Methadone

Evidence Level: L4 Predicted Indications: 7

Table of Contents

  1. Methadone
    1. Pharmacist Assessment Report
    2. Methadone: From Opioid Dependence/Pain Management to Tourette Syndrome
    3. One-Sentence Summary
    4. Quick Overview
    5. Why is This Prediction Reasonable?
    6. Clinical Trial Evidence
    7. Literature Evidence
    8. Australia Market Information
    9. Safety Considerations
    10. Other Predicted Indications (Context)
    11. Conclusion and Next Steps
    12. Disclaimer

Pharmacist Assessment Report

Methadone: From Opioid Dependence/Pain Management to Tourette Syndrome

One-Sentence Summary

Methadone is a synthetic mu-opioid agonist and NMDA receptor antagonist. The data compiled for this report do not include a TGA-approved indication text for the Australian product, though methadone is established in opioid substitution therapy and pain management. The TxGNN model predicts it may be effective for Tourette syndrome, but there are no registered clinical trials, and only 1 directly relevant publication (a 1992 case report) supports this direction.

Quick Overview

Item Content
Original Indication Not available in the data compiled for this report (the ARTG entry has no indication text)
Predicted New Indication Tourette syndrome
TxGNN Prediction Score 0.9976
Evidence Level L4
Australia Market Status Listed on the PBS Schedule (1 of 1 items) – TGA (ARTG) registration status is not included in this data
Number of PBS Items 1 (valid: 1)
Recommended Decision Hold

Why is This Prediction Reasonable?

Detailed mechanism of action data are not available in the compiled data. Based on known pharmacology, methadone is a mu-opioid receptor agonist with NMDA receptor antagonist activity. Opioid modulation of dopaminergic and serotonergic (5-HT2A/C) pathways is a plausible link to tic and compulsive symptoms.

Preclinical and review literature notes that opioid drugs have been reported as effective in treatment-refractory obsessive-compulsive disorder and Tourette syndrome. The 5-HT2A-related head-twitch behaviour in animals has been related to tics and compulsive symptoms. A 1992 report describes methadone treatment of Tourette’s disorder, but it is old, small and likely case-level.

This is a theoretical link only. The prediction has not been tested in controlled studies, and the original indication text was not available to assess its similarity to Tourette syndrome.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID Year Type Journal Key Findings
1728167 1992 Case report/series Am J Psychiatry Methadone treatment of Tourette’s disorder (no abstract available)
17102981 2007 Preclinical/Review Psychopharmacology Opiates are effective in treatment-refractory OCD and Tourette syndrome; 5-HT2A/C-mediated behaviour linked to tics and compulsions
15247538 2004 Review Curr Opin Neurol Review of non-genetic causes of chorea; indirect relevance
39086469 2024 Review Palliat Care Soc Pract Novel analgesics for neuropathic pain in advanced cancer; indirect relevance

Australia Market Information

ARTG Number Product Name Dosage Form Approved Indication
ARTG 12520Y METHADONE-AFT Tablet containing methadone hydrochloride 10 mg Not available in the compiled data

Safety Considerations

  • Contraindications (model-related signals, not label text): The TxGNN model (deep learning) links methadone to contraindications in:
    • Cardiac: long QT syndrome (including familial), torsades de pointes, sudden cardiac arrest, heart conduction disease
    • Respiratory: respiratory failure, asthma
    • Neurological: epilepsy, intracranial hypertension, pseudotumor cerebri
    • Gastrointestinal: paralytic ileus, intestinal obstruction, inflammatory bowel disease, Clostridium difficile colitis, perinatal necrotizing enterocolitis, familial visceral myopathy
    • Hepatic/renal/biliary: liver disease, kidney disease, gallbladder disease
    • Endocrine: hypothyroidism, myxedema, congenital hypothyroidism
    • Other: hypotensive disorder, benign prostatic hyperplasia, urethral stricture, pyoureter, substance-related disorder and substance abuse/dependence
  • Drug Interactions: The interaction query returned 100 interactions; 20 are shown in the compiled data. Major-level interactions include:
    • Alvimopan
    • Bupropion
    • Morphine
    • Dexamethasone
    • Clarithromycin
    • Cisapride
    • Picosulfuric acid
    • Polyethylene glycol (3350 with electrolytes)

    Moderate-level interactions include famotidine, cimetidine, aprepitant, loperamide, atropine, hyoscyamine, glycopyrronium, dicyclomine, clidinium, bisacodyl, castor oil and attapulgite.

  • Other signals from the literature: Methadone has been associated with bradycardia (case report) and with hyperalgesia and cluster headache at high doses (case series).

Label-based warnings and contraindications were not available. Please refer to the TGA-approved Product Information (PI) for authoritative safety information.

Other Predicted Indications (Context)

The remaining top-10 predictions are weaker or carry no supporting evidence:

Rank Predicted Indication Score Evidence Level Comment
2 Nephrogenic syndrome of inappropriate antidiuresis 0.9973 L5 Prediction only; mechanistically implausible (V2 receptor mutation)
3 Trichotillomania 0.9967 L5 Prediction only; an agonist would act opposite to the antagonist approach
4 Headache disorder 0.9935 L4 Literature mostly on opioid use disorder; guidance discourages opioids
5 Manic bipolar affective disorder 0.9932 L3 A 1982 small crossover study; otherwise comorbidity data
6 Trigeminal autonomic cephalalgia 0.9905 L4 Literature reports methadone inducing cluster headache (safety signal)
7 Common cold 0.9902 L5 Likely keyword artifact

Conclusion and Next Steps

Decision: Hold

Rationale: The Tourette syndrome prediction has a high model score, but evidence is limited to a single 1992 case report and indirect preclinical/review literature, with no registered trials. Methadone also carries significant cardiac (QT prolongation), respiratory and dependence risks that require a strong efficacy case before any new use is pursued. It is best treated as a research question rather than a candidate for clinical development.

To proceed, the following is needed:

  • Retrieval of the TGA Product Information to establish approved indications, warnings and contraindications
  • Detailed mechanism of action data (e.g., from DrugBank)
  • A systematic literature review beyond the 1992 case report, including any controlled studies in Tourette syndrome
  • Comparison with established Tourette treatments (e.g., alpha-2 agonists, antipsychotics, behavioural therapy) to assess a plausible benefit-risk case
  • A QT, respiratory depression and dependence-risk assessment in a Tourette population, which is often young
  • If pursued, a pilot or Phase 2 study design with ECG monitoring, with ethics and regulatory review (including controlled-substance requirements)

    Disclaimer

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

This site uses Just the Docs, a documentation theme for Jekyll.