Antagonist-precipitated heroin withdrawal under anaesthetic prior to maintenance naltrexone treatment: determinants of withdrawal severity

This study sought to characterize antagonist-precipitated heroin withdrawal during and immediately following anaesthesia and to identify the determinants of withdrawal severity and duration in 48 dependent heroin users. Objective withdrawal signs decreased significantly with each naloxone bolus administered under anaesthetic. The cost (amount) of the final heroin administration and the number of hours between last heroin use and commencement of anaesthesia were significant, independent predictors of the severity of withdrawal symptomatology. While 83% (40/48) of participants completed withdrawal according to objective criteria and commenced maintenance naltrexone treatment, almost half (22/48) were unable to commence naltrexone on the day of the procedure due to residual withdrawal signs. Fourteen of these 22 participants subsequently commenced naltrexone (median number of days between admission and commencement of naltrexone was 2, range 1 - 6) while eight left treatment prior to initiation of naltrexone. Significantly fewer of those with more severe withdrawal signs during anaesthesia commenced naltrexone (40% vs. 60%). While the severity and duration of withdrawal symptomatology may be moderated by encouraging participants to reduce (or cease) heroin use close to the time of withdrawal, for a substantial proportion of participants in this study, heroin withdrawal by this antagonist-precipitated procedure was neither rapid nor painless.