A narcotic is any substance that induces an anesthetizing effect on the nervous system. In medicine, it is primarily used for its analgesic effect and is used in controlled doses. Some of the well known narcotics are extremely harmful when taken randomly, including opium, morphine, and heroin. These substances can be very unsafe, and overdoses without proper medical prescription and guidance can sometimes cause death. Federal and state laws are very strict regarding usage of these drugs, particularly heroin.