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Mysoline Side Effects

Generic Name: primidone

Note: This page contains information about the side effects of primidone. Some of the dosage forms included on this document may not apply to the brand name Mysoline.

For the Consumer

Applies to primidone: oral suspension, oral tablet

In addition to its needed effects, some unwanted effects may be caused by primidone (the active ingredient contained in Mysoline). In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking primidone:

More common:
  • Shakiness and unsteady walk
  • unsteadiness, trembling, or other problems with muscle control or coordination
Less common:
  • Unusual excitement or restlessness (especially in children and in the elderly)
  • Chills
  • cough or hoarseness
  • fainting spells
  • fever and sore throat
  • fever with or without chills
  • general feeling of tiredness or weakness
  • irregular heartbeat
  • lower back or side pain
  • painful or difficult urination
  • pale skin
  • shortness of breath
  • skin rash
  • sores, ulcers, or white spots on the lips or in the mouth
  • unusual bleeding or bruising
  • unusual tiredness or weakness

If any of the following symptoms of overdose occur while taking primidone, get emergency help immediately:

Symptoms of overdose:
  • Confusion
  • continuous, uncontrolled rolling eye movements
  • double vision
  • troubled breathing

Minor Side Effects

Some of the side effects that can occur with primidone may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Clumsiness or unsteadiness
  • dizziness or lightheadedness
  • feeling of constant movement of self or surroundings
  • sensation of spinning
Less common:
  • Decreased sexual ability
  • drowsiness
  • loss of appetite
  • mood or mental changes
  • nausea or vomiting

For Healthcare Professionals

Applies to primidone: oral suspension, oral tablet

Nervous system

Nervous system effects including ataxia and vertigo have been reported most frequently.[Ref]

Ataxia and vertigo tend to disappear either with continued therapy or with the reduction of the initial dosage.[Ref]


Gastrointestinal effects including nausea, anorexia, and vomiting have been reported occasionally.[Ref]


General effects including fatigue, hyperirritability, and drowsiness have been reported occasionally.[Ref]


Psychiatric effects including emotional disturbances have been reported occasionally. A case of primidone (the active ingredient contained in Mysoline) induced catatonic schizophrenia has also been reported.[Ref]


Massive crystalluria has also been rarely been reported following acute overdoses of primidone (the active ingredient contained in Mysoline) [Ref]

Genitourinary effects including sexual impotency have been reported occasionally. A case of massive crystalluria has been reported in a patient receiving maintenance doses of primidone.[Ref]


Ocular effects including diplopia and nystagmus have been reported occasionally.[Ref]


Dermatologic effects including morbilliform skin eruptions have been reported occasionally.[Ref]


Hematologic effects including granulocytopenia, agranulocytosis, red cell hypoplasia, thrombocytopenia, and aplasia have been reported rarely. The manufacturer has reported that megaloblastic anemia may occur as a rare idiosyncrasy to primidone (the active ingredient contained in Mysoline) [Ref]

The anemia may respond to folic acid without the necessity to discontinue the primidone. The phenobarbital metabolite of primidone has been reported to have potentiated porphyrias.[Ref]


Rheumatologic side effects include drug induced lupus, frozen shoulder, and Dupuytren's contractures.[Ref]


1. "Product Information. Mysoline (primidone)" Elan Pharmaceuticals, S. San Francisco, CA.

2. Sher A, Andersen JM, Bhatia SC "Primidone-induced catatonic schizophrenia." Drug Intell Clin Pharm 17 (1983): 551-2

3. Sigg T, Leikin JB "Massive crystalluria in a patient taking primidone [letter]." Ann Emerg Med 33 (1999): 726-7

4. "Multum Information Services, Inc. Expert Review Panel"

5. Mattson RH, Cramer JA, McCutchen CB "Barbiturate-related connective tissue disorders." Arch Intern Med 149 (1989): 911-4

Not all side effects for Mysoline may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.