indication

Used for aborting second-trimester pregnancy (between the twelfth to eighteenth week of gestation) and in incomplete abortion or for therapeutic abortion in cases of intrauterine fetal death and congenital abnormalities incompatible with life. Also used at low-doses for medically indicated induction of labor at term. Also injected intra-arterially for use as a vasodilator to assist in angiography.

pharmacology

Dinoprost tromethamine is the tromethamine (THAM) salt of the naturally occurring prostaglandin F2_alpha. Prostaglandin F2_alpha has several pharmacologic effects on the female reproductive system, including stimulation of myometrial activity, relaxation of the cervix, inhibition of steroidogenesis by corpora lutea, and can potentially lyse corpora lutea.

mechanism of action

Dinoprost tromethamine appears to act directly on the myometrium, but this has not been completely established. Dinoprost stimulates myometrial contractions (via its interaction with the prostaglandin receptors) in the gravid uterus that are similar to the contractions that occur in the term uterus during labor. These contractions are usually sufficient to cause abortion. Uterine response to prostaglandins increases gradually throughout pregnancy. Dinoprost also facilitates cervical dilatation and softening.

toxicity

Although overdose by intra-amniotic administration of dinoprost has not been reported, exaggeration of the nausea, vomiting, and diarrhea that occur with normal doses would be expected.

biotransformation

Enzymatic dehydrogenation primarily in the maternal lungs and also in the liver.

absorption

Slowly absorbed from the amniotic fluid into systemic circulation.

half life

The half-life of dinoprost in amniotic fluid is 3 to 6 hours. The plasma half-life of dinoprost after intravenous administration is reported to be less than 1 minute.