Clarithromycin (Biaxin)
clarithromycin — also marketed as Biaxin XL (extended-release)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Acute bacterial exacerbation of chronic bronchitis | Adults | Monotherapy | FDA Approved |
| Acute maxillary sinusitis | Adults and pediatrics | Monotherapy | FDA Approved |
| Community-acquired pneumonia | Adults and pediatrics | Monotherapy | FDA Approved |
| Pharyngitis / tonsillitis | Adults and pediatrics | Alternative to first-line therapy | FDA Approved |
| Uncomplicated skin and skin structure infections | Adults and pediatrics | Monotherapy | FDA Approved |
| Acute otitis media | Pediatrics | Monotherapy | FDA Approved |
| Disseminated MAC — treatment and prophylaxis | Adults and pediatrics with advanced HIV | Combination (with ethambutol +/- rifabutin) | FDA Approved |
| H. pylori eradication (duodenal ulcer disease) | Adults | Combination (triple or dual therapy) | FDA Approved |
Clarithromycin is a broad-spectrum macrolide with reliable activity against common respiratory pathogens, atypical organisms, and mycobacteria. Its role in H. pylori eradication is well established, though increasing clarithromycin resistance in some regions has prompted guideline revisions favouring bismuth-based quadruple therapy or susceptibility-guided treatment. For pharyngitis, clarithromycin serves as an alternative in patients who cannot tolerate penicillin-class antibiotics.
Lyme disease (early erythema migrans): Some data support clarithromycin 500 mg twice daily for 14–21 days as a second-line option in penicillin-allergic patients. Evidence quality: Low.
Pertussis (whooping cough): Used as an alternative to azithromycin in post-exposure prophylaxis and treatment. Evidence quality: Moderate.
Legionnaires’ disease: Used when azithromycin or fluoroquinolones are not suitable. Evidence quality: Moderate.
Endocarditis prophylaxis: Alternative for penicillin-allergic patients undergoing dental procedures, though current AHA guidelines generally prefer azithromycin or clindamycin. Evidence quality: Moderate.
Dosing
Adult Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Community-acquired pneumonia — typical pathogens | 250 mg q12h | 250 mg q12h | 500 mg q12h | 7–14 days; may use XL 1000 mg daily with food For H. influenzae: 500 mg q12h x 7 days |
| Acute bacterial sinusitis | 500 mg q12h | 500 mg q12h | 500 mg q12h | 14 days; XL 1000 mg daily x 14 days is an alternative |
| Acute exacerbation of chronic bronchitis | 250–500 mg q12h | 250–500 mg q12h | 500 mg q12h | 7–14 days; dose depends on pathogen 250 mg for S. pneumoniae/M. catarrhalis; 500 mg for H. influenzae/H. parainfluenzae |
| Pharyngitis / tonsillitis (Strep pyogenes) | 250 mg q12h | 250 mg q12h | 250 mg q12h | 10 days; use only if penicillin-allergic |
| Skin & soft tissue infection (uncomplicated) | 250 mg q12h | 250 mg q12h | 250 mg q12h | 7–14 days |
| H. pylori eradication — triple therapy | 500 mg q12h | 500 mg q12h | 500 mg q12h | 10–14 days; with amoxicillin 1 g q12h + PPI Only if local clarithromycin resistance <15% |
| H. pylori eradication — dual therapy with omeprazole | 500 mg q8h | 500 mg q8h | 500 mg q8h | 14 days; with omeprazole 40 mg daily |
| Disseminated MAC — treatment | 500 mg q12h | 500 mg q12h | 500 mg q12h | Long-term; always in combination with ethambutol (FDA PI) |
| Disseminated MAC — prophylaxis (advanced HIV) | 500 mg q12h | 500 mg q12h | 500 mg q12h | Continue until immune reconstitution; can stop when CD4 >100 for ≥6 months |
Pediatric Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Respiratory and soft tissue infections (≥6 months) | 7.5 mg/kg q12h | 7.5 mg/kg q12h | 500 mg q12h | 10 days; use suspension for children unable to swallow tablets |
| MAC treatment/prophylaxis (pediatric HIV) | 7.5 mg/kg q12h | 7.5 mg/kg q12h | 500 mg q12h | Long-term; in combination with ethambutol |
Renal Impairment Adjustments
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Severe renal impairment (CrCl <30 mL/min) | 50% dose reduction | 50% of standard dose | 250 mg q12h | Applies to all indications (FDA PI) |
| Moderate renal impairment (CrCl 30–60) + atazanavir/ritonavir | 50% dose reduction | 250 mg q12h | 250 mg q12h | Due to bidirectional PK interaction with protease inhibitors |
| Severe renal impairment + atazanavir/ritonavir | 75% dose reduction | 125 mg q12h | 125 mg q12h | Maximum 1000 mg/day should not be co-administered with protease inhibitors |
Extended-release (Biaxin XL) is dosed 1000 mg once daily and must be taken with food. It is only approved for acute sinusitis, AECB, and CAP in adults. Patients experiencing GI intolerance on the immediate-release formulation often do better with XL due to lower peak concentrations and fewer GI and taste-related discontinuations.
