Clarithromycin is a semi-synthetic macrolide antibiotic derived from erythromycin. It is a broad-spectrum antibiotic with enhanced acid stability and improved oral bioavailability compared to erythromycin. It is widely used in the Indian context for treating respiratory tract infections, skin and soft tissue infections, and Helicobacter pylori eradication. It acts by inhibiting bacterial protein synthesis.
Adult: For most infections: 250-500 mg orally every 12 hours for 7-14 days. For H. pylori eradication: 500 mg twice daily as part of combination therapy for 10-14 days.
Note: Tablet can be taken with or without food. Should be swallowed whole with a full glass of water. Do not crush, chew, or break the extended-release tablets. For optimal absorption and to minimize GI upset, taking with food is often recommended.
Clarithromycin binds reversibly to the 50S subunit of the bacterial ribosome, specifically at the peptidyl transferase center. This binding inhibits the translocation step of protein synthesis, preventing the transfer of the peptidyl-tRNA from the A-site to the P-site. This results in the arrest of bacterial protein chain elongation, leading to bacteriostatic activity against susceptible organisms.
Pregnancy: Pregnancy Category C (US FDA). Animal studies have shown adverse effects. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. Not recommended for routine use, especially in first trimester.
Driving: May cause dizziness, vertigo, confusion, or hallucinations. Patients should be cautioned about operating machinery or driving until they know how the drug affects them.
| Warfarin | Increased anticoagulant effect, risk of bleeding | Major |
| Statins (Atorvastatin, Simvastatin, Lovastatin) | Increased risk of myopathy/rhabdomyolysis | Major |
| Colchicine | Increased colchicine toxicity (myelosuppression, multiorgan failure) | Contraindicated in renal/hepatic impairment |
| Midazolam, Triazolam | Increased and prolonged sedation | Major |
| Digoxin | Increased digoxin serum levels (P-gp inhibition) | Moderate |
| Theophylline | Increased theophylline serum levels | Moderate |
| Carbamazepine | Increased carbamazepine toxicity | Major |
| Protease Inhibitors (Ritonavir, Saquinavir) | Mutual inhibition of metabolism; increased risk of QT prolongation | Major |
| Cyclosporine, Tacrolimus | Increased immunosuppressant levels, risk of nephrotoxicity | Major |
| Oral Hypoglycemics (e.g., Glimepiride) | Enhanced hypoglycemic effect | Moderate |
| Sildenafil, Tadalafil | Increased PDE5 inhibitor levels and adverse effects | Moderate |
| Efavirenz, Nevirapine | Decreased clarithromycin levels; increased metabolite levels | Moderate |