What medication is likely to be prescribed to a client unable to take phenytoin due to severe vomiting?

Fosphenytoin sodium is often prescribed as an alternative to phenytoin because it is a prodrug that gets converted into phenytoin in the body but is associated with fewer side effects, particularly gastrointestinal disturbances. In patients who cannot tolerate phenytoin due to severe vomiting, fosphenytoin may be administered more safely, especially as it can be delivered intravenously and tends to be better tolerated. Its use allows for effective management of seizures without the added risk of exacerbating the patient's vomiting or related complications.

The other options present alternative antiepileptic medications but may not be the first choice in scenarios specifically involving severe gastrointestinal symptoms. Lamotrigine and valproate can be effective for various seizure types but do not directly address the issue of intolerability due to vomiting as fosphenytoin does. Topiramate is also an antiepileptic that can lead to gastrointestinal side effects in some patients and may not be suitable if vomiting is already a concern. Thus, fosphenytoin stands out as the most appropriate choice in this situation.