Primidone
1 medicine
Primidone is an anticonvulsant that the body converts into phenobarbital, used for seizures and essential tremor; it must never be stopped abruptly, since sudden withdrawal can trigger seizures even in people without epilepsy.
Key facts
- Primidone (brand name Mysoline) is an anticonvulsant that the liver converts partly into phenobarbital, a barbiturate that calms overactive electrical activity in the brain.
- It treats generalized and partial (focal) seizures, and essential tremor when other treatments have not worked well enough.
- Never stop primidone suddenly. Because your brain adapts to its calming effect, abrupt withdrawal can trigger rebound seizures, even in people who take it only for tremor. Dose changes must be gradual and doctor-directed.
- Seek urgent care for a severe rash or blistering skin, unusual bruising or bleeding, or new thoughts of self-harm.
What primidone treats
Primidone controls generalized tonic-clonic seizures and partial seizures that start in one area of the brain. It is also prescribed for essential tremor, a persistent shaking of the hands or arms that is not caused by a separate neurological disease, usually when beta-blockers have not given enough relief.
How primidone works
The liver breaks primidone down into phenobarbital and phenylethylmalonamide (PEMA), both of which are active. These compounds enhance the calming effect of GABA, the brain's main inhibitory chemical, which raises the threshold for seizures and steadies the nerve signals that produce tremor.
Before you take it
- Avoid primidone if you have porphyria, since barbiturates can trigger a dangerous attack.
- Tell your prescriber if you are pregnant or planning pregnancy. Primidone crosses the placenta, and untreated seizures also carry risks, so the choice is made individually, usually alongside folic acid supplementation.
- Avoid alcohol, opioids, sleeping tablets, and other sedatives, since their drowsiness and breathing-slowing effects add to primidone's.
- Primidone reduces the effectiveness of hormonal contraceptives; discuss additional contraception with your prescriber.
Side effects
Common effects, especially when starting treatment, include drowsiness, dizziness, unsteadiness, nausea, and blurred vision.
Stop and seek urgent medical care for any of these:
- Severe rash or blistering skin.
- Unusual bruising, bleeding, or nosebleeds.
- Marked mood changes, confusion, or thoughts of self-harm.
- Signs of a seizure returning after a missed or reduced dose.
Safety essentials
- Never stop or reduce primidone abruptly; withdrawal can cause seizures. Any change in dose must be tapered gradually under medical supervision.
- Because primidone converts to phenobarbital, its sedative effect adds up with alcohol and other sedating drugs, which can cause dangerous drowsiness or slowed breathing.
- It lowers the effectiveness of hormonal contraception, so an additional or alternative method is usually needed.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.