Pharmacology
Mechanism of Action
Clarithromycin exerts its bacteriostatic effect by binding reversibly to the 50S ribosomal subunit of susceptible organisms, blocking the translocation step of protein synthesis. This prevents the growing peptide chain from advancing along the mRNA template, effectively halting bacterial growth. Clarithromycin also undergoes hepatic oxidation to produce 14-OH-clarithromycin, an active metabolite with antimicrobial activity comparable to or exceeding that of the parent compound against certain respiratory pathogens, particularly Haemophilus influenzae. The combined activity of the parent drug and its metabolite contributes to clarithromycin’s clinical efficacy against a broad range of gram-positive cocci, atypical organisms (Mycoplasma, Chlamydophila, Legionella), and mycobacteria including M. avium complex. Unlike beta-lactams, clarithromycin achieves intracellular concentrations in macrophages and neutrophils that are substantially higher than simultaneous serum levels, making it particularly effective against intracellular pathogens.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | ~50–55% bioavailable; Tmax 2–3 h; food increases Cmax by ~24% but does not affect total AUC | Can be given with or without food for IR tablets; XL must be taken with food |
| Distribution | Vd ~2–4 L/kg; tissue concentrations exceed serum (lung 8.8 mcg/g vs serum 1.7 mcg/mL); protein binding 65–75% | Excellent respiratory tissue, tonsil, and middle ear penetration; concentrates in macrophages (I:E ratio ~9:1) |
| Metabolism | Hepatic via CYP3A4 (saturable); primary metabolite: 14-OH-clarithromycin (microbiologically active) | Non-linear PK at higher doses due to CYP3A4 autoinhibition; strong CYP3A4 inhibitor with extensive drug interaction potential |
| Elimination | t½ 3–4 h (250 mg), 5–7 h (500 mg); renal excretion 20–30% parent, 10–15% as 14-OH metabolite | Longer half-life at 500 mg reflects saturable metabolism; dose reduce in severe renal impairment (CrCl <30) |
Side Effects
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Dysgeusia (taste perversion / metallic taste) | 8–16% | Most frequent patient complaint; often dose-limiting. Resolves on discontinuation. Occurs less with XL formulation. |
| Nausea | 5–11% | Dose-related; lower incidence with XL formulation. Taking with food may reduce severity. |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Diarrhea | 3–8% | Monitor for C. difficile if persistent or bloody. More common in MAC prophylaxis trials. |
| Abdominal pain | 3–5% | May improve with food co-administration |
| Vomiting | 3–6% | More frequent at higher doses used for mycobacterial infections |
| Headache | 3–5% | Usually mild and self-limiting |
| Dyspepsia | 3–4% | More common in H. pylori combination regimens |
| Rash | 3% | Distinguish from serious hypersensitivity; discontinue if systemic features present |
| Elevated liver enzymes (AST/ALT) | 1–4% | Usually transient; >5x ULN in ~3–4% of immunocompromised patients on long-term therapy |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| QT prolongation / torsades de pointes | Rare | Any time during therapy; risk increased with concomitant QT-prolonging drugs | Obtain baseline ECG in high-risk patients; discontinue immediately if arrhythmia detected. Fatalities reported. |
| Hepatotoxicity (hepatocellular/cholestatic hepatitis) | Rare | Days to weeks | Discontinue if signs of hepatitis (jaundice, dark urine, elevated bilirubin). Hepatic failure with fatal outcome reported in patients with serious underlying disease. |
| Clostridioides difficile-associated diarrhea (CDAD) | Uncommon | During or up to 2 months after therapy | Send C. difficile toxin assay; discontinue clarithromycin; initiate targeted therapy (vancomycin or fidaxomicin PO) |
| Severe hypersensitivity (anaphylaxis, SJS/TEN, DRESS) | Very rare | Days to weeks | Permanent discontinuation; emergency management; do not re-challenge with any macrolide |
| Myasthenia gravis exacerbation | Very rare | Days | Discontinue clarithromycin; manage myasthenic crisis as indicated |
| Hearing loss | Rare | Variable; more common in elderly women and with higher doses | Usually reversible on discontinuation; perform audiometry if suspected |
| Neuropsychiatric effects (hallucinations, psychosis, confusion) | Rare | Days | Discontinue clarithromycin; effects usually resolve on stopping |
| Reason for Discontinuation | Incidence | Context |
|---|---|---|
| Taste perversion | ~3% | Most common single reason for early discontinuation in clinical trials |
| Nausea / vomiting | ~2% | More common at 500 mg q8h (H. pylori dual therapy) and MAC treatment doses |
| Diarrhea | ~1% | Rule out C. difficile in persistent cases |
| Abdominal pain | <1% | Usually resolves with dose reduction or food |
The metallic taste associated with clarithromycin is the most frequent reason patients request early discontinuation. Switching to the extended-release formulation can reduce this effect. For short courses (7–14 days), encourage patients that the taste alteration is temporary and fully reversible. Sugar-free lozenges or mints taken after each dose may help mask the taste.
