Gemeprost

Gemeprost (16, 16-dimethyl-trans-delta² PGE1 methyl ester) is a prostaglandin E1 analogue. Both in pregnant and non-pregnant animals, it causes contraction of the uterus and causes softening and decreases resistance of cervical tissue. Gemeprost depresses placental and uterine blood flow but those actions are secondary to the main uterine stimulation. In women, gemeprost is an effective cervical dilator in the first trimester in pregnancy, gemeprost is also effective at terminating pregnancy in the second trimester of gestation.

In pregnant women, although plasma levels of both the active drug and the main metabolite (de-esterified gemeprost) are very low, gemeprost induces cervical softening within three hours of insertion. Between 12 and 28% of the vaginal dose is eventually absorbed into the circulation, and 50% of this is excreted in the urine. The unabsorbed dose is largely recovered from the genital area, either washed out in the urine or from pads used to absorb postoperative blood loss.

No drug related toxicity has been observed in rodents given 6 times the therapeutic dose (3.2mmol Kg-1 daily) for up to 26 weeks.

In cynomolgus monkeys subcutaneous administration of doses up to 40 times the human therapeutic dose for 1 month caused effects such as muscular tremor, excessive salivation, poorly formed faeces and mild local reactions at injection sites.

No teratogenic effects observed in either rats or rabbits receiving intra vaginal doses 10 to 40 times the human therapeutic dose.

No mutagenic effects have been observed.