Adults

The usual dose is 500 mg every 12 hours, or 250 mg every 6 hours, for 7-14 days depending on the severity and type of infection. Some severe infections may require higher doses.

Elderly

Similar to adult dosage; however, caution should be exercised in elderly patients with hepatic impairment.

Renal_impairment

No dose adjustment is generally necessary for mild to moderate renal impairment. For severe renal impairment (creatinine clearance <10 mL/min), a dose reduction or increased dosing interval may be considered (e.g., 250-500 mg every 18-24 hours).

Onset

Therapeutic effects usually manifest within 1-2 days of starting treatment.

Excretion

Primarily excreted in the bile and feces. A small percentage (2-5%) is excreted unchanged in the urine.

Half life

Approximately 1.5 to 2 hours in adults, slightly longer in patients with severe renal impairment.

Absorption

Oral absorption of erythromycin is variable and depends on the formulation. Enteric-coated tablets (like Erybac) are designed to bypass gastric acid degradation, improving bioavailability. Peak plasma concentrations are typically reached within 1-4 hours.

Metabolism

Extensively metabolized in the liver, primarily by the cytochrome P450 3A4 (CYP3A4) isoenzyme, to inactive metabolites.

Digoxin

Increased serum digoxin levels, leading to potential toxicity.

Warfarin

Increased anticoagulant effect, leading to increased bleeding risk.

Cimetidine

May increase erythromycin levels.

Statins (e.g., Simvastatin, Lovastatin)

Increased risk of myopathy and rhabdomyolysis due to inhibition of statin metabolism.

Antacids containing aluminum or magnesium

May reduce erythromycin absorption.

Carbamazepine, Theophylline, Cyclosporine

Increased serum levels of these drugs, leading to potential toxicity.