Primidone, Oral Tablet

Medically reviewed by University of Illinois-Chicago, Drug Information Group on November 10, 2016Written by University of Illinois-Chicago, Drug Information Group on November 25, 2017

Highlights for primidone

  1. Primidone oral tablet is available as a brand-name drug and a generic drug. Brand name: Mysoline.
  2. Primidone only comes as a tablet you take by mouth.
  3. Primidone is used to treat certain types of seizures.

Important warnings

  • Drug suitability warning: You should not take primidone if you’re allergic to phenobarbital or if you have the genetic disorder porphyria.
  • Suicidal thoughts warning: This drug may cause suicidal thoughts or actions in a very small number of people. Call your doctor right away if you have any of these symptoms, especially if they are new or worsening, or if they worry you:
    • thoughts about suicide or dying
    • attempts to commit suicide
    • new or worsened depression
    • new or worsened anxiety
    • feeling agitated or restless
    • panic attacks
    • trouble sleeping
    • new or worsened 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 comes as an oral tablet.

Primidone is available as the brand-name drug Mysoline. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in every strength or form as the brand-name drug.

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.

Why it's used

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

How it works

Primidone belongs to a class of drugs called anticonvulsant drugs. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

The exact way that primidone works to prevent seizures is not known.

Primidone side effects

Primidone oral tablet may cause severe drowsiness, especially when you first start taking it. This drug 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 also cause other side effects.

More common side effects

The more common side effects of primidone can include:

  • lack of muscle control, which can cause problems with walking and moving
  • feelings of dizziness, spinning, or swaying (vertigo)

These side effects tend to go away after your body gets used to the medication or after the dosage is reduced. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Suicidal thoughts or behaviors. Symptoms can include:
    • thoughts about suicide or dying
    • attempts to commit suicide
    • new or worsened depression
    • new or worsened anxiety
    • feeling agitated or restless
    • panic attacks
    • trouble sleeping
    • new or worsened irritability
    • anger
    • acting aggressive or violent
    • acting on dangerous impulses
    • an extreme increase in activity and talking (mania)
    • other unusual behavior or mood changes
  • Decreased blood cell counts, with symptoms such as:
    • fever
    • swollen glands
    • sore throat that comes back or does not go away
    • infections that are frequent or don’t go away
    • tiredness
    • shortness of breath

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not 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.

Primidone may interact with other medications

An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well. To help prevent interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking.

To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist. Be sure to talk to them before taking primidone with other drugs that make you sleepy or dizzy.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we can not 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

This drug comes with several warnings.

Allergy warning

Primidone can cause a severe allergic reaction. Symptoms include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives
  • rash
  • sores in your mouth
  • blistering or peeling skin

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Alcohol interaction warning

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.

Worsened seizures warning

Call your doctor if your seizures get worse or if you have any new types of seizures while you’re taking this drug.

Warning for 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.)

Warnings for 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.

Primidone may harm your pregnancy if you take it while pregnant. 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 your pregnancy. This drug should be only used if the potential risk is acceptable given the drug’s potential benefit.

If you become pregnant while taking primidone, call your doctor right away. Be sure to talk to them 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.

Warnings for women who are breastfeeding

Primidone can pass into breast milk and may cause serious effects in a child who is breastfed. You and your doctor may need to decide if you’ll take primidone or breastfeed.

How to take primidone

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

Dosage for seizures (epilepsy)

Generic: Primidone

  • Form: oral tablet
  • Strengths: 50 mg, 250 mg

Brand: Mysoline

  • Form: oral tablet
  • Strengths: 50 mg, 250 mg

Adult dosage (ages 18–64 years)

  • Typical dosage if you haven’t had treatment for seizures:
    • Days 1–3: 100–125 mg by mouth at bedtime
    • Days 4–6: 100–125 mg twice per day
    • Days 7–9: 100–125 mg three times per day
    • Day 10 to maintenance: 250 mg three times per day
    • Typical maintenance dose: 250 mg taken three times per day or 250 mg taken four times per day. Your doctor may increase your dosage to 250 mg taken 5–6 times per day. Your dosage shouldn’t be more than 500 mg taken four times per day.
  • Typical dosage if you’re already taking other seizure medications:
    • Follow the dosage schedule above while slowly decreasing your other medications.

Child dosage (ages 8–17 years)

  • Typical dosage if your child hasn’t had treatment for seizures:
    • Days 1–3: 100–125 mg by mouth at bedtime
    • Days 4–6: 100–125 mg twice per day
    • Days 7–9: 100–125 mg three times per day
    • Day 10 to maintenance: 250 mg three times per day
    • Typical maintenance dosage: 250 mg taken three times per day or 250 mg taken four times per day. Your doctor may increase your child’s dosage to 250 mg taken 5–6 times per day. Your child’s dosage shouldn’t be more than 500 mg taken four times per day.
  • Typical dosage if your child is already taking other seizure medications:
    • Follow the dosage schedule above while slowly decreasing your child’s other medications. Your child should be off their other seizure medications in less than two weeks.

Child dosage (ages 0–7 years)

  • Typical dosage:
    • Days 1–3: 50 mg by mouth at bedtime
    • Days 4–6: 50 mg two times per day
    • Days 7–9: 100 mg two times per day
    • Day 10 to maintenance: 125–250 three times per day
    • Typical maintenance dosage: 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 typical adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage or a different treatment schedule.

Special dosage considerations

For people with kidney problems: If you have moderate to severe kidney problems, your doctor may instruct you to decrease your dosage 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.

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

Dosage warnings

  • The total daily dosage 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 can not guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

Primidone oral tablet is used for long-term treatment. It 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 you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest 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, 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.

Important considerations for taking primidone

Keep these considerations in mind if your doctor prescribes primidone for you.

General

  • Primidone may be taken with or without food. Taking it with food may help to decrease stomach upset.
  • You can cut or crush the tablet.

Storage

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 this drug in a light-resistant container (such as the one it came in). Keep the lid tightly closed.
  • Keep this drug away from high temperature.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t harm your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

Your doctor may do a test twice per year to check if you have the right levels of this drug in your blood. Your doctor may also check your:

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

Availability

Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead to make sure your pharmacy carries it.

Prior authorization

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 better suited for you than others. Talk to your doctor about other drug options that may work for you.

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 here in 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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