Introduction
Fosfen 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.
Fosfen is given under the supervision of a healthcare professional and should not be self administered. You should never skip any doses and finish the full course of treatment even if you feel better as stopping the medication without talking to the doctor may cause non-stop seizures and can endanger life. Be careful if you are using birth control pills as this medicine may interfere with the working of contraceptives.
Fosfen may cause few side effects such as vomiting, itching, impaired coordination and involuntary eye movement (nystagmus) . It may also cause dizziness and sleepiness in some people, so do not drive or do anything that requires mental focus. Additionally, you may notice some injection site reactions like redness or swelling. Most side effects wear off, but if they bother you or do not go away, tell your doctor. There may be ways of preventing or reducing these effects.
Side effects of Fosfen
Common
- Vomiting
- Sleepiness
- Dizziness
- Itching
- Impaired coordination
- Nystagmus (involuntary eye movement)
How to use Fosfen
Your doctor or nurse will give you this medicine. Kindly do not self administer.
How Fosfen works
Fosfen is an antiepileptic medication. It controls seizures or fits by decreasing the abnormal and excessive activity of the nerve cells in the brain.
What if you forget to take Fosfen?
If you miss a dose of Fosfen, take it as soon as possible. However, 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.
Indication
Fosphenytoin is indicated for short-term parenteral administration when other means of Phenytoin administration are unavailable, inappropriate or deemed less advantageous. Fosphenytoin can be used for the control of, generalized convulsive status epilepticus, prevention and treatment of seizures, occurring during neurosurgery or head injury. It can also be substituted, short-term, for oral Phenytoin.
Administration
Reconstitution:
Prior to IV infusion, dilute Fosphenytoin in 5% Dextrose or 0.9% Saline solution for injection to a concentration ranging from 1.5 to 25 mg PE/ml.
Adult Dose
Parenteral
Adult: As phenytoin Na equivalents (PSE):
(The dose, concentration in dosing solutions, and infusion rate of IV Fosphenytoin is expressed as Phenytoin Sodium equivalents (PE); (Fosphenytoin Sodium 1.5 mg equivalent to Phenytoin Sodium 1 mg) to avoid the need to perform molecular weight-based adjustments when converting between Fosphenytoin and Phenytoin Sodium doses.)
Status Epilepticus:
By intravenous infusion (at a rate of 100-150 mg (PE)/minute), initially 15 mg (P/E)/kg then
By intramuscular injection or By intravenous infusion (at a rate of 50-100 mg (PE)/minute), 4-5 mg (P/E)/kg daily in 1-2 divided doses,
Prophylaxis or treatment of seizures associated with neurosurgery or head injury:
By intramuscular injection or By intravenous infusion (at a rate of 50-100 mg (PE)/minute, initially 10-15 mg (PE)/kg then
4-5 mg (PE)/kg daily (in 1-2 divided doses),
Temporary substitution for oral Phenytoin:
By intramuscular injection or by intravenous infusion (at a rate of 50-100 mg (PE)/minute), same dose and dosing frequency as oral Phenytoin therapy.
Dose adjusted according to response and through plasma-phenytoin concentration.
Elderly: Lower loading dose and/or infusion rate, and lower or less frequent maintenance dose.
Hepatic impairment: Dose reduction or slower infusion may be needed.
Child Dose
Parenteral
As phenytoin Na equivalents (PSE):
(The dose, concentration in dosing solutions, and infusion rate of IV Fosphenytoin is expressed as Phenytoin Sodium equivalents (PE); (Fosphenytoin Sodium 1.5 mg equivalent to Phenytoin Sodium 1 mg) to avoid the need to perform molecular weight-based adjustments when converting between Fosphenytoin and Phenytoin Sodium doses.)
Status Epilepticus:
Child >5 years:
By intravenous infusion (at a rate of 2-3 mg (PE)/kg/minute), initially 15 mg (PE)/kg then
By intravenous infusion (at a rate of 1-2 mg (PE)/kg/minute), 4-5 mg (PE)/kg daily in 1-4 divided doses,
Prophylaxis or treatment of seizures associated with neurosurgery or head injury:
Child >5 years: By intravenous infusion (at a rate of 1-2 mg (PE)/kg/minute), initially 10-15 mg (PE)/kg then
4-5 mg (PE)/kg daily in 1-4 divided doses,
Temporary substitution for oral Phenytoin:
Child >5 years: By intravenous infusion (at a rate of 1-2 mg (PE)/kg/minute), same dose and dosing frequency as oral Phenytoin therapy.
Dose adjusted according to response and through plasma-phenytoin concentration.
Renal impairment: Dose reduction or slower infusion may be needed.
Hepatic impairment: Dose reduction or slower infusion may be needed.
Renal Dose
Renal impairment: Dose reduction or slower infusion may be needed.
