May 28, 2017
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Tridione Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Tridione (trimethadione) is a seizure medication (antiepileptic) used to control absence ("petit mal") seizures. Common side effects of Tridione include:

The usual adult dosage of Tridione is 0.9-2.4 grams daily in 3 or 4 equally divided doses (i.e., 300-600 mg 3 or 4 times daily). Tridione may interact with other drugs that cause drowsiness, including antidepressants, alcohol, antihistamines, pain relievers, anxiety medicines, other seizure medicines, and muscle relaxants. Tell your doctor all medications and supplements you use. Tridione is known to be harmful to a fetus. Malformations of the face and head, heart, and nervous system have been reported. Tell your doctor if you are pregnant or could become pregnant during treatment. It is unknown if Tridion passes into breast milk and how it might affect a nursing infant. Consult your doctor before breastfeeding.

Our Tridione (trimethadione) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Tridione FDA Prescribing Information: Side Effects
(Adverse Reactions)


The following side effects, some of them serious, have been associated with the use of TRIDIONE (trimethadione).


Nausea, vomiting, abdominal pain, gastric distress.


Drowsiness, fatigue, malaise, insomnia, vertigo, headache, paresthesias, precipitation of grand mal seizures, increased irritability, personality changes.

Drowsiness usually subsides with continued therapy. If it persists, a reduction in dosage is indicated.


Bleeding gums, epistaxis, retinal and petechial hemorrhages, vaginal bleeding, neutropenia, leukopenia, eosinophilia, thrombocytopenia, pancytopenia, agranulocytosis, hypoplastic anemia, and fatal aplastic anemia.


Acneiform or morbilliform skin rash that may progress to exfoliative dermatitis or to severe forms of erythema multiforme.


Hiccups, anorexia, weight loss, hair loss, changes in blood pressure, albuminuria, hemeralopia, photophobia, diplopia.

Fatal nephrosis has occurred.

Hepatitis has been reported rarely.

Lupus erythematosus, and lymphadenopathies simulating malignant lymphoma, have been reported.

Pruritus associated with lymphadenopathy and hepatosplenomegaly has occurred in hypersensitive individuals.

A myasthenia gravis-like syndrome has been reported.

Read the entire FDA prescribing information for Tridione (Trimethadione Tablets)

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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