Antiepileptics

Which antiepileptic drug acts primarily by blocking voltage-gated sodium channels and is known to cause gingival hyperplasia as a chronic side effect?

A 35-year-old man with a 10-year history of focal seizures (temporal lobe epilepsy) presents with recurrent breakthrough seizures despite adequate dosing of carbamazepine. Serum carbamazepine level is 8 µg/mL (therapeutic range 4–12 µg/mL). He has been compliant with medication. He is also on rifampicin for tuberculosis (recently started 3 months ago). What is the most likely explanation for his loss of seizure control?

Valproic acid exerts its antiepileptic effect through which two primary mechanisms?

A 35-year-old man with newly diagnosed focal seizures (temporal lobe origin on EEG) is started on levetiracetam 500 mg twice daily. After 1 week, he reports persistent behavioral changes: irritability, mood lability, and aggressive outbursts. His seizures remain uncontrolled. What is the most appropriate next step in management?

A 28-year-old woman with generalized tonic-clonic seizures has been seizure-free for 2 years on phenytoin monotherapy. She now presents to the outpatient clinic planning pregnancy. Her seizure control is excellent, but she is concerned about teratogenicity. On examination, she has mild gingival hyperplasia and coarse facial features. What is the most appropriate next step in her antiepileptic management?