Dictionary:

fosphenytoin

  (fŏs'fĕn'ĭ-tō'ĭn, -fə-nĭt'ō-)

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A prodrug that is metabolized to phenytoin and administered parenterally for the treatment of seizures.

[Alteration of PHOS(PHORUS) + PHENYTOIN.]

Brand names: Cerebyx®

Chemical formula:

Español:
• Fosfenitoína Sódico, Solución para inyección

Fosphenytoin Sodium Solution for injection

What is this medicine?

FOSPHENYTOIN is used to control seizures in certain types of epilepsy. It can help to prevent seizures occurring during or after surgery.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
• an alcohol abuse problem
• blood disorders or disease
• heart disease, low blood pressure
• kidney disease
• liver disease
• suicidal thoughts, plans, or attempt; a previous suicide attempt by you or a family member
• an unusual or allergic reaction to phenytoin, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I use this medicine?

This medicine is for injection into a vein or muscle or for infusion into a vein. It is given by a health-care professional in a hospital or clinic setting.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
NOTE: This medicine is only for you. Do not share this medicine with others.

What may interact with this medicine?

Do not take this medicine with any of the following medications:
• delavirdine

This medicine may also interact with the following medications:
• antibiotics known as sulfonamides
• aspirin and aspirin-like medicines
• barbiturate medicines for inducing sleep or treating seizures (convulsions)
• carbamazepine
• chloramphenicol
• chlordiazepoxide
• diazepam
• disulfiram
• ethosuximide
• female hormones, including contraceptive or birth control pills
• fluoxetine
• halothane
• heart medicines such as digoxin or digitoxin
• corticosteroid hormones such as prednisone or cortisone
• doxycycline
• furosemide
• isoniazid
• medicines for diabetes
• medicines for mental depression, anxiety or other mood problems
• medicines for stomach problems like cimetidine, famotidine, nizatidine and ranitidine
• medicines to control heart rhythm
• methsuximide
• methylphenidate
• phenothiazines like chlorpromazine, mesoridazine, prochlorperazine, thioridazine
• phenylbutazone
• reserpine
• rifampin, rifabutin or rifapentine
• theophylline
• valproic acid
• vitamin D
• warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medicine?

Visit your doctor or health care professional for regular checks on your progress. Your doctor or health care professional may schedule regular blood tests, because this medicine needs careful monitoring. Do not stop using this medicine suddenly. This increases the risk of seizures. Because your condition and the use of this medicine carry some risk, it is a good idea to carry an identification card, necklace or bracelet with details of your condition, medications and doctor or health care professional.

You may feel dizzy or drowsy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. To reduce the risk of dizzy or fainting spells, do not sit or stand up quickly, especially if you are an older patient. Alcohol can make you more dizzy, increase flushing and may cause rapid heartbeats. Avoid alcoholic drinks.

This medicine can cause unusual growth of gum tissues. Visit your dentist regularly. Problems can arise if you need dental work, and in the day to day care of your teeth. Try to avoid damage to your teeth and gums when you brush or floss your teeth.

The use of this medicine may increase the chance of suicidal thoughts or actions. Pay special attention to how you are responding while on this medicine. Any worsening of mood, or thoughts of suicide or dying should be reported to your health care professional right away.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:
• allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
• confusion
• dark yellow or brown urine
• difficulty breathing, wheezing or shortness of breath
• double vision or uncontrollable and rapid eye movement
• fever, sore throat
• headache
• loss of seizure control
• poor control of body movements or difficulty walking
• redness, blistering, peeling or loosening of the skin, including inside the mouth
• unusual bleeding or bruising, pinpoint red spots on skin
• vomiting
• worsening of mood, thoughts or actions of suicide or dying
• yellowing of the eyes or skin

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
• constipation
• difficulty sleeping
• excessive hair growth on the face or body
• nausea

This list may not describe all possible side effects.

Where should I keep my medicine?

This drug is given in a hospital or clinic and will not be stored at home.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

Fosphenytoin
Systematic (IUPAC) name
(2,5-dioxo-4,4-diphenyl-imidazolidin-1-yl)methoxyphosphonic acid
Identifiers
CAS number	93390-81-9
ATC code	N03AB05
PubChem	56339
DrugBank	APRD00241
Chemical data
Formula	C16H15N2O6P
Mol. mass	362.274 g/mol
Pharmacokinetic data
Bioavailability	100% (IM)
Protein binding	95 to 99%
Metabolism	Hepatic
Half life	15 minutes to convert to phenytoin
Excretion	Renal (as phenytoin)
Therapeutic considerations
Pregnancy cat.	D(US)
Legal status	℞ Prescription only
Routes	Intravenous, intramuscular

Fosphenytoin (Cerebyx®, Parke-Davis; Prodilantin®, Pfizer Holding France^[1]) is a water-soluble phenytoin prodrug used only in hospitals for the treatment of epileptic seizures.

