Mysoline is an anticonvulsant that is used alone or with other medications to control seizures in adults and children.

Mysoline may also be used for purposes not listed in this medication guide.

Some people have thoughts about suicide while taking seizure medicine. Tell your doctor right away if you have any sudden changes in mood or behavior, or thoughts about suicide.

Seizures may increase if you stop using Mysoline suddenly. Ask your doctor before stopping the medicine.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

You may not fully benefit from this medicine for up to several weeks. Your doctor will determine how long to treat you with this medicine.

You should not stop using Mysoline suddenly. Seizures may increase if you stop using this medicine. Ask your doctor before stopping the medicine.

You may need blood tests, and your next dose may be changed based on the results. Your doctor will need to check your progress on a regular basis.

You may be given other medications such as folic acid to help prevent serious side effects. Keep taking these medicines for as long as your doctor has prescribed.

Doses may be based on weight for children under 8 years old. Your child's dose may change if the child gains or loses weight.

Store tightly closed at room temperature, away from moisture and heat.

You should not use Mysoline if you have:

• an allergy to phenobarbital; or

• porphyria (a genetic disorder that causes symptoms affecting the skin or nervous system).

Tell your doctor if you have ever had:

• depression;

• a mood disorder; or

• suicidal thoughts or actions.

Some people have thoughts about suicide while taking seizure medicine. Stay alert to changes in your mood or symptoms. Your family or caregivers should also watch for sudden changes in your behavior.

Do not start or stop seizure medication during pregnancy without your doctor's advice. Having a seizure during pregnancy could harm both mother and baby. Tell your doctor if you become pregnant.

If you take Mysoline during pregnancy, be sure to tell the doctor who delivers your baby. Both you and the baby may need medication to prevent bleeding during delivery and just after birth.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of primidone on the baby.

Tell your doctor if you are breastfeeding. If you are breastfeeding, tell your doctor if you notice drowsiness in the nursing baby.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Avoid driving or hazardous activity until you know how Mysoline will affect you. Your reactions could be impaired.

Drinking alcohol with this medicine can cause side effects.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Tell your doctor right away if you have new or sudden changes in mood or behavior, including new or worse depression or anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, more active or talkative, or have thoughts about suicide or hurting yourself.

Mysoline may cause serious side effects. Call your doctor at once if you have:

• extreme drowsiness, falling asleep suddenly, even after feeling alert; or

• signs of infection--fever, swollen glands, shortness of breath, chills, sore throat, body aches, unusual tiredness, loss of appetite, bruising or bleeding.

Common side effects of Mysoline may include:

• dizziness, drowsiness, vertigo (spinning sensation);

• problems with walking or moving;

• nausea, vomiting, loss of appetite;

• feeling tired or irritable;

• vision problems; or

• impotence, sexual problems.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Using Mysoline with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Other drugs may affect Mysoline, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.