MYSOLINE

What it is

Mysoline contains 250 mg primidone as the active ingredient. Mysoline tablets are white or virtually white, round biconvex, uncoated tablets.

Approved indications —

Management of grand mal epilepsy — Management of psychomotor (temporal lobe) epilepsy — Management of focal or Jacksonian seizures — Management of myoclonic jerks — Management of akinetic attacks

Dosing overview

Treatment must always be planned on an individual basis and Mysoline is usually given twice daily. Begin with 1/2 tablet once daily late in the evening. Every three days, increase the daily dosage by 1/2 tablet until the patient is receiving 2 tablets daily. Thereafter, every three days, increase the daily dosage by 1 tablet in adults or 1/2 tablet in children under 9 years, until control is obtained or the maximum tolerated dosage is being given. Average daily maintenance doses are: children up to 2 years 1–2 tablets (250–500 mg); children 2–5 years 2–3 tablets (500–750 mg); children 6–9 years 3–4 tablets (750–1,000 mg); adults and children over 9 years 3–6 tablets (750–1,500 mg).

Key safety warnings

Primidone is extensively metabolised to phenobarbital and may cause fetal harm when administered to a pregnant woman. Prenatal exposure to primidone may increase the risk for congenital malformations and adverse developmental outcomes. Primidone should not be used in women of childbearing potential unless the potential benefit is judged to outweigh the risks following consideration of other suitable treatment options. Primidone may affect vitamin D metabolism, which may predispose to the development of bone disease, and long term use may lead to a reduction of bone mineral density and development of osteoporosis. Patients on long term treatment should be monitored for bone density and supplementation with vitamin D should be considered. Antiepileptic drugs, including primidone, increase the risk of suicidal thoughts or behaviour in patients taking these drugs for any indication. Patients treated with any antiepileptic drug for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behaviour, and any unusual changes in mood or behaviour. Life threatening cutaneous reactions Stevens–Johnson syndrome and toxic epidermal necrolysis have been reported with the use of primidone. Patients should be advised of the signs and symptoms and monitored closely for skin reactions. The highest risk for occurrence is within the first weeks of treatment.

Contraindications

Mysoline is contraindicated in patients with hypersensitivity or allergic reactions to primidone, or to any of the excipients, and in patients with acute intermittent porphyria.

PBS listing

Mysoline 250 mg tablets are listed on the PBS as a single item with restricted listing. The ex-manufacturer price is A$52.92.

Regulatory history

Mysoline primidone 250 mg tablets were first registered on the ARTG on 11 July 1991. In November 2019, the PBAC recommended Mysoline as a new listing for epilepsy to address a current shortage of the brand.