Orphenadrine
| Evidence Level: L5 | Predicted Indications: 7 |
Table of Contents
- Orphenadrine
- Pharmacist Assessment Report
- Orphenadrine: From Parkinsonian Disorder to Retinal Dystrophy with or without Extraocular Anomalies
- One-Sentence Summary
- Quick Overview
- Why is This Prediction Reasonable?
- Clinical Trial Evidence
- Literature Evidence
- Canada Market Information
- Safety Considerations
- Conclusion and Next Steps
- Disclaimer
Orphenadrine: From Parkinsonian Disorder to Retinal Dystrophy with or without Extraocular Anomalies
One-Sentence Summary
Orphenadrine is an anticholinergic agent originally used to treat parkinsonian disorder and Parkinson disease. The TxGNN model’s top-ranked prediction is retinal dystrophy with or without extraocular anomalies, but there are 0 clinical trials and 0 publications supporting this direction, so it rests on computation alone. The best-supported lead among the seven predictions is schizophrenia, with 16 publications (mainly older studies on managing antipsychotic-induced movement side effects), but no registered trials.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Parkinsonian disorder / Parkinson disease |
| Predicted New Indication | Retinal dystrophy with or without extraocular anomalies |
| TxGNN Prediction Score | 0.9929 |
| Evidence Level | L5 |
| Canada Market Status | Marketed (marketed DINs: 1 of 1) |
| Number of DINs | 1 (marketed: 1) |
| Recommended Decision | Hold |
Note: No approved indication text is listed in the Canadian licence record, so the original indication is not available from that record.
Why is This Prediction Reasonable?
Detailed mechanism of action data is not currently available. Orphenadrine is generally known as an anticholinergic (antimuscarinic) agent with antihistamine and NMDA-receptor-blocking properties. Its efficacy in parkinsonian disorders is established, but this does not extend to the predicted new indication.
For the top prediction (retinal dystrophy): The data compiled for this report show no plausible pathway between orphenadrine’s pharmacology and inherited retinal dystrophy. The high score (0.9929) is a computational output only, with no trials or publications behind it.
Other predictions in the list:
- Congenital disorder of glycosylation with defective fucosylation, perisylvian polymicrogyria with cerebellar hypoplasia and arthrogryposis: These are genetic or structural developmental disorders. A postnatal anticholinergic or NMDA-blocking drug is unlikely to address them.
- Charcot-Marie-Tooth disease type 1G: Orphenadrine’s muscle-relaxant and analgesic properties might ease symptoms such as cramps or pain, but nothing suggests disease modification.
- X-linked myopia (two entries): Anticholinergics such as atropine are used in myopia control, which gives only a loose class-level rationale. There is no orphenadrine-specific ocular evidence.
- Schizophrenia: The literature shows orphenadrine used as an add-on to manage antipsychotic-induced extrapyramidal symptoms (for example with haloperidol), not as a treatment for the core illness. Its NMDA-channel-blocking activity offers a speculative link to glutamate-based theories of schizophrenia. This is best read as adjunctive symptom management rather than true repurposing.
Clinical Trial Evidence
Currently no related clinical trials registered for the top prediction (retinal dystrophy) or for schizophrenia.
Literature Evidence
No literature is available for the top prediction (retinal dystrophy). For reference, the most relevant publications for the best-supported prediction, schizophrenia, are listed below.
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 29341071 | 2018 | Cochrane systematic review | Cochrane Database Syst Rev | Anticholinergic medication for antipsychotic-induced tardive dyskinesia; notes that chronic anticholinergic use may itself contribute to tardive dyskinesia |
| 10796321 | 2000 | Cochrane systematic review | Cochrane Database Syst Rev | Anticholinergics used alongside neuroleptics to reduce movement side effects |
| 3698889 | 1986 | Clinical study | L’Encephale | In 22 schizophrenic patients on haloperidol, orphenadrine significantly reduced extrapyramidal side effects, and withdrawal led to marked deterioration |
| 4571143 | 1972 | Comparative trial | Psychol Med | Amantadine vs orphenadrine vs placebo for phenothiazine-induced parkinsonism |
| 2616635 | 1989 | Naturalistic study | Pharmacopsychiatry | 44 outpatients on haloperidol plus orphenadrine assessed for residual parkinsonian and anticholinergic symptoms |
| 324238 | 1977 | Clinical study | Acta Psychiatr Scand | Need for antiparkinsonian drugs in 118 schizophrenic patients on long-term neuroleptics; none of 18 on low-potency neuroleptics needed them |
| 8369232 | 1993 | Placebo-controlled clinical study | Schizophr Res | Effects of placebo, orphenadrine and rising chlorpromazine doses on an auditory attention task in chronic schizophrenia |
| 12459931 | 2003 | Preclinical | Psychopharmacology | NMDA channel blockers and disruption of prepulse inhibition in rats, an animal model relevant to schizophrenia |
| 19524386 | 2009 | Analytical method | J Pharm Biomed Anal | HPLC method to measure orphenadrine plasma levels in schizophrenic patients |
| 3962752 | 1986 | Clinical study | Acta Neurol | Orphenadrine plasma levels and relief of extrapyramidal side effects in haloperidol-treated patients |
Canada Market Information
| DIN | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| 02243559 | SANDOZ ORPHENADRINE | Not listed | Not listed |
Safety Considerations
Contraindications (from knowledge-graph drug–disease contraindication links, not label text):
- Cardiovascular: hypertension, sudden cardiac arrest, heart conduction disease
- Neuromuscular: myasthenia gravis, neuromuscular junction disease, epilepsy
- Gastrointestinal: achalasia/megaesophagus, pyloric stenosis, peptic ulcer disease
- Urinary: benign prostatic hyperplasia, bladder neck obstruction
- Eye: glaucoma
- Organ function: liver failure/liver disease, kidney disease/impaired renal function, gallbladder disease
- Blood: thrombocytopenia, anemia, hemophilia
- Other: gout, insomnia, substance abuse/dependence, paracetamol poisoning
Drug Interactions (100 interactions found; main ones shown):
- Major: morphine (including liposomal), potassium chloride, potassium citrate
- Moderate: other anticholinergics and antimuscarinics (atropine, hyoscyamine, glycopyrronium, dicyclomine, clidinium, propantheline, methscopolamine, mepenzolate), loperamide, bupropion, metoclopramide, dronabinol, nabilone, eluxadoline, opium
Additional consideration: In schizophrenia, the anticholinergic burden may worsen cognition, which warrants attention.
For label warnings, please refer to the package insert.
Conclusion and Next Steps
Decision: Hold
Rationale: The top prediction (retinal dystrophy) has no trials, no literature and no supported mechanistic link, so it remains a computational signal only (Evidence Level L5). Schizophrenia is the only prediction with a literature base (Level L3), but that literature describes orphenadrine managing antipsychotic side effects, not treating the disease, and is largely old and small-scale. It is best handled as a research question rather than a repurposing candidate.
To proceed, the following is needed:
- Health Canada package insert warnings and contraindications (currently a blocking gap for safety screening)
- Mechanism of action data (for example from DrugBank) to test any link to the predicted indications
- Dosage form and approved indication details for the Canadian licence
- For schizophrenia: modern controlled studies, particularly on the NMDA-antagonist hypothesis and cognitive effects of anticholinergic burden
- For the other predictions: any preclinical or mechanistic evidence before further consideration
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.