Researchers at the National Addiction Centre in London identified 137 opiate addicts who were receiving detoxification as part of a 28-day inpatient treatment programme. Five patients died within 12 months after their discharge from the unit, three from a drug overdose within the first four months after discharge, and two unrelated to overdose.
To test whether loss of tolerance increased the risk of overdose, the team grouped the patients into three categories according to their opiate tolerance at the point of leaving treatment. Forty-three "still tolerant" patients who failed to complete detoxification; 57 "reduced tolerance" patients who prematurely left the treatment programme; and 37 "lost tolerance" patients who completed the treatment programme.
The three overdose deaths that occurred within four months after treatment were all from the "lost tolerance" group. The two deaths unrelated to overdose were one "lost tolerance" patient and one "reduced tolerance" patient. No deaths occurred in the "still tolerant" group. The five patients who died were all men and had generally stayed longer in the inpatient unit.
The clustering of the deaths from overdose in the patients who had successfully completed treatment is counterintuitive and illogical – unless it relates to loss of tolerance and consequent unpredictability of resumed heroin use, say the authors.
If these results are confirmed by further studies, they will need to be urgently addressed within existing inpatient, residential, and custodial and associated aftercare programmes, they conclude.