Formulary
Primidone: Indications, Dosing, Side Effects and Interactions
Primidone is partially converted to phenobarbital, but is also considered to have some antiepileptic action in its own right.
MedNext Academy | 3 min read
Primidone: Indications, Dosing, Side Effects and Interactions
Primidone is partially converted to phenobarbital, but is also considered to have some antiepileptic action in its own right.
Drug action
Primidone is partially converted to phenobarbital, but is also considered to have some antiepileptic action in its own right.
Indications and dose
**All forms of epilepsy except typical absence seizures**
- **Child** (By Mouth): 9-17 years Initially 125 mg once daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, increased to 250 mg twice daily, then increased in steps of 250 mg every 3 days (max. per dose 750 mg twice daily), adjusted according to response.
- **Adult** (By Mouth): Initially 125 mg once daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, increased to 500 mg daily in 2 divided doses, then increased in steps of 250 mg every 3 days, adjusted according to response; maintenance 0.75-1.5 g daily in 2 divided doses.
**Essential tremor**
- **Adult** (By Mouth): Initially 50 mg daily, then adjusted according to response to up to 750 mg daily, dose to be increased over 2-3 weeks.
**All forms of epilepsy except typical absence seizures for primidone**
- **Child 1 month-1 year** (By mouth): Initially 125 mg daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, adjusted according to response; maintenance 125-250 mg twice daily.
- **Child 2-4 years** (By mouth): Initially 125 mg once daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, adjusted according to response; maintenance 250-375 mg twice daily.
- **Child 5-8 years** (By mouth): Initially 125 mg once daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, adjusted according to response; maintenance 375-500 mg twice daily.
- **Child 9-17 years** (By mouth): Initially 125 mg once daily, dose to be taken at bedtime, then increased in steps of 125 mg every 3 days, increased to 250 mg twice daily, then increased in steps of 250 mg every 3 days (max. per dose 750 mg twice daily), adjusted according to response.
Cautions
Avoid in Acute porphyrias ; children; debilitated; elderly (in adults); history of alcohol abuse; history of drug abuse; respiratory depression (consider dose reduction) Cautions, further information MHRA advises consider vitamin D supplementation in patients who are immobilised for long periods or who have inadequate sun exposure or dietary intake of calcium.
Side effects
Common or very common Apathy; movement disorders; nausea; nystagmus; visual impairment Uncommon Dizziness; headache; hypersensitivity; skin reactions; vomiting Rare or very rare Arthralgia; bone disorders; Dupuytren's contracture; leucopenia; lymphadenopathy; megaloblastic anaemia (may be treated with folic acid); psychotic disorder; severe cutaneous adverse reactions (SCARs); systemic lupus erythematosus (SLE); thrombocytopenia Frequency not known Bone fracture; confusion; drowsiness; hallucination; suicidal behaviours
Interactions
**Severe interactions:**
- Contraindications of concomitant use Primidone and its main metabolite phenobarbital are strong inducers of cytochrome P450 and thus lead to life-threatening situations due to the risk of decreased...
- Possible toxicity with phenytoin on stopping primidone); stiripentol, tiagabine, valproic acid, zonisamide.
**Other interactions (2):**
- Concomitant use not recommended Risk of decreased plasma concentrations due to increased metabolism induced by primidone for: - Drugs affecting nervous system* (except anti-epileptics): mianserin,...
- Precautions including dose adjustment: Risk of decreased plasma concentrations due to increased metabolism induced by primidone for: - Other anti-epileptics: carbamazepine; felbamate; lamotrigine;...
Pregnancy
Important safety information For primidone MHRA/CHM advice: Antiepileptics: risk of suicidal thoughts and behaviour (August 2008) See Epilepsy . MHRA/CHM advice: Antiepileptic drugs: updated advice on switching between different manufacturers' products (November 2017) See Epilepsy and see also Prescribing and dispensing information . MHRA/CHM advice: Antiepileptic drugs in pregnancy: updated advice following comprehensive safety review (January 2021) See Epilepsy .
Hepatic impairment
Manufacturer advises caution. Dose adjustments Manufacturer advises consider dose reduction.
Renal impairment
Use with caution. M Dose adjustments Consider dose reduction. M
Medicinal forms
Capsule,Tablet,Suspension
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
Inside MedNext for this topic
- 411 MedNext-authored chapters
- 80,000+ MCQ bank
- 15 study modes
- Growing visual cheat sheets
Study modes
- Notes
- MCQ
- Audio
- Video
- Visual
- 3D Anatomy
- Trace
- Flashcards
- Mnemonics
- Image Bank
- Clinical
- Microscopy
- Audio QBank
- Cadaver
- Book Match
Continue reading
Subject HubPharmacology Hub
All pharmacology resources in one place.
Drug SchedulesIndian Drug Schedules
Schedule H, H1, X and G classifications.
FormularyBrowse all drugs
Search 1,850+ drug profiles.
Study Primidone in the MedNext app
Challenge yourself with targeted pharmacology MCQs on this drug class. Every explanation links back to the chapter that teaches the concept.
Start drug challengeExplore the full formulary

