In a small study,
phenytoin-induced seizures occurred most often in patients with serum
phenytoin concentrations of 50 mcg/ml or higher.[393] Peripheral neuropathy, usually occurring weeks to months after drug initiation, has also been reported in patients receiving phenytoin. A single case report describes the onset of neuropathy within a few hours of drug administration.[9780]
Adverse GI effects of phenytoin therapy include nausea/vomiting, constipation, abdominal pain, and anorexia.