Pharmacokinetics in the human of a new synthetic vasopressin and oxytocin uterine antagonist.

The pharmacokinetics in the human of 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-vasotocin (dE-TVT), was studied after iv and intranasal administration in 11 subjects at 12 experiments each route. The plasma concentration of the analogue was analysed by means of an arginine vasopressin antibody, which cross-reacted with dE-TVT to 4.7%. When given intravenously as bolus injection (10 nmol/kg/body weight), the total body clearance amounted to 0.623 +/- 0.099 (SEM) l/h kg and the half-life to 16.2 +/- 2.4 min. After intranasal administration (100 nmol/kg/body weight), the bioavailability was 10.5 +/- 2.9%. Peak concentrations in plasma appeared 2-8 min after iv and 10-45 min after intranasal administration. At the end of an observation period of 2 h measurable amounts in plasma were still found in one of the iv and seven of the intranasal experiments. It is concluded that the moderately long half-life is suitable for the treatment of hospitalized patients in premature labour where promising results with intravenous infusion (50 micrograms/min) of dE-TVT have been obtained. It is still uncertain whether or not the absorption of dE-TVT is sufficient for intranasal administration to out-patients with uterine hyperactivity in late pregnancy and to patients with primary dysmenorrhoea, where significant relief of symptoms were seen after iv administration (10 micrograms/kg body weight).