What the label lists and what reports show
Methsuximide side effects
Methsuximide's FDA label lists its adverse reactions in its own words. FAERS holds 181 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is convulsion (14 reports).
- Generic approved
Check it at the source: the methsuximide FDA label on DailyMed (effective April 7, 2026, Parke-Davis Div of Pfizer Inc); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of CELONTIN?See "What is the most important information I should know about CELONTIN?" CELONTIN may cause other serious side effects, including: • Grand mal seizures can happen more often or become worse The most common side effects of CELONTIN include: • drowsiness • dizziness • headache • blurred vision • nausea or vomiting • constipation • diarrhea • weight loss • problems with walking and coordination (unsteadiness) • stomach pain • loss of appetite Tell your healthcare provider about any side effect that bothers you or that does not go away. These are not all the possible side effects with CELONTIN. For more information, ask your healthcare provider or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1‑800‑FDA‑1088 .
Source: FDA drug label, Parke-Davis Div of Pfizer Inc, effective April 7, 2026 (SPL set 64a6ee88-c6b1-4e13-8208-b6772ef65a74), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsGastrointestinal System: Gastrointestinal symptoms occur frequently and have included nausea or vomiting, anorexia, diarrhea, weight loss, epigastric and abdominal pain, and constipation. Hemopoietic System: Hemopoietic complications associated with the administration of methsuximide have included eosinophilia, leukopenia, monocytosis, and pancytopenia with or without bone marrow suppression. Nervous System: Neurologic and sensory reactions reported during therapy with methsuximide have included drowsiness, ataxia or dizziness, irritability and nervousness, headache, blurred vision, photophobia, hiccups, and insomnia. Drowsiness, ataxia, and dizziness have been the most frequent side effects noted. Psychologic abnormalities have included confusion, instability, mental slowness, depression, hypochondriacal behavior, and aggressiveness. …
Source: FDA drug label, Parke-Davis Div of Pfizer Inc, effective April 7, 2026 (SPL set 64a6ee88-c6b1-4e13-8208-b6772ef65a74), via openFDA; the full label on DailyMed
What do FAERS reports show?
181 reports list methsuximide among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2 are coded as a death and 39 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 3 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Methsuximide: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions