What is the recommended dose of clarithromycin (Biaxin) for adults?

Clarithromycin Dosing for Adults

For most adult infections, clarithromycin should be dosed at 500 mg twice daily for 7-14 days depending on the indication, or alternatively 1000 mg once daily using the extended-release formulation. 1, 2, 3

Standard Adult Dosing by Indication

Respiratory Tract Infections

• Community-acquired pneumonia: 500 mg twice daily for 7-14 days (immediate-release) OR 1000 mg once daily for 7 days (extended-release) 4, 3
• Acute bacterial exacerbation of chronic bronchitis: 500 mg twice daily for 7 days (immediate-release) OR 1000 mg once daily for 7 days (extended-release) 3
• Acute maxillary sinusitis: 500 mg twice daily for 14 days (immediate-release) OR 1000 mg once daily for 14 days (extended-release) 3
• Group A streptococcal pharyngitis: 250 mg twice daily for 10 days 4

Mycobacterial Infections

• Mycobacterium avium complex (MAC) treatment: 500 mg twice daily in combination with ethambutol 15 mg/kg daily 1
• MAC prophylaxis in AIDS (CD4 <50 cells/μL): 500 mg twice daily 1
• Pertussis: 500 mg twice daily for 7 days 1

Critical Dosing Considerations

Renal Impairment

• Severe renal impairment (CrCl <30 mL/min): Reduce dose by 50% 2, 3
• Moderate renal impairment (CrCl 30-60 mL/min) with concomitant ritonavir or atazanavir: Reduce dose by 50% 4, 3
• Severe renal impairment (CrCl <30 mL/min) with concomitant ritonavir or atazanavir: Reduce dose by 75% 4, 3

Special Populations

• Elderly patients (>70 years) or low body weight (<50 kg): Consider reducing to 250 mg twice daily due to increased risk of gastrointestinal intolerance 1
• No dosage adjustment required for hepatic impairment alone 5

Administration Guidelines

Extended-Release Formulation

• Must be taken with food to maximize bioavailability (30% reduction in absorption when taken fasting) 3, 6
• Swallow tablets whole—do not chew, break, or crush 3
• Extended-release provides equivalent bioavailability to immediate-release with lower peak concentrations and reduced gastrointestinal side effects 6

Immediate-Release Formulation

• Can be taken with or without food 7
• Absorption is unaffected by food 7

Drug Interaction Adjustments

HIV Antiretrovirals

• With ritonavir or lopinavir-ritonavir: Reduce clarithromycin dose by 50% if CrCl <60 mL/min; reduce by 75% if CrCl <30 mL/min 4, 2
• With efavirenz: Clarithromycin AUC decreases by 39%; efficacy may be uncertain, monitor closely for treatment failure 4, 2
• With nevirapine: Clarithromycin AUC decreases by 35%; monitor closely for treatment failure 4

Contraindicated Combinations

• Absolutely contraindicated with cisapride, pimozide, astemizole, or terfenadine due to risk of fatal cardiac arrhythmias (torsades de pointes) 2, 3
• Contraindicated with colchicine in patients with renal or hepatic impairment 3
• Contraindicated with lomitapide, lovastatin, or simvastatin due to risk of rhabdomyolysis 3

Common Pitfalls to Avoid

Adverse Effects

• Gastrointestinal symptoms (metallic taste, nausea, vomiting, diarrhea) are dose-related and most common 1, 6
• Doses >1000 mg/day are poorly tolerated in most adults and should be avoided 1
• Extended-release formulation has significantly less severe gastrointestinal adverse events compared to immediate-release (P = 0.018) 6

Resistance Considerations

• Macrolide resistance in Streptococcus pneumoniae and Staphylococcus aureus is well-documented and varies geographically 4, 3
• Use 500 mg twice daily (not 250 mg twice daily) when treating H. pylori to minimize resistance development 8
• Susceptibility testing should be performed when clinically indicated 3

CYP3A4 Interactions

• Clarithromycin is a potent CYP3A4 inhibitor and can increase levels of carbamazepine, cyclosporine, digoxin, theophylline, warfarin, and midazolam 2, 5
• Monitor closely and adjust doses of these medications as needed 5