Mysoline: Uses and Side Effects

Approved for epilepsy and benign essential tremor

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Mysoline (primidone) is an anti-seizure medication that is FDA-approved for preventing seizures in people with epilepsy. It is also commonly used off-label for the treatment of a condition called benign essential tremor.

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Mysoline may be prescribed for certain types of seizures. It may also be used in the treatment of benign essential tremor, typically after other treatments have failed.

For Seizure Prevention 

Mysoline is an anti-seizure medication indicated for generalized tonic-clonic seizures as well as complex partial seizures.

Because Mysoline is indicated for all of these types of seizures, it can be used for multiple types of epilepsy. It's sometimes used as monotherapy (as the only anti-seizure medication), and it can be used alongside one or more other seizure drugs.

Mysoline is indicated for adults and children of all ages. It's a maintenance medication that you take on a regular basis to prevent seizures, and it is not generally used to stop seizures in an emergency situation.

For Benign Essential Tremor 

Mysoline is often used to reduce tremors in people who have a condition called benign essential tremor.

With this condition, people experience frequent tremors, typically of the hands and/or mouth. Tremors of the mouth, throat, or larynx (voice box) can manifest as a shaky voice.

Unlike tremors associated with Parkinson’s disease, which occur at rest, benign essential tremor is a fine motor tremor that is worse with activity and often worsens with anxiety. The cause may be genetic, but often healthcare providers don't know why someone develops the condition.

Benign essential tremor is a condition that normally affects older adults and not children.

How It Works

Mysoline is in the barbiturate class of medications. Your body metabolizes it to phenobarbital, a well-known barbiturate. This class of medications suppresses electrical activity in the brain, specifically the sodium channels, which can diminish the erratic electrical activity associated with seizures. Barbiturates are also known to interact with the inhibitory neurotransmitter GABA, slowing down electrical activity in the brain.

The mechanism by which Mysoline helps with tremor is likely due to the same effects on electrical activity and GABA.

This mechanism of action is responsible for the therapeutic effects, as well as the side effects of the medication.


Mysoline comes in oral (by mouth) form in 50 milligram (mg) and 250 mg tablets. It can also be given as an oral suspension liquid for young babies or people who cannot swallow pills. Generally, Mysoline should be taken with food.

The dose of Mysoline is higher when it is used for seizure control than when it's used for tremor.

Dosing for Seizures

The usual adult dose for seizure prevention is 250 mg three or four times a day. Lower doses may also be effective, especially if taken with another anti-seizure drug.

Mysoline should be started at a dose of about 100 to 125 mg per day and gradually increased to the target dose over a period of about a week.

For children, the target dose for seizure prevention is between 10 and 25 mg/kg per day. As with adults, it's usually started at a lower dose and gradually increased.

When you take Mysoline for seizure control, it is important to maintain a steady state of the medication in your body, as variations can make seizures more likely. Abrupt withdrawal is dangerous because it can trigger seizures.

Dosing for Tremors

When Mysoline is used to control benign essential tremors, the recommended dose is typically 100 mg per day, which is usually taken in two doses of 50 mg each.

Maintaining a steady state of the medication is not as vital for treating tremors as it is for seizures. However, in spite of the lower dose, abrupt withdrawal still may trigger a seizure.

Side Effects

Mysoline has a number of side effects, including:

  • Drowsiness
  • Dizziness
  • Nausea

If you experience these side effects or others, you should tell your healthcare provider.


People who have certain conditions cannot take Mysoline. These conditions include red blood cell disorders (such as porphyria and anemia) and platelet disorders.

As with many other epilepsy medications, you should not drink alcohol if you take Mysoline. Taking Mysoline and alcohol together can make you drowsy and may dangerously increase your chances of losing consciousness. It can also interfere with seizure control.


Mysoline can cause birth defects if taken during pregnancy. If you are pregnant or planning to become pregnant, you and your healthcare provider should carefully consider your anti-seizure medications. Remember that seizures during pregnancy are dangerous for both you and your baby.


If you are not happy with the effects of the medication, either because it is not controlling your symptoms or because intolerable side effects, then you need to discuss your concerns with your healthcare provider instead of stopping the medication on your own. If you have epilepsy, you may need to start another anti-seizure medication as you slowly decrease your Mysoline dose.

If you have tremors, you will probably gradually discontinue Mysoline and may begin another medication to control the tremors after you stop taking Mysoline completely. This should be done under a healthcare provider's supervision and according to his or her instructions for weaning off of the drug.

A Word From Verywell

You may need to try several medications and other treatment options before your epilepsy is under control. Communicating with your healthcare provider is essential, as is taking medications exactly as prescribed. Epilepsy (and benign essential tremors) is highly treatable. In the rare instance that your epilepsy cannot be controlled with medication, you might need to have epilepsy surgery, which is a safe and effective option.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.