Aim: To evaluate whether effective methadone treatment affects cocaine use.

Methods: Four hundred twenty-one consecutive patients admitted to a methadone maintenance clinic in Israel (1993-2002) were prospectively studied. Patients' urine samples were analyzed for cocaine during months 1 and 13.

Results: On admission 55(13.1%) of 421 patients had urine positive for cocaine and 366 had negative. Of the 55 cocaine-positive patients, 45(81.8%) stayed in treatment at least one year, as did 267(73%) cocaine-negative. After one year (n = 312) 31 of 45 cocaine users stopped and 25 of 267 started. Methadone dose was highest in 31 patients who stopped cocaine (176.1 ± 42.1 mg/ day), followed by 14 who did not stop (161.4 ± 37.5 mg/day), and 25 who started during treatment (122.9 ± 48.7 mg/day), or 242 who never used cocaine (119.5 ± 48.4 mg/day) (ANOVA, F = 15.6, p < 0.0005).

Conclusions: High methadone dose may reduce cocaine use in patients addicted to both heroin and cocaine.