Pharmacokinetics of intravenous cefetamet (Ro 15-8074) and oral cefetamet pivoxil (Ro 15-8075) in young and elderly subjects

The purpose of this investigation was to evaluate the effect of advanced age on the pharmacokinetics of cefetamet and its prodrug, cefetamet pivoxil. A secondary objective of this study was to assess the effect of food on the absorption of cefetamet pivoxil in the elderly. Twenty-four healthy subjects (twelve young and twelve elderly) received (in a Latin square design) a single-dose, 515-mg infusion of cefetamet, a single 1,000-mg oral dose of cefetamet pivoxil during fasted conditions, and a single 1,000-mg oral dose of cefetamet pivoxil 10 min after a standardized low-fat breakfast. Serial blood and urine samples were collected over a 36-h period and analyzed by high-performance liquid chromatography. Intravenous and oral pharmacokinetic parameters were obtained by using model-independent techniques. The systemic clearance and renal clearance of cefetamet were significantly lower (P less than 0.05) in elderly subjects compared with in young controls after intravenous administration. No significant difference was observed in the apparent volumes of distribution at steady state between the two groups. Consequently, half-life and mean residence time were prolonged. A trend toward a lower renal clearance/creatinine clearance ratio was observed in our elderly population. Oral clearance of cefetamet was only slightly reduced in our elderly subjects, consistent with an increase in plasma half-life. Otherwise, oral pharmacokinetic parameters were comparable between elderly and young subjects. Additionally, the same effects of food were observed on the absorption characteristics of cefetamet (no change in maximum concentration of drug in plasma and an increase in both time to maximum concentration of drug in plasma and bioavailability) in our elderly subjects as in our young volunteers. Age did not appear to alter the deesterification and bioavailability of cefetamet pivoxil. We conclude that the small reduction in the elimination of cefetamet in the elderly would not require dose adjustment for this population.