Effects of procainamide and chloramphenicol on acute vasospasm.

The basilar artery of the dog was exposed through the clivus and made spastic by puncture or by topical application of 5% barium chloride. Injections of procainamide or chloramphenicol into the vertebral artery or into a peripheral vein had no discernable effect on the acute vasospasm. Topical application of 0.1% to 10% concentrations of either of these drugs effected definite vasodilation, with the extent and rapidity of vasodilation increasing with increasing concentrations. Lesser concentrations were ineffective.