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 arginine have been shown to increase fatal oxygen availability when administered to pregnant ewes. 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) on the pregnant dam when administered during pregnancy. This study 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. SC was given as a subcutaneous injection (150 mg/d), also split over three time periods to the SC and AA + SC groups. 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.