Pharmacology.
Amoxicillin differs from ampicillin by the presence of a hydroxyl group on the amino side chain. It has activity essentially identical to ampicillin.
Adult Dosage.
PO 250–500 mg q 8 hr or 500-875 mg bid, to a maximum of 4.5 g/day. PO for endocarditis prophylaxis 2 g 1 hr before dental or upper airway procedures.
Pediatric Dosage.
PO 20–40 mg/kg/day in 3 equally divided doses q 8 hr. PO for endocarditis prophylaxis 50 mg/kg 1 hr before dental or upper airway procedures.
Dosage Forms.
Cap 250, 500 mg; Chew Tab 125, 200, 250, 400 mg; Drp 50 mg/mL; Susp 25, 50 mg/mL; Tab 500, 875 mg.
Pharmacokinetics.
Amoxicillin is completely absorbed, with about 85% bioavailability because of a small first-pass effect. Serum concentrations are greater than those after equal doses of ampicillin; postabsorptive pharmacokinetics are identical to those of ampicillin.
Adverse Reactions.
Adverse effects are similar to those of ampicillin, although diarrhea and rashes are much less frequent with amoxicillin.
