zonisamide

zonisamide /zo·nis·am·ide/ (zo-nis´ah-mīd″) a sulfonamide that acts as an anticonvulsant, used in the treatment of partial seizures in adults.

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zonisamide

[zo-nis′ah-mīd′]

a sulfonamide that acts as an anticonvulsant, used as an adjunct in the treatment of partial seizures in adults. It is administered orally.

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zonisamide

Zonegran

Pharmacologic class: Sulfonamide

Therapeutic class: Anticonvulsant

Pregnancy risk category C

Action

Raises seizure threshold and reduces seizure duration, probably by stabilizing neuronal membranes through action on sodium and calcium channels

Availability

Capsules: 25 mg, 50 mg, 100 mg

⊘Indications and dosages

➣ Adjunctive treatment of partial seizures

Adults and children older than age 16: Initially, 100 mg P.O. daily for 2 weeks, then, if required, increased to 200 mg P.O. daily for at least 2 weeks. May increase in 100-mg increments at 2-week intervals to 300 to 400 mg daily as required. Daily dosage ranges from 100 to 600 mg.

Dosage adjustment

• Hepatic or renal impairment
• Elderly patients

Off-label uses

• Infantile spasms
• Progressive myoclonic epilepsy
• Weight loss

Contraindications

• Hypersensitivity to drug or other sulfonamides

Precautions

Use cautiously in:
• hepatic or renal disease
• pregnant or breastfeeding patients
• children younger than age 16 (safety not established).

Administration

• Give with or without food.

Route	Onset	Peak	Duration
P.O.	Unknown	2-6 hr	24 hr

Adverse reactions

CNS: drowsiness, fatigue, agitation, irritability, depression, dizziness, psychomotor slowing, psychosis, asthenia, abnormal gait, incoordination, tremor, ataxia, headache, confusion, impaired memory, hyperesthesia, paresthesia, seizures

EENT: diplopia, amblyopia, nystagmus, tinnitus, rhinitis, pharyngitis

GI: nausea, vomiting, diarrhea, dyspepsia, dry mouth, anorexia

GU: renal calculi

Hematologic: anemia, leukopenia

Respiratory: cough

Skin: rash, pruritus, bruising, Stevens-Johnson syndrome

Other: abnormal taste, weight loss, allergic reactions, oligohidrosis and hyperthermia (in children), flulike symptoms, accidental injury

Interactions

Drug-drug. Carbamazepine, phenobarbital, phenytoin, valproic acid: decreased zonisamide blood level and effects

CYP450-3A4 inducers: decreased zonisamide half-life

CYP450-3A4 inhibitors: increased zonisamide blood level

Drug-diagnostic tests. Blood urea nitrogen, creatinine: increased levels

Platelets, white blood cells: decreased counts

Patient monitoring

• Monitor CBC with white cell differential.
• Assess neurologic status; report significant adverse reactions.
• Monitor renal function tests. Watch for signs and symptoms of renal calculi.
☞ Monitor for rash, which may be first sign of Stevens-Johnson syndrome. If rash occurs, discontinue drug and notify prescriber immediately.

Patient teaching

• Explain therapy to patient. Instruct him to keep seizure diary and show it to prescriber.
• Instruct patient to swallow capsules whole. Advise him to drink 6 to 8 glasses of water daily to help prevent kidney stones.
☞ Warn patient that stopping drug abruptly may cause status epilepticus.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects him and until seizures are well controlled.
☞ Tell patient to immediately report rash, fever, sore throat, sudden back pain, depression, speech or language problems, or painful urination.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.