Combination of the dopaminergic agent, phentermine, and the serotonergic agent, fenfluramine, in the treatment of cocaine dependence

Psychostimulant drugs for cocaine dependence

BACKGROUND

Cocaine dependence is a severe disorder for which no medication has been approved. Like opioids for heroin dependence, replacement therapy with psychostimulants could be an effective therapy for treatment.

OBJECTIVES

To assess the effects of psychostimulants for cocaine abuse and dependence. Specific outcomes include sustained cocaine abstinence and retention in treatment. We also studied the influence of type of drug and comorbid disorders on psychostimulant efficacy.

SEARCH METHODS

This is an update of the review previously published in 2010. For this updated review, we searched the Cochrane Drugs and Alcohol Group Trials Register, CENTRAL, MEDLINE, Embase and PsycINFO up to 15 February 2016. We handsearched references of obtained articles and consulted experts in the field.

SELECTION CRITERIA

We included randomised parallel group controlled clinical trials comparing the efficacy of a psychostimulant drug versus placebo.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 26 studies involving 2366 participants. The included studies assessed nine drugs: bupropion, dexamphetamine, lisdexamfetamine, methylphenidate, modafinil, mazindol, methamphetamine, mixed amphetamine salts and selegiline. We did not consider any study to be at low risk of bias for all domains included in the Cochrane 'Risk of bias' tool. Attrition bias was the most frequently suspected potential source of bias of the included studies. We found very low quality evidence that psychostimulants improved sustained cocaine abstinence (risk ratio (RR) 1.36, 95% confidence interval (CI) 1.05 to 1.77, P = 0.02), but they did not reduce cocaine use (standardised mean difference (SMD) 0.16, 95% CI -0.02 to 0.33) among participants who continued to use it. Furthermore, we found moderate quality evidence that psychostimulants did not improve retention in treatment (RR 1.00, 95% CI 0.93 to 1.06). The proportion of adverse event-induced dropouts and cardiovascular adverse event-induced dropouts was similar for psychostimulants and placebo (RD 0.00, 95% CI -0.01 to 0.01; RD 0.00, 95% CI -0.02 to 0.01, respectively). When we included the type of drug as a moderating variable, the proportion of patients achieving sustained cocaine abstinence was higher with bupropion and dexamphetamine than with placebo. Psychostimulants also appeared to increase the proportion of patients achieving sustained cocaine and heroin abstinence amongst methadone-maintained, dual heroin-cocaine addicts. Retention to treatment was low, though, so our results may be compromised by attrition bias. We found no evidence of publication bias.

AUTHORS' CONCLUSIONS

This review found mixed results. Psychostimulants improved cocaine abstinence compared to placebo in some analyses but did not improve treatment retention. Since treatment dropout was high, we cannot rule out the possibility that these results were influenced by attrition bias. Existing evidence does not clearly demonstrate the efficacy of any pharmacological treatment for cocaine dependence, but substitution treatment with psychostimulants appears promising and deserves further investigation.

Efficacy of psychostimulant drugs for cocaine dependence

BACKGROUND

Cocaine dependence is an increasingly prevalent disorder for which no medication is approved yet. Likewise opioid for heroin dependence, replacement therapy with psychostimulant could be efficacious for cocaine dependence.

OBJECTIVES

To ascertain the efficacy of psychostimulants for cocaine dependence on cocaine use, sustained cocaine abstinence and retention in treatment. The influence of type of drug, comorbid disorders and clinical trial reporting quality over psychostimulants efficacy has also been studied.

SEARCH STRATEGY

MEDLINE, EMBASE, PsycINFO, CENTRAL, references of obtained articles and experts in the field.

SELECTION CRITERIA

Randomized parallel group controlled clinical trials comparing the efficacy of a psychostimulant against placebo have been included.

DATA COLLECTION AND ANALYSIS

Two authors evaluated and extracted data. The Relative Risk (RR) was used to assess dichotomous outcomes except for adverse event (AE) induced dropouts for which the risk difference (RD) was preferred. The Standardized Mean Difference (SMD) was used to assess continuous outcomes. To determine the influence of moderating variables, a stratified analysis was conducted. Funnel plots were drawn to investigate the possibility of publication bias.

MAIN RESULTS

Sixteen studies have been included, which have enrolled 1,345 patients. Seven drugs with psychostimulant effect or metabolized to a psychostimulant have been investigated: bupropion, dexamphetamine, methylphenidate, modafinil, mazindol, methamphetamine and selegiline. Psychostimulants did not reduce cocaine use (SMD 0.11, 95%CI: -0.07 to 0.29), showed a statistical trend over improving sustained cocaine abstinence (RR 1.41, 95%CI: 0.98 to 2.02, p=0.07) and did not improve retention in treatment (RR 0.97, 95%CI: 0.89 to 1.05). The proportion of AE induced dropouts was similar for psychostimulants and placebo (RD 0.01, 95%CI: -0.02 to 0.03). When the type of drug was included as a moderating variable, it was shown that the proportion of patients achieving sustained cocaine abstinence was higher with bupropion and dextroamphetamine, and also with modafinil, at a statistical trend of significance, than with placebo. Nevertheless, no studied drug was efficacious on any of the remaining outcomes. Besides, psychostimulants appeared to increase the proportion of patients achieving sustained cocaine and heroin abstinence amongst methadone maintained dual heroin-cocaine addicts. The main findings did not seem to be influenced by clinical trial reporting quality. No evidence of publication bias was found.

AUTHORS' CONCLUSIONS

This review found mixed results, therefore evidence of the efficacy of psychostimulants for cocaine dependence is inconclusive. Nevertheless promising results exist for methadone maintained dual heroin-cocaine addicts and for some specific drugs such as dexamphetamine and bupropion.