Pharmacokinetics of amoxicillin and ampicillin: crossover study of the effect of food.

The effect of food on the absorption of amoxicillin and ampicillin was studied in 16 normal subjects in a double-blind crossover study after each subject was given a single oral 500-mg dose. Serum drug levels were analyzed, assuming a one-compartment linear model with first-order absorption and absorption delay, area under the curve, and urinary recovery. Variations in kinetic parameters were examined by using analysis of variance. The results showed little or no effect of fasting versus nonfasting on amoxicillin absorption, as evidenced by peak serum levels (8.9 mug/ml, fasting, 8.8 mug/ml, nonfasting), area under the curve (26.9 mug/ml per 70 kg, fasting, 22.2 mug/ml per 70 kg, nonfasting), and urinary recovery (47%, fasting; 44%, nonfasting). Ampicillin absorption was significantly decreased in the nonfasted group by the same parameters (peak level: 5.4 mug/ml, fasting, 4.0 mug/ml, nonfasting; area under the curve, 17.4 h.mug/ml, fasting, 12.0 h.mug/ml, nonfasting; urinary recovery, 37%, fasting, 29%, nonfasting). These results confirm the reliable absorption of orally administered amoxicillin in the fed as well as the fasted state.