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Indications & Uses
Fosphenytoin Sodium is given by injection (parenterally) for a short time, when other ways of giving Phenytoin are unavailable, unsuitable or thought to be less advantageous. It can be used to control generalized convulsive status epilepticus. It is also used to prevent and treat seizures that occur during neurosurgery or after a head injury. Fosphenytoin Sodium can also take the place of oral Phenytoin for a short period. For this use, safety and effectiveness have not been systematically evaluated beyond 5 days.
Pharmacology
Fosphenytoin Sodium injection is a pro-drug meant for parenteral use, and its active metabolite is Phenytoin. It comes in ampoules as a ready-mixed solution in Water for Injection BP and Tromethamine USP (TRIS). The buffer is adjusted to pH 8.6 to 9.0 with either Hydrochloric Acid NF or Sodium Hydroxide NF.
Dosage Reference
Reference Information Only
Dosages shown are general references from official sources. Always consult your doctor or pharmacist for personalized dosing.
Adults:
The dose, the concentration of dosing solutions and the infusion rate of IV Fosphenytoin are all expressed as Phenytoin Sodium equivalents (Fosphenytoin Sodium 1.5 mg is equivalent to Phenytoin Sodium 1 mg). This way, no molecular weight-based adjustment is needed when converting between Fosphenytoin and Phenytoin Sodium doses. Products with particulate matter or discoloration should not be used. Before IV infusion, dilute Fosphenytoin in 5% Dextrose or 0.9% Saline solution for injection to a concentration of 1.5 to 25 mg PE/ml.
Status Epilepticus: Give an intravenous infusion at a rate of 100 to 150 mg/minute, starting with 15 mg/kg. After that, give 4 to 5 mg/kg daily in 1 to 2 divided doses, either by intramuscular injection or by intravenous infusion (at a rate of 50 to 100 mg/minute). The dose is adjusted according to response and plasma-phenytoin concentration. Child 5 years and over: Give an intravenous infusion at a rate of 2 to 3 mg/kg/minute, starting with 15 mg/kg. Then give 4 to 5 mg/kg daily in 1 to 4 divided doses by intravenous infusion (at a rate of 1 to 2 mg/kg/minute), adjusting the dose according to response and plasma-phenytoin concentration.
Prophylaxis or treatment of seizures associated with neurosurgery or head injury: Give by intramuscular injection or by intravenous infusion (at a rate of 50 to 100 mg/minute), starting with 10 to 15 mg/kg. After that, give 4 to 5 mg/kg daily (in 1 to 2 divided doses) by intramuscular injection or by intravenous infusion (at a rate of 50 to 100 mg/minute). The dose is adjusted according to response and plasma-phenytoin concentration. Child 5 years and over: Give an intravenous infusion at a rate of 1 to 2 mg/kg/minute, starting with 10 to 15 mg/kg, then 4 to 5 mg/kg daily in 1 to 4 divided doses. Adjust the dose according to response and plasma-phenytoin concentration.
Temporary substitution for oral Phenytoin: Give by intramuscular injection or by intravenous infusion (at a rate of 50 to 100 mg/minute), using the same dose and dosing frequency as the oral Phenytoin therapy. Child 5 years and over: Give an intravenous infusion at a rate of 1 to 2 mg/kg/minute, with the same dose and dosing frequency as the oral Phenytoin therapy.
Patients with Renal or Hepatic Disease: After IV Fosphenytoin is given to patients with renal and/or hepatic disease, or to those with hypoalbuminemia, the clearance of Fosphenytoin to Phenytoin may go up without a similar rise in Phenytoin clearance. This could increase the frequency and severity of adverse events.
Elderly: Age has no significant effect on the pharmacokinetics of Fosphenytoin after it is given. Phenytoin clearance is decreased slightly in elderly patients, so a lower or less frequent dose may be required.
Side Effects
The most serious side effects of giving Fosphenytoin Sodium or Phenytoin by IV are cardiovascular collapse and central nervous system depression. Hypotension can happen if either drug is given too fast by the IV route, so the rate should not go above 150 mg PE/min. The side effects seen most often were nystagmus, dizziness, pruritus, paresthesia, headache, somnolence and ataxia. General Safety Advice IV infusion of Fosphenytoin Sodium has been linked with severe cardiovascular reactions, including asystole, ventricular fibrillation and cardiac arrest. Hypotension, bradycardia and heart block have also been reported. The safety advice is as follows. Monitor heart rate, blood pressure and respiratory function for the whole length of the infusion, and watch the patient for at least 30 minutes after it ends. If hypotension occurs, slow the infusion rate or stop the infusion. In elderly patients, and in patients with renal or hepatic impairment, reduce the dose or the infusion rate.
