Effect of traditional Chinese herbal medicines on the pharmacokinetics of western drugs in Sprague-Dawley rats of different ages (II): Aminophylline-huan shao tan and aminophylline-pu chung yi chi tang.

The effect of Chinese herbal medicines (Huan Shao Tan and Pu Chung Yi Chi Tang) and western drugs (sodium phenobarbital and cimetidine) on the serum concentration and pharmacokinetic parameters of theophylline and cytochrome P-450 of Sprague-Dawley (SD) rats of three different ages were examined. The older rats without pretreatment with Chinese herbal medicines and western drugs exhibited higher serum theophylline concentration and lower pharmacokinetic parameters of theophylline than middle-aged and younger rats (P < 0.05), but there was no difference in cytochrome P-450 activity among the three different ages of rats. All rats when pretreated with sodium phenobarbital showed lower serum theophylline concentration and higher pharmacokinetics parameters of theophylline. Also, the activity of cytochrome P-450 was higher (P < 0.05). When cimetidine was pre-administered in SD rats of three age groups, all rats exhibited lower serum theophylline concentration and higher pharmacokinetics parameters (P < 0.05), but the activity of cytochrome P-450 remained unchanged (P > 0.05). The results were opposite to other studies, probably because the dose and dosing intervals were different. No single effect occurred on the younger and middle-aged rats after pretreatment with Huan Shao Tan and Pu Chung Yi Chi Tang: their serum theophylline concentration, pharmacokinetics parameters and cytochrome P-450 activity were the same as the control group. However, the older rats after pretreatment with Huan Shao Tan or Pu Chung Yi Chi Tang showed lower serum theophylline concentration and higher pharmacokinetics parameters than the younger and middle-aged rats pretreated with similar Chinese herbal medicines. This indicates that Huan Shao Tan and Pu Chung Yi Chi Tang may perhaps improve the elimination of theophylline in older rats. This might be attributed to the increase in hepatic blood flow or in liver volume, since the activity of cytochrome P-450 was not affected by the administration of Chinese herbal medicines.