Pharmacokinetic analysis of the effects of different foods on absorption of cefaclor.

Cefaclor is an oral cephalosporin antibiotic which has a broad antibacterial spectrum. The purpose of this study was to investigate the effect of food on the absorption of cefaclor and to analyze kinetically the absorption process of this drug. Cefaclor was given to eight volunteers at five test times: after overnight fasting, after two rice meals (350 and 700 cal [1 cal = 4.184 J]), and after two bread meals (500 and 1,000 cal). Urinary recoveries of cefaclor and concentrations of the drug in plasma were determined for each administration. Areas under the concentration-time curves and urinary recoveries were not affected by food intake, but the maximum concentration of drug in serum was reduced and the time to maximum concentration of drug in serum was prolonged depending on the type and the quantity of the meal. The larger the quantity of the meal, the more the maximum concentration of drug in serum and the time to maximum concentration of drug in serum were affected. The rice meals affected the absorption process of cefaclor more than the bread meals. The concentrations of cefaclor in plasma following administration after overnight fasting were well fitted to a conventional one-compartment model with a first-order absorption process, but those after the other administrations were not fitted to the model. For the pharmacokinetic analysis of those data, it was necessary to introduce a transfer process from administration site to absorption site to the conventional model. The concentrations in plasma after rice and bread meals were best fitted to the model with a zero-order transfer process than to that with a first-order process. The velocity of the transfer process depended on the type and volume of the meal.