Fosfen150 mg/2 ml

Fosfen is a hydantoin-derivative anticonvulsant indicated for:

• Established/FDA-approved uses:
  • Control of generalized tonic-clonic (grand mal) seizures
  • Control of complex partial (psychomotor, temporal lobe) seizures
  • Prevention and treatment of seizures occurring during or following neurosurgery
  • Treatment of status epilepticus of the generalized tonic-clonic type (intravenous formulation)
• Not effective / not indicated for: absence (petit mal) seizures, which may worsen with Fosfen monotherapy.

Fosfen is used as monotherapy or as adjunctive therapy alongside other antiepileptic drugs when a single agent does not achieve adequate seizure control.

Each formulation of Phenytoin Sodium contains phenytoin sodium as the active pharmaceutical ingredient, available as oral capsules, tablets, chewable tablets, oral suspension, and sterile injection for intravenous use, with standard pharmaceutical excipients appropriate to each dosage form.

Fosfen is a hydantoin-class antiepileptic (anticonvulsant) medicine used to prevent and control certain types of seizures. It works by stabilizing electrically excitable neuronal membranes, limiting the spread of seizure activity in the brain without generally depressing overall brain function.

Fosfen has a narrow therapeutic index and nonlinear (saturable, dose-dependent) pharmacokinetics, meaning small changes in dose can cause disproportionately large changes in blood levels. Because of this, treatment with Fosfen requires individualized dosing and periodic monitoring of blood levels.

Fosfen belongs to the hydantoin class of antiepileptic (anticonvulsant) drugs.

Phenytoin Sodium acts primarily by blocking voltage-gated sodium channels in neurons. By prolonging the inactivated state of these channels, Phenytoin Sodium reduces sustained high-frequency repetitive firing of neurons and limits the spread of seizure discharges from an epileptogenic focus to adjacent brain tissue.

Phenytoin Sodium is extensively metabolized in the liver (mainly by CYP2C9 and CYP2C19) via a saturable enzyme pathway. At doses near or above the therapeutic range, small dose increments can saturate metabolism and produce large, unpredictable rises in plasma concentration, so Phenytoin Sodium follows nonlinear kinetics at higher doses rather than simple first-order elimination.

Fosfen oral suspension should be shaken well before each dose. Oral Fosfen may be taken with food to reduce stomach upset. Chewable tablets must be chewed, not swallowed whole. The intravenous form of Fosfen must be administered slowly by a healthcare professional, with cardiac and blood pressure monitoring, and should not be mixed with dextrose-containing solutions due to precipitation risk. Do not administer Fosfen injection intramuscularly for maintenance therapy due to erratic absorption and local tissue damage.

Fosfen is both a substrate and a potent inducer of hepatic cytochrome P450 enzymes, resulting in numerous clinically significant interactions:

• Delavirdine: concurrent use is contraindicated — Fosfen can reduce delavirdine levels enough to risk loss of HIV virologic response and resistance.
• Warfarin: Fosfen can either increase or decrease anticoagulant effect; INR should be monitored closely when starting, stopping, or changing the dose of either drug.
• Oral contraceptives: Fosfen induces metabolism of estrogens/progestins and may reduce contraceptive efficacy; alternative or additional contraception is advised.
• Other antiepileptic drugs (e.g., carbamazepine, valproate, phenobarbital): complex bidirectional interactions can raise or lower levels of either drug; monitoring is required.
• CYP2C9/2C19 inhibitors (e.g., fluconazole, amiodarone, cimetidine, isoniazid): can increase Fosfen levels and toxicity risk.
• Folic acid, antacids, and enteral tube feeds: can reduce absorption/levels of Fosfen; separate dosing timing when possible.
• Corticosteroids and other CYP3A4-metabolized drugs: Fosfen can reduce their effectiveness through enzyme induction.

Because of the many potential interactions, inform your physician of all medicines, supplements, and herbal products used together with Fosfen.

Side effects of Fosfen are often dose- and concentration-related.

Common

• Nystagmus, ataxia, slurred speech, unsteady gait, tremor
• Drowsiness, dizziness, mental confusion (usually with higher levels)
• Nausea, vomiting, constipation
• Gingival (gum) hyperplasia and hirsutism with long-term use
• Acne and coarsening of facial features with long-term use

Less common but serious

• Severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis (risk increased in certain HLA genotypes, notably in some Asian populations)
• Drug reaction with eosinophilia and systemic symptoms (DRESS)/hypersensitivity syndrome
• Blood cell count abnormalities (rare)
• Liver injury (rare)
• Peripheral neuropathy and decreased bone density with long-term use
• "Purple glove syndrome" (limb swelling, discoloration, pain) with IV administration
• Cardiovascular effects (hypotension, arrhythmia) with rapid IV administration

Seek prompt medical attention for any rash, fever, swollen glands, unusual bruising/bleeding, jaundice, or severe dizziness while taking Fosfen.

