How can we reduce heroin 'overdose' deaths?

The toxicological data from the study of Zador and colleagues in this issue of the Journal suggest that heroin "overdose" is a misnomer. In only a minority of cases was morphine (the metabolite of heroin) the only drug detected at autopsy, and in a third of cases blood morphine levels were below the level usually regarded as toxic for opioid-naive individuals. More typically, morphine was found in combination with intoxicating levels of alcohol or other central nervous system depressants, such as benzodiazepines. These data are consistent with the findings of other studies of fatal overdoses^1,4,5 and with what heroin users have reported about their use of alcohol and other drugs at the time of their most recent non-fatal overdoses.^1,2,6

Opioid overdoses are not confined to inexperienced drug users.² A recent survey of 329 Sydney heroin users, for example, found that non-fatal opioid "overdoses" are common among experienced users.^2,3 Two-thirds of these 30-year-old users had experienced an average of three non-fatal overdoses during their 10 years of heroin use. A third had been given naloxone, and four out of five had been present when someone else had "overdosed".^2,3

Contrary to media and drug-user folklore, fatal heroin "overdoses" are probably only rarely a consequence of unexpectedly high purity. Variations in purity can cause overdoses, but they appear to be a minor factor in fatal overdoses. Moreover, the fact that four out of five heroin users had been present when someone else had overdosed^2,3 suggests that individuals in a group using the same batch of street heroin commonly experience overdose.

A first priority for prevention must be to reduce the frequency of drug overdoses. We should inform heroin users about the risks of combining heroin with alcohol and other depressant drugs. Not all users will act on such information, but if there are similar behavioural changes to those that occurred with needle-sharing⁷ overdose deaths could be substantially reduced. Heroin users should also be discouraged from injecting alone and thereby denying themselves assistance in the event of an overdose.

It has recently been suggested that supervised injectable heroin maintenance programs may also reduce opioid overdose deaths. This argument has been used in favour of the proposed trial of injectable heroin maintenance in the Australian Capital Territory, with media stories suggesting that providing heroin under medical supervision will reduce overdose deaths allegedly caused by uncertainty about the purity of heroin.¹⁰ This is one of the least cogent reasons for a "heroin trial", because it exaggerates the contribution of heroin purity to drug overdose, and ignores the role of concurrent alcohol and other drug use.

Media misconstructions of the aims of the "heroin trial" also create unrealistic expectations of its outcome. Even if heroin maintenance reduces opioid overdoses, the proposed trial is unlikely to detect such a reduction because only 40 heroin users will be involved in its first phase. As these users will be recruited from the ACT methadone program, their risks of opioid overdose will be small, and hence it will be extremely difficult to detect any reduction in risk. Even in the larger trial proposed in the second phase, the number of heroin users would be too small a fraction of the population of heroin users to have a detectable effect on overall opioid mortality.

A second priority for prevention is to reduce the number of fatal overdoses by improving heroin users' responses to the overdoses of their peers. Heroin users could be taught simple cardiopulmonary resuscitation skills so that they can keep comatose users alive until help arrives. Users also need to be encouraged to call an ambulance earlier than they do at present.³ Their understandable fears of police involvement need to be addressed, and relations between ambulance officers and heroin users need to be improved. A serious analysis should also be made of the benefits and costs of distributing the opiate antagonist naloxone to high risk heroin users so that they can reverse the opioid contribution to drug overdoses.¹¹

Peer-based health education programs and the increased availability of clean needles and syringes appear to have maintained low rates of HIV infection among Australian injecting drug users.⁶ The public health challenge is to ensure that information about the causes of heroin "overdose" is acted upon so that drug overdose deaths can be reduced.

Wayne D Hall
Director, National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW

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