Includes heroin, methadone, Diconal, morphine, dipapanone, pethidine, codeine, Distalgesic (dextropropoxyphene), Temgesic (buprenorphine). Also known as smack, junk, H, skag, dikes (for Diconal), amps (injectable ampoules).

Opiates are drugs made from the opium poppy. Opium is the dried 'milk' of the poppy. It contains morphine and codeine, both effective painkillers and from morphine it is not difficult to produce heroin. In pure form heroin is a white powder and twice as strong as morphine. A number of man–made opioids are also manufactured as painkillers, such as methadone, Morphine Sulfate and Oxymorphone Numorphon. They can be injected, smoked or sniffed.

When taken, opiates depress the nervous system and have a euphoric effect. Many people report a feeling of drowsiness, warmth, well–being and contentment. These pleasurable feelings are associated with the fact that opiates induce relaxed detachment from the impact of pain and anxiety and from desires for food and sex etc, yet at the same time as the person remains fully aware.

Injection of opiates into the veins intensifies these effects and makes them almost instantaneous, producing a short–lived burst of pleasurable sensation (`rush'). Injection under the skin or into the muscle gives a slower and more intense effect than intravenous injection. When smoked, the effects of heroin can be expected to come on about as quickly as intravenous injection, but to be much less intense as the available dose is used over a period of time rather than injected all at once.

Tolerance develops to opiates so that someone in search of frequently repeated euphoria must increase the dose and/or change their method of administration. However, there comes a point when no further increase in dose can restore the positive effects of the drug and it is taken just to feel `normal'.

Intravenous injection maximises the effects of a given amount of heroin and produces a much more intense immediate experience, so as tolerance develops (and perhaps as money runs short) there may be a tendency to move from sniffing or smoking heroin to injection.

Since (unlike barbiturates) tolerance also develops to the respiratory depressant effects of opiates, gradual escalation of dose does not in itself lead to risk of death through overdose. However, fatal overdoses can happen when opiate users take their usual dose after a break during which tolerance has faded.

After as little as several weeks on high and frequent doses, sudden withdrawal results in a variable degree of discomfort generally comparable to a bout of flu. The effects start 8 to 24 hours after the last `fix' and include aches, tremor, sweating and chills, sneezing and yawning, muscular spasms. They generally fade in seven to ten days but feelings of weakness, loss of well–being and sleep disturbance can last for several months. Abrupt opiate withdrawal is rarely life threatening and is considerably less dangerous than withdrawal from alcohol or barbiturates.

Physical dependence is not as significant as the strong psychological dependence developed by some long–term users. Dependence of any kind is not inevitable and some people use heroin on an occasional basis. The physiological effects of long–term opiate use are rarely serious in themselves. They include respiratory complaints, constipation and irregular periods. At higher doses chronic sedation can occur, but at lower doses users can function normally.

However the consequences of injecting opiates and of a drug–using lifestyle can be serious. Among regular injectors, there is commonly physical damage associated with poor hygiene and the injection of contaminants. Contaminants contribute to respiratory disease, skin lesions, tetanus (with injection under the skin) and other complications depending on the agent used and the individual's sensitivity. Decreased appetite and apathy can contribute to disease caused by poor nutrition, self–neglect and bad housing. Repeated heroin sniffing may damage structures in the nose.

On the other hand, because opiates in themselves are relatively safe drugs, addicts in receipt of opiates on prescription and who maintain a stable, hygienic lifestyle can be virtually indistinguishable from non–drug users, and suffer no serious physical damage. However as opiates are the most commonly injected drugs of misuse in Britain, those users who do inject face a high risk of becoming infected with HIV if they share needles.

Methadone is a form of opiate usually supplied on prescription to addicts as an alternative to injecting. It is usually taken as a liquid, although it is available in ampules. In order to withdraw from opiate use addicts may gradually reduce their dose of methadone over a long period of time in order to reduce physical and psychological dependence on the drug. Opiate use during pregnancy may result in smaller babies, who suffer severe withdrawal symptoms after birth.