From the FDA Drug Label
DOSAGE AND ADMINISTRATION Usual Dosage Patients 8 years of age and older who have received no previous treatment may be started on primidone tablets according to the following regimen using either 50 mg or scored 250 mg primidone tablets: Days 1 to 3: 100 to 125 mg at bedtime. Days 4 to 6: 100 to 125 mg twice a day. Days 7 to 9: 100 to 125 mg three times a day Day 10 to maintenance: 250 mg three times a day. For most adults and children 8 years of age and over, the usual maintenance dosage is three to four 250 mg primidone tablets in divided doses (250 mg three times a day or four times a day). Pediatric Dosage For children under 8 years of age, the following regimen may be used: Days 1 to 3: 50 mg at bedtime. Days 4 to 6: 50 mg twice a day. Days 7 to 9: 100 mg twice a day. Day 10 to maintenance: 125 mg three times a day to 250 mg three times a day.
The recommended primidone dose and frequency are as follows:
- For patients 8 years of age and older:
- Initial dose: 100 to 125 mg at bedtime, increasing to 100 to 125 mg twice a day, then to 100 to 125 mg three times a day
- Maintenance dose: 250 mg three times a day, with a maximum of 500 mg four times a day 1
- For children under 8 years of age:
- Initial dose: 50 mg at bedtime, increasing to 50 mg twice a day, then to 100 mg twice a day
- Maintenance dose: 125 mg three times a day to 250 mg three times a day, or 10 to 25 mg/kg/day in divided doses 1
From the Research
Primidone should be started at a low dose of 125 mg once daily and gradually increased to minimize side effects, with most adults requiring a maintenance dose of 250 mg three times daily (750 mg total daily dose) 2. The dose and frequency of primidone can vary depending on the individual patient's response and tolerance to the medication.
- The initial dose is typically 125 mg once daily, usually taken at bedtime, to minimize side effects such as drowsiness, dizziness, and fatigue.
- After 3-4 days, the dose can be increased to 125 mg twice daily, and further increases should occur gradually.
- Some patients may need up to 2000 mg daily, divided into multiple doses, while others may respond to lower doses of 125-250 mg daily.
- Elderly patients or those with liver impairment should start at lower doses, typically 125 mg at bedtime, with slower titration 3, 4, 5. The medication works by converting to phenobarbital in the body and directly affecting brain activity to reduce abnormal electrical discharges.
- Common side effects include drowsiness, dizziness, and fatigue, which often improve as the body adjusts to the medication.
- Taking primidone with food can help reduce gastrointestinal side effects.
- Regular blood level monitoring may be necessary to ensure appropriate dosing and therapeutic effect 6. It is essential to note that the treatment of essential tremor depends on the tremor severity, location, and risk-benefit ratios, and primidone is one of the first-line treatments for limb tremor 5.