Primidone

Actions

Barbiturate.

• Prolongs GABA-mediated chloride channel openings
• Blocks kainate receptors

Metabolism

Hepatic

Elimination

Renal ~65%

Enzyme induction

• CYP1A2
• CYP2B6
• CYP2C8
• CYP2C9
• CYP3A4

Therapeutic serum concentration range

5-12 μg/ml

Half-life

Primidone: 5-18 hours, as phenobarbital: 50 to 150 hours

Plasma protein binding

25%

Important side-effects

Suicidal behavior and ideation

CNS depression

Indications

Focal and generalized seizures.

Dosing recommendation

Start with 62.5 mg/day.

Increase to target dose over about 3 weeks.

Target dose: 500–1500 mg/day divided in 2-3 doses.

Renal impairment

Careful titration and monitoring of serum concentration is advised in patients with impaired renal function.

Hepatic impairment

Careful titration and monitoring of serum concentration is advised in patients with impaired hepatic function.