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an anticonvulsant used in the treatment of epilepsy; administered orally.


Apo-Primidone (CA), Mysoline

Pharmacologic class: Barbiturate

Therapeutic class: Anticonvulsant

Pregnancy risk category NR


Unknown. May raise seizure threshold by decreasing neuronal firing after being converted to phenobarbital.


Suspension: 250 mg/5 ml

Tablets: 50 mg, 250 mg

Indications and dosages

Grand mal, psychomotor, or focal epileptic seizures

Adults and children ages 8 and older: Initially, 100 to 125 mg P.O. at bedtime on days 1 to 3, then 100 to 125 mg P.O. b.i.d. on days 4 to 6, then 100 to 125 mg P.O. t.i.d. on days 7 to 9, followed by a maintenance dosage of 250 mg P.O. three or four times daily

Children younger than age 8: Initially, 50 mg P.O. at bedtime on days 1 to 3, then 50 mg P.O. b.i.d. on days 4 to 6, then 100 mg P.O. b.i.d. on days 7 to 9. For maintenance, 125 to 250 mg t.i.d. or 10 to 25 mg/kg/day in divided doses.

Dosage adjustment

• Renal impairment

Off-label uses

• Benign familial (essential) tremor


• Hypersensitivity to drug or phenobarbital
• Porphyria


Use cautiously in:
• hepatic, renal, or chronic obstructive pulmonary disease
• pregnant or breastfeeding patients
• hyperactive children.


• Don't change brands. Bioequivalency problems have occurred.

Don't stop therapy suddenly. Dosage must be tapered.
• Know that drug may be given alone or with other anticonvulsants.

Adverse reactions

CNS: headache, dizziness, stimulation, drowsiness, sedation, confusion, hallucinations, psychosis, ataxia, vertigo, hyperirritability, emotional disturbances, paranoid symptoms, coma

EENT: diplopia, nystagmus, eyelid edema

GI: nausea, vomiting, anorexia

GU: erectile dysfunction

Hematologic: megaloblastic anemia,


Skin: flushing, rash


Drug-drug.Acetazolamide, succinimide: decreased primidone blood level Carbamazepine: decreased primidone blood level, increased carbamazepine blood level

Hydantoins, isoniazid, nicotinamide: increased primidone blood level

Drug-diagnostic tests.Hemoglobin, platelets: decreased levels

Liver function tests: altered results

Patient monitoring

• Monitor primidone and phenobarbital blood levels.
• Monitor CBC and blood chemistry. Watch for evidence of blood dyscrasias.
• Assess neurologic status regularly. Stay alert for excessive drowsiness and emotional status changes.

Patient teaching

Caution patient not to discontinue therapy suddenly. Advise him to discuss dosage changes with prescriber.

Instruct patient to immediately report unusual bleeding, bruising, or rash.
• Tell patient drug may cause sexual dysfunction. Advise him to discuss this issue with prescriber.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.


/prim·i·done/ (prim´ĭ-dōn) an anticonvulsant used in the treatment of generalized tonic-clonic, nocturnal myoclonic, and partial seizures.


an anticonvulsant.
indications It is prescribed in the treatment of seizure disorders, including tonic-clonic, psychomotor, and focal epilepsy-like seizures, and has an unlabeled use for treating familial (essential) tremor.
contraindications Porphyria, pregnancy, or known hypersensitivity to this drug or to phenobarbital, a metabolite of primidone, prohibits its use. The drug must be used with caution in those having renal, hepatic, or pulmonary insufficiency.
adverse effects The most serious adverse effect, seen on rare occasions, is megaloblastic anemia. Drowsiness, ataxia, and dizziness are common. Drug dependency and other adverse effects of phenobarbital may occur.


Desoxyphenobarbital Neurology An anticonvulsant used as a monotherapy for partial seizures–eg, secondary generalized seizures. See Phenobarbital, Seizures.


