Fosphenytoin Sodium

Introduction: Fosphenytoin Sodium is a prescription medicine used for the treatment of epilepsy (seizures). It controls seizures by decreasing the abnormal and excessive activity of the nerve cells in the brain.

How it works: Fosphenytoin is a water-soluble prodrug of phenytoin. After administration, plasma esterases convert fosphenytoin to phosphate, formaldehyde, and phenytoin as the active moiety. Phenytoin stabilises neuronal membranes and decreases seizure activity by regulating sodium ion flux across cell membranes.

Important Information: This medicine is given under the supervision of a healthcare professional and should not be self-administered. Do not stop the medication without talking to your doctor as it may cause non-stop seizures and can endanger life.

• Control of generalized convulsive status epilepticus
• Prevention and treatment of seizures occurring during neurosurgery or head injury
• Short-term substitution for oral Phenytoin

Adjunct anti-epileptic drugs

Hydantoin anticonvulsant

Fosphenytoin Sodium injection is a pro-drug intended for parenteral administration and its active metabolite is Phenytoin. Fosphenytoin Sodium injection is supplied in ampoule as a ready-mixed solution in Water for Injection and Tromethamine, buffer adjusted to pH 8.6 to 9.0 with either Hydrochloric Acid or Sodium Hydroxide.

Fosphenytoin is converted to phenytoin by plasma esterases, which stabilizes sodium channels in neuronal membranes and reduces repetitive neuronal firing, thereby controlling seizure activity.

Adult Dose (Parenteral):

• Status Epilepticus: IV infusion (100-150 mg/min), initial 15 mg/kg, then IM or IV infusion (50-100 mg/min), 4-5 mg/kg/day (1-2 divided doses).
• Neurosurgery or head injury seizure prophylaxis/treatment: IM or IV infusion (50-100 mg/min), initial 10-15 mg/kg, then 4-5 mg/kg/day.
• Temporary substitution for oral Phenytoin: IM or IV infusion (50-100 mg/min), same dose and frequency as oral Phenytoin.

Children (5+ years):

• Status Epilepticus: IV infusion (2-3 mg/kg/min), initial 15 mg/kg, then IV infusion (1-2 mg/kg/min), 4-5 mg/kg/day (1-4 divided doses).

Elderly, Hepatic & Renal Impairment: Dose reduction or slower infusion may be needed.

* Use as directed by the registered physician

Intravenous (IV) or intramuscular (IM) injection. Your doctor or nurse will give you this medicine. Do not self-administer. Prior to IV infusion, dilute in 5% Dextrose or 0.9% Saline to a concentration of 1.5-25 mg PE/ml.

If you miss a dose, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular schedule. Do not double the dose.

Common Side Effects:

• Vomiting
• Sleepiness
• Dizziness
• Itching
• Impaired coordination
• Nystagmus (involuntary eye movement)
• Paresthesia
• Headache
• Ataxia

Serious Side Effects: Cardiovascular collapse, CNS depression, hypotension, bradycardia, heart block, asystole, ventricular fibrillation.

Precautions:

• Use with caution in patients with hypotension and severe myocardial insufficiency.
• Discontinue if a skin rash appears.
• Discontinue and do not readminister if acute hepatotoxicity occurs.
• Hemopoietic complications (thrombocytopenia, leukopenia, agranulocytosis) may occur - regular blood tests required.
• Do not abruptly discontinue antiepileptic drugs (may cause status epilepticus).
• Monitor blood glucose levels in diabetic patients.

Contraindications:

• Hypersensitivity to Fosphenytoin, Phenytoin or other Hydantoins
• Sinus bradycardia, sino-atrial block, second and third degree A-V block, Adams-Stokes syndrome

Drug Interactions:

• Drugs that increase plasma Phenytoin concentrations: Acute alcohol intake, Amiodarone, Chloramphenicol, Cimetidine, Diazepam, Disulfiram, Estrogens, Fluoxetine, Isoniazid, Phenothiazines, Sulfonamides, etc.
• Drugs that decrease plasma Phenytoin concentrations: Carbamazepine, chronic alcohol abuse, Reserpine.
• Concomitant use with delavirdine may cause loss of virologic response.

Food Interactions:

• Unsafe to consume alcohol with Fosphenytoin Sodium.

Use in Pregnancy: Unsafe during pregnancy. Prenatal exposure to Phenytoin may increase the risks for congenital malformations and other adverse developmental outcomes.

Use in Lactation: Breast-feeding is not recommended for women receiving Fosphenytoin.

Pediatric Use: Dosage available for children 5 years and older. Safety and efficacy in children under 5 years have not been established.

Geriatric Use: Age does not have a significant impact on pharmacokinetics, but Phenytoin clearance is decreased slightly in elderly patients and lower or less frequent dosing may be required.

Renal & Hepatic Impairment: Fosphenytoin clearance may be increased in renal and/or hepatic disease. Dose reduction or slower infusion may be needed.

Overdose:

• Symptoms: Nausea, vomiting, lethargy, tachycardia, bradycardia, asystole, cardiac arrest, hypotension, syncope, hypocalcemia, metabolic acidosis.
• Treatment: No specific antidote. Monitor respiratory and circulatory systems and provide supportive measures. Hemodialysis may be considered.

Storage: Store at 2°C to 8°C (in a refrigerator). Do not keep in deep freeze. Do not store at room temperature for more than 48 hours.

Fosphenytoin Sodium Injection