Erythromycin

Chemical Structure / Formula of Erythromycin

• Formula: C₃₇H₆₇NO₁₃
• Core Structure: 14-membered lactone ring with deoxy sugars (cladinose and desosamine).

Mechanism of Action

• Binds to the 50S ribosomal subunit, inhibiting translocation of the growing peptide chain.
• Bacteriostatic at low concentrations but bactericidal at high concentrations.

Uses of Erythromycin

• Respiratory tract infections (pneumonia, pertussis, diphtheria).
• Chlamydia infections (alternative to doxycycline).
• Gastroparesis treatment (prokinetic effect via motilin receptor activation).

Side Effects

• GI upset (nausea, vomiting, diarrhea: stimulates motilin receptors).
• QT prolongation → risk of torsades de pointes.
• Cholestatic hepatitis (rare).
• CYP3A4 inhibition → increases levels of other drugs (e.g., warfarin, theophylline).

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