Rationale: The role of dopamine in cocaine abuse has been long recognized. Cocaine use can profoundly alter dopaminergic functioning through depletion of this monoamine and changes in receptor functioning. Based on these facts, levodopa (L-dopa) pharmacotherapy may be helpful in reducing or abolishing cocaine use. Objective: The current studies sought to evaluate the safety, tolerability and efficacy of L-dopa as a treatment for cocaine dependence. Methods: In Study 1, 67 cocaine-dependent subjects were randomized in a 5-week, double-blind, placebo-controlled safety trial. Subjects received either placebo, or 400 mg L-dopa plus 100 mg of the peripheral decarboxylase inhibitor, carbidopa, in a sustained-release preparation (Sinemet CR®). In Study 2, 122 cocaine-dependent subjects were enrolled in a 9-week, randomized, double-blind, placebo-controlled trial to compare placebo to 400/100 mg and 800/200 mg L-dopa/carbidopa treatments. Placebo or L-dopa were administered twice daily in both studies. Results: L-dopa was well tolerated with similar retention and medication adherence rates compared to placebo. Only two side effects occurred more often in L-dopa-treated patients: nausea and dizziness. L-dopa lowered diastolic blood pressure in a dose-dependent fashion. In these trials, L-dopa had no effect on cocaine use, cocaine craving, or mood. Conclusion: These two studies demonstrate the safety and tolerability of L-dopa pharmacotherapy in cocaine-dependent patients. No evidence for greater efficacy of L-dopa compared to placebo was observed. The possibility of enhancing treatment effects by combining L-dopa with other behavioral or pharmacological interventions is discussed.
Bibliographical noteFunding Information:
The first author is supported by National Institute of Drug Abuse (NIDA) grant K01-DA-019446. This research was supported by the NIDA grants R01-DA-6143 and P50-DA-9262. The current studies were presented at the annual meeting of the College of Problems on Drug Dependence in 2004 by Howard Rhoades, Ph.D. ( Rhoades et al., 2004 ). The authors wish to thank Peter B. Silverman Ph.D., J.D. for his important early contributions to our examination of L-dopa/carbidopa as a candidate medication for the treatment of cocaine dependence. We express particular appreciation to Shelly Sayre, Clayton Dreyer, Patricia Hokanson, and Howard Rhoades for their contributions to the conduct of these trials. We are indebted to the participants for taking part in these studies.
- Side effects