TRIDIONE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TRIDIONE (TRIDIONE).
Increases seizure threshold by modulating voltage-gated sodium channels and enhancing GABA-ergic inhibition.
| Metabolism | Primarily hepatic via CYP450 enzymes; active metabolite dimethadione. |
| Excretion | Renal: ~70% as unchanged drug and metabolites (including dimethadione); biliary/fecal: minimal (<10%). |
| Half-life | 16-24 hours (trimethadione); dimethadione (active metabolite) has a half-life of ~6-12 days, leading to drug accumulation. |
| Protein binding | <10% bound to plasma proteins. |
| Volume of Distribution | 0.5-0.7 L/kg, indicating distribution into total body water. |
| Bioavailability | PO: ~100%. |
| Onset of Action | PO: 2-4 hours (anticonvulsant effect). |
| Duration of Action | 6-8 hours (single dose); chronic use: sustained due to long-lived metabolite. |
| Molecular Weight | 240.24 |
300-600 mg orally three times daily; titrate to seizure control.
| Dosage form | CAPSULE |
| Renal impairment | Contraindicated in severe renal impairment (GFR <30 mL/min). For GFR 30-60 mL/min, reduce dose by 50%. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh C). For Child-Pugh B, reduce dose by 50%. |
| Pediatric use | Initial 25-50 mg/kg/day in 3-4 divided doses; maintenance 100-200 mg/kg/day. |
| Geriatric use | Start at lowest effective dose; monitor for renal function and CNS side effects. |
| 1st trimester | Associated with increased risk of major congenital malformations, particularly cleft lip/palate and cardiac defects. First-trimester exposure is contraindicated unless no safer alternative. |
| 2nd trimester | Continued risk of teratogenicity. Use only if clearly needed and no safer alternative. |
| 3rd trimester | Risk of neonatal hemorrhage, hepatic toxicity, and withdrawal. Avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for TRIDIONE (TRIDIONE).
| Placental transfer | Extensive placental transfer; drug and metabolites achieve therapeutic concentrations in fetal plasma. |
| Breastfeeding | Excreted into breast milk in clinically relevant amounts; may cause neonatal sedation, poor feeding, and metabolic disturbances. Breastfeeding is not recommended during therapy. |
■ FDA Black Box Warning
May cause fatal hepatotoxicity and blood dyscrasias (aplastic anemia, agranulocytosis).
| Serious Effects |
Hypersensitivity to trimethadione or paramethadioneSevere hepatic impairmentSevere renal impairmentPorphyriaPregnancy (unless no safer alternative)
| Precautions | Hepatotoxicity risk, Bone marrow suppression, Teratogenicity, SLE-like syndrome, Visual disturbances (glare phenomenon), Renal impairment |
| Food/Dietary | No specific food interactions reported. Advise to take with food to reduce gastrointestinal upset. Avoid alcohol due to additive CNS depression. |
| Clinical Pearls |
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| Lactation Rating |
| Avoid |
| Teratogenic Risk | First trimester: High risk of major congenital malformations including neural tube defects, cleft lip/palate, and congenital heart defects. Second/third trimester: Risk of intrauterine growth restriction, microcephaly, and neurodevelopmental delay. Avoid in pregnancy unless benefit outweighs teratogenic risk. |
| Fetal Monitoring | Maternal: CBC, liver function tests, renal function, and urinalysis at baseline and periodically. Fetal: Ultrasound for malformations, fetal growth monitoring, and consider fetal echocardiography. Monitor for neonatal bleeding if used near term. |
| Fertility Effects | May impair female fertility due to inhibition of ovulation; reversible upon discontinuation. Male fertility: No well-documented effects, but potential for decreased spermatogenesis based on animal data. |
| TRIDIONE (trimethadione) is an oxazolidinedione anticonvulsant used for absence seizures. Monitor for severe idiosyncratic reactions including blood dyscrasias (aplastic anemia, agranulocytosis), hepatitis, and nephrosis. Perform baseline and periodic CBC, urinalysis, and LFTs. Avoid in pregnancy due to high teratogenicity (trimethadione syndrome). May cause photophobia, myasthenia gravis-like syndrome, and sedation. Dose adjustments needed in renal impairment. |
| Patient Advice | Take exactly as prescribed; do not stop abruptly as seizure frequency may increase. · Report any unusual bleeding, bruising, fever, sore throat, or jaundice immediately (signs of bone marrow suppression or liver injury). · Use effective contraception during therapy; this drug causes severe birth defects. · Avoid alcohol and other central nervous system depressants. · May cause blurred vision or sensitivity to light; wear sunglasses and avoid driving if affected. · Do not take with other medications without consulting your doctor, especially other anticonvulsants or anticoagulants. |