indication

Used in the treatment of acute pain, myocardial infarction, acute pulmonary oedema, and chronic pain.

pharmacology

The onset of heroin's effects is dependent on the method of administration. Taken orally, heroin is totally metabolized in vivo into morphine before crossing the blood-brain barrier; so the effects are the same as oral morphine. Take by injection, heroin crosses into the brain. Once in the brain, heroin is rapidly metabolized into morphine by removal of the acetyl groups, therefore, it is known as a prodrug. It is the morphine molecule that then binds with opioid receptors and produces the subjective effects of the heroin high.

mechanism of action

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).

biotransformation

Hepatic.

absorption

Bioavailability is less than 35%.

half life

2-3 hours

route of elimination

90% renal as glucuronides, rest biliary