Effects of administration of sildenafil citrate and amino acids on selected physiological, blood gas and biochemical parameters in pregnant twin-bearing sheep in late gestation.

Sildenafil citrate (SC) and specific amino acids such as arginine have been shown to increase fetal oxygen availability when administered individually to pregnant ewes, however, the effects of both compounds in combination are not well known. It is therefore important to understand the physiological effects of combining SC with amino acids (AA) in the pregnant ewe when administered during pregnancy. This preliminary study, which was designed as a safety trial, investigated physiological, blood gas and biochemical parameters in twin-bearing ewes when SC and arginine were supplemented in an AA blend. During late gestation, 32 twin-bearing Merino ewes were allocated to one of four groups: control, AA blend, SC and AA blend + SC (AA + SC). The AA blend was intravenously administered over three infusion periods, daily, to the AA and AA + SC groups. The SC and AA + SC groups were given SC as a subcutaneous injection (150 mg/d), also split over three time periods. Reverse osmosis water and saline were used as controls within treatments. Blood ketone and glucose levels were monitored daily, and heart rate (bpm), respiration rate (bpm), rectal temperature ( °C) and venous blood gases were measured at 0, 2, 6 and 10 d of treatment. Average parameters did not measure outside of normal reported ranges for sheep and no adverse effects were observed, indicating the safety of arginine in an AA blend in combination with sildenafil citrate to twin bearing ewes. It is important to be aware of the potential effects of administration of arginine and sildenafil citrate combined, in various dosage rates, for future studies.