Adverse cardiovascular effects of oxytetracycline preparations and vehicles in intact awake calves.

Comparisons were made of cardiovascular effects in intact, awake, previously instrumented calves given the following oxytetracycline (OXY) preparations and components: polyvinylpyrrolidine vehicle (PVP), OXY HCl in PVP (OXY-PVP), OXY HCl (USP) in saline solution, propylene glycol, 77.8% (PG), propylene glycol vehicle (PGV), and OXY HCl in PGV (OXY-PGV). The 3 preparations containing PG caused significant increases in pulmonary arterial pressures and significant decreases in cardiac output and stroke volume. Aortic pressures were significantly decreased, as were heart rates. Both pulmonic and systemic resistances were significantly increased. There were no direct effects measured on left ventricular contractility. The aqueous OXY caused no significant changes. The PVP preparation and vehicle caused no changes in pulmonary pressures, pulmonary resistance, cardiac output, or stroke volume. Significant increases were observed in aortic pressure, heart rate, and systemic resistance. Left ventricular contractility was not changed. Seemingly, the PG-induced changes were a result of histamine release which did not appear to be dependent on prior sensitization of the calves.