Prostin E2 (Dinoprostone Vaginal) - Description and Clinical Pharmacology

DESCRIPTION

PROSTIN E2 Vaginal Suppository, an oxytocic, contains dinoprostone as the naturally occurring prostaglandin E2 (PGE2).

Its chemical name is (5Z,11α,13E,15S)-11,15-Dihydroxy-9-oxo-prosta-5,13-dien-1-oic acid and the structural formula is represented below:

The molecular formula is C₂₀H₃₂O₅. The molecular weight of dinoprostone is 352.5. Dinoprostone occurs as a white crystalline powder. It has a melting point within the range of 64° to 71°C. Dinoprostone is soluble in ethanol and in 25% ethanol in water. It is soluble in water to the extent of 130 mg/100 mL.

Each suppository contains 20 mg of dinoprostone in a mixture of glycerides of fatty acids.

CLINICAL PHARMACOLOGY

PROSTIN E2 Vaginal Suppository administered intravaginally stimulates the myometrium of the gravid uterus to contract in a manner that is similar to the contractions seen in the term uterus during labor. Whether or not this action results from a direct effect of dinoprostone on the myometrium has not been determined with certainty at this time. Nonetheless, the myometrial contractions induced by the vaginal administration of dinoprostone are sufficient to produce evacuation of the products of conception from the uterus in the majority of cases.

Dinoprostone is also capable of stimulating the smooth muscle of the gastrointestinal tract of man. This activity may be responsible for the vomiting and/or diarrhea that is not uncommon when dinoprostone is used to terminate pregnancy.

In laboratory animals, and also in man, large doses of dinoprostone can lower blood pressure, probably as a consequence of its effect on the smooth muscle of the vascular system. With the doses of dinoprostone used for terminating pregnancy this effect has not been clinically significant. In laboratory animals, and also in man, dinoprostone can elevate body temperature. With the clinical doses of dinoprostone used for the termination of pregnancy some patients do exhibit temperature increases.