Warnings & Recalls for Fosphenytoin
Black Box Warning
Fosphenytoin has a “black box” warning that denotes that the rate of intravenous administration of this drug should not exceed 150mg of phenytoin sodium equivalence (PE) per minute because of the risk of serious low blood pressure and irregular heartbeats. Careful cardiac monitoring is necessary both during and after administration of
Fosphenytoin. While the risk of cardiovascular toxicity rises with infusion rates above the recommended dosage, events such as these have also been reported at at or below the recommended infusion rate. Therefore the reduction or the discontinuation of the dosing of this drug may be recommended.
Contraindications
Fosphenytoin has contraindications associated with it that hinder a patient’s ability to be administered it if they’ve got the following preexisting conditions:
- Adams-Stokes syndrome
- Atrioventricular block (2nd or 3rd degree)
- Concurrent use with delavirdine
- Hypersensitivity to the drug itself, its product components, phenytoin or other hydantoins
- Sino-atrial block
- Sinus bradycardia
Who Should Not Take This Drug
The patients with the following preexisting conditions should never consider taking this drug or being administered it. These include:
- Patients who drink excessive amounts of alcohol
- Patients with diabetes mellitus
- Patients with hypotension
- Patients with severe myocardial insufficiency
- Elderly or gravely ill patients
- Patients with hepatic illnesses
- Patients with HLA-B*1502-positive diagnosis
- Patients with hypoalbuminemia
- Patients whose phosphate intakes are restricted
- Patients with porphyria
- Patients who are pregnant
- Patients with renal diseases
- Patients suffering from hypoglycemic or other metabolic causes
Pregnancy Warning
Fosphenytoin has been given a rating of “D” by the FDA, entailing that it should be avoided at all costs during the pregnancy because it poses a serious risk to both the expectant mother as well as her child.
Fosphenytoin Treatment and Use
Fosphenytoin | Cerebyx is a water-soluble phenytoin injectable prescription used only in hospitals for the treatment of epileptic seizures. The marketing and manufacturing of the generic versions of it had been approved by the FDA on November 18th, 2004. Fosphenytoin was first approved by the FDA on August 5th, 1996.
Fosphenytoin is approved in the US for treatments that last for the duration of 5 days or fewer as a treatment for epilepsy only when more widely used means of administering phenytoin is not available or would present a threat to the patient’s ailment.
To get more information on Fosphenytoin’s “black box” warning, please refer to the “Warnings and Recalls” tab.
How This Drug Works
Fosphenytoin is a prodrug that exerts its anticonvulsant effects when its converted to phenytoin. In regards to the cellular level, phenytoin is responsible for the modulation of voltage-dependent sodium and calcium channels as well as the enhancement of sodium-potassium ATPase activities. The anticonvulsant properties of Fosphenytoin is chiefly attributed to the modulation of sodium channels.
Dosage Information
The safety and the efficacy of administering this drug on pediatric patients has as of yet not been established.
The following is the dosage information for this drug when it comes to adult patients:
- Loading dosage: 10-20mg of phenytoin sodium equivalents per kilogram at a rate of 100-150mg/minute
- Maximum dosage: 2,000mg
- Maintenance dosage: 4-6mg/kg/day administered in an IV in 3-4 divided doses
There’s an attached risk of hypotension with this drug, hence Fosphenytoin should be injected at an increment no faster than 150mg PE/minute.
