Trimethadione Side Effects

Medically reviewed by Drugs.com. Last updated on Aug 24, 2023.

Applies to trimethadione: oral capsule, oral tablet chewable.

Warning

You should not stop using trimethadione suddenly. Stopping suddenly may make your condition worse.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have:

vision problems, droopy eyelids;
the first sign of any skin rash, no matter how mild;
unusual muscle weakness, trouble speaking or swallowing;
swelling in your feet or ankles;
low blood cell counts--fever, chills, flu-like symptoms, swollen gums, mouth sores, skin sores, rapid heart rate, pale skin, easy bruising, unusual bleeding, feeling light-headed;
lupus-like syndrome--joint pain or swelling with fever, swollen glands, muscle aches, chest pain, butterfly-shaped skin rash on your cheeks;
kidney problems--little or no urinating, painful or difficult urination, rapid weight gain;
liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common side effects may include:

nausea;
drowsiness;
changes in mood or behavior; or
increased seizures.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to trimethadione: oral capsule, oral tablet chewable.

Dermatologic

Frequency not reported: Acneiform or morbilliform skin rash that may progress to exfoliative dermatitis or to severe forms of erythema multiforme, lupus erythematosus and lymphadenopathies simulating malignant lymphoma, pruritus (associated with lymphadenopathy and hepatosplenomegaly)^[Ref]

Gastrointestinal

Frequency not reported: Nausea, vomiting, abdominal pain, gastric distress, bleeding gums^[Ref]

Genitourinary

Frequency not reported: Vaginal bleeding, albuminuria^[Ref]

Hematologic

Frequency not reported: Neutropenia, leukopenia, eosinophilia, thrombocytopenia, pancytopenia, agranulocytosis, hypoplastic anemia, fatal aplastic anemia^[Ref]

Hepatic

Rare (less than 0.1%): Hepatitis^[Ref]

Musculoskeletal

Frequency not reported: Myasthenia gravis-like syndrome^[Ref]

Nervous system

Frequency not reported: Drowsiness, fatigue, malaise, insomnia, vertigo, headache, paresthesias, precipitation of grand mal seizures, increased irritability^[Ref]