Gabapentin for Bipolar & Cannabis Use Disorders

Phase 2

Completed

Conditions: Bipolar II Disorder
Bipolar I Disorder
Substance Use Disorders
Cannabis Use Disorder

Interventions: Drug: Gabapentin
Drug: Placebo Oral Capsule

Registration Number: NCT03334721

Lead Sponsor: Medical University of South Carolina

Brief Summary: The proposed 2-week, double-blind, crossover, proof of concept study aims to measure and manipulate core neurochemical (i.e., dysregulated brain GABA/glutamate homeostasis) and neurobehavioral (i.e., elevated impulsivity) dysfunctions characteristic of individuals with cannabis use disorder (CUD) and Bipolar Disorder (BD), using a medication that has been shown to increase cortical GABA (i.e., gabapentin) levels in past research, and to evaluate medication-related changes in response inhibition (go no-go) and cannabis cue reactivity functional Magnetic Resonance Imaging tasks, as well as cannabis use, mood symptoms (including anxiety and sleep), and impulsivity in individuals with CUD+BD.

Detailed Description: Bipolar disorder (BD) is the Axis I condition most strongly associated with cannabis use disorder (CUD); there is a six-fold increase in the prevalence of CUD in individuals with BD relative to the general population. Individuals with co-occurring CUD and BD (CUD+BD) have substantially worse clinical outcomes than those with either BD or CUD alone. Response to mood stabilizing medications appears to be poor, yet little is known about optimal treatment for CUD+BD, as there have been no randomized medication trials for CUD+BD to date. Convergent evidence supports dysregulated brain γ-Aminobutyric acid (GABA)/glutamate homeostasis as a candidate target for pharmacological intervention in CUD+BD. Preclinical and clinical studies have demonstrated that CUD and BD are each associated with prefrontal GABA and glutamate disturbances and that impulsivity, a core neurobehavioral feature of both CUD and BD and a key Research Domain Criteria (RDoC) construct, is causally related to GABAergic/glutamatergic functioning. Gabapentin has been consistently shown in preclinical research to modulate GABA and glutamate transmission. In human Proton Magnetic Resonance Spectroscopy (1H-MRS) studies, both acute and chronic gabapentin dosing have been shown to increase brain GABA levels, however, few studies have investigated gabapentin effects on glutamate levels. Researchers propose that gabapentin may impact clinical outcomes in CUD+BD individuals both directly and indirectly through their impact on impulsivity.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 23

Inclusion Criteria

Meets DSM-V criteria for Bipolar Disorder
Meets DSM-V criteria for Cannabis Use Disorder
Using at least one mood stabilizing medication

Exclusion Criteria

Serious medical or non-inclusionary psychiatric disease
Concomitant use of benzodiazepine medications or any medications hazardous if taken with gabapentin
History of clinically significant brain injury
Presence of non-MRI safe material, or clinically significant claustrophobia.

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Gabapentin, Then Placebo Oral Capsule	Placebo Oral Capsule	Week 1: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (i.e., 1,200mg gabapentin) (Days 1-5), MRI (Day 5), and medication washout (Days 5-7). Week 2: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (Days 1-5), MRI (Day 5), and medication washout (Days 5-7).
Placebo Oral Capsule, Then Gabapentin	Placebo Oral Capsule	Week 1: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (Days 1-5), MRI (Day 5), and medication washout (Days 5-7). Week 2: 1-week condition will consist of an in-person study visit for assessment and dispensing of Gabapentin medication (Day 1), titration to maximum dose (i.e., 1,200mg gabapentin) (days 1-5), MRI (Day 5), and medication washout (Days 5-7).
Placebo Oral Capsule, Then Gabapentin	Gabapentin	Week 1: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (Days 1-5), MRI (Day 5), and medication washout (Days 5-7). Week 2: 1-week condition will consist of an in-person study visit for assessment and dispensing of Gabapentin medication (Day 1), titration to maximum dose (i.e., 1,200mg gabapentin) (days 1-5), MRI (Day 5), and medication washout (Days 5-7).
Gabapentin, Then Placebo Oral Capsule	Gabapentin	Week 1: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (i.e., 1,200mg gabapentin) (Days 1-5), MRI (Day 5), and medication washout (Days 5-7). Week 2: 1-week condition will consist of an in-person study visit for assessment and dispensing of medication (Day 1), titration to maximum dose (Days 1-5), MRI (Day 5), and medication washout (Days 5-7).

Primary Outcome Measures

Name	Time	Method
Prefrontal GABA Concentrations Through Proton Magnetic Resonance Spectroscopy	Day 5 of each experimental condition	Concentrations of GABA, normalized to water and corrected for CSF%, in dorsal anterior cingulate measured via Proton Magnetic Resonance Spectroscopy.

Secondary Outcome Measures