What does the choice of drug used to treat epilepsy depend on?

Seizures. Entirely on the clinician and standards of care.
Good question! Factors include: type of epilepsy, age, sex, finances, ability to take medications regularly, and what other conditions or problems the person might have. Other factors to consider may also include whether we need to start the medication in a hurry, and whether we need to have an IV form available. Also, some folks tolerate some side effects better than others. .
Many factors. There are multiple factors that go into the decision, including: - type of epilepsy (primary generalized, partial onset, etc.) - age and gender (some drugs are less appropriate for women of reproductive age, etc.) - other medications a patient is taking (so no drug interactions occur) - other medical problems that the drug could worsen (or, in some cases, help) - how rapidly the drug needs to act.