data + articles · 2 listed
newest 2005spec sheet10 rows
Trimethadione is an oxazolidinedione anticonvulsant that was historically used to control absence (petit mal) seizures. It works chiefly by blocking low-threshold T-type calcium channels in thalamic neurons, dampening the rhythmic firing that drives absence seizures. It has largely been replaced by safer drugs and is now mostly of historical and research interest.
- Effective against absence seizures historically
- Clear T-type calcium channel mechanism
- Orally active
- Foundational anticonvulsant research value
- Bone marrow suppression
- Serious teratogenicity in pregnancy
- Sedation and glare sensitivity
- Liver and kidney effects
Mechanism
Trimethadione and its active dimethadione reduce current through low-threshold T-type calcium channels, which are important for the burst firing of thalamocortical neurons that generates the spike-and-wave pattern of absence seizures. By raising the threshold for this rhythmic activity, it suppresses the abnormal synchronized discharges without acting mainly through sodium channels or . This T-type-focused action is the classic mechanism attributed to the oxazolidinedione class.
receptor fingerprint
T-type calcium channelsblocker
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
Trimethadione is considered relatively toxic by modern standards and was associated with serious risks including bone marrow suppression, kidney and liver effects, and a well-documented pattern of birth defects (fetal trimethadione syndrome), so it is strongly avoided in pregnancy. It can also cause sedation, visual disturbances such as glare sensitivity, and rash. It has largely been superseded by safer anticonvulsants. Not medical advice.
Subjective profileweighing the evidence above
Rightly abandoned. Bone-marrow suppression and a well-documented pattern of birth defects are not tradeoffs anyone needs to accept when safer absence-seizure drugs exist. Read about it as history; there is no current reason for it to be in anyone's hands.
Resources
This entry is here for reference.
Research
- 1.The antihyperalgesic effects of the T-type calcium channel blockers ethosuximide, trimethadione, and mibefradil
- 2.Tridione therapy in epilepsy; a review of results in 156 patients with petit mal epilepsy with special reference to side reactions
2 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
What was trimethadione used for?
It was one of the early drugs used to treat absence (petit mal) seizures before safer options became available.
How does it stop seizures?
Mainly by blocking T-type calcium channels in thalamic neurons, which reduces the rhythmic firing that produces absence seizures.
Why is it rarely used now?
Because of serious toxicity, including blood, organ, and severe fetal effects, it has been replaced by safer anticonvulsants.
Adverse effects
- Bone marrow suppression
- Serious teratogenicity in pregnancy
- Sedation and glare sensitivity
- Liver and kidney effects