Measuring Outcome in the Treatment of Cocaine Dependence

Targeting white matter neuroprotection as a relapse prevention strategy for treatment of cocaine use disorder: Design of a mechanism-focused randomized clinical trial

Cocaine use continues to be a significant public health problem with limited treatment options and no approved pharmacotherapies. Cognitive-behavioral therapy (CBT) remains the mainstay treatment for preventing relapse, however, people with chronic cocaine use display cognitive impairments that are associated with poor response to CBT. Emerging evidence in animal and human studies suggests that the peroxisome proliferator-activated receptor-gamma (PPAR- γ) agonist, pioglitazone, improves white matter integrity that is essential for cognitive function. This project will determine whether adjunctive use of pioglitazone enhances the effect of CBT in preventing relapse during the early phase of recovery from cocaine use disorder. This paper describes the design of a mechanism-focused phase 2 randomized clinical trial that aims first to evaluate the effects of pioglitazone on targeted mechanisms related to white matter integrity, cognitive function, and cocaine craving; and second, to evaluate the extent to which improvements on target mechanisms predict CBT response. Positive results will support pioglitazone as a potential cognitive enhancing agent to advance to later stage medication development research.

Within-treatment frequency of use versus abstinence as a predictor of longitudinal post-treatment follow-up assessments of drug use

BACKGROUND

Abstinence is a widely-used endpoint in clinical trials of stimulant use disorders. A quantitative measure of frequency of use may be a more sensitive endpoint; however, it is important to establish that it is associated with post-treatment drug use. We examine and compare how within-treatment abstinence and frequency of use are related to two post-treatment longitudinal measures of drug use.

METHODS

For each of three existing stimulant use disorder clinical trial datasets, we examined the association between within-treatment frequency of use (based on urine screens), within-treatment abstinence, and post-treatment follow-up assessments of drug use (urine screens and reported days of use). In joint analyses that simultaneously model the effects of within-treatment abstinence and frequency of use, it is possible to discern their relative importance as predictors of post-treatment drug use during the 12 months following the end of treatment.

RESULTS

Results indicate a quantitative measure of within-treatment frequency of use was associated with longitudinal post-treatment follow-up assessments of drug use. Results from joint analyses of post-treatment follow-up drug use assessed by urine screens suggest that within-treatment frequency of use, rather than abstinence per se, is predictive of post-treatment drug use. However, results from joint analyses of self-report of days of use are equivocal.

CONCLUSION

Results lend support to the use of a quantitative measure of within-treatment drug use as an alternative to complete abstinence. They suggest that some within-treatment use that fall short of complete abstinence may potentially represent clinically important improvements given their association with post-treatment drug use.

Statistical considerations in the choice of endpoint for drug use disorder trials

BACKGROUND

To date, the US Food and Drug Administration (FDA) requires drug use disorder trials developing new medications to use abstinence, a clinically meaningful endpoint, as the primary outcome. Although abstinence is the gold standard, only a relatively small percentage of participants in drug use disorder trials ever achieve this endpoint. This has prompted clinical trialists to consider quantitative measures of frequency of use, recognizing that some reductions in drug use that fall short of complete abstinence may potentially represent clinically important improvements. While much of the discussion concerning alternative outcomes to abstinence has focused on their clinical relevance, there are important statistical considerations that should also be taken into account.

PURPOSE

In this paper, we demonstrate and highlight the degree to which use of a quantitative measure of frequency of use, relative to a binary measure of abstinence, yields a very discernible increase in statistical power for assessing efficacy or effectiveness of treatments for drug use disorders.

CONCLUSION

While it is well established that dichotomizing a quantitative measure invariably results in loss of statistical power, what is less well recognized is the degree of loss in the context of drug use disorder trials. In some cases, the required sample size must be almost doubled to achieve the same level of power.

Measures of outcome for stimulant trials: ACTTION recommendations and research agenda

BACKGROUND

The development and approval of an efficacious pharmacotherapy for stimulant use disorders has been limited by the lack of a meaningful indicator of treatment success, other than sustained abstinence.

METHODS

In March, 2015, a meeting sponsored by Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) was convened to discuss the current state of the evidence regarding meaningful outcome measures in clinical trials for stimulant use disorders. Attendees included members of academia, funding and regulatory agencies, pharmaceutical companies, and healthcare organizations. The goal was to establish a research agenda for the development of a meaningful outcome measure that may be used as an endpoint in clinical trials for stimulant use disorders.