An ANTICONVULSANT drug used in the treatment of EPILEPSY. A brand name is Mysoline.


an anticonvulsant related to phenobarbital. Used in dogs to control seizures of epilepsy and encephalitis.
References in periodicals archive ?
Zesiewicz said in an interview, adding that patients not responding to primidone or propranolol, or in whom these are con-traindicated, might benefit from any of the currently recommended second-line agents with level B supporting evidence.
Features Distinguishing Essential Tremor (ET) From Tremor of Parkinson's Disease (PD) Feature PD ET Tremor Occurs at rest, often Present when holding present during a posture or with walking; decreases at action least transiently with posture holding or action Frequency 3-6 Hz 5-12 Hz Distribution Asymmetric Usually symmetric Body parts Hands and legs Hands, head, voice Writing Micrographia (small Tremulous handwriting) Course Progressive Stable or slowly progressive Family history Less common Common Other Neurologic Bradykinesia, None Signs rigidity, decreased postural reflexes Substances That Levodopa, dopamine Alcohol, propranolol, Improve Tremor agonists, primidone anticholinergics ET = essential tremor; PD = Parkinson's disease.
Primidone Tablets USP, in strengths of 50mg and 250mg, an AB-Rated, therapeutically equivalent alternative to Mysoline(R) (a trademark of Valeant Pharmaceuticals) which, used alone or concomitantly with other anticonvulsants, is indicated in the control of grand mal, psychomotor, and focal epileptic seizures.
And some of these drugs--particularly phenytoin, primidone (Mysoline), and phenobarbital--inhibit the transfer of vitamin K across the placenta.
Lamotrigine is indicated as adjunctive therapy for partial seizures (the generalized seizures of Lennox-Gastaut syndrome), is indicated for conversion to monotherapy in adults with partial seizures who are receiving treatment with carbamazepine, phenytoin, phenobarbital, primidone, or valproate as the single AED, and is indicated for the maintenance treatment of Bipolar I Disorder to delay the time to occurrence of mood episodes (depression, mania, hypomania, mixed episodes) in patients treated for acute mood episodes with standard therapy.
The older seizure medicines (such as phenytoin, phenobarbital, primidone, carbamazepine, and valproate) have been shown to have higher rates of major birth defects with valproate showing the greatest risk, especially when used along with other seizure medicines.
All of the older P450 enzyme-inducing drugs--carbamazepine, phenytoin, primidone, and phenobarbital--metabolize through the cytochrome P450 system.
Backup contraception would be warranted when taking phenytoin, carbamazepine, primidone, ethosuximide, methylphenobarbital, paramethadione, Phenobarbital, topiramate, rifampin, or griseofulvin and St John's wort.
Simultaneous measurement of phenobarbital, phenytoin, primidone, ethosuximide, and carbamazepine in serum by high-pressure liquid chromatography.
Classification and Pharmacologic Management of Seizures Seizure First Line Agents New/Alternative Agents Simple Partial phenytoin primidone carbamazepine phenobarbital valproic acid gabapentin lamotrigine felbamate topiramate ethotoin mephenytoin Complex partial phenytoin primidone carbamazepine valproic acid phenobarbital mephobarbital gabapentin lamotrigine felbamate topiramate amobarbital Absence clonazepam methsuximide ethosuximide phensuximide valproic acid lamotrigine trimethadione Myoclonic valproic acid clonazepam Tonic Clonic phenytoin/fosphenytoin phenobarbital carbamazepine primidone valproic acid topiramate Stares epilepticus phenytoin/fosphenytoin diazepam lorazepam phenobarbital diazepam secobarbital pentobarbital
The immediate-release formulation of Lamictal is indicated 1) as adjunctive therapy for partial seizures, primary generalized tonic-clonic seizures, and the generalized seizures of Lennox-Gastaut syndrome in adults and pediatric patients as young as 2 years and 2) for conversion to monotherapy in adults with partial seizures taking carbamazepine, phenytoin, phenobarbital, primidone, or valproate as the single AED.
Many of the older seizure medicines (such as phenytoin, carbamazepine, phenobarbital, primidone and valproate) fall into this group of drugs.