Effects of chronic heroin

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As with most illegal drugs, the chronic use of heroin possesses both long-term and short-term effects. Whether injected, snorted or smoked, heroin will begin to affect the body's central nervous system almost immediately after it is used. This report aims to analyse these effects of chronic heroin use and the concept of building up tolerance to heroin with reduced effectiveness of the drug.


Heroin, or diacetylmorphine is also commonly referred to as diamorphine, it is a semi-synthetic opioid drug synthesized from morphine, a derivative of the Asian opium poppy plant (NIDA, 2009). It is the 3,6-diacetyl ester of morphine (di (two)-acetyl-morphine). The white crystalline form is commonly the hydrochloride salt diacetylmorphine hydrochloride, though often adulterated thus dulling the sheen and consistency from that to a matte white powder, which however heroin freebase typically is.

As with other opioids, heroin is used as both a pain-killer and a recreational drug and has an extremely high potential for abuse. Frequent and regular administration is associated with tolerance, moderate physical dependence, and severe psychological dependence which develops into addiction.

According to Kreet et al (2005) opiates are drugs derived from the resin or sap of the opium poppy, which include "morphine, codeine, their congeners (e.g., heroin and oxycodone), and other semi-synthetic derivatives of the-baine". These opium-derived drugs are branded as opioids or narcotic analgesics. Opioids consist of all agonist drugs, which possess morphine-like properties, whether they are naturally occurring or synthetic (made).

Other drugs in the opioid class include pethidine and methadone, which are synthetically manufactured. Heroin is a central nervous system depressant, which means it slows down the workings of the brain and spinal cord. It is mixed or 'cut' with other substances, such as glucose, to boost profits. This means the user has no idea if the dose will be strong or weak. Heroin usually takes the form of granules or powder, and can be white, pink or brown. It is usually injected intravenously, but some users snort or smoke it instead. Common slang terms for heroin include 'smack', 'horse' and 'hammer'.

Dependent heroin users are characterised by the persistence of use in spite of the difficulties they experience with health, law, social achievements and personal relationships (Ferri et al, 2003).


Heroin (diacetylmorphine) is rapidly hydrolysed to 6-monoacetylmorphine which in turn is hydrolysed to morphine following intravenous administration in humans (Goodman & Gilman, 1991). The blood concentration of morphine, the metabolite of heroin, depends on route of administration, drug dose, body weight, time elapsed since the last dose and individual pharmacokinetics (Aderjan et al, 1995). Heroin is mainly excreted in the urine as free and conjugated morphine.

Cardinal signs of heroin toxicity include reduced level of consciousness from drowsiness or a stuporous state to coma, pinpoint pupils and a depressed respiratory rate. Cyanosis, hypotension, bradycardia, hypothermia may also be present. Death is usually due to respiratory failure (Goodman & Gilman, 1991).



Central nervous system:

  • Drowsiness
  • Disorientation
  • Delirium


  • Analgesia
  • Tolerance
  • Addiction (Physical Dependence)


  • Addiction (Psychological Dependence)
  • Anxiolysis
  • Confusion
  • Euphoria
  • Somnolence


People who are physically dependent on heroin usually develop tolerance to the drug, making it necessary to take more and more to get the desired effects. Eventually, a dose plateau is reached, at which no amount of the drug is sufficient. When this level is achieved, the person may continue to use heroin, but largely for the purpose of delaying withdrawal symptoms




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