The Vampire (1957)

Dr. Matthew Campbell has been experimenting on methods to regress the mind to primitive instincts so that we can find methods to improve our brains and not get taken in by cheap horror movie hogwash. He's developed a drug made from vampire bat blood and has begun treating himself with it. But instead of improving his mind, he's become ill and addicted.

He dies, but not before trying to warn fellow doctor Paul Beecher. Fortunately for us, he dies before he can say more than that pills are to blame. While still at Campbell's house, Paul finds a bottle of pills and pockets them. He's also got another bottle of pills in his other pocket that he takes for frequent migraine attacks. He goes home, puts his jacket on a rack, and then he's struck with a migraine. He asks his daughter to give him the pills in his jacket pocket, and of course she gives him the pills of evil. He is instantly addicted and he must take one pill every day. Each time he takes a pill he turns into a hairy and very insane killer, and he doesn't remember what he's done, except as a vague dream. Can the police and the other scientists who work nearby figure out who the killer is and stop him before he kills the beauteous new nurse that he has just hired?