Risks

Risks of non-medical use

* For intravenous users of heroin (and any other substance), the use of non-sterile needles and syringes and other related equipment leads to several serious risks:
o the risk of contracting blood-borne pathogens such as HIV and hepatitis
o the risk of contracting bacterial or fungal endocarditis and possibly venous sclerosis
o abscesses
* Poisoning from contaminants added to “cut” or dilute heroin
* Chronic constipation
* Addiction and increasing tolerance
* Physical dependence can result from prolonged use of all opioids, resulting in withdrawal symptoms on cessation of use
* Decreased kidney function (although it is not currently known if this is due to adulterants used in the cut)[23]

Many countries and local governments have begun funding programs that supply sterile needles to people who inject illegal drugs in an attempt to reduce these contingent risks and especially the contraction and spread of blood-borne diseases. The Drug Policy Alliance reports that up to 75% of new AIDS cases among women and children are directly or indirectly a consequence of drug use by injection. But despite the immediate public health benefit of needle exchanges, some see such programs as tacit acceptance of illicit drug use. The United States federal government does not operate needle exchanges, although some state and local governments do support needle exchange programs.

A heroin overdose is usually treated with an opioid antagonist, such as naloxone (Narcan), or naltrexone, which has high affinity for opioid receptors but does not activate them. This reverses the effects of heroin and other opioid agonists and causes an immediate return of consciousness and the beginning of withdrawal symptoms when administered intravenously. The half-life of naloxone is much shorter than that of most opioid agonists, so that antagonist typically has to be administered multiple times until the opiate has been metabolized by the body.

Depending on drug interactions and numerous other factors, death from overdose can take anywhere from several minutes to several hours due to anoxia because the breathing reflex is suppressed by µ-opioids. An overdose is immediately reversible with an opioid antagonist injection. Heroin overdoses can occur due to an unexpected increase in the dose or purity or due to diminished opiate tolerance. However, many fatalities reported as overdoses are probably caused by interactions with other depressant drugs like alcohol or benzodiazepines.[24] It should also be noted that since heroin can cause nausea and vomiting, a significant number of deaths attributed to heroin overdose are caused by aspiration of vomitus by an unconscious victim.

The LD50 for a physically addicted person is prohibitively high,[citation needed] to the point that there is no medical consensus on where to place it. In fact, there is no upper limit to the amount of tolerance that can occur in a heavy user. Several studies done in the 1920s gave users doses of 1,600–1,800 mg of heroin, and no adverse effects were reported. Even for a non-user, the LD50 can be placed above 350 mg[citation needed] though some sources give a figure of between 75 and 375 mg for a 75 kg person.[25]

Street heroin is of widely varying and unpredictable purity. This means that the user may prepare what they consider to be a moderate dose while actually taking far more than intended. Also, tolerance typically decreases after a period of abstinence. If this occurs and the user takes a dose comparable to their previous use, the user may experience drug effects that are much greater than expected, potentially resulting in a dangerous overdose.

It has been speculated that an unknown portion of heroin related deaths are the result of an overdose or allergic reaction to quinine, which may sometimes be used as a cutting agent.[26]

A final factor contributing to overdoses is place conditioning. Heroin use is a highly ritualized behavior. While the mechanism has yet to be clearly elucidated, longtime heroin users display increased tolerance to the drug in locations where they have repeatedly administered heroin. When the user injects in a different location, this environment-conditioned tolerance does not occur, resulting in a greater drug effect. The user’s typical dose of the drug, in the face of decreased tolerance, becomes far too high and can be toxic, leading to overdose.[27]

A small percentage of heroin smokers and occasionally IV users may develop symptoms of toxic leukoencephalopathy. The cause has yet to be identified, but one speculation is that the disorder is caused by an uncommon adulterant that is only active when heated.[28][29][30] Symptoms include slurred speech and difficulty walking.

http://en.wikipedia.org/wiki/Heroin#Usage_and_effects