Adults

Standard adult dosage: 250 mg to 500 mg every 8 hours, or 500 mg to 875 mg every 12 hours, depending on the severity and type of infection. For severe infections, up to 1 gram three times daily may be prescribed.

Elderly

Similar to adult dosage, but caution is advised in elderly patients, especially those with renal impairment. Dosage adjustment may be required.

Renal_impairment

Dosage adjustment is necessary. For creatinine clearance 10-30 mL/min, 250-500 mg every 12 hours. For creatinine clearance <10 mL/min, 250-500 mg every 24 hours. Hemodialysis patients require an additional dose during and at the end of dialysis.

Onset

Antibacterial effect typically begins within 30-60 minutes.

Excretion

Primarily via renal excretion (50-70% as unchanged drug) in urine within 6-8 hours. Also excreted in bile and feces.

Half life

Approximately 1-1.5 hours in adults with normal renal function. It is prolonged in patients with impaired renal function.

Absorption

Rapidly and well absorbed (75-90%) from the gastrointestinal tract, reaching peak plasma concentrations within 1-2 hours after oral administration. Food does not significantly affect absorption.

Metabolism

Limited metabolism; a small proportion (10-25%) is metabolized to inactive penicilloic acid.

Allopurinol

Concomitant use with amoxicillin may increase the incidence of skin rash.

Methotrexate

Amoxicillin may reduce the renal tubular secretion of methotrexate, thereby increasing its plasma concentration and potential toxicity.

Oral Contraceptives

May reduce the efficacy of oral contraceptives in some cases. Advise additional non-hormonal contraception.

Warfarin and other oral anticoagulants

May prolong prothrombin time and increase the risk of bleeding. Close monitoring of coagulation parameters is recommended.

Tetracyclines, Chloramphenicol, Macrolides, Sulfonamides

These bacteriostatic drugs may interfere with the bactericidal effect of amoxicillin.