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Drugs reference index «Mysoline»



Generic name: PrimidoneBrand names: Mysoline

Why is Mysoline prescribed?

Mysoline is used to treat epileptic and other seizures. It can be used alone or with other anticonvulsant drugs. It is chemically similar to barbiturates.

Most important fact about Mysoline

Mysoline should not be stopped suddenly; this could cause you to have seizures. If you no longer need the medication, your doctor will reduce the dosage gradually.

How should you take Mysoline?

Take Mysoline exactly as prescribed. Do not change from one manufacturer's product to another without consulting your doctor.

If using Mysoline Suspension, shake well before using.

  • If you miss a dose...Take it as soon as you remember. If it is within an hour of your next dose, skip the one you missed and go back to your regular schedule. Never take 2 doses at the same time.
  • Storage instructions...Store at room temperature in a tightly closed container, away from light.

What side effects may occur?

Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking Mysoline.

  • Side effects may include:Lack of muscle coordination, vertigo or severe dizziness

Why should Mysoline not be prescribed?

You should not take Mysoline if you have porphyria (an inherited metabolic disorder) or if you are allergic to phenobarbital.

Special warnings about Mysoline

Remember that you must not stop taking Mysoline suddenly.

It can take several weeks for the full effectiveness of Mysoline to be seen.

Since Mysoline is generally given for long periods of time, your doctor will check your blood count every 6 months.

Possible food and drug interactions when taking Mysoline

If Mysoline is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining Mysoline with the following:

Antidepressants called MAO inhibitors, such as phenelzine and tranylcypromineBlood-thinning drugs such as warfarinDoxycyclineEstrogen-containing oral contraceptivesGriseofulvinSteroid drugs such as dexamethasone

Avoid alcoholic beverages while you are taking Mysoline.

Special information if you are pregnant or breastfeeding

Although the effects of Mysoline in pregnancy and nursing infants are not known, recent studies show an increase in birth defects in infants born to epileptic women taking anticonvulsant medications (particularly phenytoin and phenobarbital). Although most pregnant women taking anticonvulsant medication give birth to normal, healthy babies, this possibility may also exist with Mysoline. If you are pregnant or plan to become pregnant, inform your doctor immediately. Mysoline appears in breast milk and can affect a nursing infant, causing excessive sleepiness and drowsiness. If Mysoline is essential to your health, your doctor may advise you to stop breastfeeding.

Recommended dosage for Mysoline


For people 8 years of age and older who have not been treated before, the doctor will start Mysoline as follows, using either 50-milligram or scored 250-milligram Mysoline tablets:

Days 1 to 3: 100 to 125 milligrams at bedtime

Days 4 to 6: 100 to 125 milligrams 2 times a day

Days 7 to 9: 100 to 125 milligrams 3 times a day

Day 10 to maintenance: 250 milligrams 3 times a day

For most adults and children 8 years of age and over, the usual maintenance dosage is 250 milligrams 3 or 4 times a day. If you need more, your doctor may increase the dose to five or six 250-milligram tablets. You should not take more than 500 milligrams 4 times a day (2000 milligrams or 2 grams).

In patients already receiving other anticonvulsants, the usual starting dose of Mysoline is 100 to 125 milligrams at bedtime; your doctor will gradually increase this dose to a maintenance level as the other drug is gradually decreased. Your doctor will either find a working level for the combination or withdraw the other medication completely. When Mysoline is to be used as a single drug, it will take at least 2 weeks to make the transition from two drugs to one.


Days 1 to 3: 50 milligrams at bedtime

Days 4 to 6: 50 milligrams 2 times a day

Days 7 to 9: 100 milligrams 2 times a day

Day 10 to maintenance: 125 milligrams 3 times a day to 250 milligrams 3 times day

The usual maintenance dosage is 125 to 250 milligrams 3 times daily or 10 to 25 milligrams per 2.2 pounds of body weight per day, divided into smaller doses.


Any medication taken in excess can have serious consequences. If you suspect a Mysoline overdose, seek medical attention immediately.

  • Mysoline Prescribing Information (FDA)
  • Mysoline MedFacts Consumer Leaflet (Wolters Kluwer)
  • Mysoline Concise Consumer Information (Cerner Multum)
  • Mysoline Advanced Consumer (Micromedex) - Includes Dosage Information
  • Primidone Prescribing Information (FDA)
  • Primidone Professional Patient Advice (Wolters Kluwer)

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