Pharmacokinetics of 3H-terguride in elderly volunteers

Blood and plasma levels and excretion of labeled compounds and of the unchanged drug were measured after i.v. injection of 54 micrograms and p.o. administration of 540 micrograms of the ergoline derivative, terguride (CAS 37686-84-3), labeled with tritium, in 6 elderly male volunteers. Following i.v. injection plasma levels of terguride declined with a half-life of 0.5 h and those of radiolabeled compounds with half-lives of 0.5 h, 7 h and 19 h. The total clearance was 17 ml/min/kg and the volume of distribution was 0.7 l/kg. After p.o. administration terguride was rapidly and completely absorbed. The bioavailability was around 20%. Elimination of labeled compounds was complete within 7 days and proceeded mainly via the urine. Computer simulation of plasma levels after 4-times-a-day multiple administrations indicated slight accumulation of metabolites (factor 3) and no accumulation of terguride (factor 1).