Effect of age on the pharmacokinetics of orally and intravenously administered terazosin

Terazosin, a new long-acting selective alpha 1-receptor antagonist, was studied in a crossover trial to assess the effect of age on oral and intravenous pharmacokinetics. Thirty healthy male and female volunteers between the ages of 23 and 75 years received 1-mg oral and intravenous doses of terazosin. For both routes of administration, the only pharmacokinetic variables significantly correlated with age were terminal elimination rate constant and the area under the plasma concentration-time curve (AUC). However, the differences in half-life and AUC between the youngest and oldest subjects were modest and not of practical clinical significance. There was no evidence of an enhanced pharmacologic or toxic effect in older subjects. From these data, we conclude that the dosage of terazosin does not need to be adjusted on the basis of age alone; the dose of terazosin is titrated in all patients to the lowest effective dose that is well tolerated.