Trimethadione targets T-type calcium channels in thalamic neurons. It acts as a channel blocker, reducing the low-threshold (T-type) calcium currents that are responsible for the generation of the rhythmic burst firing characteristic of absence seizures. By inhibiting these channels, trimethadione stabilizes neuronal membranes, raises the threshold for repetitive activities in the thalamus, and inhibits corticothalamic transmission. This mechanism of action is similar to that of other drugs used to treat absence seizures, such as ethosuximide.

In vitro, trimethadione has been shown to reduce T-type calcium currents in thalamic neurons. This effect has been demonstrated using patch-clamp electrophysiology on isolated neurons. The compound's ability to block these channels is responsible for its anticonvulsant activity. In cell-based assays, trimethadione reduces the firing rate of thalamic neurons and stabilizes their membrane potential. These in vitro studies confirm the compound's mechanism of action as a T-type calcium channel blocker.

In vivo, trimethadione is effective in reducing the frequency and severity of absence seizures in patients with petit mal epilepsy. It is used as a second-line agent when other drugs, such as ethosuximide, are not effective. The compound's slow onset of action means that it takes several days to achieve therapeutic levels and clinical efficacy. It is not effective against other types of seizures, such as tonic-clonic or partial seizures.

In vitro enzyme or receptor binding (non-cell) assays for trimethadione are not typically performed, as it is not a direct enzyme inhibitor or receptor ligand. Its mechanism of action involves the modulation of ion channels. However, the compound's effects on T-type calcium channels can be studied using electrophysiological techniques on isolated membrane patches or using calcium flux assays in cells expressing the channels. Radioligand binding assays using specific T-type calcium channel ligands can also be used to study the compound's interaction with the channel.

In vitro cell-based assays for trimethadione are performed using neuronal cell lines or primary thalamic neurons. Cells are treated with the compound, and the effects on T-type calcium currents are measured using patch-clamp electrophysiology. Calcium imaging using fluorescent dyes can also be used to monitor changes in intracellular calcium levels. The compound's effects on neuronal firing rate and membrane potential are assessed. These assays confirm the compound's mechanism of action as a T-type calcium channel blocker.

In vivo animal experiments for trimethadione are conducted using rodent models of absence epilepsy, such as the genetic absence epilepsy rat from Strasbourg (GAERS) or the WAG/Rij rat. The compound is administered, and its effects on the number and duration of spike-wave discharges (SWDs) are measured using electroencephalography (EEG). These models are standard for evaluating the efficacy of drugs against absence seizures. The compound's effects on behavior and motor function are also assessed.

Metabolism / Metabolites
Trimethyldiketone's known metabolites include dimethyldiketone.
Pharmacokinetic (PK) properties of trimethadione indicate that it is well-absorbed after oral administration. The compound has a molecular weight of 143.14 and a molecular formula of C6H9NO3. It is a white to light yellow powder with a melting point of 44-48°C. The compound is metabolized in the liver to its active metabolite, dimethadione. The half-life of trimethadione is relatively long, and it requires several days to reach steady-state concentrations. The compound is excreted renally.

Toxicity Summary
Diketoacids reduce T-type calcium currents in thalamic neurons, including thalamic relay neurons, by inhibiting voltage-dependent T-type calcium channels. This raises the threshold for repetitive thalamic activity and inhibits corticothalamic transmission. Consequently, the abnormal thalamic cortical rhythmicity thought to be associated with 3 Hz spike-and-wave discharges observed on absence seizure EEG is diminished.

---

Protein Binding
90%
Toxicology (toxicology) data for trimethadione indicate that it can cause a range of adverse effects. Common side effects include drowsiness, dizziness, and gastrointestinal disturbances. More serious side effects include blood dyscrasias (e.g., neutropenia, aplastic anemia), systemic lupus erythematosus, and nephrotic syndrome. It is teratogenic and should not be used during pregnancy. The compound is contraindicated in patients with liver or kidney disease.

