Clarithromycin

Pronunciation: kla-RITH-roe-MYE-sin.

Generic name
clarithromycin
Drug class
Macrolide antibiotic
Form
Film-coated tablet, extended-release tablet, oral suspension, IV infusion
Route
Oral (also intravenous in hospital settings)
Legal status
Prescription-only

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Clarithromycin Sandoz / Clarithro (6) · Full directory

What clarithromycin is and how it works

Clarithromycin is a macrolide antibiotic used to treat a range of bacterial infections, including certain respiratory tract infections, skin infections, and (combined with other medicines) Helicobacter pylori stomach infections. It works by stopping susceptible bacteria from making proteins they need to grow. (1) (3)

Clarithromycin is prescribed for a specific bacterial infection and a defined course length -- completing the full course as directed matters for effectiveness and to reduce antibiotic resistance. It carries two genuine cardiovascular warnings worth knowing about: a link to increased mortality appearing a year or more after treatment in people with existing coronary artery disease, and a risk of QT interval prolongation (a heart rhythm effect) that is a recognised effect of this class of antibiotics.

Mechanism of action: how clarithromycin works

Clarithromycin is a semi-synthetic macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, giving it bacteriostatic (and at higher concentrations, bactericidal) activity against a range of Gram-positive and some Gram-negative organisms, plus atypical pathogens and H. pylori. (1) (5)

What clarithromycin is used for

Respiratory tract infections

Used to treat acute bacterial exacerbation of chronic bronchitis, community-acquired pneumonia, acute maxillary sinusitis, and pharyngitis/tonsillitis caused by susceptible bacteria. (1) (3)

Skin and soft tissue infections

Used to treat uncomplicated skin and skin-structure infections caused by susceptible bacteria. (1) (3)

Helicobacter pylori eradication

Used, combined with other antibiotics and an acid-reducing medicine, to help eradicate H. pylori infection in people with peptic ulcer disease. (1)

Ear infections and mycobacterial disease

Used to treat acute otitis media (middle ear infection) and, in some cases, disseminated mycobacterial infections. (1)

Before taking clarithromycin

Do not take / not appropriate for

  • Do not take clarithromycin if you have had a serious allergic reaction to it or to other macrolide antibiotics. (all countries where authorised) (1)
  • Do not take clarithromycin together with cisapride, pimozide, ergot alkaloids, lomitapide, lovastatin, or simvastatin, since dangerous interactions can occur. (all countries where authorised) (1)
  • Do not take clarithromycin if you have low blood potassium (hypokalaemia), a history of QT interval prolongation, or a history of dangerous heart rhythm problems (ventricular arrhythmia), unless your clinician has specifically decided the benefit outweighs this risk. (Australia, Canada) (6) (5)
  • Do not take clarithromycin if you have had liver problems (jaundice) linked to a previous course of clarithromycin. (all countries where authorised) (1)

Tell your clinician about

  • Any heart problems, especially coronary artery disease (heart artery disease), heart rhythm problems, or a family history of QT prolongation.
  • Any personal history of low potassium or low magnesium levels.
  • Any liver or kidney problems.
  • Any history of myasthenia gravis, since clarithromycin can worsen symptoms.
  • All other medicines you take, since clarithromycin has many significant drug interactions.
  • Whether you are pregnant, planning pregnancy, or breastfeeding.
(1) (5)

How to take clarithromycin

  • Take exactly as prescribed, at evenly spaced intervals, with or without food depending on the formulation your prescriber recommends.
  • Complete the full prescribed course, even if you feel better before it is finished, unless your clinician tells you otherwise -- stopping early can allow the infection to return and contributes to antibiotic resistance.
  • Extended-release tablets should be swallowed whole, not crushed or chewed.
(1) (3)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7)

Missed dose

Take the missed dose as soon as you remember, unless it is nearly time for your next dose, in which case skip the missed dose and continue your normal schedule -- do not take a double dose. Contact your prescriber or pharmacist if you are unsure or have missed several doses.

Overdose

Seek urgent medical attention if you think you have taken too much clarithromycin, especially if you notice an irregular or racing heartbeat, severe nausea/vomiting, or abdominal pain. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Nausea, vomiting, or abdominal discomfort.

What to notice: Nausea, vomiting, or abdominal discomfort.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Diarrhoea.

What to notice: Diarrhoea.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Altered taste (a metallic or bitter taste is common).

What to notice: Altered taste (a metallic or bitter taste is common).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (3)

Headache.

What to notice: Headache.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (3)

Serious warnings

Increased risk of death in people with coronary artery disease (heart artery disease) — high caution

Symptoms: Not a symptom to notice at the time -- this is a longer-term risk identified in a large clinical trial (the CLARICOR trial), appearing a year or more after a course of clarithromycin.