RESULTS AND CONCLUSIONS

Based on guidelines for the selection of clinical trial endpoints, the lessons learned from prior addiction clinical trials, and the process that led to identification of a meaningful indicator of treatment success for alcohol use disorders, several recommendations for future research were generated. These include a focus on the validation of patient reported outcome measures of functioning, the exploration of patterns of stimulant abstinence that may be associated with physical and/or psychosocial benefits, the role of urine testing for validating self-reported measures of stimulant abstinence, and the operational definitions for reduction-based measures in terms of frequency rather than quantity of stimulant use. These recommendations may be useful for secondary analyses of clinical trial data, and in the design of future clinical trials that may help establish a meaningful indicator of treatment success.

Changes in health outcomes as a function of abstinence and reduction in illicit psychoactive drug use: a prospective study in primary care

AIMS

To test (1) whether abstinence and reduction in illicit psychoactive drug use were associated with changes in health outcomes in primary care patients and (2) whether these associations varied by drug type.

DESIGN

Secondary analysis of data from a randomized controlled trial that tested a brief intervention for drug use in primary care patients (589 enrolled, 574 completed a 6-month assessment). Analyses were conducted overall and stratified by the most commonly self-identified main drugs (marijuana, cocaine and opioids).

SETTING AND PARTICIPANTS

Patients who screened positive for illicit drug use at an urban primary care clinic in Boston, Massachusetts, USA.

MEASUREMENTS

Differences in past-month main drug use at baseline and 6-month outcome were categorized as continued or increased use, decreased use without abstinence and abstinence. Primary outcomes were 6-month changes in drug use consequences [Short Inventory of Problems scores (range 0-45)], depressive symptoms and health-related quality of life (HRQol).

FINDINGS

Abstinence was associated with a greater decrease in adverse drug use consequences than continued or increased use among the full sample and cocaine and opioids subgroups (adjusted means, full sample: -8.11 versus -0.05, P < 0.001; cocaine: -13.33 versus +1.09, P < 0.001, opioids; -16.84 versus -2.10, P < 0.001). Differences were not significant between those who decreased use compared with those who continued or increased use. There were no significant associations between drug use and depressive symptoms or HRQol. Neither abstinence nor decreased use was associated significantly with consequences in the marijuana subgroup.

CONCLUSIONS

Among primary care patients in the United States who use illicit psychoactive drugs, abstinence but not reduction in use without abstinence appears to be associated with decreased adverse drug use consequences.

A two-phased screening paradigm for evaluating candidate medications for cocaine cessation or relapse prevention: modafinil, levodopa-carbidopa, naltrexone

BACKGROUND

Cocaine pharmacotherapy trials are often confounded by considerable variability in baseline cocaine-use levels, obscuring possible medication efficacy. Testing the feasibility of using a prerandomization, abstinence-induction protocol, we screened three candidate medications to explore treatment response in patients who did, or did not, achieve abstinence during an extended baseline phase.

METHOD

Eligible treatment-seeking, cocaine-dependent subjects entered a 4-week baseline period (Phase I) with high-value abstinence contingent vouchers and two motivational interviewing sessions, followed by a 12-week medication trial (Phase II) with random assignment stratified on Phase I abstinence status to (1) modafinil (400mg/d), (2) levodopa/carbidopa (800/200mg/d), (3) naltrexone (50mg/d), or (4) placebo. Treatment consisted of thrice-weekly clinic visits for urine benzoylecgonine testing and weekly cognitive behavioral therapy with contingency management targeting medication compliance.

RESULTS

Of the 118 subjects enrolled, 81 (80%) completed Phase I, with 33 (41%) achieving abstinence, defined a priori as 6 consecutive cocaine-negative urines. Tests of the interaction of each medication (active versus placebo) by baseline status (abstinent versus nonabstinent) permitted moderator effect analysis. Overall, baseline abstinence predicted better outcome. Cocaine-use outcomes for levodopa and naltrexone treatment differed as a function of Phase I abstinence status, with both medications producing benefit in nonabstinent but not baseline-abstinent subjects. There was no evidence of a moderator effect for modafinil.

CONCLUSIONS

The two-phase screening trial demonstrated that subgrouping of patients with respect to baseline abstinence status is feasible and clinically useful for exploring cocaine cessation and relapse-prevention effects of candidate medications.