You give little by way of the facts here. However, basically in a suit for medical malpractice there must have been damages suffered as a result of negligence (specifically, the standard duty of care having being breached).Since your father overdosed there has been an injury and the fact that it happened on more than one medicaction would be consistant with a claim of negligence.At this point you should consult directly with a personal injury attorney who specializes in malpractice cases. They can best advise after going over all of the facts.