torsade de Pointes). Concurrent use is contraindicated.
  • Colchicine — erythromycin possibly increases the risk of colchicine toxicity.
    • Stop or reduce the dose of colchicine.
    • Avoid concurrent use in renal or hepatic impairment.
  • Drugs that prolong the QT interval (such as amiodarone, amisulpride, fluconazole, sildenafil, mizolastine, hydroxyzine) — macrolides can also prolong the QT interval, increasing the risk of arrhythmias (such as Torsades de Pointes).
    • Concurrent use of drugs that prolong the QT interval is contraindicated.
  • Drugs that cause hypokalaemia (such as diuretics, corticosteroids, short-acting beta-2 agonists) — hypokalaemia is a risk factor for QT prolongation. Monitor potassium levels closely. 
  • Digoxin — erythromycin may increase the concentration of digoxin. 
    • Monitor digoxin concentration.
  • Edoxaban — erythromycin slightly increases edoxaban levels. Decrease dose of edoxaban to 30 mg once daily. Monitor for signs and symptoms of bleeding. 
  • Ergot alkaloids (such as ergotamine and dihydroergotamine) — concurrent use with erythromycin may result in acute ergot toxicity. 
    • Concurrent use is contraindicated.
  • Lomitapide — concurrent use with erythromycin increases transaminase levels and is contraindicated.
  • Protease inhibitors (ritonavir, saquinavir) — erythromycin levels may be increased. Monitor for adverse effects. 
  • Rivaroxaban — erythromycin slightly increases levels, but this is not considered clinically significant. 
  • Statins — there is an increased risk of myopathy (due to cytochrome P450 enzyme CYP3A4 inhibition) [MHRA, 2014].    
    • Lovastatin, simvastatin  — concurrent use is contraindicated. If erythromycin treatment cannot be avoided, withhold the statin during the course of the treatment.
    • Atorvastatin — levels of atorvastatin increased slightly with concurrent use. Temporarily withhold the statin, or if necessary give the lowest dose of statin and advise the person to seek medical advice if they experience symptoms of myopathy (for example muscle pain, tenderness, or weakness).
    • Pravastatin — prescribe erythromycin with caution, and advise the person to report any muscle pain, tenderness, or weakness.
  • Quetiapine — erythromycin increases the plasma concentration of quetiapine and both drugs are associated with QT interval prolongation.
    • Concurrent use is contraindicated, but if necessary, monitor for quetiapine adverse effects (for example somnolence, dry mouth, tachycardia) and reduce the dose if needed.
  • Warfarin — erythromycin may cause a minor increase in warfarin effects. 
    • Consider increased monitoring of the international normalized ratio (INR) when both drugs are used (particularly in elderly people), and adjust the warfarin dose accordingly. 
• Oral hormonal contraception — additional contraceptive precautions are not required during or after a course of erythromycin. 
  • 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 Contraception - progestogen-only methods. 
• For a complete list of possible drug interactions for erythromycin, see the electronic Medicines Compendium (eMC) or the British National Formulary (BNF).

[MHRA, 2020; BNF, 2026; Preston, 2026]

Can erythromycin be used during pregnancy or breastfeeding?

Pregnancy

• Erythromycin should only be used if the potential benefits outweigh the possible risks.  
  • The majority of data do not provide evidence that macrolide use during pregnancy increases the risk of adverse pregnancy outcomes. However, a limited number of studies have described small increased risks of malformation and miscarriage. Macrolide use should be reserved for compelling indications where there are no suitable alternatives with adequate pregnancy safety data, and should only be used if the expected benefits outweigh any small increased risks [MHRA, 2021]. 
• Erythromycin is the preferred macrolide antibiotic for use in pregnancy where a macrolide is clinically indicated, for example, in true penicillin allergy. The available evidence is insufficient to confirm with certainty the presence or absence of a small increased risk of malformations or miscarriage with macrolide use in early pregnancy, but erythromycin remains the preferred macrolide in this context.

Breastfeeding

• Erythromycin is excreted in breast milk in small amounts, and it is not known to be harmful [LactMed, 2024]. 
  • Monitor the infant for irritability and possible effects on the gastrointestinal flora, such as diarrhoea, candidiasis (thrush, nappy rash). 
• However the manufacturer advises exercising caution due to reports of infantile hypertrophic pyloric stenosis in breastfed infants [EMC, 2025a]. 

What are the contraindications and cautions for clarithromycin?

• Do not prescribe clarithromycin in people with:
  
  • A history of QT prolongation (congenital or acquired) or ventricular cardiac arrhythmia, including Torsades de Pointes.
  • Electrolyte disturbances (such as hypokalaemia or hypomagnesaemia) — due to the risk of arrhythmia associated with QT interval prolongation.
  • Severe hepatic impairment if renal impairment is also present.
• Prescribe clarithromycin with caution in people with:
  • Coronary artery disease, severe cardiac insufficiency, conduction disturbances or clinically relevant bradycardia, or taking drugs that prolong the QT interval. 
  • Impaired hepatic function, or receiving potentially hepatotoxic drugs.
  • Renal impairment — reduce dose by half if estimated glomerular filtration rate (eGFR) is less than 30 mL/minute/1.73 m².
    • Avoid clarithromycin m/r preparations if eGFR is less than 30 mL/minute/1.73 m². 
  • Myasthenia gravis.

[EMC, 2025b; BNF, 2026]

What are the adverse effects of clarithromycin?

