Manipulation of duration of action of a synthetic prostaglandin analogue (TPT) assessed in the pregnant beagle bitch.

Beagle bitches were treated on days 20-22 of pregnancy with TPT as an aqueous solution administered subcutaneously via a minipump at a rate of 10 micrograms per hour for either 24 (I) or 48 hours (II). Additional animals received a single subcutaneous injection of 200 micrograms of TPT as an aqueous solution (III) or dissolved in polyethylene glycol 400 (IV) or the methyl ester of TPT dissolved in polyethylene glycol 400 (V). The duration of action was assessed by the nadir in circulating progesterone levels. By this criterion the duration of action in the different groups ranked I=III<II=IV<V, the nadir occurring at 2, 3 and 3-4 days post treatment, respectively. Duration of action correlated with the incidence of abortion. Salivation, emesis and diarrhea or hypothermia side effects, previously noted for this agent, were not affected by the manipulations of duration of action.