A legal defense used by manufacturers of drugs and medical devices which grants them immunity from strict products liability for design defects or “failure to warn” if they properly warned the physician who prescribed the treatment or medical intervention. The physician is considered the “learned intermediary”. The manufacturer’s duty to warn the patient is relieved if the physician was properly warned. The theory of this defense is that prescription drugs and devices are by their nature dangerous, but the value to society outweighs the danger so manufacturers must be protected from suit. This protection will serve as an incentive to do more research in the medical field and introduce new devices and drugs for the good of society. There are three recognized exceptions: vaccines, birth control pills and intrauterine devices. In these areas the manufacturer has a duty to directly warn the ultimate users of the products.