Contraindication
Fosphenytoin is contraindicated in patients who have demonstrated hypersensitivity to Fosphenytoin or its ingredients, or to Phenytoin or other Hydantoins. Fosphenytoin is also contraindicated in patients with sinus bradycardia, sino-atrial block, second and third degree A-V block, and Adams-Stokes syndrome.
Mode of Action
Fosphenytoin is a diphosphate ester salt of phenytoin which acts as a water soluble prodrug of phenytoin. After admin, plasma esterases convert fosphenytoin to phosphate, formaldehyde, and phenytoin as the active moiety; phenytoin stabilises neuronal membranes and decreases seizure activity by increasing efflux or decreasing influx of Na ions across cell membranes in the motor cortex during generation of nerve impulses.
Precaution
Patient w/ phosphate restriction, hypoalbuminaemia, hypotension, severe myocardial insufficiency, DM. May exacerbate porphyria. Not effective for the treatment of absence seizures and seizures associated w/ hypoglycaemia or other metabolic causes. Avoid abrupt withdrawal. Renal and hepatic impairment. Elderly. Pregnancy and lactation. Patient Counselling May impair ability to drive or operate machinery. Monitoring Parameters Monitor BP, cardiac and resp function; vital signs, haematologic and hepatic function, plasma phenytoin concentrations.
Side Effect
>10%
IV
Pruritis (40-50%),Dizziness (31%),Somnolence (20%),Ataxia (11%)
IM
Nystagmus (15%)
1-10%
IV
Tinnitus (6-10%),Deafness (2-5%)
IM
Somnolence (6-10%),Bruising (7%),Pruritis (2-5%),Nausea (5%),Vomiting (3%),Weakness (4%)
<1%
Taste change (>1%)
Frequency Not Defined
Hypotension (esp with high rates of IV infusion)
Hypertension
Dysarthria
Fever
Increased reflex
Intracranial HTN
Hypesthesia
Sensory disturbances (burning, itching, paresthesia), withdrawal-precipitated seizures
Rash
Constipation
Hypokalemia
Cytopenias (can be fatal)
Hepatic injury
Myasthenia
Pneumonia
IV
Hypotension, vasodilation, tachycardia
Agitation, asthenia, headache, EPS, paresthesia, stupor, tremor
Dry mouth, nausea, vomiting
Pelvic and back pain
Diplopia, nystagmus
Body as a Whole: Allergic reactions in the form of rash and rarely more serious forms (DRESS) or anaphylaxis; coarsening of facial features, systemic lupus erythematosus, periarteritis nodosa, and immunoglobulin abnormalities
Special Senses: Altered taste sensation including metallic taste
Urogenital: Peyronie’s disease
IM
Asthenia, ataxia, decreased reflex, dizziness, headache, paresthesia, tremor
Nausea, vomiting
Eccymosis
Pregnancy Category Note
Pregnancy
In humans, prenatal exposure to phenytoin (the active metabolite of fosphenytoin) may increase risks for congenital malformations and other adverse development outcomes; an increased incidence of major malformations (such as orofacial clefts and cardiac defects) and abnormalities characteristic of fetal hydantoin syndrome (dysmorphic skull and facial features, nail and digit hypoplasia, growth abnormalities [including microcephaly], and cognitive deficits) reported among children born to epileptic women who took phenytoin alone or in combination with other antiepileptic drugs during pregnancy; there have been several reported cases of malignancies, including neuroblastoma, in children whose mothers received phenytoin during pregnancy
Lactation
It is not known whether fosphenytoin is secreted in human milk; following administration of phenytoin (the active metabolite of fosphenytoin), phenytoin is secreted in human milk; the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for therapy and any potential adverse effects on breastfed infant from therapy or from underlying maternal condition
Interaction
No drugs are known to interfere with the conversion of Fosphenytoin to Phenytoin. Drugs that may increase plasma Phenytoin concentrations include: Acute alcohol intake, Amiodarone, Chloramphenicol, Chlordiazepoxide, Cimetidine, Diazepam, Dicumarol, Disulfiram, Estrogens, Ethosuximide, Fluoxetine, H2-Antagonists, Halothane, Isoniazid, Methylphenidate, Phenothiazines, Phenylbutazone, Salicylates, Succinimides, Sulfonamides, Tolbutamide, Trazodone. Drugs that may decrease plasma phenytoin concentrations include: Carbamazepine, chronic alcohol abuse, Reserpine. Drugs that may either increase or decrease plasma Phenytoin concentrations include: Phenobarbital, Valproic Acid, and Sodium Valproate. Similarly, the effects of Phenytoin on Phenobarbital, Valproic Acid and Sodium plasma Valproate concentrations are unpredictable.
Potentially Fatal: May cause loss of virologic response and possible resistance to delavirdine or to the class of non-nucleoside reverse transcriptase inhibitors.