Hemodynamic effects of long term feeding of sympathomimetic amines to swine

The hemodynamic effects of long term feeding of sympathomimetic amines (SPMA) to swine were studied. Three groups of female swine (N = 20 for each group) were fed either aminorex fumarate, d-amphetamine sulfate, or dextrose (control) for as long as 8 months in dosages up to 15 mg/kg/day. After 4 months of this feeding regiment, the weight gain of the pigs fed either aminorex or amphetamine was significantly less than the control animals. Hemodynamic measurements on awake swine indicated no elevation of pulmonary arterial blood pressure in the pigs fed SPMA. Measurement of systemic hemodynamics revealed that cardiac index was lower in the treated pigs than in control animals, but that heart rate and systemic arterial blood pressure were not altered by the drugs. In addition to baseline measurements of hemodynamic variables, the animals were exposed to acute hypoxia (12 percent O2 in N2) for 5 minutes. Although pulmonary arterial blood pressure increased similarly in the 3 groups of pigs, total pulmonary resistance increased to a greater extent in the pigs fed SPMA, indicating perhaps an enhancement of the hypoxic pulmonary pressor response after chronic ingestion of either amphetamine or aminorex. In a limited number of pigs, SPMA were fed for a period of 8 months, of which the last 3 months were during pregnancy. Hemodynamic measurements on sedated (metomidate, IV) swine revealed no difference in pulmonary arterial blood pressures between treated and control animals. We conclude that chronic ingestion of large doses of aminorex or amphetamine in swine does not lead to pulmonary arterial hypertension, but that slight reductions in cardiac output and subtle alterations in the pulmonary pressor response to acute hypoxia may occur.