Drug Interactions
Clarithromycin is a strong CYP3A4 inhibitor and also inhibits P-glycoprotein (P-gp). It forms a metabolic intermediate complex with CYP3A4, resulting in mechanism-based (irreversible) inhibition that persists beyond drug discontinuation. This property drives the majority of its clinically significant interactions. The interaction risk is among the highest of all macrolides and should be systematically reviewed before prescribing.
Rifampicin, rifabutin, efavirenz, and phenytoin induce CYP3A4 and substantially reduce clarithromycin plasma concentrations while increasing 14-OH-clarithromycin levels. Since the metabolite has reduced activity against MAC, alternative antibiotics should be considered when treating mycobacterial infections in patients on enzyme inducers. Rifabutin co-administration also increases the risk of uveitis from elevated rifabutin levels.
Monitoring
-
Hepatic Function
Baseline if risk factors; during therapy if symptoms arise
Trigger-based AST, ALT, bilirubin. Discontinue immediately if signs of hepatitis develop (jaundice, dark urine, abdominal tenderness). Higher vigilance in patients with pre-existing liver disease or on hepatotoxic co-medications. -
Renal Function
Baseline
Routine CrCl or eGFR before initiation to determine need for dose reduction. Re-check if renal function deteriorates during therapy, particularly in elderly patients receiving concurrent CCBs or colchicine. -
ECG
Baseline in high-risk patients
Trigger-based Obtain baseline QTc in patients with cardiac risk factors, electrolyte disturbances, or those receiving other QT-prolonging drugs. Avoid if baseline QTc is prolonged. -
INR (if on warfarin)
Within 3–5 days of starting; again after completion
Trigger-based Clarithromycin potentiates warfarin effect. INR may continue to rise for several days after macrolide initiation due to mechanism-based CYP inhibition. -
Digoxin Level
During concurrent use
Trigger-based Check digoxin concentration before starting clarithromycin and again 3–5 days into therapy, especially if level was in the upper therapeutic range. -
Clinical Response
48–72 h after initiation
Routine Reassess clinical improvement. If no response by 72 hours, consider broadening coverage, obtaining cultures, or imaging as appropriate. -
H. pylori Eradication
≥4 weeks after completing therapy
Routine Confirm eradication with urea breath test or stool antigen. Do not test during PPI therapy. Clarithromycin resistance should be suspected if eradication fails.
Contraindications & Cautions
Absolute Contraindications
- Hypersensitivity to clarithromycin, erythromycin, or any macrolide antibiotic
- History of cholestatic jaundice or hepatic dysfunction associated with prior clarithromycin use
- Concurrent cisapride or pimozide — risk of fatal cardiac arrhythmias
- Concurrent ergotamine or dihydroergotamine — risk of acute ergotism
- Concurrent lovastatin or simvastatin — risk of rhabdomyolysis
- Concurrent lomitapide — risk of severe transaminase elevations
- Concurrent lurasidone — risk of increased lurasidone toxicity
- Colchicine in patients with renal or hepatic impairment — life-threatening toxicity reported
Relative Contraindications (Specialist Input Recommended)
- Known QT prolongation or concurrent QT-prolonging drugs — torsades de pointes risk; consider azithromycin or a non-macrolide alternative
- Uncorrected hypokalaemia or hypomagnesaemia — correct electrolytes before initiating
- Coronary artery disease — observational data suggest possible increased long-term all-cause mortality; weigh benefit vs risk
- Severe hepatic impairment with concurrent renal impairment — unpredictable drug levels; specialist PK guidance recommended
Use with Caution
- Myasthenia gravis — exacerbation and new-onset myasthenic symptoms reported
- Renal impairment (CrCl <30 mL/min) — reduce dose by 50%
- Elderly (≥65 years) — increased susceptibility to QT prolongation and acute kidney injury with concurrent CCBs
- Pregnancy — animal teratogenicity (cardiovascular anomalies, cleft palate); use only if no alternative available
- Concurrent oral hypoglycaemics or insulin — risk of hypoglycaemia through CYP3A4 inhibition
In the CLARICOR trial, patients with coronary artery disease randomized to clarithromycin showed an increased risk of all-cause mortality at 1–10 years after treatment compared to placebo (HR 1.10, 95% CI 1.00–1.21 at 10-year follow-up). The mechanism is not established. The FDA advises clinicians to weigh this potential risk against the treatment benefit when prescribing clarithromycin to patients with known or suspected coronary artery disease.