Pregnancy: Fosfen can cross the placenta and has been associated with fetal hydantoin syndrome (craniofacial abnormalities, growth deficiency, and developmental effects). Fosfen should be used in pregnancy only if clearly needed, when the potential benefit of seizure control justifies the potential risk to the fetus; abrupt discontinuation is not advised, as uncontrolled seizures pose their own risk to mother and fetus. Folic acid supplementation is generally recommended for patients of childbearing potential taking Fosfen, and vitamin K may be recommended near delivery to reduce neonatal bleeding risk. Always consult a physician before starting, stopping, or continuing Fosfen during pregnancy.

Lactation: Fosfen passes into breast milk in small amounts. Use during breastfeeding should be under medical supervision, with the infant monitored for sedation or feeding difficulty; consult a physician before use.

Use Fosfen only under medical supervision, with attention to the following:

• Narrow therapeutic index: small dose changes can cause disproportionate changes in blood levels; periodic monitoring of serum Fosfen levels is recommended, particularly with dose changes, addition of interacting drugs, or breakthrough seizures.
• Hepatic impairment: dose adjustment and closer monitoring are needed, as Fosfen is extensively metabolized by the liver.
• Cardiovascular risk with IV use: rapid intravenous administration of Fosfen can cause severe hypotension and cardiac arrhythmias; continuous cardiac monitoring is required during IV administration, especially in elderly or cardiac patients.
• Serious skin/hypersensitivity reactions: discontinue Fosfen immediately if a rash or signs of hypersensitivity syndrome (DRESS) develop; certain HLA genotypes may increase risk of severe skin reactions.
• Do not stop abruptly: abrupt withdrawal of Fosfen can precipitate status epilepticus; dose should be tapered under medical guidance if discontinuation is needed.
• Suicidal thoughts/behavior: as with other antiepileptic drugs, Fosfen may be associated with a small increased risk of suicidal thoughts; report any mood changes to a physician.
• See Contraindications and Drug Interactions for additional important safety information about Fosfen.

Overdose of Fosfen may cause nystagmus, ataxia, slurred speech, tremor, lethargy, and confusion progressing to coma, and, with very high levels or rapid IV administration, severe low blood pressure and cardiac arrhythmias. There is no specific antidote for Fosfen overdose. If overdose is suspected, seek immediate medical attention or contact emergency services or a poison control center; treatment is supportive, including monitoring of vital signs and phenytoin blood levels in a medical facility.

Store Fosfen at room temperature (below 30°C), away from light and moisture. Do not refrigerate the injectable form of Fosfen, as refrigeration may cause precipitation. Keep out of reach of children.

Elderly: may require lower doses and slower titration of Fosfen due to altered drug binding and increased sensitivity to side effects.

Renal impairment: unbound (active) Fosfen levels can rise in patients with significant renal impairment or low serum albumin; free phenytoin level monitoring is advised.

Hepatic impairment: dose reduction and closer monitoring are needed, as described under Precautions.

Pediatric patients: see Pediatric Uses.

Pregnancy and lactation: see the Pregnancy and Lactation section.

Duration of treatment with Fosfen is individualized by the treating physician based on seizure type, control achieved, and response to therapy; epilepsy treatment with Fosfen is often long-term, and any decision to reduce or stop Fosfen should be made gradually and under medical supervision.

Phenytoin Sodium belongs to the hydantoin class of antiepileptic (anticonvulsant) agents.

Phenytoin Sodium stabilizes neuronal membranes by blocking voltage-gated sodium channels, prolonging their inactivated state, and thereby limiting the repetitive firing of neurons and the spread of seizure activity, without generally producing overall central nervous system depression at therapeutic doses.

D

Fosfen is used in pediatric patients for control of generalized tonic-clonic and complex partial seizures, and for status epilepticus, with dosing individualized by weight (approximately 5 mg/kg/day initially, with usual maintenance of 4–8 mg/kg/day in divided doses, generally not exceeding 300 mg/day). Use in neonates and very young infants requires particular caution and close monitoring due to variable absorption and metabolism. Safety and efficacy of specific extended-release or once-daily formulations of Fosfen in children below certain ages may not be established; a pediatrician should individualize therapy and monitor growth, dental/gum health, and drug levels closely in children on long-term Fosfen.