Methylnaltrexone
| Evidence Level: L5 | Predicted Indications: 10 |
Table of Contents
- Methylnaltrexone
- Methylnaltrexone: From Opioid-Induced Constipation to Congenital Hypotrichosis Milia
Methylnaltrexone: From Opioid-Induced Constipation to Congenital Hypotrichosis Milia
One-Sentence Summary
Methylnaltrexone is a peripherally acting mu-opioid receptor antagonist, used to treat constipation caused by opioid analgesics. The TxGNN model predicts it may be effective for congenital hypotrichosis milia, but there are 0 clinical trials and 0 publications supporting this direction. The prediction rests on knowledge-graph proximity alone and has no known biological rationale.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the Singapore licence record. Pharmacology data describes use for opioid-induced constipation when other laxatives are insufficient |
| Predicted New Indication | Congenital hypotrichosis milia |
| TxGNN Prediction Score | 78.35% |
| Evidence Level | L5 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 1 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available in the data compiled for this report. Pharmacology data shows that methylnaltrexone binds the mu, delta and kappa opioid receptors. It is a peripherally restricted antagonist that does not appreciably cross the blood-brain barrier. This lets it relieve opioid-induced constipation without reversing central pain relief.
The predicted condition is a genetic disorder of hair follicle development. No known role for opioid receptor signalling exists in this process, so no plausible mechanistic link could be identified. The TxGNN score appears to reflect proximity in the knowledge graph rather than biological rationale. Similarity between the original and predicted indications has not yet been assessed.
Other top predictions show the same pattern. All were reviewed, and none has clinical trial support:
| Rank | Predicted Disease | Score | Evidence Level | Assessment |
|---|---|---|---|---|
| 2 | Hypotrichosis simplex of the scalp | 77.28% | L5 | No mechanistic link; computational prediction only |
| 3 | Exercise-induced malignant hyperthermia | 76.59% | L5 | Involves skeletal muscle calcium release (e.g., RYR1); no link to opioid antagonism |
| 4 | Common cold | 76.41% | L5 | Self-limiting viral infection; no relevant activity |
| 5 | Alopecia | 75.44% | L5 | Score likely reflects similarity to other hair-related predictions |
| 6 | Diffuse alopecia areata | 75.29% | L5 | Autoimmune (JAK/STAT) condition; no immunomodulatory action |
| 7 | Respiratory failure | 71.98% | L4 | Only indirect link, in opioid-induced respiratory depression; the drug does not cross the blood-brain barrier, so it is not expected to reverse central respiratory depression. Designated a research question |
| 8 | Familial periodic paralysis | 71.31% | L5 | Muscle channelopathy; no link to opioid antagonism |
| 9 | Obsolete hyperuricemia (disease) | 71.23% | L5 | Unrelated to purine metabolism; ontology term is obsolete |
| 10 | Trigeminal autonomic cephalalgia | 67.58% | L5 | No established role for a peripherally restricted antagonist |
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
Currently no related literature available for the top-ranked prediction (congenital hypotrichosis milia).
For reference, the only literature found across the top 10 predictions concerns rank 7, respiratory failure:
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 41087032 | 2025 | Preclinical (animal) | Am J Physiol Lung Cell Mol Physiol | Examines the roles of peripheral and central µ1-opioid receptors in fentanyl-induced apnea and respiratory depression in rats |
| 21164413 | 2010 | Review | Critical Care Medicine | General review of intensive care unit management; no direct relevance to methylnaltrexone |
Singapore Market Information
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN13783P | Relistor Solution For Injection 12mg/0.6mL | Injection, solution | Not stated in the licence record |
Safety Considerations
Drug Interactions: 10 moderate-level interactions were identified:
- Other opioid antagonists: alvimopan, naloxone, naldemedine, nalmefene, naloxegol, naltrexone
- Other drugs: capmatinib, pitolisant, risdiplam, gilteritinib
Please refer to the package insert for warnings and contraindications.
Conclusion and Next Steps
Decision: Hold
Rationale: The top prediction has no clinical trials and no literature, and no plausible mechanistic link to a peripherally acting opioid antagonist. The score appears to reflect knowledge-graph proximity rather than biology. None of the other nine top predictions has clinical support either.
To proceed, the following is needed:
- Detailed mechanism of action data, to allow proper mechanistic analysis
- Package insert warnings and contraindications from the HSA website, which are required before any safety screening
- Any experimental evidence linking opioid receptor signalling to hair follicle development
- Route compatibility and similarity assessments, currently pending
- If any direction is pursued, rank 7 (respiratory failure) is the only prediction with even indirect supporting literature, and it would be a preclinical research question rather than a repurposing candidate
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.