Risky Decision Making in Methamphetamine Users: The Role of Opioid Blockade
The purpose of this protocol is to learn more about impulsive decision making in people who use methamphetamines. The investigators would like to know if a medication called naltrexone changes how people make decisions. The investigators would also like to know whether changes in decision making can be observed by MRI (magnetic resonance imaging).
|Study Design:||Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Caregiver, Investigator)
|Official Title:||Risky Decision Making in Methamphetamine Users: The Role of Opioid Blockade|
- Discounting Tasks [ Time Frame: 28 days ] [ Designated as safety issue: No ]Delay Discounting economic task that asks subjects to choose between an immediate reward and a second reward that varies in delay until receipt. Probes the neural mechanism of the effect of endogenous opioid blockade on impulsive choice in MA users.
- Neural Mapping [ Time Frame: 28 days ] [ Designated as safety issue: No ]We expect to identify a map of regions for each component of delay discounting: delay magnitude, reward magnitude and choice. Our preliminary assignment of delay sensitivity to middle frontal gyrus may reflect magnitude sensitivity. This would suggest that discounting (calculation of the value of a delayed reward) is a separate cognitive function from representation of the magnitude of the alternative reward. We expect increased ventrolateral prefrontal and ventral striatal activity with increased immediate reward magnitude in the overall group. We expect increased medial prefrontal activity to scale with decreased delay magnitude, and for dorsal regions (inferior parietal lobule, insula, and dorsolateral prefrontal cortex) to exhibit more activity in Decision trials than No Decision trials.
- Methamphetamine use [ Time Frame: 28 days ] [ Designated as safety issue: No ]Any methamphetamine use in the 28 days since injection of study drug or placebo, by self report and urine drug screen.
- HIV risk behaviors [ Time Frame: 28 days ] [ Designated as safety issue: No ]Unprotected sex or sharing of needles/works in the 28 days since injection of study drug or placebo.
- Antiretroviral adherence [ Time Frame: 28 days ] [ Designated as safety issue: No ]Any missed doses of antiretroviral medications in 28 days since injection of study drug or placebo, by self-report.
|Study Start Date:||May 2013|
|Estimated Study Completion Date:||January 2015|
|Estimated Primary Completion Date:||January 2015 (Final data collection date for primary outcome measure)|
Experimental: Extended release naltrexone
One dose of intramuscular injection of 380mg extended-release naltrexone.
Drug: Extended release naltrexone
Other Name: Vivitrol
Placebo Comparator: Placebo
One dose of intramuscular injection of placebo.
We propose a randomized placebo-controlled study of the effect of endogenous opioid blockade with extended release naltrexone (XR-NTX) on delay discounting and its neural substrate in methamphetamine (MA) users. Recently abstinent MA users recruited from the community and addiction treatment centers in Portland, Oregon will be assessed with fMRI (functional magnetic resonance imaging), delay discounting tasks, drug use, and HIV risk behaviors at baseline and 28-days following randomization.
AIM 1: Determine the neural basis of impulsive choice in MA users. This aim will identify brain regions that can be used to characterize the neural basis for impulsive choice in the proposed study sample. We will extend results of previous studies and our preliminary data to assess specific brain regions whose activity scales with magnitude of reward, length of delay and the act of making a decision. Aim 1 is essential for developing neural predictors hypothesized in Aim 2 to be more sensitive to and predictive of a clinical response to XR-NTX than behavioral measures alone.
Hypothesis 1.1: We hypothesize that activity (a) in ventral striatum (VS) and ventrolateral prefrontal cortex (VLPFC) will scale with magnitude of reward, (b) in anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC) with length of delay and (c) in anterior insula and the inferior parietal lobule (IPL) with the process of making a decision.
AIM 2: Assess the effect of endogenous opioid blockade on impulsivity and its neural substrate. We will build on Aim 1 findings to assess how endogenous opioid blockade with XR-NTX affects cortical decision-making.
Hypothesis 2.1: Subjects randomized to XR-NTX will show decreased impulsivity (preference for immediate rewards) from baseline compared to those randomized to placebo. Hypothesis 2.2: Subjects with the greatest decrements in impulsivity will exhibit decreased cerebral response to reward magnitude in VS and VLPFC and decreased response to length of delay in ACC and DLPFC. These effects will be more pronounced in the XR-NTX group.
AIM 3 (Exploratory): Examine the effect of endogenous opioid blockade on the association between risky behaviors and activity of the neural substrates of impulsive choice.
Hypothesis 3.1: Subjects with brain regions demonstrating robust responses to NTX will demonstrate the greatest decreases in MA use and HIV risk behaviors (e.g., unprotected sex, needle sharing).
AIM 4 (Exploratory): Assess the effect of endogenous opioid blockade on impulsivity and its neural substrate in HIV-infected methamphetamine users. Pending supplemental funding, we will enroll an additional 10 HIV-infected subjects who meet other inclusion and exclusion criteria to demonstrate the feasibility of conducting proposed study procedures in HIV-infected subjects.
|Contact: Sarann Bielavitz, BSemail@example.com|
|United States, Oregon|
|Oregon Health & Science University||Recruiting|
|Portland, Oregon, United States, 97239|
|Principal Investigator: Philip T Korthuis, MD, MPH|
|Portland VA Medical Center||Recruiting|
|Portland, Oregon, United States, 97239|
|Sub-Investigator: Willliam Hoffman, PhD, MD|
|Principal Investigator:||Philip T Korthuis, MD, MPH||Oregon Health and Science University|