Failure of Daily Injections of Ketamine HCI to Adversely Alter Menstrual Cycle Length, Blood Estrogen, and Progesterone Levels in the Rhesus Monkey

Abstract

Adult female rhesus monkeys were studied to determine effects of daily administration of ketamine hydrochloride (8-10 mg/kg) upon menstrual cycle length, incidence of ovulatory menstrual cycles and blood estrogen and progesterone levels throughout the cycle. In physically restrained control monkeys (25 cycles subjected to daily blood sampling) there were 14 of 25 or 56% ovulatory cycles, and in ketamine-treated monkeys (32 menstrual cycles subjected to daily blood sampling) there were 28 of 32 or 88% ovulatory cycles. Length of the menstrual cycle was the same in both groups. The levels and time course of peripheral serum estrogen and progesterone levels were the same in the ovulatory cycles of both groups. In some of the control cycles (30%) and in some of the ketamine-treated cycles (25%), there were luteal phases in which preovulatory estrogen levels were normal and in which luteal-phase progesterone levels were low and variable 6-8 days after the preovulatory surge. Daily use of ketamine HCl did not significantly alter menstrual cycle length or serum estrogen or progesterone levels throughout the menstrual cycle. It reduced the incidence of anovulatory cycles and premature menstrual induction probably by reducing the stress of restraining the monkey for the purpose of taking a blood sample.