Cocaine dependence is a major public health problem; an effective primary treatment for cocaine dependent individuals has yet to be found. The purpose of this study is to examine the effectiveness of levodopa and carbidopa in treating cocaine dependent individuals. In addition, this study will examine the effects of incentive rewards for treatment compliance.

Cocaine is a strong central nervous system stimulant that is widely abused throughout the United States. Due to its widespread use, it is important to develop an effective treatment for cocaine dependence. Levodopa is a medication that is used alone or in combination with carbidopa to treat Parkinson's disease. The purpose of this study is to determine the possible interactions between behavioral interventions and carbidopa/levodopa in order to treat cocaine dependent individuals.

This study will last 12 weeks and will involve two phases. The first phase will include three therapy conditions: 1) clinical management only, 2) clinical management and relapse prevention therapy, and 3) clinical management, relapse prevention therapy, and contingency management. All of the conditions in the first phase will be evaluated incrementally under active and placebo conditions while participants receive carbidopa/levodopa.

The second phase of the study will examine the contingency management procedure applications. Each of the three contingency management procedure applications targets specific behaviors that, when reinforced, may interact with carbidopa/levodopa to produce clinical benefits. Participants will receive relapse prevention therapy combined with a contingency management procedure that targets clinic attendance, medication compliance, and cocaine abstinence. Study visits will occur weekly throughout the study. In addition, participants will complete a one-year follow-up visit.

Inclusion Criteria:

• Meets DSM-IV criteria for current cocaine dependence
• Provides at least one positive urine test for cocaine during study screening
• Good general health, based on a physical exam, lab tests, and an electrocardiogram
• Reads and writes English at a sixth grade level

Exclusion Criteria:

• Current Axis I depressive, psychotic, or anxiety disorder
• Currently in jail
• Pregnant or breastfeeding
• Requires certain medications