Primidone 250mg

Primidone, Mysoline
Description: Anticonvulsant, Miscellaneous; Barbiturate

CSA NA – FDA Approved – REMS (N) – Cannot Ship To US – Not on DEA diversion, but is still a barbiturate

Primidone, Mysoline decreases neuron excitability and raises seizure threshold similar to phenobarbital.  Primidone has two active metabolites, phenobarbital and phenylethylmalonamide (PEMA). PEMA may enhance the activity of phenobarbital.

Management of grand mal, psychomotor, and focal seizures

Before starting Primidone, Mysoline make sure your physician is aware of any allergies or medications you currently take, if you have porphyria, depression, hepatic impairment, hypoadrenalism, renal impairment, respiratory disease, a history of substance abuse, are pregnant, or breastfeeding. Primidone, Mysoline use has been associated with rare but serious adverse events such as CNS depression and suicidal ideation.

Oral: 

Days 1 to 3: 100 – 125 mg/day at bedtime

Days 4 to 6: 100 – 125 twice daily 

Days 7 to 9: 100 – 125 mg 3 times daily

Usual dose: 750 to 1,500 mg/day in divided doses 3 to 4 times/day with maximum dosage of 2 g/day

How to Take: Administer without regard to food; may consider food to decrease GI upset.  To avoid folic acid deficiency and megaloblastic anemia, some clinicians recommend giving patients on anticonvulsants prophylactic doses of folic acid and cyanocobalamin.  Primidone use has been associated with low serum concentrations of vitamin B2 (riboflavin), B6 (pyridoxine), and B12 (cyanocobalamin), which may contribute to hyperhomocysteinemia. Hyperhomocysteinemia may contribute to cardiovascular disease, venous thromboembolic disease, dementia, neuropsychiatric symptoms, and poor seizure control. Some clinicians recommend administering riboflavin, pyridoxine, and cyanocobalamin supplements in patients taking primidone.

You Need to Avoid:  Anticonvulsants should not be discontinued abruptly because of the possibility of increasing seizure frequency.  Therapy should be withdrawn gradually to minimize the potential of increased seizure frequency unless safety concerns require a more rapid withdrawal. 

Ataxia, drowsiness, emotional disturbance, fatigue, hyperirritability, suicidal ideation, vertigo, morbilliform rash, anorexia, nausea, vomiting, impotence, agranulocytosis, granulocytopenia, megaloblastic anemia (idiosyncratic), pure red cell aplasia, red cell hypoplasia, diplopia, nystagmus

Note the frequency of side effects is not established in a clinical trial.

1. What do I do if side effects are intolerable?
   If side effects are causing a lot of distress speak to your physician as soon as possible to discuss options.