Drug Index

Fosphenytoin

 
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Mechanism :

Fosphenytoin is a prodrug of phenytoin and accordingly, its anticonvulsant effects are attributable to phenytoin


Indication :

• Epilepsy- Generalized Tonic Clonic Seizures

• Status epilepticus


Contraindications :

Known hypersensitivity to hydantoin products. Because of its effect on ventricular automaticity, i.v. phenytoin is contraindicated in sinus bradycardia, sinoatrial block, second and third-degree AV block, patients with Adams-Stokes syndrome.


Dosing :

The dosage of fosphenytoin is expressed in terms of phenytoin equivalents (PE); 150 mg of fosphenytoin sodium is equivalent to 100 mg of phenytoin sodium.

Loading doses: 15-20 mg/kg IV. Maintenance doses start 12 hours after loading doses. Usual maintenance doses are 4 to 8 mg/kg/day, in 2 or 3 divided doses. Maximum rate of infusion 150 mg/minute.


Adverse Effect :

Nystagmus dizziness, pruritus, somnolence, ataxia, transient pruritus, tinnitus, hypertension, fever, injection-site reaction, constipation, hypokalemia, pneumonia.


Interaction :

Amiodarone, Chloramphenicol, Cimetidine, Disulfiram, Erythromycin, Fluconazole, Fluoxetine, Isoniazid, Ketoconazole, Methylphenidate, Omeprazole, Phenylbutazone, Salicylates, Sulfonamides, Trazodone, Warfarin and Acute Alcohol Ingestion: Drugs may increase phenytoin serum levels.
Carbamazepine, Chronic Alcohol Abuse, Diazoxide, Rifampin and Theophylline: Drugs may decrease phenytoin levels.
Phenobarbital, Valproic Acid, and Sodium Valproate: Drugs may either increase or decrease phenytoin serum levels. Similarly, the effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable.
Corticosteroids, Diazoxide, Digitalis Glycosides, Doxycycline, Estrogens, Furosemide, Levodopa, Methadone, Oral Contraceptives, Quinidine, Theophylline, Vitamin D and Warfarin: Drugs whose efficacy is impaired by phenytoin.
Sucralfate, Enteral Feeds, Antacids or Calcium Preparations: Administration of phenytoin with sucralfate, enteral feeds, antacids or calcium preparations should be separated by at least 3 hours to prevent a decrease in phenytoin absorption.

I.V. Phenytoin with Lidocaine or Propranolol: Concurrent use of i.v. phenytoin with lidocaine or propranolol may produce additive cardiac depressant effects.


07/19/2019 03:24:13 Fosphenytoin
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