Heroin is an opioid painkiller and the 3,6-diacetyl ester of morphine. Heroin is prescribed as an analgesic, cough suppressant and as an antidiarrhoeal. It is also used as a recreational drug for its euphoric effects. Frequent and regular administration is associated with tolerance and physical dependence. In some countries it is available for prescription to long-term users as a form of opioid replacement therapy alongside counseling.