Efficacy of M640 in Acute Lumbosacral Musculoskeletal Conditions.

May 8, 2026 updated by: Primus Pharmaceuticals

Efficacy of Modified Release Metaxalone 640 mg in Acute Lumbosacral Musculoskeletal Conditions With Spinal Stenosis and Sciatica

The goal of this clinical trial is to learn if a modification to metaxalone 640 mg can reduce low back and leg pain. The participants will be 18 to 80 years old, healthy with newly occurring back or leg pain. The main question aims to compare a group taking active treatment and a group taking a look-alike substance containing no active treatment. All participants will answer questions on Day 1, before treatment, and on 7-day after treatment, about:

  • Amount and quality of pain
  • Interference with physical activity
  • Interference with sleep

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Double-blind, randomized, placebo-controlled, multi-center study of metaxalone 640 mg plus standard of care for patients with acute lumbo sacral musculoskeletal conditions with spinal stenosis and sciatica. Participants will be randomized 1:1. Following the initial pilot-study a second study will randomize a larger population of patients with appropriate power.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Alabama
      • Auburn, Alabama, United States, 36830
        • Active, not recruiting
        • East Alabama Arthritis Center
    • California
      • Valley Village, California, United States, 91607
        • Active, not recruiting
        • Sean Wollaston, MD
    • Florida
      • Aventura, Florida, United States, 33180
        • Active, not recruiting
        • Arthritis and Osteoporosis Center
      • Boca Raton, Florida, United States, 33431
        • Active, not recruiting
        • William Sunshine, MD
      • Clearwater, Florida, United States, 33765
      • Coral Springs, Florida, United States, 33065
      • Jupiter, Florida, United States, 33458
        • Active, not recruiting
        • 4. Palm Beach Rheumatology and Wellness
      • Loxahatchee Groves, Florida, United States, 33458
        • Active, not recruiting
        • Family Arthritis Center
      • Margate, Florida, United States, 33063
        • Active, not recruiting
        • Arthritis and Rheumatology Center of South Florida
      • Miami, Florida, United States, 33180
        • Recruiting
        • Arthritis and Osteoporosis Treatment and ResearchCenter
        • Contact:
      • Miami Beach, Florida, United States, 33140
      • Oldsmar, Florida, United States, 34677
      • South Miami, Florida, United States, 33143
        • Active, not recruiting
        • Arthritis and Rheumatic Care Center
    • Georgia
      • Stockbridge, Georgia, United States, 30281
        • Active, not recruiting
        • Arthritis Research and Treatment Center
    • Michigan
      • Sterling Heights, Michigan, United States, 48310
    • New Mexico
      • Clovis, New Mexico, United States, 88101
        • Active, not recruiting
        • Jayashree Sinha, MD 1
    • North Carolina
      • Fayetteville, North Carolina, United States, 28304
        • Active, not recruiting
        • Carolina Rheumatology
    • Ohio
      • Springboro, Ohio, United States, 45066
        • Active, not recruiting
        • Ohio Arthritis and Osteoporosis Center of Southwest Ohio
    • Tennessee
      • Crossville, Tennessee, United States, 38555
    • Texas
      • Colleyville, Texas, United States, 76034
      • Harlingen, Texas, United States, 78550
        • Active, not recruiting
        • Integrative Rheumatology of South Texas
      • Mesquite, Texas, United States, 75150
        • Active, not recruiting
        • Southwest Research Group
      • Red Oak, Texas, United States, 75154
        • Active, not recruiting
        • DFW Rheumatology
    • Virginia
      • Annandale, Virginia, United States, 22003
        • Active, not recruiting
        • Northern Virginia Center for Arthritis

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • No clinically significant conditions impacting quality or quantity of pain
  • Baseline Numeric Pain Scale ≥ 6
  • Capable of answering text or email survey reminders
  • Low back pain with or without sciatica

Exclusion Criteria:

  • Current use of other skeletal relaxants
  • Current use of other pain relievers
  • Current use of cimetidine or monoamine oxidase inhibitors

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Active M640
Metaxalone micronized 640 mg over encapsulated tablet Taken orally every 6 hours for 7 days
Drug: Metaxalone 640 mg Oral Tablet
Metaxalone 640 mg used for the treatment of discomforts associated with acute, musculoskeletal pain.
Other Names:
  • Skelaxin un-micronized
  • M640
  • metaxalone micronized
Placebo Comparator: Placebo
Inactive placebo capsule 640 mg Taken orally every 6 hours for 7 days
Drug: Metaxalone 640 mg Oral Tablet
Metaxalone 640 mg used for the treatment of discomforts associated with acute, musculoskeletal pain.
Other Names:
  • Skelaxin un-micronized
  • M640
  • metaxalone micronized

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change of Numeric Pain Scale
Time Frame: Day 1 to Day 7
Change from Baseline in low back pain and leg pain as measured by the Numeric Pain Rating Scale (NPRS) at Day 7
Day 1 to Day 7

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Primus Pharmaceuticals

Collaborators

Illumination Health

Investigators

  • Study Director: S Sodhi, Illumination Health

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

November 15, 2023

Primary Completion (Estimated)

November 15, 2026

Study Completion (Estimated)

November 15, 2026

Study Registration Dates

First Submitted

November 27, 2023

First Submitted That Met QC Criteria

November 27, 2023

First Posted (Actual)

December 5, 2023

Study Record Updates

Last Update Posted (Actual)

May 12, 2026

Last Update Submitted That Met QC Criteria

May 8, 2026

Last Verified

August 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PMMSS-01

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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