• Metabolism: Hepatic. Route of Elimination: 90% renal as glucuronides, rest biliary Half Life: <10 minutes
• Uses/Sources: Used in the treatment of acute pain, myocardial infarction, acute pulmonary oedema, and chronic pain.
• Route of Exposure: Bioavailability is less than 35%.

Heroin is a mu-opioid agonist. It acts on endogenous mu-opioid receptors that are spread in discrete packets throughout the brain, spinal cord and gut in almost all mammals. Heroin, along with other opioids, are agonists to four endogenous neurotransmitters. They are beta-endorphin, dynorphin, leu-enkephalin, and met-enkephalin. The body responds to heroin in the brain by reducing (and sometimes stopping) production of the endogenous opioids when heroin is present. Endorphins are regularly released in the brain and nerves, attenuating pain. Their other functions are still obscure, but are probably related to the effects produced by heroin besides analgesia (antitussin, anti-diarrheal).