The present study was carried out in 2 successive phases. In the first, 91 inpatients admitted for opioid dependence were evaluated. All were treated with α2-agonists during the withdrawal period. Shortly after admission, a urine sample was taken and analyzed (EMIT and GC/MS). The presence of the cocaine metabolite benzoilecgonine in urine was a predictor of dropout probability during hospitalization (P < 0.01). A second study on a sample of 612 inpatients later admitted for similar reasons was carried out according to a simpler protocol (using only EMIT) in order to replicate the previous results. Again, the presence of benzoilecgonine in urine indicated dropout probability (P = 0.00004). Thus, the use of cocaine prior to admission for a treatment of opiate withdrawal syndrome with α2-agonists seems to predict therapeutic failure.
