Heroin or diacetylmorphine is a strong analgesic (commonly known as pain killer medicine, as they are used in treatment of pain) medication. In the United Kingdom and other countries (such as Netherlands) where heroin is available legally with proper prescription by appropriate physician, the drug is administered by intramuscular, subcutaneous, intravenous or intrathecal (directly into cerebrospinal fluid or CSF in the spinal cord) route.
The medical use of heroin is in acute pain conditions such as due to severe physical trauma/injury, post surgical pain, myocardial infarction (commonly known as heart attack) and chronic painful conditions such as cancer pains of end stage cancer (which are very severe and can not be managed by conventional pain medications), pain of some terminal illnesses. Heroin is used in severe painful conditions, which can not be treated (pain reduction) with conventional pain killers such as NSAIDs (non steroidal anti inflammatory drugs) or other pain medications. In countries where heroin is not available legally, morphine is used in those conditions mentioned above.