Phenobarbital
| Evidence Level: L5 | Predicted Indications: 10 |
Table of Contents
Phenobarbital: From Epilepsy to Trigeminal Nerve Neoplasm
One-Sentence Summary
Phenobarbital is a long-established antiseizure drug, originally used for epilepsy (including generalized tonic-clonic and partial seizures), migraine-related conditions and Lennox-Gastaut syndrome. The TxGNN model's top-ranked prediction is trigeminal nerve neoplasm, but there are 0 clinical trials and only 1 publication (a Sturge-Weber syndrome case series that does not address a tumour), so the evidence for this prediction is essentially absent. Of the other predicted indications, the seizure-related ones (such as micturition-induced seizures, startle epilepsy and audiogenic seizures) are more credible because they sit close to phenobarbital's established use.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Epilepsy (including generalized tonic-clonic and partial epilepsy), migraine disorders, Lennox-Gastaut syndrome. The Singapore licence records contain no approved indication text. |
| Predicted New Indication | Trigeminal nerve neoplasm |
| TxGNN Prediction Score | 99.96% |
| Evidence Level | L5 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 2 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Detailed mechanism-of-action data is not available in the data compiled for this report. Based on general pharmacological knowledge, phenobarbital is a barbiturate that enhances GABA-A receptor-mediated inhibition in the brain. This explains its antiseizure activity.
For the top-ranked prediction, trigeminal nerve neoplasm, there is no plausible mechanistic link. Phenobarbital has no known antineoplastic activity. The only retrieved paper describes Sturge-Weber syndrome, a neurocutaneous vascular disorder with seizures, not a trigeminal tumour. The high score most likely reflects proximity in the knowledge graph through seizure- and trigeminal-related nodes, not true therapeutic evidence. The same applies to beta-ketothiolase deficiency (rank 10), an inborn error of metabolism with no rationale for phenobarbital.
The remaining predictions are more coherent. Micturition-induced, orgasm-induced, thinking, startle, eating, audiogenic and reading seizures are all reflex or stimulus-triggered seizure types. A general antiseizure GABAergic mechanism could plausibly apply to them. Even so, no retrieved paper shows phenobarbital efficacy in any of these specific conditions. Trigeminal neuralgia (rank 9) is treated with anticonvulsants, but carbamazepine is first line and phenobarbital is not a recommended therapy.
Clinical Trial Evidence
Currently no related clinical trials registered for trigeminal nerve neoplasm or for any of the other predicted indications.
Literature Evidence
For the top prediction (trigeminal nerve neoplasm):
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 9157801 | 1997 | Case series | Anales espanoles de pediatria | Review of 14 Sturge-Weber syndrome cases; not a trigeminal tumour and not evidence for this indication |
Strongest indirect evidence from the other seizure-related predictions (none specific to the predicted conditions):
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 32385134 | 2020 | RCT | Pediatrics | Levetiracetam vs phenobarbital for neonatal seizures |
| 37873971 | 2023 | Systematic review | Cochrane Database Syst Rev | Anti-seizure medications for neonates with seizures |
| 37655702 | 2023 | Guideline | Epilepsia | ILAE recommendations on treating neonatal seizures |
| 40350217 | 2025 | Review | Clinics in Perinatology | Updates in neonatal seizures; phenobarbital remains a first-line option |
| 24726506 | 2014 | Case follow-up | Seizure | 50-year follow-up of a case of neonatal eating epilepsy |
| 15036433 | 2004 | Case report | Brain & Development | Startle epilepsy complicating aspartylglucosaminuria |
| 26690830 | 2017 | Veterinary RCT | J Feline Med Surg | Levetiracetam vs phenobarbital in feline audiogenic reflex seizures |
| 11129121 | 2000 | Review | Drugs | Anticonvulsants for neuropathic pain syndromes |
These papers concern general or neonatal seizures, animal models, or carbamazepine. None addresses the specific predicted conditions, so they support only an extrapolation.
Singapore Market Information
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN02457P | Phenobarbitone Tablet 10 mg (PT Actavis Indonesia) | Tablet | Not stated in the registration record |
| SIN03709P | Phenobarbitone Tablet 60 mg (PT Actavis Indonesia) | Tablet | Not stated in the registration record |
Both authorizations are valid single-ingredient oral tablets.
Safety Considerations
- Contraindications (from knowledge-graph disease associations, not label text): The following conditions are flagged, including: liver failure and liver disease, kidney disease, porphyria (inherited porphyria and other porphyrin metabolism diseases), chronic obstructive pulmonary disease, thrombocytopenia, hypothyroidism, hyperglycemia, systemic lupus erythematosus, peptic/gastric ulcer and gastritis, hypertension, anxiety and other mental disorders (including psychotic and schizoaffective disorders), insomnia and gallbladder disease.
- Drug Interactions: 100 interactions were identified. Examples:
- Major: morphine (including liposomal), eliglustat, naldemedine, naloxegol, rolapitant.
- Moderate: corticosteroids (dexamethasone, prednisone, prednisolone, hydrocortisone, betamethasone, triamcinolone), doxycycline, metronidazole, bupropion, pioglitazone, aprepitant, dronabinol, cholecalciferol, pyridoxine.
- Other considerations from the literature: Neonatal exposure to phenobarbital has been linked to adverse neurodevelopmental effects in preclinical studies. A trial in children with febrile seizures reported lower IQ with phenobarbital.
Please refer to the package insert for label warnings and contraindications.
Conclusion and Next Steps
Decision: Hold
Rationale: The top-ranked prediction, trigeminal nerve neoplasm, has no trials, no relevant literature and no plausible antineoplastic mechanism, so the high TxGNN score does not reflect real therapeutic evidence. Seizure-related predictions (for example micturition-induced seizures, startle epilepsy and audiogenic seizures) are plausible extrapolations of phenobarbital's established use, but they are supported only by indirect evidence and are better treated as research questions.
To proceed, the following is needed:
- Package insert warnings and contraindications for the Singapore-registered products, which are currently missing and block safety screening
- Detailed mechanism-of-action data
- Confirmation of the approved indications for the two Singapore licences
- For any seizure-related prediction, direct clinical evidence of phenobarbital efficacy in that specific condition
- Review of the major interactions (opioids and others) and the safety signals in specific populations (neonates, hepatic or renal impairment, porphyria)
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.