[1]. Synthesis and anticonvulsant activity of bioisosteres of trimethadione, N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides from α-hydroxyamides. Bioorg Med Chem. 2013 Feb 15;21(4):841-6.

[2]. The antihyperalgesic effects of the T-type calcium channel blockers ethosuximide, trimethadione, and mibefradil. Eur J Pharmacol. 2005 Oct 3;521(1-3):79-85.

Trimethadione may cause developmental toxicity depending on state or federal labeling requirements. Trimethadione is an oxazolidinone drug with the structure 1,3-oxazolidin-2,4-dione, substituted with methyl groups at positions 3, 5, and 6. It is an antiepileptic drug with anti-aging and anticonvulsant effects. It is an anticonvulsant effective for absence seizures, but due to its toxicity, it is usually used only in refractory cases. (Excerpt from JAMA Drug Evaluation Yearbook, 1994, p. 378) Trimethadione is an antiepileptic drug. The physiological action of trimethadione is achieved by reducing disordered electrical activity in the central nervous system. Trimethadione is a diketone anticonvulsant with antiepileptic activity. Trimethadione reduces T-type calcium currents in thalamic neurons, thereby stabilizing the neuronal membrane, increasing the threshold for repetitive thalamic activity, and inhibiting corticothalamic transmission. This reduces abnormal thalamic cortical rhythms, which are thought to be the basis of the paroxysmal three-cycle-per-second spike-and-wave pattern that appears in absence seizures (petit mal seizures). Trimethadione is only found in individuals who have used or taken this drug. It is an anticonvulsant effective for absence seizures, but due to its toxicity, it is usually used only in refractory cases. (From JAMA Drug Evaluation Yearbook, 1994, p. 378) Trimethadione reduces T-type calcium currents in thalamic neurons, including thalamic relay neurons. Its mechanism of action is through inhibition of voltage-dependent T-type calcium channels. This raises the threshold for repetitive thalamic activity and inhibits corticothalamic transmission. Therefore, the abnormal thalamic cortical rhythms thought to be associated with 3 Hz spike-and-wave discharges observed on absence seizure EEG are suppressed.
An antiepileptic drug effective for absence seizures, but due to its toxicity, it is usually used only in refractory cases. (Excerpt from JAMA Drug Evaluation Yearbook, 1994, p. 378) Drug Indications For the control of absence seizures (petit mal seizures) unresponsive to other drug treatments. Mechanism of Action Diketone antiepileptic drugs reduce T-type calcium currents in thalamic neurons (including thalamic relay neurons) by inhibiting voltage-dependent T-type calcium channels. This increases the threshold for repetitive thalamic activity and inhibits corticothalamic transmission. Therefore, the abnormal thalamic cortical rhythmicity thought to be associated with 3 Hz spike-and-wave discharges observed on absence seizure EEG is suppressed. Pharmacodynamics Methyldione and trimethyldione are anticonvulsants indicated for the control of absence seizures (petit mal seizures) unresponsive to other drug treatments. Diketone anticonvulsants are used to treat epilepsy. They act on the central nervous system (CNS) to reduce the frequency of seizures.
Other information: Trimethadione is an anticonvulsant used for the treatment of petit mal (absence) seizures. It is a second-line agent that is used when other drugs are ineffective. The compound is also known as Tridione. Its use has declined due to the availability of safer and more effective drugs, such as ethosuximide. Its CAS number is 127-48-0.

C6H9NO3

143.142

143.058

127-48-0

5576

White to off-white solid powder

1.171g/cm3

78-80°C 5mm

45-46°C

78-80°C/5mm

2.98mmHg at 25°C

1.457

0.311

0

3

0

10

197

0

IRYJRGCIQBGHIV-UHFFFAOYSA-N

InChI=1S/C6H9NO3/c1-6(2)4(8)7(3)5(9)10-6/h1-3H3

3,5,5-trimethyl-1,3-oxazolidine-2,4-dione

Trimetin; Trimethadione; Tridione

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 40 mg/mL (~279.45 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (17.47 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (17.47 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 2.5 mg/mL (17.47 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)