• Gastrointestinal — diarrhoea, vomiting, dyspepsia, nausea, abdominal pain (common).
  • Rarely: pancreatitis, pseudomembranous colitis. For more information, see the CKS topic on Diarrhoea - antibiotic associated.
• Nervous system — headache, dysgeusia (common), dizziness, somnolence, tremor (uncommon).
  • Rarely: convulsions, paraesthesia.
• Psychiatric — insomnia (common), anxiety, nervousness (uncommon).
  • Rarely or very rarely: psychotic disorders, depression, mania, hallucination.
• Skin — rash, hyperhidrosis (common), pruritus, urticaria (uncommon).
  • Rarely, or very rarely: drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalized exanthematous pustulosis (AGEP).
• Other adverse effects reported rarely, or very rarely, include: 
  • Anaphylaxis.
  • Arrhythmias.
  • Deafness.
  • Hepatic failure, jaundice.
  • Pancreatitis. 
  • QT interval prolongation.

 [EMC, 2025b; BNF, 2026]

What are the drug interactions of clarithromycin?

• Calcium channel blockers (CCBs) (verapamil, amlodipine, diltiazem) — clarithromycin increases exposure to CCBs. Monitor for adverse effects (for example, bradycardia, hypotension, headache, oedema) and reduce the calcium-channel blocker dose as necessary.
• Ciclosporin — clarithromycin can affect clearance of ciclosporin. If concurrent use is necessary, monitor ciclosporin levels and adjust the dose accordingly.
• Colchicine — clarithromycin moderately increases the levels of colchicine. The manufacturer advises that concurrent use is contraindicated. 
• CYP3A enzyme inducers (rifampicin, carbamazepine, phenobarbital) — these may induce the metabolism of clarithromycin, resulting in sub-therapeutic levels.
  • It may be necessary to monitor the levels of these drugs, as CYP3A is inhibited by clarithromycin leading to higher plasma levels of the inducer.
• Digoxin — clarithromycin significantly increases digoxin levels. Monitor for signs of adverse effects, measure digoxin levels, and reduce the digoxin dose if required.
• Eplerenone — clarithromycin may increase exposure to eplerenone, concurrent use is contraindicated.
• Ergot alkaloids — concurrent administration is contraindicated, due to the risk of acute ergot toxicity.
• Edoxaban — manufacturer advises caution with concurrent treatment with edoxaban, particularly in those with a high risk of bleeding.
• Ivabradine — concomitant treatment is contraindicated, owing to CYP3A4 inhibition by clarithromycin which can cause elevated levels of ivabradine.
• Oral hormonal contraception — additional contraceptive precautions are not required during or after courses of clarithromycin.
  • However, women should be advised that if diarrhoea, vomiting, or breakthrough bleeding occur there is a possibility of contraceptive failure. For further information, see the sections on vomiting or diarrhoea in the CKS topics on Contraception - combined hormonal methods and Contraception - progestogen-only methods.
• Oral hypoglycaemic drugs (sulfonylureas) and insulin — the concurrent use of clarithromycin and oral hypoglycaemic drugs and/or insulin can result in significant hypoglycaemia. Monitor glucose levels.
• Statins — these are extensively metabolized by CYP3A4. Concurrent administration with clarithromycin increases the plasma levels and the risk of myopathy.
  • Lovastatin, simvastatin — concurrent use is contraindicated. If treatment with clarithromycin cannot be avoided, stop treatment with statin temporarily.
  • Atorvastatin — levels moderately increased with concurrent use. Temporarily withhold statin, or if necessary, reduce dose and warn patients to report any unexplained muscle pain or weakness. 
• Ticagrelor — levels markedly increased. Concurrent use is contraindicated.
• Warfarin — clarithromycin increases the anticoagulant effect of warfarin. Monitor the international normalized ratio (INR), and adjust the warfarin dose accordingly.
• Drugs that prolong the QT interval — all macrolides can prolong the QT interval, and caution is advised with concurrent use. Concurrent use is contraindicated with domperidone, ivabradine, mizolastine, astemizole, cisapride, pimozide, and terfenadine.
• For a complete list of possible drug interactions for clarithromycin, see the electronic Medicines Compendium (eMC) or the British National Formulary (BNF). 

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

Can clarithromycin be used during pregnancy or breastfeeding?

Pregnancy

• Avoid clarithromycin in pregnancy if possible — erythromycin is the preferred macrolide where a macrolide antibiotic is required in pregnancy.
• The available evidence is insufficient to confirm with certainty whether there is a small increased risk of malformations or miscarriage when macrolides are taken in early pregnancy.
• If a macrolide antibiotic is clinically necessary and no suitable alternative is available, the potential benefits and risks should be discussed with the patient [MHRA, 2021].

Breastfeeding

• Clarithromycin is acceptable in nursing mothers. Only low levels pass into breastmilk and the small amounts present are unlikely to cause adverse effects in the infant.
• Monitor the infant for possible effects on gastrointestinal flora, such as diarrhoea and candidiasis [LactMed, 2022].
  • Earlier concerns about a possible increased risk of infantile hypertrophic pyloric stenosis (IHPS) with maternal macrolide use during breastfeeding have not been confirmed — two subsequent meta-analyses have failed to demonstrate this relationship
• The manufacturer advises that clarithromycin use should be avoided in women who are breastfeeding unless the potential benefits outweigh the possible risks.

[EMC, 2025b; BNF, 2026]