trimethadione trimethadione trimethadione (tridione) is an oxazolidinedione anticonvulsant. it is most commonly used to treat epileptic conditions that are resistant to other treatments. trimethadioneclinical datatrade namestridioneahfs/drugs.commicromedex detailed consumer informationpregnancycategory x routes ofadministrationby mouthatc coden03ac02 (who) legal statuslegal status in general: ℞ (prescription only) pharmacokinetic databioavailabilityhighmetabolismdemethylated to dimethadioneelimination half-life12–24 hours (trimethadione)6–13 days (dimethadione)excretionrenalidentifiers iupac name 3,5,5-trimethyl-1,3-oxazolidine-2,4-dione cas number127-48-0 ypubchem cid5576iuphar/bps7316drugbankdb00347 ychemspider5374 yuniir7gv3h6fq4keggd00392 ychebichebi:9727chemblchembl695 ycomptox dashboard (epa)dtxsid9021396 echa infocard100.004.406 chemical and physical dataformulac6h9no3molar mass143.142 g·mol−13d model (jsmol)interactive image smiles o=c1n(c(=o)oc1(c)c)c inchi inchi=1s/c6h9no3/c1-6(2)4(8)7(3)5(9)10-6/h1-3h3 ykey:iryjrgciqbghiv-uhfffaoysa-n y (verify) it is primarily effective in treating absence seizures, but can also be used in refractory temporal lobe epilepsy. it is usually administered 3 or 4 times daily, with the total daily dose ranging from 900 mg to 2.4 g. treatment is most effective when the concentration of its active metabolite, dimethadione, is above 700 µg/ml. severe adverse reactions are possible, including steven johnson syndrome, nephrotoxicity, hepatitis, aplastic anemia, neutropenia, or agranulocytosis. more common adverse effects include drowsiness, hemeralopia, and hiccups. fetal trimethadione syndrome if administered during pregnancy, fetal trimethadione syndrome may result causing facial dysmorphism (short upturned nose, slanted eyebrows), cardiac defects, intrauterine growth restriction (iugr), and mental retardation. the fetal loss rate while using trimethadione has been reported to be as high as 87%.