Immediate haemodynamic and metabolic effects of intravenous labetalol in the exercising forearm.

Dynamic forearm exercise was performed in healthy subjects before and after intravenous labetalol, 1 mg/kg body weight. Labetalol produced a sustained fall in arterial blood pressure. Forearm blood flow decreased by 17.2% partly due to the reduced driving pressure and partly due to an increased vascular resistance. Forearm oxygen uptake decreased by 14.6%, suggesting an increased mechanical efficiency. Lactate release from the exercising forearm decreased by 17.6%. Forearm uptake of glucose and free fatty acids remained unchanged.