Patient Counselling
Purpose of Therapy
Clarithromycin is an antibiotic that works by stopping the growth of bacteria causing the infection. It treats a range of infections including respiratory tract infections, sinusitis, skin infections, and stomach ulcers caused by the bacterium H. pylori. It is important to complete the full prescribed course even if symptoms improve, as stopping early may allow bacteria to become resistant.
How to Take
Immediate-release tablets can be taken with or without food every 12 hours. Extended-release tablets (Biaxin XL) must be taken with food and swallowed whole — do not crush, split, or chew. The liquid suspension should be shaken well before each dose, stored at room temperature (not in the refrigerator), and discarded after 14 days.
Sources
- Clarithromycin tablets USP — Full Prescribing Information (Aurobindo Pharma). Revised 10/2023. drugs.com/pro/clarithromycin Primary source for dosing, contraindications, adverse reaction incidence rates, and drug interaction data.
- Biaxin (clarithromycin) tablets and oral suspension — FDA-approved labeling. Revised 2017. accessdata.fda.gov Original branded product label with detailed clinical trial data including MAC prophylaxis and H. pylori eradication outcomes.
- Clarithromycin extended-release tablets — DailyMed (NLM). dailymed.nlm.nih.gov Source for XL-specific indications and GI tolerability comparisons with immediate-release formulation.
- Jespersen CM, et al. Randomised placebo controlled multicentre trial to assess short term clarithromycin for patients with stable coronary heart disease: CLARICOR trial. BMJ. 2006;332(7532):22-27. doi:10.1136/bmj.38666.653600.55 Pivotal trial demonstrating signal of increased all-cause mortality in CAD patients receiving clarithromycin, leading to FDA safety communication.
- Winkel P, Hilden J, Fischer Hansen J, et al. Clarithromycin for stable coronary heart disease increases all-cause and cardiovascular mortality and cerebrovascular morbidity over 10 years in the CLARICOR randomised, blinded clinical trial. Int J Cardiol. 2015;182:459-465. doi:10.1016/j.ijcard.2015.01.020 10-year follow-up confirming persistent mortality signal (HR 1.10, 95% CI 1.00–1.21) and increased cerebrovascular events in clarithromycin-treated CAD patients.
- Oldfield EC, Wallace MR. Triple-therapy eradication of H. pylori. Pharmacotherapy. 2001;21(10):1259-1272. doi:10.1592/phco.21.15.1259.33899 Review of triple therapy efficacy data supporting clarithromycin-PPI-amoxicillin regimens in H. pylori eradication.
- Chey WD, Leontiadis GI, Howden CW, Moss SF. ACG Clinical Guideline: Treatment of Helicobacter pylori Infection. Am J Gastroenterol. 2017;112(2):212-239. doi:10.1038/ajg.2016.563 Current ACG guideline recommending clarithromycin triple therapy only when local resistance is below 15%.
- Panel on Opportunistic Infections in Adults and Adolescents with HIV. Guidelines for the prevention and treatment of opportunistic infections. NIH. clinicalinfo.hiv.gov Source for MAC prophylaxis and treatment recommendations in HIV-positive patients.
- Rodvold KA. Clinical pharmacokinetics of clarithromycin. Clin Pharmacokinet. 1999;37(5):385-398. doi:10.2165/00003088-199937050-00003 Comprehensive PK review covering bioavailability, tissue distribution, and the role of the 14-OH metabolite.
- Polasek TM, et al. Modeling the autoinhibition of clarithromycin metabolism during repeated oral administration. Antimicrob Agents Chemother. 2009;53(6):2519-2523. doi:10.1128/AAC.01193-08 Describes mechanism-based CYP3A4 autoinhibition and its clinical implications for non-linear PK and drug interactions.
- Fraschini F, et al. The pharmacokinetics of clarithromycin and its 14-OH metabolite. J Antimicrob Chemother. 1991;27(Suppl A):97-105. doi:10.1093/jac/27.suppl_A.97 Early PK characterisation establishing protein binding (~72%), volume of distribution, and first-pass metabolism data.
- Traunmuller F, et al. Pharmacokinetics of single- and multiple-dose oral clarithromycin in soft tissues determined by microdialysis. Antimicrob Agents Chemother. 2007;51(11):3185-3189. doi:10.1128/AAC.00532-07 Microdialysis study demonstrating free tissue concentrations in adipose and muscle relative to plasma.
- LeBel M. Pharmacokinetic properties of clarithromycin: a comparison with erythromycin and azithromycin. Can J Infect Dis. 1993;4(3):148-152. PMC3250788 Comparative PK analysis highlighting clarithromycin’s superior bioavailability and tissue penetration over erythromycin.