Erythromycin is a macrolide antibiotic derived from *Streptomyces erythreus*. It is a broad-spectrum bacteriostatic agent, primarily used to treat infections caused by Gram-positive bacteria, atypical pathogens, and some Gram-negative organisms. It is a key alternative for patients with penicillin or beta-lactam allergies. In India, it is widely used for respiratory, skin, and soft tissue infections, and for prophylaxis in certain surgical procedures.
Adult: 250-500 mg every 6 hours, or 333 mg every 8 hours, or 500 mg every 12 hours (for specific formulations). For severe infections: 4 g/day in divided doses. Usual dose: 1-2 g/day in divided doses.
Note: Erythromycin base and stearate tablets should be taken on an empty stomach (1 hour before or 2 hours after meals) with a full glass of water. Enteric-coated tablets can be taken without regard to food. Do not crush, chew, or break enteric-coated tablets. Complete the full prescribed course even if symptoms improve.
Erythromycin inhibits bacterial protein synthesis by reversibly binding to the 50S ribosomal subunit of susceptible microorganisms. This binding blocks the translocation step, preventing the transfer of the tRNA from the A-site to the P-site on the ribosome, thereby inhibiting the elongation of the peptide chain.
Pregnancy: US FDA Category B. Erythromycin base and stearate are considered generally safe. Erythromycin estolate is contraindicated due to risk of hepatotoxicity in the pregnant patient. Use only if clearly needed.
Driving: May cause dizziness or vertigo. Patients should not drive or operate machinery if they experience these effects.
| Warfarin | Increased anticoagulant effect, risk of bleeding | Major |
| Carbamazepine | Increased carbamazepine levels, risk of toxicity (ataxia, dizziness) | Major |
| Theophylline | Increased theophylline levels, risk of nausea, seizures | Major |
| Digoxin | Increased digoxin bioavailability, risk of toxicity | Major |
| Simvastatin/Atorvastatin | Increased statin levels, high risk of rhabdomyolysis | Contraindicated |
| Midazolam/Triazolam | Increased sedation and prolonged effect | Major |
| Cyclosporine | Increased cyclosporine levels, risk of nephrotoxicity | Major |
| Sildenafil | Increased sildenafil levels, risk of hypotension, priapism | Major |
| Oral Contraceptives | Potential reduction in contraceptive efficacy; advise backup method | Moderate |
Same composition (Erythromycin (500mg)), different brands: