Pain perception of intravenous heroin users on maintenance therapy with levomethadone.

Methadone is a very potent analgesic drug. Accordingly, maintenance therapy of heroin addicts with methadone may conceal pain producing processes. Here we report on the pain perception of 42 patients on a levomethadone maintenance treatment for intravenous heroin users. Pain perception was measured by single-blind, non-invasive pressure stimulation of the nociceptors located in the dorsal extension aponeurosis and the underlying periosteum of the middle phalanx of a digit before and respectively 1,2, and 4 hours after oral routine drug administration. Measures were related to the individual levomethadone plasma levels. Under steady-state conditions, the pain perception of the patients did not differ from a drug-free placebo control group and was not related to individual levomethadone plasma levels, although an analgesic effect in the reabsorption phase was observed. It is concluded that the individual pain perception of maintained patients is adapted to a normal response range and that even prolonged opioid consumption does not diminish dynamic analgesic responsiveness to levomethadone.