Contingency Management Treatment in Cocaine Using Methadone Patients with and without Concurrent Marijuana Use

Methadone maintenance (MM) reduces opioid use, but it has limited impact on cocaine use. Contingency management (CM) is efficacious for reducing cocaine use, but many of these patients also use marijuana, which may affect outcomes.

In five clinical trials, 507 MM patients were randomized to 12 weeks of standard MM or the same plus CM for cocaine abstinence. Patients were  M age = 39.0, 52% female, 53% Caucasian, 29% African American, and 18% other/multiracial.

We assessed marijuana use via Timeline Followback at baseline and up to weekly during treatment.  Overall, 26% of patients reported any use of marijuana pre-treatment and during it. Cocaine outcomes included longest duration of objective abstinence (LDA) during treatment and negative cocaine urine toxicology sample at the 6-month follow-up.

An ANCOVA evaluated effects of pre- and during-treatment marijuana use, treatment condition, and the interaction of treatment condition and pre-treatment marijuana use on LDA while controlling for baseline cocaine toxicology and study. A cocaine positive toxicology result at baseline, self-reported marijuana use during treatment, and standard care assignment were significantly associated with shorter LDA,  F (6,502)=35.2,  p  < .01 ,  η 2 =0.33.

A logistic regression evaluated odds of cocaine abstinence at the 6-month follow-up. Step 1 included pre-treatment marijuana use and study,  χ  25 = 29.5,  p  < .01. Step 2 included treatment condition, LDA, during treatment marijuana use, and the interaction of treatment condition and pre-treatment marijuana use,  χ  29 = 131.8,  p <.01. Greater LDA and no pre-treatment marijuana use was associated with likelihood of submitting a cocaine-negative sample. The interaction of pre-treatment marijuana use and treatment condition was also significant, Wald  χ  2 = 6.24,  p <.01. Patients who were using marijuana pre-treatment had increased odds of cocaine abstinence at follow-up if they were assigned to CM, but not if they received standard care alone. 

During treatment marijuana use was significantly related to shorter durations of sustained abstinence from cocaine throughout the 12 weeks of the study. In addition, pre-treatment marijuana use was associated with decreased odds of a cocaine-negative urine toxicology sample at follow-up, but adding CM improved outcomes in these polysubstance use patients.