Fosphenytoin (Cerebyx) is a prodrug of phenytoin, an antiepileptic drug used to treat seizures. Unlike phenytoin, which is poorly soluble in water and can cause severe local irritation if injected into the muscle, fosphenytoin is water-soluble and can be administered intravenously without causing tissue damage.
Fosphenytoin is rapidly converted to phenytoin in the body and works by stabilizing the neuronal membrane and reducing the abnormal electrical activity in the brain that causes seizures. As an intensivist, I’ve occasionally used this in the ICU for status epilepticus – a medical emergency in which a patient experiences prolonged seizures that can cause brain damage or death.
The most common side effects include dizziness, headache, nausea, and vomiting, but in rare instances, dermatologic emergencies like Stevens-Johnson syndrome and toxic epidermal necrolysis can occur.