Pharmacokinetics of piracetam: a study on the bioavailability with special regard to renal and non-renal elimination.

The basis of this investigation was a trial on the relative bioavailability of a recently developed galenic formulation of piracetam. The open, randomized, single-blind crossover study was performed in 16 healthy male volunteers aged between 20 and 31 years. Under fasting conditions, they were given a single oral dose of 1600 mg piracetam either of the test drug or the reference drug. Blood samples and urine specimens were collected over 24 hours. The quantitative analysis was performed with a high sensitive HPLC-method. The pharmacokinetic analysis was carried out with the PC-based program TopFit. An identical bioavailability of the test drug was found (AUC0-24, AUC0-infinity, Cmax, by comparison to the reference drug. No relevant difference in piracetam excretion between test and reference drug was found, however, in contrast to previous references only about two thirds of the given oral dose could be detected in the urine after administration. A statistically significant difference (p = 0.001) between total clearance and renal clearance was observed. Because an incomplete absorption of the drug in the upper gastrointestinal tract is excluded, an additional extrarenal pathway of piracetam must be discussed; the hypothesis of an exclusive renal elimination of this drug should be overruled.