9-deoxy-9-methylene-16,16-dimethyl Prostaglandin E2 (Meteneprost) is a potent analog of prostaglandin E2 (PGE2) with an extended half-life in vivo. In combination with various other prostaglandin derivatives, it results in the termination of first trimester pregnancy in monkeys. A single intramuscular injection containing 0.5 mg of meteneprost and 7.5 mg of 17-phenyl trinor PGF1α is very effective in terminating early pregnancy.¹ This prostaglandin mixture is ineffective on monkeys in their third trimester of pregnancy.¹ Meteneprost, when compared to PGE2 and PGF1α, in monkey and rat, does not result in unwanted side effects such as fever or gastrointestinal problems.^1,2