Cautions & Contraindications
Contraindications
Fosphenytoin must not be given to anyone who has shown hypersensitivity to Fosphenytoin or any of its ingredients, or to Phenytoin or other Hydantoins. It is also contraindicated in patients with sinus bradycardia, sino-atrial block, second and third degree A-V block, or Adams-Stokes syndrome.
Pregnancy & Breastfeeding
Fosphenytoin is Pregnancy Category D, and it is contraindicated during pregnancy. The reason is that exposure to Phenytoin before birth may raise the risk of congenital malformations and other adverse developmental outcomes. Women who are receiving Fosphenytoin are not recommended to breast-feed.
⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
Overdose
Overdose with Fosphenytoin Sodium has been reported to cause nausea, vomiting, lethargy, tachycardia, bradycardia, asystole, cardiac arrest, hypotension, syncope, hypocalcemia, metabolic acidosis and death. The first signs of acute Phenytoin toxicity are nystagmus, ataxia and dysarthria.
Treatment is nonspecific, because there is no known antidote to overdose of Fosphenytoin Sodium or Phenytoin. The patient's breathing and circulation should be watched closely, and suitable supportive measures given. Hemodialysis can be considered, since Phenytoin is not completely bound to plasma proteins. Total exchange transfusion has been used to treat severe intoxication in children.
In acute overdose, think also of other CNS depressants, including alcohol, as a possible cause.
⚠️ In an emergency call 999 or go to the nearest hospital emergency department.
Storage
Keep Fosphenytoin Sodium in a refrigerator at 2°C to 8°C, and don't put it in a deep freeze. It can stay at room temperature for no more than 48 hours. If an ampoule develops particulate matter, don't use it. Keep the medicine out of the reach of children.
Drug Interactions
Common questions about Sizaject 100 mg/2 ml
What is Sizaject 100 mg/2 ml Injection?
Sizaject 100 mg/2 ml Injection is a medicine that contains Fosphenytoin Sodium. It is made by Incepta Pharmaceuticals Ltd. It belongs to the Adjunct anti-epileptic drugs group of medicines.
What is Sizaject used for?
Fosphenytoin Sodium is given by injection (parenterally) for a short time, when other ways of giving Phenytoin are unavailable, unsuitable or thought to be less advantageous. It can be used to control generalized convulsive status epilepticus.
What are the side effects of Sizaject?
The most serious side effects of giving Fosphenytoin Sodium or Phenytoin by IV are cardiovascular collapse and central nervous system depression. Hypotension can happen if either drug is given too fast by the IV route, so the rate should not go above 150 mg PE/min.
Can I take Sizaject during pregnancy or while breastfeeding?
Fosphenytoin is Pregnancy Category D, and it is contraindicated during pregnancy. The reason is that exposure to Phenytoin before birth may raise the risk of congenital malformations and other adverse developmental outcomes. Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
What happens if I take too much Sizaject?
Overdose with Fosphenytoin Sodium has been reported to cause nausea, vomiting, lethargy, tachycardia, bradycardia, asystole, cardiac arrest, hypotension, syncope, hypocalcemia, metabolic acidosis and death. The first signs of acute Phenytoin toxicity are nystagmus, ataxia and dysarthria. In an emergency call 999 or go to the nearest hospital emergency department.
How should I store Sizaject?
Keep Fosphenytoin Sodium in a refrigerator at 2°C to 8°C, and don't put it in a deep freeze. It can stay at room temperature for no more than 48 hours.
Can I take other medicines with Sizaject?
Some medicines can interact with Fosphenytoin Sodium, for example: Tinidazole, Ifosfamide, Methylphenidate Hydrochloride, Carbamazepine, Phenytoin, Halothane. Tell your doctor or pharmacist about every medicine you take.
Do I need a prescription for Sizaject?
Sizaject is a prescription (Rx) medicine. Take it as your doctor advises.