Methsuximide

A to Z Drug Facts

 Action Elevates seizure threshold and suppresses paroxysmal spike wave activity associated with lapses of consciousness common in absence (petite mal) seizures.

Absorption: It is readily absorbed. T_max is 1 to 4 hr.

Elimination: The t_1/2 is 2.6 to 4 hr. Less than 1% recovered unchanged in urine.

 Indications Control of absence (petite mal) seizures that are refractory to other drugs.

 Contraindications Hypersensitivity to succinimides.

 Route/Dosage

Adults and children: PO Initial dose: 300 mg/day for the first week. Dosage may be increased at weekly intervals by 300 mg/day (max, 1200 mg/day).

 Interactions

Hydantoins (eg, phenytoin), phenobarbital: Plasma concentrations may be elevated by methsuximide, increasing the risk of side effects.

Lamotrigine: Plasma concentrations may be reduced by methsuximide, decreasing the therapeutic effects.

 Lab Test Interferences None well documented.

 Adverse Reactions

CARDIOVASCULAR: Hyperemia. CNS: Drowsiness; ataxia; dizziness; irritability; nervousness; headache; blurred vision; insomnia; confusion; instability; mental slowness; depression; hypochondriacal behavior; auditory hallucinations. DERMATOLOGIC: Urticaria; Stevens-Johnson syndrome; pruritic erythematous rash. EENT: Periorbital edema. GI: Nausea; vomiting; anorexia; diarrhea; weight loss; epigastric and abdominal pain; constipation; hiccups. GU: Proteinuria; microscopic hematuria. HEMATOLOGIC: Eosinophilia; leukopenia; monocytosis; pancytopenia (with and without bone marrow suppression). OTHER: Photophobia.

 Precautions

Pregnancy: Anticonvulsant drugs have been associated with an increase in the incidence of birth defects.

Hematologic: Blood dyscrasias, including fatal cases, have occurred.

Hepatic or renal impairment: Use with caution.

Systemic lupus: Systemic lupus has occurred.

Dosage adjustment: Proceed slowly when increasing or decreasing the dose; do not withdraw drug abruptly as this may precipitate absence (petit mal) seizures.

 Administration/Storage

• May be used alone or in combination with other anticonvulsants.
• Administer once or twice daily.
• May be administered without regard to meals. Administer with food if GI upset occurs.
• Administer capsules whole. Do not chew or break the capsule.
• Dose is gradually increased at 1 wk intervals.
• Store capsules at controlled room temperature (59° to 86°F). Protect from moisture and light.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note history of renal or hepatic impairment.
• Ensure that periodic blood counts are performed during therapy.
• Ensure that baseline renal function studies are performed before starting therapy and periodically during therapy.
• Monitor patient for seizure activity. Report seizure activity to health care provider.
• Monitor patient for GI, CNS, psychiatric, and general body side effects. Report to health care provider if noted and significant.
• Implement safety precautions for patients who experience dizziness or ataxia.

 Patient/Family Education

• Explain name, dose, action, and potential side effects of drug.
• Instruct patient to take exactly as prescribed and to not change the dose or stop taking unless advised by health care provider.
• Advise patient that dose may be gradually increased no more often than every week until maximum benefit is achieved.
• Advise patient to swallow capsule whole and to not chew or break the capsule.
• Advise patient that each dose may be taken without regard to meals but to take with food if GI upset occurs.
• Advise patient that if a dose is missed to take it as soon as possible. Caution patient that if several hours have passed or it is nearing time for the next dose to not double the dose in an effort to catch up and to take the next dose as scheduled.
• Advise patient that if medication needs to be discontinued it will be slowly withdrawn over a period of 2 wks or more unless safety concerns (eg, rash) require a more rapid withdrawal.
• Caution patient that drug may cause drowsiness, dizziness, or blurred vision and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
• Advise women to contact their health care provider if pregnant, planning to become pregnant, or breastfeeding.
• Instruct patient to contact health care provider immediately if any of the following occur: rash; joint pain; fever, sore throat or other signs of infection; unusual bruising or bleeding; depression; aggressive behavior or other behavioral changes.
• Instruct patient to inform health care provider if seizures get worse of if new types of seizures occur.
• Advise patient to not take any prescription or OTC medications or dietary supplements unless advised by health care provider.
• Advise patient that laboratory tests and follow-up visits will be required to monitor therapy and to and keep appointments.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts