Beyond Bedlam (1994)

Dr. Stephanie Lyell works for Neurological Research, and is testing a seemingly safe personality-altering drug on Marc Gilmour a notorious Serial Killer. But when a pair of bizarre suicides occur at Dr. Lyell's apartment complex, Homicide Detective Terry Hamilton connects the mysterious deaths to the drug's diabolical side effects on Gilmour. Only after they too begin to experience horrible dreams and hallucinations do Terry and Stephanie realize they are trapped in Gilmour's nightmarish world, from which there is no hope of escape.