The natural history of amphetamine misuse

Sir: Though Moselhy et al (Psychiatric Bulletin, February 2002, 26, 61-62) describe a reluctance by some services to make use of amphetamine substitution therapy, across the UK as a whole there is a large number of individuals who are receiving it. The fact that it is yet to be subjected to a randomised controlled trial is therefore of some concern.

With more substantial evidence lacking, there is a danger that amphetamine substitution will be regarded as entirely analogous to methadone substitution. This would be erroneous. Long-term prescribing of methadone can be justified, and has been shown to be effective, because heroin dependence has the quality of a long-term relapsing illness. Unfortunately, little is known about the natural history of amphetamine use, and users may be much better able to make changes without the help of a prescription.

An analysis of 156 amphetamine and heroin users who presented for treatment in Cornwall on more than one occasion over 7 years, showed that amphetamine users were more likely to switch both their main drug and their main route of use between presentations (details available from the author upon request). Taken together with the fact that cohorts of amphetamine users in the UK have been found to be younger than comparable heroin users, this would imply that amphetamine users are less likely to experience long-term patterns of problematic use over many years. If this is the case, long-term prescribing may do more harm than good.