Chlorzoxazone

Evidence Level: L5

Predicted Indications: 8

Chlorzoxazone

Pharmacist Assessment Report

Chlorzoxazone: From Musculoskeletal Conditions to Migraine Disorder

One-Sentence Summary

Chlorzoxazone is a centrally acting skeletal muscle relaxant, marketed in India as a single-ingredient product (the license records list no approved indication text). The TxGNN model predicts it may be effective for migraine disorder, but no clinical trials and only 3 indirect publications (two reviews on vertigo and cerebellar disorders and one mouse study) are linked to this prediction. This is a model-only prediction with very weak supporting evidence.

Quick Overview

Item	Content
Original Indication	Not stated in the Indian license records (chlorzoxazone is generally known as a muscle relaxant for musculoskeletal pain and spasm)
Predicted New Indication	Migraine disorder
TxGNN Prediction Score	0.9973
Evidence Level	L5
India Market Status	Listed in a compiled Indian medicine price dataset (at least 20) – CDSCO approval status is not included in this data
Number of Listed Products	at least 20
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available from the data compiled for this report. Based on known information, chlorzoxazone is a centrally acting muscle relaxant that also activates Ca²⁺-dependent K⁺ channels (SK/IK/BK).

The one mechanistic thread is a preclinical study (PMID 23115190). In mice carrying a CACNA1A mutation that enhances CaV2.1 currents, Ca²⁺-dependent K⁺-channel activators relieved cerebellar ataxia. CACNA1A mutations are also linked to familial hemiplegic migraine, so a plausible but indirect connection exists. The scores come from the TxGNN model (deep learning) and may reflect similarities the model learned between related diseases (such as migraine with brainstem aura), not biological evidence.

This link has clear limits. The ataxia study is in mice and does not test migraine. The other two papers are reviews of vertigo and cerebellar disorders and do not address migraine treatment. No data in migraine patients were provided.

Other predictions were also reviewed, and none is better supported:

Rheumatoid arthritis (score 0.9905, L4, “Research Question”): the only other prediction with clinical-type literature, but it is limited to symptomatic pain and spasm relief.
The remaining predictions (nephrogenic syndrome of inappropriate antidiuresis, pulmonary hypertension, atrophoderma vermiculata, ulerythema ophryogenesis, kyphoscoliotic heart disease): no trials or literature were supplied.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
27083881	2016	Review	J Neurol	Overview of drug treatment for cerebellar and central vestibular disorders (e.g., 4-aminopyridine for downbeat nystagmus); does not address migraine therapy
24000301	2013	Review	Dtsch Arztebl Int	Treatment and natural course of peripheral and central vertigo; vestibular migraine accounts for about 11.4% of cases
23115190	2012	Preclinical (mouse)	J Neurosci	Ca²⁺-dependent K⁺-channel activators relieved ataxia caused by enhanced CaV2.1 currents in Cacna1a(S218L) mutant mice; this gene is also linked to hemiplegic migraine

None of these papers evaluates chlorzoxazone in migraine patients.

India Market Information

Twenty valid single-ingredient registrations are on file. The first five are listed below; no approved indication text is recorded for any of them.

Authorization Number	Product Name	Dosage Form	Approved Indication
65210	Dicron-MR Tablet	Strip of 10 tablets	Not recorded
71722	Difquick MR 250mg/50mg/325mg Tablet	Strip of 10 tablets	Not recorded
204842	Stalogesic Forte 250mg/50mg/325mg Tablet	Strip of 10 tablets	Not recorded
70543	Demofen MR 250mg/50mg/325mg Tablet	Strip of 10 tablets	Not recorded
111667	Inflacure MR 500mg/50mg/500mg Tablet	Strip of 10 tablets	Not recorded

All products are oral tablets. The strengths in several product names (for example 250mg/50mg/325mg) suggest fixed-dose combination products, even though they are classified as single-ingredient in the records.

Safety Considerations

Contraindication signals from the knowledge graph (not label text): liver failure, liver disease, gallbladder disease, substance abuse/dependence, drug-induced liver injury, paracetamol poisoning.
Drug interactions: 72 interactions were identified. The main ones:
- Major: morphine, liposomal morphine
- Moderate: dronabinol, nabilone, metoclopramide, naltrexone, opium, sibutramine, ethanol, promethazine
- Several others (for example warfarin, metformin, omeprazole) have an unclassified severity level.
Overdose: a case report (PMID 19606800) describes methemoglobinemia after a multi-drug overdose that included chlorzoxazone. The drug’s own contribution cannot be separated from the other agents taken.

Package insert warnings and contraindications were not available. Please refer to the package insert for complete safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: The prediction rests on a high model score and a single indirect preclinical link (K⁺-channel activation in a CaV2.1 mouse model). No clinical trials or migraine-specific studies exist in the data compiled for this report. The liver-related contraindication signals and the sedative interactions with opioids and alcohol also call for caution.

To proceed, the following is needed:

Package insert warnings and contraindications from Indian regulatory sources (a blocking gap for safety screening)
Mechanism of action data from DrugBank
A targeted literature search for chlorzoxazone in migraine and tension-type headache, and preclinical testing of K⁺-channel activation in migraine models
Confirmation of the original approved indications in India
If preclinical results are supportive, a small exploratory clinical study with hepatic monitoring
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.