Action: If you have known coronary artery disease (heart artery disease) or significant heart disease, discuss this specific risk with your clinician before starting clarithromycin -- a 10-year follow-up of a major trial found a real, statistically significant increase in all-cause and cardiovascular mortality in people with coronary artery disease given a 2-week course, prompting a 2018 FDA safety communication recommending caution and considering other antibiotics in this group. (1) (2)

Signs of an abnormal heart rhythm (QT prolongation) — emergency

Symptoms: Fainting, palpitations, dizziness, or a racing/irregular heartbeat.

Action: Seek emergency medical help immediately -- clarithromycin can prolong the QT interval and, rarely, cause a dangerous heart rhythm called torsades de pointes. This risk is higher with low potassium/magnesium, existing QT prolongation, or other QT-prolonging medicines. (1) (3)

Signs of liver problems — high caution

Symptoms: Yellowing of the skin or eyes, dark urine, severe tiredness, loss of appetite, or right-upper abdominal pain.

Action: Contact your clinician promptly -- hepatotoxicity, including hepatic dysfunction and jaundice, has been reported. (1)

Severe or persistent diarrhoea — high caution

Symptoms: Watery or bloody diarrhoea, with or without fever and abdominal cramping, especially if it starts during or after treatment (even up to two months later).

Action: Contact your clinician promptly -- Clostridium difficile-associated diarrhoea can occur with almost any antibiotic, including clarithromycin, and can range from mild to life-threatening. (1)

Signs of a serious allergic reaction — emergency

Symptoms: Swelling of the face/throat, difficulty breathing, or a widespread rash.

Action: Seek emergency medical help immediately -- severe acute hypersensitivity reactions, including anaphylaxis, have been reported. (1)

Interactions

  • Certain statins (lovastatin, simvastatin) and lomitapide must not be combined with clarithromycin due to increased risk of muscle damage/toxicity. (1)
  • Cisapride, pimozide, ergot alkaloids, and lurasidone must not be combined with clarithromycin due to serious interaction risks, including cardiac arrhythmia. (1)
  • Colchicine combined with clarithromycin can cause serious, potentially fatal toxicity, particularly in patients with kidney or liver impairment. (1)
  • Other QT-prolonging medicines (including some antiarrhythmics, antipsychotics, and hydroxychloroquine/chloroquine) can increase the risk of dangerous heart rhythm problems when combined with clarithromycin. (7)
  • Warfarin and other blood thinners: clarithromycin can increase their effect, raising bleeding risk, and may need closer monitoring. (3)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Use only if the potential benefit justifies the potential risk to the fetus; embryo-fetal toxicity has been observed in animal studies. Discuss with your prescriber, especially in the first trimester. (1) (2) (3) (4) (5) (6) (7)

Breastfeeding

Clarithromycin passes into breast milk; discuss the benefits and risks with your prescriber. (1) (2) (3) (4) (5) (6) (7)

Children

Approved for use in children for various infections, with weight-based dosing set by a paediatrician. (1) (2) (3) (4) (5) (6) (7)

Elderly

May be at higher risk of QT prolongation and drug interactions; used with caution and appropriate monitoring. (1) (2) (3) (4) (5) (6) (7)

Hepatic_impairment

Use with caution; not recommended in patients with a history of clarithromycin-associated hepatic dysfunction/jaundice. (1) (2) (3) (4) (5) (6) (7)

Renal_impairment

Dose adjustment needed in significant renal impairment; particular caution with colchicine co-administration in renal impairment (contraindicated). (1) (2) (3) (4) (5) (6) (7)

Monitoring

Before starting

  • Personal/family history of QT prolongation or heart rhythm problems
  • Coronary artery disease/heart disease history
  • Baseline potassium/magnesium if at risk
  • Liver and kidney function if relevant
  • Full medication review for interacting drugs

During treatment

  • Watch for signs of an abnormal heart rhythm (palpitations, fainting, dizziness).
  • Watch for signs of liver problems.
  • Watch for severe or persistent diarrhoea, including after finishing the course.
  • Complete the full course as directed.
(1)

Storage

Store at room temperature, away from moisture and heat, in the original packaging, and out of the reach of children. Oral suspension should be used within the period stated on the label after reconstitution.

Study the drug class: Macrolides

Professional information

Clinician-facing context only, sourced from the current US prescribing information and UK SmPC; verify against the current full label before prescribing.

United States, United Kingdom, European Union, Canada, Australia, New Zealand

Indication: Susceptible bacterial infections (respiratory, skin/soft tissue, H. pylori, otitis media, some mycobacterial infections)

Dose summary: Typically 250-500 mg orally twice daily for 6-14 days depending on indication and severity; extended-release formulation dosed once daily in some markets. IV formulation available for hospital use.

Renal context: Dose reduction recommended in significant renal impairment (e.g. CrCl <30 mL/min); colchicine co-administration contraindicated in renal (and hepatic) impairment. (1) (3)

Mechanism of action

Hepatic guidance

Avoid in patients with a history of clarithromycin-associated hepatic dysfunction/cholestatic jaundice; use with caution in other hepatic impairment.

