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Interaction of CYP2B6 Genotype and Efavirenz With Methadone and Tizanidine PK

NCT05789173 · Status: RECRUITING · Phase: EARLY_PHASE1 · Type: INTERVENTIONAL · Enrollment: 60

Last updated 2026-02-12

No results posted yet for this study

Summary

The main goal of this clinical study is to test how CYP2B6 genetic variations and efavirenz (cornerstone in HIV-1 therapy) dictate the disposition (PK) of CYP2B6 substrate (methadone) and PK and effect (PD) of CYP1A2 substrate (tizanidine). Specifically, the investigators will test whether efavirenz produces CYP2B6 genotype dependent unanticipated DDIs with CYP2B6 (methadone) and CYP1A2 (tizanidine), leading to lack of efficacy or increased toxicity. Healthy volunteers genotyped for CYP2B6\*6 and \*18 alleles will be grouped in to three genotype predicted phenotype groups: 20 normal metabolizer (NM) (CYP2B6\*1/\*1); 20 intermediate metabolizer (IM) (\*1/\*6, or \*1/\*18); and 20 poor metabolizer (PM) (\*6/\*6, \*6/\*18 or \*18/\*18). Each phenotype group will receive methadone and tizanidine (separated by a washout period) on two occasions: at baseline (control) and after treatment with efavirenz (600 mg/day for 17 days).

Conditions

  • Drug-Drug Interaction

Interventions

DRUG

Methadone and Tizanidine

Each CYP2B6 genotype predicted phenotypes will receive methadone (10 mg) and tizanidine (4 mg) by mouth at baseline (control)

DRUG

Efavirenz, Methadone and Tizanidine

Each CYP2B6 genotype predicted phenotypes will receive methadone (10 mg) and tizanidine (4 mg) by mouth after pretreatment with efavirenz (600 mg PO for 16 days)

Sponsors & Collaborators

  • National Institute of General Medical Sciences (NIGMS)

    collaborator NIH

  • Indiana University

    lead OTHER

Study Design

Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Model
SEQUENTIAL

Eligibility

Min Age
18 Years
Max Age
65 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2023-10-06
Primary Completion
2026-04-15
Completion
2026-04-15
FDA Drug
Yes

Countries

  • United States

Study Locations

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Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT05789173 on ClinicalTrials.gov