On 18 November 2004, Sicor (a subsidiary of Teva) received a tentative approval letter from the United States Food and Drug Administration for a generic version of fosphenytoin.^[2]

Uses

Approved

Fosphenytoin is approved in the United States for the short term (five days or less) treatment of epilepsy when more widely used means of phenytoin administration are not possible or are ill-advised,^[3] such as endotracheal intubation, status epilepticus or some other type of repeated seizures; vomiting, and/or the patient is unalert or not awake or both.^[4]

Unapproved/off-label/investigational

In April of 2003, Applebaum and colleagues at the Ben-Gurion University of the Negev in Beersheba reported that even though anticonvulsants are often very effective in mania, and acute mania requires rapid treatment, fosphenytoin had no antimanic effect even 60 minutes after administration of doses used in status epilepticus.^[5]

Fosphenytoin was more successfully used to relieve pain refractory to opiates in a 37-year-old woman with neuroma, according to Dr. Gary J. McCleane of the Rampark Pain Center in Lurgan, Northern Ireland.^[6] She was given 1,500 phenytoin equivalent units of fosphenytoin over a 24 hour period, producing pain relief that last three to fourteen weeks after each infusion, allowing her to use less opiates.^[6]

Metabolism

One mmol (millimole) of phenytoin is produced for every mmol of fosphenytoin administered; the hydrolysis of fosphenytoin also yields phosphate and formaldehyde, the latter of which is subsequently metabolized to formate, which is in turn metabolized by a folate dependent mechanism.^[3]

Side effects

Side effects are similar to phenytoin, except that fosphenytoin causes less hypotension and more paresthesia.^[7] Fosphenytoin can cause hyperphosphatemia in end-stage renal failure patients.^[8]

History

Phenytoin, in both its acidic and sodium salt forms, is erratically bioavailable whether it is injected or taken orally due to its high melting point, weak acidity, and its being only sparingly soluble in water.^[9] Simply putting patients on other drugs is not always an option; this was especially true before 1993, when the number of anticonvulsants available was much more limited.^[10] One solution was to develop a prodrug that did not have these drawbacks.

Fosphenytoin was approved by the Food and Drug Administration (FDA) on August 5, 1996 for use in epilepsy.^[11]

Notes and references

1. ^ PRODILANTIN 75 mg/ml sol inj IM et p perf IV. VIDAL, l'information de référence sur les produits de santé. Retrieved on 23 October, 2005.
2. ^ Fosphenytoin Sodium Approval History. Retrieved on 20 October, 2005.
3. ^ ^{a b} Parke-Davis (2001). Cerebyx®: Fosphenytoin Sodium Injection - Labeling Revision (PDF). Cerebyx Approval History. Warner-Lambert Company. Retrieved on 20 October, 2005.
4. ^ Johnson J, Wrenn K (2001). "Inappropriate fosphenytoin use in the ED". American Journal of Emergency Medicine 19 (4): 293-4. PMID 11447516.  Fulltext options List of Library Holdings Worldwide
5. ^ Applebaum J, Levine J, Belmaker RH (2003). "Intravenous fosphenytoin in acute mania" (PDF). Journal Clinical Psychiatry 64 (4): 408-9. PMID 12716241. 
6. ^ ^{a b} McCleane GJ (2002). "Intravenous infusion of fosphenytoin produces prolonged pain relief: a case report". The Journal of Pain 3 (2): 156-8. PMID 14622802.  List of Library Holdings Worldwide
7. ^ Browne TR. (1997). "Fosphenytoin (Cerebyx)". Clinical Neuropharmacology 20 (1): 1-12. PMID 9037568.  List of Library Holdings Worldwide
8. ^ McBryde KD, Wilcox J, Kher KK (2005). "Hyperphosphatemia due to fosphenytoin in a pediatric ESRD patient" (PDF). Pediatric Nephrology (Berlin, Germany) 20 (8): 1182-5. PMID 15965770. 
9. ^ Yamaoka Y, Roberts RD, Stella VJ. "Low-melting phenytoin prodrugs as alternative oral delivery modes for phenytoin: a model for other high-melting sparingly water-soluble drugs." Journal of Pharmaceutical Science. 1983 Apr;72(4):400-5. PMID 6864479
10. ^ Anticonvulsants before 1993 Neuroland
11. ^ Cerebyx Approval History. Retrieved on 20 October, 2005.

See also

• hydantoin
• ethotoin
• mephenytoin
• phenytoin

Anticonvulsants (N03)
Barbiturates	Barbexaclone, Metharbital, Methylphenobarbital, Phenobarbital, Primidone
Hydantoins	Ethotoin, Fosphenytoin, Mephenytoin, Phenytoin
Oxazolidinediones	Ethadione, Paramethadione, Trimethadione
Succinimides	Ethosuximide, Mesuximide, Phensuximide
Benzodiazepines	Clobazam, Clonazepam, Clorazepate, Diazepam, Lorazepam, Midazolam, Nitrazepam, Temazepam
Carboxamides	Carbamazepine, Oxcarbazepine, Rufinamide
Fatty acid derivatives	Valpromide, Valnoctamide
Carboxylic acids	Valproic acid (Sodium valproate & Valproate semisodium), Tiagabine
Others	GABA analogs: Gabapentin, Pregabalin, Progabide, Vigabatrin -- Monosaccharides: Topiramate -- Aromatic allylic alcohols: Stiripentol -- Ureas: Phenacemide, Pheneturide -- Phenyltriazines: Lamotrigine Carbamates: Emylcamate, Felbamate, Meprobamate -- Pyrrolidines: Brivaracetam, Levetiracetam, Nefiracetam, Seletracetam Sulfa drugs: Acetazolamide, Ethoxzolamide, Sultiame, Zonisamide -- Propionates: Beclamide -- Aldehydes: Paraldehyde -- Bromides: Potassium bromide, Sodium bromide

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