Therapeutic Classification: anticonvulsants
Pharmacologic Classification: glutamate receptor antagonists
Absorption: Rapidly and completely absorbed following oral administration.
Distribution: Unknown.
Protein Binding: 95–96%.
Metabolism/Excretion: Extensively metabolized by CYP3A4/5 enzyme systems; excreted in urine and feces primarily as metabolites.
Half-Life: 105 hr.
Partial-Onset Seizures
- PO (Adults and Children ≥4 yr): 2 mg once daily at bedtime initially; may ↑ by 2 mg/day at weekly intervals (usual dosage range = 4–12 mg once daily); Concurrent use of moderate or strong CYP3A4 enzyme-inducers (e.g. phenytoin, carbamazepine, oxcarbazepine): 4 mg once daily at bedtime initially; may ↑ by 2 mg/day at weekly intervals (maximum dose = 12 mg once daily).
- PO Geriatric Patients ): 2 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (usual dosage range = 4–12 mg once daily); Concurrent use of moderate or strong CYP3A4 enzyme-inducers (e.g. phenytoin, carbamazepine, oxcarbazepine): 4 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (maximum dose = 12 mg once daily).
Hepatic Impairment
- PO (Adults and Children ≥4 yr): Mild hepatic impairment: 2 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (maximum dose = 6 mg once daily); Moderate hepatic impairment: 2 mg once daily at bedtime initially; may ↑ by 2 mg/day after 2 wk up to 4 mg once daily.
Primary Generalized Tonic-Clonic Seizures
- PO (Adults and Children ≥12 yr): 2 mg once daily at bedtime initially; may ↑ by 2 mg/day at weekly intervals (usual dosage range = 8–12 mg once daily); Concurrent use of moderate or strong CYP3A4 enzyme-inducers (e.g. phenytoin, carbamazepine, oxcarbazepine): 4 mg once daily at bedtime initially; may ↑ by 2 mg/day at weekly intervals (maximum dose = 12 mg once daily).
- PO Geriatric Patients ): 2 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (usual dosage range = 4–12 mg once daily); Concurrent use of moderate or strong CYP3A4 enzyme-inducers (e.g. phenytoin, carbamazepine, oxcarbazepine): 4 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (maximum dose = 12 mg once daily).
Hepatic Impairment
- PO (Adults and Children ≥12 yr): Mild hepatic impairment: 2 mg once daily at bedtime initially; may ↑ by 2 mg/day every 2 wk (maximum dose = 6 mg once daily); Moderate hepatic impairment: 2 mg once daily at bedtime initially; may ↑ by 2 mg/day after 2 wk up to 4 mg once daily.
