Mysoline: Uses and Side Effects

Anti-seizure medication approved for epilepsy and benign essential tremor

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

How It Works

Mysoline is in the barbiturate class of medications. It becomes metabolized 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.

For Seizure Prevention 

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

  • Generalized seizures are seizures that affect the whole brain, typically resulting in impairment of or loss of consciousness.
  • Tonic-clonic seizures are seizures characterized by shaking and jerking of the body.
  • Generalized tonic-clonic seizures are characterized by jerking movements with impairment of consciousness.

Partial seizures are seizures that only impact brain activity in a limited region of the brain, and complex seizures affect consciousness. Complex partial seizures are characterized by movements that typically begin in one part of the body and involve impairment of consciousness.

Because Mysoline is indicated for all of these types of seizures, it can be used for a variety of types of epilepsy. Mysoline can be used as monotherapy (as the only anticonvulsant to control seizures) or it can be used in combination with one or more other anticonvulsants. 

Mysoline is indicated for adults and children of all ages. It is considered a maintenance medication that you would have to take on a regular basis for the prevention of 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. Benign essential tremor is a condition in which 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.

It is not the same as Parkinson’s disease. Parkinson’s disease is characterized by a tremor that occurs at rest, as well as shuffling when walking, and an expressionless face that is described as a masked face. Parkinson’s disease generally worsens over time, is associated with dopamine deficiency, and is treated with dopaminergic medications.

Benign essential tremor, on the other hand, is a fine motor tremor that is worse with action and often worsens with anxiety. It is not typically associated with the other characteristics of Parkinson’s disease. The two conditions are treated with different medications. The cause of essential tremor may be genetic, but often it is not known why someone develops the condition.


Mysoline comes in oral (by mouth) form and generally should be taken with food. It normally comes as a tablet, but it can be given as an oral suspension liquid form for young babies or for people who cannot swallow pills.

Mysoline Dose

The dose of Mysoline is higher when it is used for seizure control than when it is used for control of tremors in benign essential tremor.

Mysoline Dose for Seizures

Mysoline comes in 50 mg and 250 mg tablets. The usual dose for an adult for seizure prevention is 250 mg, three times a day or four times per day, but lower doses may also be effective, especially if Mysoline is taken along with another anticonvulsant. It should be started at a dose of about 100 mg or 125 mg per day and gradually increased to the target dose over a period of approximately one week.

For children, the target dose for seizure prevention is 10-25 mg/kg/day, and, as with adults, it is usually started at a lower dose and gradually increased over a period of approximately a week.

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

Mysoline Dose for Tremors

When Mysoline is used for control of benign essential tremors, the recommended dose is lower than it is for seizures, typically 100 mg/ day, and is generally taken as 50 mg twice per day. Benign essential tremor is a condition that normally affects older adults and not children.

While maintaining a steady state of the medication is not as vital for treatment of tremors as it is for seizures, abrupt withdrawal is dangerous in both situations because it can trigger a seizure.


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 doctor instead of stopping the medication on your own. If you have epilepsy, your doctor may need to start another anti-seizure medication as you slowly decrease your Mysoline dose.

If you have tremors, you will probably gradually discontinue the Mysoline and may begin another medication to control the tremors after you stop taking Mysoline completely.

Side Effects

There are a number of side effects of Mysoline, including drowsiness, dizziness, and nausea. If you experience these side effects, you should tell your doctor.


People who have certain conditions cannot take Mysoline. These conditions include porphyria, and anemia, which are red blood cell disorders, and disorders of platelets, which are cells that the body uses for blood clotting.

As with many other anticonvulsants, you should not drink alcohol if you take Mysoline. Alcohol can interfere with seizure control, and taking Mysoline and alcohol in combination can make you drowsy, and may dangerously increase your chances of loss of consciousness.


Mysoline can cause birth defects if taken during pregnancy. If you are pregnant or planning to become pregnant, your doctor will carefully consider your anticonvulsant medications, because seizures during pregnancy are also dangerous for the mother and the baby.

A Word From Verywell

Mysoline is an anti-seizure medication and is also used to control tremors for people who have benign essential tremor. Do not be concerned if your doctor prescribes Mysoline for your tremors—this does not mean that you have seizures or will get seizures from the medication.

If you are taking Mysoline for epilepsy, rest assured that epilepsy is a treatable condition, and that medication can control your seizures. 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.

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