Can primary dysmenorrhea be alleviated by a vasopressin antagonist? Results of a pilot study

In order to study the etiological role of vasopressin in primary dysmenorrhea the therapeutic effect of an antagonist of vasopressin action on the uterus (1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-oxytocin) was investigated in 14 patients with moderate to severe symptoms. The women participated in the study at two menstruations and each time one intravenous bolus injection of the analogue (10 micrograms/kg body weight) and one of the placebo (saline) were given, randomized and double-blind with at least a 2 hour interval. The effect was monitored by overall ratings and by pain diagrams described by the patients. In the former parameter the vasopressin antagonist was significantly more effective (p less than 0.01). In the pain diagrams, however, a significant reduction of symptoms occurred both after the analogue administrations and after placebo given as second injection. The results support a causative role of vasopressin in primary dysmenorrhea, but further studies with higher doses and/or other routes of administration or delivery systems are required in order to delineate the therapeutic value of vasopressin antagonists in the condition.