Overdose note

Manage supportively with close cardiac (ECG/QT) monitoring and correction of any electrolyte abnormalities (particularly potassium/magnesium); no specific antidote is described in the sources reviewed. (1) (5)

Frequently asked questions

Is it true clarithromycin can increase the risk of death in people with heart disease?

This is a real, verified finding, not a rumour. A large randomised trial (the CLARICOR trial, in Denmark) found that a 2-week course of clarithromycin was linked to a statistically significant increase in all-cause and cardiovascular mortality in people with existing coronary artery disease (heart artery disease), an effect that appeared a year or more after treatment and was strongest in the first 3 years of follow-up. Based on a 10-year follow-up of this trial, the FDA issued a Drug Safety Communication in February 2018 advising caution when prescribing clarithromycin to people with heart disease, and suggesting clinicians consider other antibiotics in this group. It is not a 'boxed warning' (the most serious FDA label category) but it is a real, currently-labelled warning that your clinician should weigh if you have coronary artery disease. (1) (2)

What is the QT prolongation risk with clarithromycin?

Clarithromycin, like other macrolide antibiotics, can prolong the QT interval -- a measure of how long it takes the heart to reset electrically between beats. In rare cases, this has led to a dangerous heart rhythm called torsades de pointes. The risk is higher if you have low blood potassium or magnesium, an existing QT prolongation problem, or take other medicines that also affect the QT interval. Clarithromycin and erythromycin have a stronger effect on this specific heart channel than some other macrolides, so this is taken particularly seriously for these two drugs. (1) (3) (7)

What medicines should never be combined with clarithromycin?

Clarithromycin is contraindicated with cisapride, pimozide, ergot alkaloids, lomitapide, lovastatin, simvastatin, and lurasidone, because of serious interaction risks including dangerous heart rhythms, ergotism, or muscle toxicity. It should also not be combined with colchicine in people with kidney or liver impairment. Always give your clinician and pharmacist a full list of your medicines before starting clarithromycin. (1)

What is the mechanism of action of clarithromycin?

Clarithromycin is a semi-synthetic macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, giving it bacteriostatic (and at higher concentrations, bactericidal) activity against a range of Gram-positive and some Gram-negative organisms, plus atypical pathogens and H. pylori. (1) (5)

What is the generic name of Clarithromycin?

The generic name is clarithromycin. (1) (3)

What class of drug is clarithromycin?

Clarithromycin is classed as: Macrolide antibiotic. (1) (3)

References

  1. CLARITHROMYCIN tablet -- full prescribing information (Revised 5/2023)U.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-30 · source 1
  2. FDA Drug Safety Communication: Clarithromycin and increased risk of heart problems or death in patients with heart disease (February 2018)U.S. Food and Drug Administration -- Drug Safety Communication · United States · accessed 2026-07-30 · source 2
  3. Clarithromycin 500mg Film-coated Tablets -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom · United Kingdom · accessed 2026-07-30 · source 3
  4. Clarithromycin -- list of nationally authorised medicinal products (PSUSA/00000788)European Medicines Agency (EMA) / CMDh -- periodic safety update single assessment (PSUSA) for clarithromycin · European Union · accessed 2026-07-30 · source 4
  5. CLARITHROMYCIN (clarithromycin tablets) -- Health Canada Product MonographsHealth Canada product monographs (multiple manufacturers: Taro, Viatris/Biaxin, generics) · Canada · accessed 2026-07-30 · source 5
  6. Clarithromycin (Sandoz, Clarithro, and other brands) -- Product Information and ARTG entries (e.g. 101265, 101271)Therapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 6
  7. KLACID / KLACID IV (clarithromycin) -- New Zealand Data Sheets; MARC review 'Macrolides and cardiovascular death'Medsafe (New Zealand regulator) -- data sheets and Medicines Adverse Reactions Committee (MARC) · New Zealand · accessed 2026-07-30 · source 7

Brand names by country

Single-ingredient clarithromycin names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Biaxin / generic clarithromycin (1)FDA approved current dailymed confirmed no boxed warning

United Kingdom

  • Clarithromycin (generic) / Klaricid (3)MHRA licensed emc smpc confirmed PL 14894 0160 · 250 mg, 500 mg

Canada

  • BIAXIN BID
  • BIAXIN
  • BIAXIN XL
  • ACT CLARITHROMYCIN XL
  • APO-CLARITHROMYCIN XL

Australia

  • Clarithromycin Sandoz / Clarithro (6)TGA ARTG 101265 101271 registered · 250 mg, 500 mg

New Zealand

  • Klacid / Klacid IV (7)medsafe data sheet confirmed · Medsafe's Medicines Adverse Reactions Committee has conducted a dedicated review titled 'Macrolides and cardiovascular death'.
View brands in additional countries.

European Union

Klacid / Clarithromycin Sandoz / Clarithromycin 1A Pharma (nationally authorised) (4)

This page provides general reference information about clarithromycin and is not a substitute for advice from the clinician who prescribed it. Complete the full course as directed, and discuss the cardiovascular warnings above with your clinician if you have heart disease.

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