Primidone: uses, dosing, side effects & brands

Primidone is an anti-epileptic agent sold in the U.S. under 2 brand and generic names, for partial epilepsies, tonic-clonic epilepsy and tremor. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.

By the pharmaranks editorial teamReviewed against the FDA (openFDA label, NDC Directory & Enforcement) sourcesUpdated Jul 24, 2026How we research

Key facts

Drug class: Anti-Epileptic Agent
Treats: Partial Epilepsies, Tonic-Clonic Epilepsy and Tremor
Available as: Tablet
Sold as: 2 products — Mysoline and Primidone
Prescription?: Prescription only
Generic available?: Yes
What the pharmacy pays: about $3 for a 30-count supply — not your price

How primidone is dosed

From the FDA label for Mysoline (application NDA009170). Other primidone products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.

Usual Dosage Patients 8 years of age and older who have received no previous treatment may be started on MYSOLINE according to the following regimen using either 50 mg or scored 250 mg MYSOLINE 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 MYSOLINE tablets in divided doses (250 mg three times a day or four times a day). If required, an increase to five or six 250 mg tablets daily may be made, but daily doses should not exceed 500 mg four times a day. Dosage should be individualized to provide maximum benefit. In some cases, serum blood level determinations of primidone may be necessary for optimal dosage adjustment. The clinically effective serum level for primidone is between 5 to 12 mcg/mL. INITIAL: ADULTS AND CHILDREN OVER 8 KEY: •=50 mg tablet; ●=250 mg tablet DAY 1 2 3 4 5 6 AM •• •• •• NOON PM •• •• •• •• •• •• DAY 7 8 9 10 11 12 AM •• •• •• ● Adjust to Maintenance NOON •• •• •• ● PM •• •• •• ● Patients Already Receiving Other Anticonvulsants MYSOLINE should be started at 100 to 125 mg at bedtime and gradually increased to maintenance level as the other drug is gradually decreased. This regimen should be continued until…

Primidone side effects

The most frequently occurring early side effects are ataxia and vertigo. These tend to disappear with continued therapy, or with reduction of initial dosage. Occasionally, the following have been reported: nausea, anorexia, vomiting, fatigue, hyperirritability, emotional disturbances, sexual impotency, diplopia, nystagmus, drowsiness, and morbilliform skin eruptions. Granulocytopenia, agranulocytosis, and red-cell hypoplasia and aplasia, have been reported rarely. These and, occasionally, other persistent or severe side effects may necessitate withdrawal of the drug. Megaloblastic anemia may occur as a rare idiosyncrasy to MYSOLINE and to other anticonvulsants. The anemia responds to folic acid without necessity of discontinuing medication. To report SUSPECTED ADVERSE REACTIONS, contact Bausch Health US, LLC at 1-800-321-4576 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Who shouldn’t take primidone

Primidone is contraindicated in: 1) patients with porphyria and 2) patients who are hypersensitive to phenobarbital (see ACTIONS ).

Every primidone product we track (2)

Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.

Primidone products
#	Drug	Rating	Type	Form	Generic?	Pharmacy pays
1	Mysoline	70/100	Prescription	Tablet	Generic	$3	View →
2	Primidone	70/100	Prescription	Tablet	Generic	$3	View →

What primidone pills look like

Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.

Primidone pill imprints
Imprint	Strength	Colour	Shape	Maker
AN;44	50 mg	white	round	—
AN;44	50 mg	white	round	—
AN;545	250 mg	white	round	—
AN;44	50 mg	white	round	—
AN;545	250 mg	white	round	—
DAN;DAN;5321	250 mg	white	round	—
684;O	50 mg	white	round	—
685;O	250 mg	yellow	round	—

Primidone recalls

From the FDA Enforcement database. A recall covers specific lots — not the drug as a whole.

How long primidone keeps

No primidone label we read sets a separate limit for after opening, but they do specify how it must be stored — and the stability behind any date assumes those conditions.

Does primidone expire? The in-use limits and storage rules from its labels

Primidone and breastfeeding

From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.

Ample evidence exists that primidone taken during nursing can affect the breastfed infant. Infant serum levels of primidone and its metabolites are often near or in the therapeutic range and symptoms of sedation and poor nursing have been reported. On the other hand, infants exposed in utero sometimes have withdrawal symptoms that are either alleviated by breastfeeding or worsened when breastfeeding is abruptly stopped. If the mother requires primidone, it is not a reason to discontinue breastfeeding. However, the infant must be monitored for sedation, poor feeding, poor weight gain., and developmental milestones, especially in younger, exclusively breastfed infants and when using combinations of anticonvulsant drugs. Measurement of an infant serum level might help rule out toxicity if there is a concern.

Full LactMed record for primidone: levels in milk, effects in breastfed infants, and the drugs it would consider instead

National Institute of Child Health and Human Development, record revised September 15, 2024. LactMed states its information is not a substitute for professional judgement.

What people report to the FDA about primidone

The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 8,936 reports naming primidone, and the FDA flagged 64% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:

fatigue597 reports
fall592 reports
tremor520 reports
diarrhoea446 reports
dizziness433 reports
nausea408 reports
somnolence349 reports
headache342 reports

Read these as a signal, not a rate. A report does not mean primidone caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.

Source: openFDA drug/event (FAERS), retrieved August 26, 2026.

Related calculators

How long it stays in your system →

Frequently asked questions

What is primidone?

Mysoline (Primidone) is an anti-epileptic agent used to treat Partial Epilepsies, Tonic-Clonic Epilepsy, Tremor.

What kind of drug is primidone?

The FDA classifies primidone as an anti-epileptic agent. Anti-epileptic (anticonvulsant) drugs calm the abnormal, excessive electrical activity that triggers seizures. They do this by stabilizing overactive sodium or calcium channels in nerve cells, boosting the brain's natural calming chemical GABA, or dampening excitatory signals, which makes nerves less likely to fire uncontrollably. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

Can you take primidone with other medicines?

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run primidone against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

What brand names is primidone sold under?

We track 2 primidone-containing products in the U.S.: Mysoline and Primidone. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

What forms does primidone come in?

Across the brands we track, primidone is currently marketed as tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Is there a generic primidone?

Yes. Our catalog lists 1 generic primidone product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

Has primidone been recalled?

The FDA's Enforcement database lists at least 5 recall records whose product description mentions primidone. The most recent: Primidone Tablets (Jun 3, 2026). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Cite this page

APA: pharmaranks. (2026, July 24). Primidone: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/primidone
MLA: “Primidone: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/primidone.

We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.

Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.

Read the full FDA label for primidone on DailyMed (NIH) ↗.