Fosfen
Generic Name
fosfen-150-mg-injection
Manufacturer
Generic Manufacturer
Country
Various
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Price Details
Current market pricing information
| Variant | Unit Price | Strip Price |
|---|---|---|
| fosfen 150 mg injection | ৳ 70.26 | N/A |
Description
Overview of the medicine
Fosphenytoin (represented by 'Fosfen' here) is a water-soluble prodrug of phenytoin, an anticonvulsant. It is primarily used for the treatment of status epilepticus and for seizure prophylaxis when oral phenytoin administration is not feasible.
Uses & Indications
Dosage
Adults
Status Epilepticus: Loading dose of 15-20 mg phenytoin equivalent (PE)/kg IV at a rate of 100-150 mg PE/min. Non-emergent loading: 10-20 mg PE/kg IV/IM. Maintenance: 4-6 mg PE/kg/day IV/IM.
Elderly
Lower initial doses and slower infusion rates may be considered due to altered pharmacokinetics and increased sensitivity to adverse effects.
Renal_impairment
No dose adjustment is typically required for fosphenytoin. However, monitor phenytoin levels, especially in severe renal impairment, as protein binding may be altered.
How to Take
For IV administration, dilute in 5% Dextrose or 0.9% Sodium Chloride and infuse slowly at a rate not exceeding 150 mg PE/min. For IM administration, inject directly.
Mechanism of Action
Fosphenytoin is converted to phenytoin in the body. Phenytoin works by stabilizing neuronal membranes, prolonging the inactivation of voltage-gated sodium channels. This reduces neuronal excitability and prevents the spread of seizure activity.
Pharmacokinetics
Onset
IV: 10-20 minutes for phenytoin effects. IM: 30-60 minutes for phenytoin effects.
Excretion
Phenytoin metabolites are primarily excreted in the urine.
Half life
Fosphenytoin: Approximately 15 minutes. Phenytoin (after conversion): Variable, typically 7-60 hours (dose-dependent).
Absorption
Rapidly and completely converted to phenytoin after intramuscular (IM) or intravenous (IV) administration. Peak phenytoin levels are achieved within 30 minutes following IV administration and 30-60 minutes following IM administration.
Metabolism
Fosphenytoin is converted to phenytoin by phosphatases in the blood and tissues. Phenytoin is extensively metabolized in the liver by cytochrome P450 enzymes (primarily CYP2C9 and CYP2C19).
Side Effects
Contraindications
- Hypersensitivity to fosphenytoin, phenytoin, or other hydantoins
- Sinus bradycardia, sinoatrial (SA) block, second- or third-degree atrioventricular (AV) block, or Stokes-Adams syndrome
Drug Interactions
Alcohol
Increased phenytoin metabolism and CNS depression with chronic alcohol use; acute alcohol use may inhibit metabolism.
Warfarin
Phenytoin may alter the anticoagulant effect of warfarin.
Oral Contraceptives
Phenytoin may reduce the effectiveness of oral contraceptives.
Cimetidine, Omeprazole
May inhibit phenytoin metabolism, leading to increased phenytoin levels.
Carbamazepine, Phenobarbital, Rifampin
May induce phenytoin metabolism, leading to decreased phenytoin levels.
Storage
Store at controlled room temperature (20-25°C), protect from light. Do not refrigerate or freeze.
Overdose
Symptoms of overdose include nystagmus, ataxia, dysarthria, tremor, hyperreflexia, lethargy, slurred speech, blurred vision, nausea, and vomiting. In severe cases, coma, hypotension, and respiratory depression may occur. Management is supportive, including maintaining vital signs and monitoring phenytoin levels.
Pregnancy & Lactation
Pregnancy Category D. Fosphenytoin is a prodrug of phenytoin, which is associated with fetal hydantoin syndrome. Use only if potential benefit outweighs risk. Phenytoin is excreted in breast milk; breastfeeding is generally not recommended.
Side Effects
Contraindications
- Hypersensitivity to fosphenytoin, phenytoin, or other hydantoins
- Sinus bradycardia, sinoatrial (SA) block, second- or third-degree atrioventricular (AV) block, or Stokes-Adams syndrome
Drug Interactions
Alcohol
Increased phenytoin metabolism and CNS depression with chronic alcohol use; acute alcohol use may inhibit metabolism.
Warfarin
Phenytoin may alter the anticoagulant effect of warfarin.
Oral Contraceptives
Phenytoin may reduce the effectiveness of oral contraceptives.
Cimetidine, Omeprazole
May inhibit phenytoin metabolism, leading to increased phenytoin levels.
Carbamazepine, Phenobarbital, Rifampin
May induce phenytoin metabolism, leading to decreased phenytoin levels.
Storage
Store at controlled room temperature (20-25°C), protect from light. Do not refrigerate or freeze.
Overdose
Symptoms of overdose include nystagmus, ataxia, dysarthria, tremor, hyperreflexia, lethargy, slurred speech, blurred vision, nausea, and vomiting. In severe cases, coma, hypotension, and respiratory depression may occur. Management is supportive, including maintaining vital signs and monitoring phenytoin levels.
Pregnancy & Lactation
Pregnancy Category D. Fosphenytoin is a prodrug of phenytoin, which is associated with fetal hydantoin syndrome. Use only if potential benefit outweighs risk. Phenytoin is excreted in breast milk; breastfeeding is generally not recommended.
Frequently Asked Questions
Common questions about this medicine
Pack Sizes
Shelf Life
Refer to the product label for specific shelf life. Store as directed.
Availability
Hospitals and Pharmacies
Approval Status
FDA Approved
Patent Status
Patent Expired
WHO Essential Medicine
YesClinical Trials
Fosphenytoin has undergone extensive clinical trials for its efficacy and safety in treating and preventing seizures, leading to its approval. Ongoing research may explore new indications or formulations.
Lab Monitoring
- Phenytoin plasma levels (total and free)
- Complete Blood Count (CBC) with differential
- Liver Function Tests (LFTs)
- ECG monitoring (especially during rapid IV infusion)
Doctor Notes
- Monitor phenytoin levels (total and free) carefully, especially when initiating therapy or adjusting dose, and in patients with hepatic/renal impairment.
- Administer IV infusions slowly to minimize cardiovascular risks.
- Be aware of potential drug interactions, especially with narrow therapeutic index drugs.
Patient Guidelines
- Inform your doctor about all medical conditions and medications before starting treatment.
- Report any unusual side effects or worsening of seizures immediately.
- Do not stop the medication abruptly without consulting your doctor, as this can trigger severe seizures.
Missed Dose Advice
Since this is an injection administered by a healthcare professional, missed doses are unlikely. If a dose is missed, inform your doctor immediately to reschedule. Do not double dose.
Driving Precautions
Fosfen injection may cause dizziness, drowsiness, or visual disturbances. Avoid driving or operating heavy machinery until you know how the medication affects you.
Lifestyle Advice
- Avoid consuming alcohol while on this medication, as it can worsen side effects or alter drug levels.
- Maintain good oral hygiene to minimize the risk of gingival hyperplasia (a common side effect of phenytoin).
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