Primidone | Side Effects, Dosage, Uses & More
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Generic Name:

primidone, Oral tablet

All Brands

  • Mysoline
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Highlights for primidone

Oral tablet
1

Primidone is an oral drug that’s used to treat certain types of seizures.

2

This drug may cause suicidal thoughts or actions in a very small number of people, about 1 in 500. Call you doctor right away if you have any thoughts about suicide, especially if they are new, worse, or worry you.

3

Common side effects include walking problems and dizziness. These side effects tend to go away after your body gets used to the medicine or after the dose is reduced.

4

You shouldn’t take primidone if you’re allergic to phenobarbital or have the genetic disorder called porphyria.

5

If you’re pregnant or plan to become pregnant, this drug may harm your unborn baby. Tell your doctor right away if you become pregnant while taking primidone.

IMPORTANT INFORMATION

Who shouldn’t take this drug

You should not take primidone if you’re allergic to phenobarbital or if you have the genetic disorder porphyria.

Suicidal thoughts

This drug may cause suicidal thoughts or actions in a very small number of people, about 1 in 500. Call you doctor right away if you have any of these symptoms, especially if they are new, worse, or worry you:

  • thoughts about suicide or dying
  • attempts to commit suicide
  • new or worse depression
  • new or worse anxiety
  • feeling agitated or restless
  • panic attacks
  • trouble sleeping (insomnia)
  • new or worse irritability
  • anger
  • acting aggressive or violent
  • acting on dangerous impulses
  • an extreme increase in activity and talking (mania)
  • other unusual behavior or mood changes

What is primidone?

Primidone is a prescription drug. It’s available as an oral tablet.

Primidone may be used as part of a combination therapy. This means you may need to take it with other drugs used to prevent seizures.

Primidone is a generic drug. It’s also available as a brand-name drug called Mysoline. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version. Talk to your doctor to see if the generic version will work for you.

Why it's used

Primidone is used alone or with other medicines to treat people with:

  • generalized tonic-clonic (grand mal) seizures
  • complex partial (psychomotor) seizures
  • partial (focal) epileptic seizures

How it works

Primidone belongs to a class of drugs called anticonvulsant drugs. A class of drugs refers to medications that work similarly. They are often used to treat similar conditions.

Primidone works by increasing the action of a certain chemical in your brain (GABA). This helps prevent seizures.

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primidone Side Effects

Oral tablet

Most Common Side Effects

The most common side effects of primidone include:

  • lack of muscle control, which can cause problems with walking and moving

  • feelings of dizziness, spinning, or swaying (vertigo)

The side effects tend to go away after your body gests used to the medicine or after the dose is reduced. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life-threatening or if you think you’re experiencing a medical emergency, call 9-1-1.

  • thoughts or behaviors of hurting yourself. Symptoms include:

    • thoughts about suicide or dying
    • attempts to commit suicide
    • new or worse depression
    • new or worse anxiety
    • feeling agitated or restless
    • panic attacks
    • trouble sleeping (insomnia)
    • new or worse irritability
    • anger
    • acting aggressive or violent
    • acting on dangerous impulses
    • an extreme increase in activity and talking (mania)
    • other unusual behavior or mood changes
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Primidone may cause drowsiness, and may slow your thinking and movements. You shouldn’t drive, use machinery, or do other tasks that require alertness until you know how this drug affects you.

Primidone can cause severe sleepiness, especially when you first start taking the medicine.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
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primidone May Interact with Other Medications

Oral tablet

There are no formal studies done to see which drugs interact with primidone. However, it can still interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Alcohol interaction

You shouldn’t drink alcohol while taking primidone. Taking this drug with alcohol can make some of the drug’s side effects worse. These include sleepiness or dizziness.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
Primidone warnings
porphyria
People with porphyria

You should not take primidone if you have the genetic disorder called porphyria. (This is a rare condition that mainly affects the skin or nervous system.)

Pregnant women
Pregnant women

Primidone is a category D pregnancy drug. That means two things:

  1. Research in humans has shown adverse effects to the fetus when the mother takes the drug.
  2. This drug should only be used during pregnancy in serious cases where it's needed to treat a dangerous condition in the mother.

Talk to your doctor if you’re pregnant or planning to become pregnant. Ask your doctor to tell you about the specific harm that may be done to the fetus. This drug should be only used if the potential risk to the fetus is acceptable given the drug’s potential benefit.

If you become pregnant while taking primidone, talk to your doctor about registering with the North American Antiepileptic Drug (NAAED) Pregnancy Registry. The purpose of this registry is to collect information about the safety of seizure medications used during pregnancy.

breast-feeding
Women who are breast-feeding

Primidone can pass into breast milk and may cause serious effects in a breastfeeding child.

You and your doctor may need to decide if you’ll take primidone or breastfeed.

call the doctor
When to call the doctor

Tell your doctor if your seizures get worse or if you have any new types of seizures.

allergies
Allergies

Primidone can cause a severe allergic reaction. Symptoms include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives
  • rash

If you have an allergic reaction, call your doctor right away. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it or phenobarbital before. Taking it a second time after an allergic reaction could be fatal.

