Introduction
Biaxin (clarithromycin) is a semi-synthetic macrolide antibiotic derived from erythromycin. It is widely used in clinical practice for its broad-spectrum activity against various Gram-positive and Gram-negative bacteria, as well as atypical pathogens. Biaxin is available in immediate-release and extended-release formulations, as well as granules for oral suspension.
Mechanism of Action
Clarithromycin exerts its antibacterial effect by binding to the 50S ribosomal subunit of susceptible microorganisms, thereby inhibiting protein synthesis. This bacteriostatic action prevents bacterial replication by interfering with translocation steps during protein synthesis. The drug demonstrates concentration-dependent killing against certain organisms and time-dependent killing against others.
Indications
FDA-approved indications include:
- Upper respiratory tract infections (pharyngitis/tonsillitis, acute maxillary sinusitis)
- Lower respiratory tract infections (acute bacterial exacerbation of chronic bronchitis, community-acquired pneumonia)
- Uncomplicated skin and skin structure infections
- Disseminated Mycobacterium avium complex (MAC) infection
- Helicobacter pylori eradication (in combination with other agents)
- Duodenal ulcer disease (as part of combination therapy)
Off-label uses include:
- Pertussis prophylaxis and treatment
- Lyme disease
- Mycobacterial infections
- Toxoplasmosis prophylaxis
Dosage and Administration
Adults:- Most infections: 250-500 mg every 12 hours for 7-14 days
- MAC prophylaxis: 500 mg twice daily
- H. pylori eradication: 500 mg twice daily (as part of combination therapy)
- Extended-release: 1000 mg once daily for 7-14 days
- 7.5 mg/kg every 12 hours (maximum 500 mg/dose)
- MAC treatment: 7.5 mg/kg twice daily (maximum 500 mg/dose)
- CrCl <30 mL/min: Reduce dose by 50% or double dosing interval
- Hemodialysis: Administer after dialysis
- Take with or without food (food improves tolerability)
- Extended-release tablets must be swallowed whole
- Oral suspension should be shaken well before use
Pharmacokinetics
Absorption: Well-absorbed from GI tract (50% bioavailability); food delays absorption but does not affect extent Distribution: Widely distributed to tissues and fluids; tissue concentrations exceed serum levels; CSF penetration poor Protein binding: 42-70% bound to plasma proteins Metabolism: Extensive hepatic metabolism via CYP3A4 to active 14-hydroxy metabolite Elimination: Half-life 3-7 hours; primarily excreted in urine (20-40% as unchanged drug); fecal elimination 15%Contraindications
- Known hypersensitivity to clarithromycin, other macrolides, or any component
- Concomitant use with cisapride, pimozide, ergot alkaloids, or HMG-CoA reductase inhibitors extensively metabolized by CYP3A4 (lovastatin, simvastatin)
- History of QT prolongation or ventricular arrhythmias
- Hypokalemia or hypomagnesemia (relative contraindication)
Warnings and Precautions
Black Box Warning:- Increased risk of death in patients with coronary artery disease
- QT prolongation and torsades de pointes
- Clostridium difficile-associated diarrhea
- Hepatotoxicity (monitor LFTs)
- Exacerbation of myasthenia gravis
- Development of drug-resistant bacteria
- Hearing loss (reversible in most cases)
- Interaction with colchicine in patients with renal/hepatic impairment
Drug Interactions
Major interactions:- CYP3A4 inhibitors/inducers: Altered clarithromycin levels
- Drugs that prolong QT interval: Additive effect
- Warfarin: Increased INR (monitor closely)
- Colchicine: Increased colchicine toxicity
- Digoxin: Increased digoxin levels
- Theophylline: Increased theophylline levels
- Carbamazepine: Increased carbamazepine levels
- Oral hypoglycemics: Enhanced hypoglycemic effect
- Triazolam, midazolam: Increased sedation
Adverse Effects
Common (≥1%):- Diarrhea (6%)
- Nausea (5%)
- Abnormal taste (7%)
- Dyspepsia (3%)
- Abdominal pain (3%)
- Headache (3%)
- QT prolongation and torsades de pointes
- Hepatotoxicity (including fatal hepatic failure)
- Stevens-Johnson syndrome
- Acute kidney injury
- Pseudomembranous colitis
- Hearing loss
- Blood dyscrasias
Monitoring Parameters
- Clinical response to therapy
- Signs of superinfection
- Liver function tests (baseline and periodic)
- Renal function (baseline and periodic)
- ECG in patients at risk for QT prolongation
- INR in patients on warfarin
- Serum drug levels of concomitant medications with narrow therapeutic indices
- Hearing assessment in prolonged therapy
Patient Education
- Complete full course of therapy even if feeling better
- Take exactly as prescribed; do not skip doses
- Report severe diarrhea, abdominal pain, or bloody stools
- Report palpitations, dizziness, or fainting
- Report yellowing of skin/eyes, dark urine, or unusual fatigue
- Use non-hormonal contraception during therapy (may reduce efficacy of oral contraceptives)
- Be aware of potential metallic taste (usually temporary)
- Avoid grapefruit juice during therapy
- Inform all healthcare providers about Biaxin use
References
1. Biaxin [package insert]. North Chicago, IL: AbbVie Inc.; 2021. 2. Liu C, et al. Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children. Clin Infect Dis. 2011;52(3):e18-e55. 3. Ray WA, et al. Oral erythromycin and the risk of sudden death from cardiac causes. N Engl J Med. 2004;351(11):1089-1096. 4. FDA Drug Safety Communication: Clarithromycin and risk of heart problems or death in patients with heart disease. FDA.gov. 2018. 5. Gilbert DN, et al. The Sanford Guide to Antimicrobial Therapy. 52nd ed. Antimicrobial Therapy, Inc.; 2022. 6. Micromedex Solutions. Clarithromycin. Truven Health Analytics. 2023. 7. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases; 2012.