zonisamide
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zonisamide
[zo-nis´ah-mīd″]zonisamide
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.
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, pancreatitis
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, creatine kinase, 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.