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How to Take primidone (Dosage)

Oral tablet

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Seizures (epilepsy)

Brand: Mysoline

Form: Oral tablet
Strengths: 50 mg, 250 mg

Generic: primidone

Form: Oral tablet
Strengths: 50 mg, 250 mg
Adult dosage (ages 18–64 years)

If you haven’t had treatment for seizures, follow this dosing schedule:

  • Days 1–3: take 100–125 mg by mouth at bedtime
  • Days 4–6: take 100–125 mg twice per day
  • Days 7–9: take 100–125 mg three times per day
  • Day 10 to maintenance: take 250 mg three times per day
  • The usual maintenance dose is 250 mg taken three times per day or 250 mg taken four times per day. Your doctor may increase your dose to 250 mg taken 5–6 times per day. Your dose shouldn’t be more than 500 mg taken four times per day.

If you’re already taking other seizure medicines:

Follow the same primidone schedule while slowly decreasing your other medicines. You should be off of your other seizure medicines in less than two weeks.

Child dosage (ages 8–17 years)

If you haven’t had treatment for seizures, follow this dosing schedule:

  • Days 1–3: take 100–125 mg by mouth at bedtime
  • Days 4–6: take 100–125 mg twice per day
  • Days 7–9: take 100–125 mg three times per day
  • Day 10 to maintenance: take 250 mg three times per day
  • The usual maintenance dose is 250 mg taken three times per day or 250 mg taken four times per day. Your doctor may increase your dose to 250 mg taken 5–6 times per day. Your dose shouldn’t be more than 500 mg taken four times per day.

If you’re already taking other seizure medicines:

Follow the same primidone schedule while slowly decreasing your other medications. You should be off of your other seizure medications in less than two weeks.

Child dosage (ages 0–7 years)

Follow this dosing schedule:

  • Days 1–3: take 50 mg by mouth at bedtime
  • Days 4–6: take 50 mg two times per day
  • Days 7–9: take 100 mg two times per day
  • Day 10 to maintenance: take 125–250 three times per day
  • The usual maintenance dose is 125–250 mg taken three times per day or 10–25 mg/kg of body weight per day in divided doses.
Senior dosage (ages 65 years and older)

Older adults may process drugs more slowly. A normal adult dose may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dose or a different schedule.

Special considerations

People with kidney problems: If you have moderate to severe kidney problems, your doctor may instruct you to decrease the dose by only taking the drug 2–3 times per day. If you have severe kidney problems, you may be instructed to take the drug only 1–2 times per day.

People with liver problems: If you have liver problems, your doctor may start you on a lower dose and monitor you more closely.

Warnings

The total daily dose for primidone shouldn’t be more than 2 grams (2,000 mg).

To make sure you have the right level of primidone in your blood, your doctor may check to see if your blood primidone levels are between 5–12 micrograms per milliliter.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Primidone comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all

If you don’t take primidone at all, you may keep having seizures. Stopping primidone suddenly may cause serious problems, such as having more seizures, or seizures that don’t stop.

If you miss doses or don’t take the drug on schedule

Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much

You could have dangerous levels of the drug in your body. Your breathing could slow down so much that you stop breathing. You could also have extreme drowsiness, nausea, vomiting, or poor muscle control. Or you could become confused or slip into a coma.

If you think that you’ve taken too much primidone, call your doctor or local poison control center, or go to the emergency room right away.

What to do if you miss a dose

If you forget to take your dose, take it as soon as you remember. If it’s just a few hours before the time for your next dose, then wait and only take one dose at that time. Never try to catch up by taking two doses at once. This can cause dangerous side effects.

How to tell if the drug is working

You should have fewer seizures.

Primidone is a long-term drug treatment.

Important considerations for taking primidone

Primidone may be taken with or without food

Taking it with food may help to decrease stomach upset.

Primidone must be stored at the right temperature

  • Store primidone at room temperature between 68°F (20°C) and 77°F (25°C).
  • Don’t freeze primidone.
  • Keep it in a light-resistant container (such as the one it came in). Keep the lid tightly closed.
  • Keep it away from high temperature.
  • Keep your drugs away from areas where they could get wet, such as bathrooms. Store this drug away from moisture and damp locations.

Travel

When traveling with your medication:

  • Always carry your medication with you, such as in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff your pharmacy’s label to clearly identify the medication. Keep the original prescription label with you when traveling.
  • Don’t leave this medicine in the car, especially when the temperature is hot or freezing.

Clinical monitoring

Your doctor may do a test two times per year to check if you have the right levels of this drug in your blood. For people over 5 years of age, your blood primidone levels should be between 5–12 micrograms per milliliter.

Your doctor may also check your:

  • kidney function
  • liver function
  • blood cell counts
  • seizure control
  • mental health (suicide risk)
  • phenobarbital levels

Insurance

Many insurance companies require a prior authorization for this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

What does the pill look like?

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How Much Does primidone Cost?

Oral tablet

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These prices represent the lowest priced national pharmacies for primidone on GoodRx. They may be lower than your insurance.

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Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on August 27, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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