Effect of labetalol on intracranial pressure in dogs with and without intracranial hypertension.

Intracranial pressure measurements and ventricular volume pressure response curves were made during induced hypotension with labetalol, a combined alpha- and beta-adrenoceptor antagonist, in dogs without (group I) and with (group II) intracranial hypertension. The administration of 600 mg labetalol resulted in a percentage decrease of mean systemic arterial blood pressure (MAP) of 27% (+/- 10%) in group I, and 32% (+/- 9%) in group II from control values without changes in intracranial pressure and the ventricular volume pressure response curve. Larger decreases in MAP were not possible, even with a dose 3 times that clinically recommended. Labetalol may be a safe hypotensive agent to supplement neurolept analgesia, but it is not the drug of choice to induce deliberate hypotension.