Which of the following drugs is NOT typically used to treat tonic-clonic seizures?

Lithium is primarily used to treat bipolar disorder and depression, not to manage seizures. It acts as a mood stabilizer and works through mechanisms that are distinct from those involved in seizure activity. In contrast, the other drugs listed—valproate, phenytoin, and carbamazepine—are all anticonvulsants specifically effective for tonic-clonic seizures.

Valproate is well-known for its broad-spectrum anticonvulsant properties, particularly in epilepsy. Phenytoin is effective for generalized tonic-clonic seizures and partial seizures. Carbamazepine is also used for partial and generalized tonic-clonic seizures. Therefore, these three medications are integral to the management of epilepsy, while lithium does not have those properties. This distinction clarifies that lithium is not utilized for the treatment of tonic-clonic seizures.