Changes in patterns of drug injection concurrent with a sustained reduction in the availability of heroin in Australia.

Between 1996 and 2000, heroin was the drug most frequently injected in Australia, and viable heroin markets existed in six of Australia's eight jurisdictions. In 2001, there was a dramatic and sustained reduction in the availability of heroin that was accompanied by a substantial increase in its price, and a 14% decline in the average purity of seizures analysed by forensic laboratories. The shortage of heroin constitutes a unique natural experiment within which to examine the impact of supply reduction. This paper reviews one important correlate of the shortage, namely changes in patterns of illicit drug injection. A number of studies have consistently suggested that between 2000 and 2001, there was a sizeable decrease in both prevalence and frequency of heroin injection among injecting drug users. These changes were accompanied by increased prevalence and frequency of stimulant injection. Cocaine was favoured in NSW, the sole jurisdiction in which a cocaine market was established prior to the heroin shortage; whereas methamphetamine predominated in other jurisdictions. Some data suggest that, at least in the short-term, some drug injectors left the market altogether subsequent to the reduced heroin availability. However, the findings that (1) some former heroin users switched their drug preference to a stimulant; and (2) subsequently attributed this change to the reduced availability of heroin, suggests that reducing the supply of one drug may serve to increase the use of others. Given the differential harms associated with the use of stimulants and opiates, this possibility has grave implications for Australia, where the intervention and treatment system is designed primarily to accommodate opiate use and dependence.