What is the recommended oral dose of clarithromycin for an adult (≥ 18 years) for typical infections?

Clarithromycin Oral Dosage for Adults

For most typical infections in adults, clarithromycin is dosed at 500 mg orally twice daily (every 12 hours), or alternatively 1000 mg once daily using the extended-release formulation. 1

Standard Dosing by Indication

Respiratory Tract Infections

• Community-acquired pneumonia: 500 mg twice daily for 7-14 days, or 1000 mg once daily (extended-release) for 7 days 1
• Acute bacterial exacerbation of chronic bronchitis: 500 mg twice daily for 7 days, or 1000 mg once daily (extended-release) for 7 days 1
• Acute maxillary sinusitis: 500 mg twice daily for 10-14 days, or 1000 mg once daily (extended-release) for 14 days 1

Mycobacterial Infections

• Mycobacterium avium complex (MAC) treatment: 500 mg twice daily in combination with ethambutol 15 mg/kg daily 2
• MAC prophylaxis in AIDS patients (CD4 <50 cells/μL): 500 mg twice daily 2
• Disseminated MAC in AIDS: 500-1000 mg twice daily (doses up to 2000 mg/day have been used) 3

Other Infections

• Pertussis: 500 mg twice daily for 7 days (total daily dose: 1 g/day) 4, 5
• Helicobacter pylori eradication: 500 mg twice daily for 14 days as part of triple therapy with a proton pump inhibitor and amoxicillin or metronidazole 5
• Skin and soft tissue infections: 250 mg four times daily 2

Critical Dosing Adjustments

Renal Impairment

• Severe renal impairment (CrCl <30 mL/min): Reduce dose by 50% 1
• Moderate renal impairment (CrCl 30-60 mL/min) with concomitant atazanavir or ritonavir: Reduce dose by 50% 1
• Severe renal impairment (CrCl <30 mL/min) with concomitant atazanavir or ritonavir: Reduce dose by 75% 1

Drug Interaction Adjustments

• With ritonavir or lopinavir-ritonavir and CrCl <60 mL/min: Reduce dose by 50% 4
• With ritonavir or lopinavir-ritonavir and CrCl <30 mL/min: Reduce dose by 75% 4
• With atazanavir: Reduce clarithromycin dose by 50% 1
• With efavirenz or nevirapine: Monitor closely for treatment failure as clarithromycin levels decrease by 35-39% 4

Special Populations

• Elderly patients (>70 years) or those weighing <50 kg: Consider reducing to 250-500 mg/day due to increased risk of gastrointestinal intolerance 4
• Hepatic impairment: No dosage adjustment required unless concurrent severe renal impairment 6

Administration Guidelines

Formulation-Specific Instructions

• Immediate-release tablets: Can be taken with or without food; 500 mg twice daily (every 12 hours) 2, 4
• Extended-release tablets: Must be taken with food; swallow whole, do not crush, chew, or break; 1000 mg once daily 1, 7

Maximum Dosing Considerations

• Doses >1000 mg/day are poorly tolerated in most adults and should be avoided for routine infections 4
• The FDA-approved maximum is 1000 mg twice daily for MAC infections, though doses up to 2000 mg/day have been used in AIDS patients with disseminated MAC 3

Common Pitfalls to Avoid

Tolerability Issues

• Gastrointestinal symptoms (metallic taste, nausea, vomiting, diarrhea) are dose-related and represent the most common adverse effects 2, 4
• The extended-release formulation has significantly less severe gastrointestinal adverse events compared to immediate-release (P = 0.018) 7
• Taking extended-release tablets without food reduces bioavailability by 30% 7

Drug Interactions

• Contraindicated combinations: cisapride, pimozide (risk of fatal cardiac arrhythmias), colchicine in renal/hepatic impairment, lomitapide, lovastatin, simvastatin 1
• Clarithromycin is a potent CYP3A4 inhibitor and can increase levels of drugs with narrow therapeutic indices (carbamazepine, cyclosporine, digoxin, theophylline, warfarin) 6
• Rifampin and rifabutin significantly decrease clarithromycin concentrations; avoid concurrent use when possible 6

Resistance Considerations

• Macrolide resistance in Streptococcus pneumoniae and Staphylococcus aureus is well-documented and varies geographically; susceptibility testing should be performed when clinically indicated 1
• Short-term monotherapy for MAC may lead to bacterial resistance; always use combination therapy for mycobacterial infections 3

Monitoring Requirements

• ECG monitoring: Baseline and at 2 weeks for patients at risk of QT prolongation 2
• Audiometry: Baseline and if symptoms develop, as hearing loss and tinnitus are reported with long-term use 2
• Routine laboratory monitoring: Complete blood count, renal and liver function tests during prolonged treatment 2