Which drug is primarily used in the management of seizures, including tonic-clonic types?

Phenytoin is primarily used in the management of seizures, especially tonic-clonic seizures. It works as an anticonvulsant by stabilizing neuronal membranes and reducing the excessive firing of neurons that can lead to seizure activity. Phenytoin achieves this by blocking voltage-gated sodium channels, which decreases the presynaptic release of excitatory neurotransmitters. This mechanism makes it particularly effective for treating generalized tonic-clonic seizures and partial seizures.

Other medications listed do not primarily target seizure management. Dextromethorphan is primarily an antitussive used for cough suppression and does not have anticonvulsant properties. Lithium is used primarily for mood stabilization in bipolar disorder and does not have a role in managing seizures. Hydroxyurea is mainly used for certain hematological disorders, such as sickle cell disease and some cancers, and is not indicated for seizure control. Therefore, phenytoin stands out as the correct choice due to its established efficacy in treating various types of seizures.