Providing free heroin to addicts participating in research - ethical concerns and the question of voluntariness.

Providing heroin to people with heroin addiction taking part in medical trials assessing the effectiveness of the drug as a treatment alternative breaches ethical research standards, some ethicists maintain. Heroin addicts, they say, are unable to consent voluntarily to taking part in these trials. Other ethicists disagree. In our view, both sides of the debate have an inadequate understanding of 'voluntariness'. In this article we therefore offer a fuller definition of the concept, one which allows for a more flexible, case-to-case approach in which some heroin addicts are considered capable of consenting voluntarily, others not. An advantage of this approach, it is argued, is that it provides a safety net to minimise the risk of inflicting harm on trial participants.