What is the recommended dosing for clarithromycin (antibiotic) in adults?

Clarithromycin Dosing in Adults

For most common infections in adults, clarithromycin is dosed at 500 mg twice daily (immediate-release) or 1000 mg once daily (extended-release), with duration varying by indication from 7-14 days. 1, 2

Standard Adult Dosing by Indication

Respiratory Tract Infections

• Pertussis: 1 g per day divided into two 500 mg doses for 7 days 1
• Community-acquired pneumonia: 500 mg twice daily for 7-10 days (immediate-release) OR 1000 mg once daily for 7 days (extended-release) 2
• 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) 2
• Acute maxillary sinusitis: 500 mg twice daily for 14 days (immediate-release) OR 1000 mg once daily for 14 days (extended-release) 2

Mycobacterial Infections

• Mycobacterium avium complex (MAC): 500 mg twice daily in combination with ethambutol 15 mg/kg daily 1
• Maximum tolerated dose: Most adults cannot tolerate more than 1000 mg/day due to dose-related toxicity 1

Helicobacter pylori

• Triple therapy: 500 mg twice daily for 14 days (combined with PPI and amoxicillin or metronidazole) 3

Critical Dosing Considerations

Elderly and Low Body Weight Patients

• Patients <50 kg or >70 years: Consider reducing to 250-500 mg/day due to increased risk of gastrointestinal intolerance 1
• Low creatinine clearance: Elderly patients often require lower doses (250-500 mg/day) even without formal renal impairment due to age-related decreases in clearance 1

Renal Impairment Adjustments

• Severe renal impairment (CrCl <30 mL/min): Reduce dose by 50% 1, 2
• Moderate renal impairment (CrCl 30-60 mL/min) with ritonavir or atazanavir: Reduce dose by 50% 1, 2
• Severe renal impairment (CrCl <30 mL/min) with ritonavir or atazanavir: Reduce dose by 75% 1, 2

Drug Interaction Adjustments

• With atazanavir: Decrease clarithromycin dose by 50% 2
• With ritonavir or lopinavir-ritonavir: Reduce dose by 50% if CrCl <60 mL/min; reduce by 75% if CrCl <30 mL/min 1
• With efavirenz or nevirapine: Clarithromycin efficacy may be reduced by 35-39%; monitor closely for treatment failure 1

Administration Guidelines

Extended-Release Formulation

• Must be taken with food to maximize bioavailability (30% reduction when taken fasting) 2, 4
• Swallow whole: Do not chew, break, or crush tablets 2
• Bioequivalent to immediate-release when taken with food based on AUC 4

Immediate-Release Formulation

• Can be taken with or without food 5, 6
• Twice-daily dosing required 1, 3

Common Pitfalls to Avoid

Toxicity Recognition

• Gastrointestinal symptoms (metallic taste, nausea, vomiting) are dose-related and most common adverse effects 1
• Doses >1000 mg/day are poorly tolerated in most adults and should be avoided 1
• Ototoxicity can occur, particularly at higher doses; consider audiometry if hearing symptoms develop 3

Contraindications

• Absolute contraindications: History of hypersensitivity to macrolides, cholestatic jaundice/hepatic dysfunction with prior clarithromycin use, concomitant use with cisapride or pimozide 1, 2
• Do not combine with: Lovastatin, simvastatin, or lomitapide due to risk of rhabdomyolysis and hepatotoxicity 2
• Avoid with colchicine in patients with renal or hepatic impairment 2

Drug Interactions via CYP3A4

• Clarithromycin is a potent CYP3A4 inhibitor and increases levels of drugs metabolized by this pathway 1, 6
• High-risk interactions: Carbamazepine, cyclosporine, digoxin, theophylline, warfarin, benzodiazepines, sildenafil 1, 6
• Separate from antacids and cation preparations by >2 hours if using quinolones concurrently 1

Pregnancy Considerations

• FDA Pregnancy Category C: Animal studies show adverse fetal effects; use only if benefit outweighs risk 1
• Azithromycin preferred in pregnancy over clarithromycin due to teratogenicity concerns 1