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.
Dinoprost tromethamine is the tromethamine (THAM) salt of the naturally occurring prostaglandin F2alpha. Prostaglandin F2alpha 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.
Enzymatic dehydrogenation primarily in the maternal lungs and also in the liver.
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.