Primidone

Primidone
Clinical data
Trade names	Lepsiral, Mysoline, Resimatil, others
Other names	desoxyphenobarbital, desoxyphenobarbitone
AHFS/Drugs.com	Monograph
MedlinePlus	a682023
License data	US DailyMed: Primidone;
Pregnancy; category	AU: D;
Routes of; administration	By mouth
Drug class	Anticonvulsant, barbiturate
ATC code	N03AA03 (WHO) ;
Legal status
Legal status	AU: S4 (Prescription only); BR: Class C1 (Other controlled substances); CA: ℞-only; UK: POM (Prescription only); US: ℞-only;
Pharmacokinetic data
Bioavailability	~100%
Protein binding	25%
Metabolism	Liver
Elimination half-life	Primidone: 5-18 h,; Phenobarbital: 75-120 h,; PEMA: 16 h; Time to reach steady state:; Primidone: 2-3 days,; Phenobarbital&PEMA 1-4weeks
Excretion	Kidney
Identifiers
	IUPAC name 5-Ethyl-5-phenyl-1,3-diazinane-4,6-dione;
CAS Number	125-33-7 ;
PubChem CID	4909;
DrugBank	DB00794 ;
ChemSpider	4740 ;
UNII	13AFD7670Q;
KEGG	D00474 ; C07371 ;
ChEBI	CHEBI:8412 ;
ChEMBL	ChEMBL856 ;
CompTox Dashboard (EPA)	DTXSID7023510 ;
ECHA InfoCard	100.004.307
Chemical and physical data
Formula	C12H14N2O2
Molar mass	218.256 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES O=C1NCNC(=O)C1(c2ccccc2)CC;
	InChI InChI=1S/C12H14N2O2/c1-2-12(9-6-4-3-5-7-9)10(15)13-8-14-11(12)16/h3-7H,2,8H2,1H3,(H,13,15)(H,14,16) ; Key:DQMZLTXERSFNPB-UHFFFAOYSA-N ;
	(verify)

Primidone, sold under various brand names (including Mysoline), is a barbiturate medication that is used to treat partial and generalized seizures and essential tremors. It is taken by mouth.

Its common side effects include sleepiness, poor coordination, nausea, and loss of appetite. Severe side effects may include suicide and psychosis. Use during pregnancy may result in harm to the fetus. Primidone is an anticonvulsant of the barbiturate class; however, its long-term effect in raising the seizure threshold is likely due to its active metabolite, phenobarbital. The drug’s other active metabolite is Phenylethylmalonamide (PEMA).

Primidone was approved for medical use in the United States in 1954. It is available as a generic medication. In 2020, it was the 269th most commonly prescribed medication in the United States, with more than 1 million prescriptions.