Effects of age, dosage regimen, dose level, and routes of administration on the pharmacokinetics of acrylamide (ACR) and theophylline (TP) in Fischer 344 rats have been studied. ACR treatment consisted of administration of a single subtoxic dose or of multiple doses known to induce neurotoxicity to 5 and 11 week old rats. The effects of age and dosing regimen on the determination of pharmacokinetic parameters were studied. Multiply dosed rats had significantly longer plasma half lives than the singly dosed animals. Clearance values in the plasma were also significantly decreased following multiple dosing. Animals treated with TP received a single dose at different dose levels either intravenously or orally. No statistical difference was found between beta, Vbeta , and Cl based on dose level. All pharmacokinetic parameters were similar in magnitude to literature values for humans. Following oral dosing, plasma levels of TP were constant for the duration of the experiment. (Abstract shortened with permission of author.)