Chlorzoxazone

證據等級: L5

預測適應症: 10 個

Chlorzoxazone: From Skeletal Muscle Spasm to Migraine Disorder

One-Sentence Summary

Chlorzoxazone is a centrally-acting skeletal muscle relaxant traditionally used for relief of discomfort associated with acute painful musculoskeletal conditions. The TxGNN model predicts it may be effective for Migraine Disorder, with 0 clinical trials and 3 publications currently supporting this direction.

Quick Overview

Item	Content
Original Indication	Skeletal muscle spasm and musculoskeletal pain (centrally-acting muscle relaxant; no India registration on record)
Predicted New Indication	Migraine Disorder
TxGNN Prediction Score	99.73%
Evidence Level	L4
India Market Status	✗ Not Marketed
Number of Registrations	0
Recommended Decision	Hold

Why Is This Prediction Reasonable?

Detailed mechanism of action data from DrugBank is currently unavailable (data gap pending resolution). However, based on existing pharmacological literature, chlorzoxazone is recognised as a BK channel (KCa1.1/KCNMA1) activator in addition to its classical central muscle relaxant properties. This ion-channel activity provides the key mechanistic bridge to migraine biology.

The biological rationale centres on the CACNA1A gene, which encodes the CaV2.1 voltage-gated calcium channel. Gain-of-function mutations in this gene are responsible for both Familial Hemiplegic Migraine Type 1 (FHM1) and spinocerebellar ataxia type 6 (SCA6), establishing CaV2.1 hyperactivation as a shared pathological basis across these neurological disorders. An animal study (PMID 23115190) demonstrated that BK channel activation can counteract neuronal hyperexcitability caused by enhanced CaV2.1 currents in Purkinje cells of CACNA1A-mutant mice — providing an indirect but biologically plausible mechanistic rationale for chlorzoxazone’s potential relevance in migraine.

It is important to note that this inference remains at the preclinical and theoretical level. The three supporting publications are reviews and one animal study focused on vestibular/cerebellar disorders that share pathological pathways with migraine, rather than directly evaluating chlorzoxazone as a migraine treatment. No clinical trials have been conducted. The prediction is mechanistically credible but is not yet supported by direct efficacy evidence.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
23115190	2012	Animal/Experimental Study	The Journal of Neuroscience	Core mechanistic evidence: BK channel (Ca²⁺-dependent K⁺ channel) activation alleviates cerebellar ataxia driven by enhanced CaV2.1 currents in CACNA1A (S218L) mutant mice — directly supports BK channel activation as a strategy against CaV2.1 hyperactivity that also underlies FHM1
27083881	2016	Narrative Review	Journal of Neurology	Overview of pharmacotherapy for central vestibular and cerebellar syndromes; highlights that ion channel modulators (potassium channel blockers/activators) are effective in disorders driven by aberrant neuronal firing — contextually relevant to migraine pathophysiology
24000301	2013	Narrative Review	Deutsches Ärzteblatt International	Reviews treatment and natural course of vestibular vertigo; identifies vestibular migraine as comprising 11.4% of cases, reinforcing the mechanistic and clinical overlap between cerebellar/vestibular disorders and migraine

India Market Information

Chlorzoxazone is currently not marketed in India. No approved product registrations were found (0 licenses on record). Any future development would require a full regulatory submission to CDSCO.

Safety Considerations

Drug Interactions (72 interactions identified; key interactions listed below):

Severity	Interacting Drug	Clinical Implication
Major	Morphine	Significant CNS/respiratory depression risk; avoid combination
Major	Morphine (liposomal)	Significant CNS/respiratory depression risk; avoid combination
Moderate	Ethanol	Additive CNS depression; advise patients to avoid alcohol
Moderate	Promethazine	Additive CNS sedation
Moderate	Opium	Additive CNS depression
Moderate	Dronabinol	Moderate interaction; monitor CNS effects
Moderate	Nabilone	Moderate interaction; monitor CNS effects
Moderate	Naltrexone	Moderate interaction
Moderate	Sibutramine	Moderate interaction
Moderate	Metoclopramide	Moderate interaction

Note: Formal prescribing information including warnings and contraindications is pending acquisition from the package insert (TFDA/CDSCO source). This is classified as a Blocking data gap and must be resolved before any safety evaluation can be completed. Please refer to the package insert for comprehensive safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: The TxGNN prediction score is high (99.73%) and the mechanistic connection — BK channel activation opposing CaV2.1 hyperactivity via the CACNA1A/FHM1 pathway — is biologically plausible. However, there are no clinical trials and only 3 indirect supporting publications, none of which directly assess chlorzoxazone efficacy in migraine patients. The drug is not currently marketed in India, and critical safety data (package insert warnings and contraindications) remain unavailable. At evidence level L4, advancement to clinical evaluation is premature without foundational preclinical and regulatory groundwork.

To proceed, the following is needed:

Safety gap (Blocking): Acquire and review the full package insert to extract official warnings and contraindications before any clinical evaluation can begin
MOA confirmation (High priority): Retrieve and confirm detailed mechanism of action data from DrugBank to substantiate the BK channel activation hypothesis
Targeted preclinical studies: Design and conduct studies specifically testing chlorzoxazone in validated migraine animal models (e.g., cortical spreading depression models, FHM1 CACNA1A knock-in mice)
PK/CNS penetration assessment: Determine whether chlorzoxazone achieves therapeutically relevant CNS concentrations at standard clinical doses, as central BK channel engagement is essential to the proposed mechanism
Interaction risk review: Given 2 major interactions (morphine class) and 8 moderate interactions, a full DDI risk assessment is needed before patient study design, particularly if migraine patients may be using concurrent analgesics or CNS-active agents
Regulatory pathway planning: Since chlorzoxazone has no India registration, establish a regulatory development plan for any future IND/clinical trial application with CDSCO
Disclaimer

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