Details About Generic Salt ::  Phenytoi

Main Medicine Class:: Anticonvulsant,Hydantoin   

(FEN-ih-toe-in)

Phenytoin

Dilantin Infatab, Dilantin-125

Phenytoin Sodium

Dilantin, Dilantin Kapseals

Class: Anticonvulsant/Hydantoin

 

Action Appears to act at motor cortex in inhibiting spread of seizure activity. Possibly works by promoting sodium efflux from neurons, thereby stabilizing threshold against hyperexcitability. Also decreases post-tetanic potentiation at synapse.

 

Indications Control of grand mal and psychomotor seizures; prevention and treatment of seizures occurring during or after neurosurgery; control of grand mal type of status epilepticus (parenteral administration). Unlabeled use(s): Control of arrhythmias, (particularly cardiac glycoside-induced arrhythmias); control of convulsions in severe preeclampsia; treatment of trigeminal neuralgia (tic douloureux), recessive dystrophic epidermolysis bullosa and junctional epidermolysis bullosa.

 

Contraindications Hypersensitivity to phenytoin or other hydantoins; sinoatrial block; sinus bradycardia; second- and third-degree atrioventricular block; Adams-Stokes syndrome.

 

Route/Dosage

Individualize dose within clinically effective therapeutic serum level of 10 to 20 mcg/ml.

Seizures

ADULTS: PO 100 mg (or 125 mg of suspension) tid initially. Maintenance: 300 to 400 mg/day (maximum 600 mg/day). Sometimes initial 1 g loading dose is divided into 3 doses (400 mg, 300 mg, and 300 mg) and is given at 2 hr interval). Once seizure control is established, extended release form (300 mg) may be administered for once-a-day dosing. CHILDREN: PO 5 mg/kg/day in 2 to 3 divided doses initially. Maintenance: 4 to 8 mg/kg/day (maximum 300 mg/day).

Status Epilepticus

ADULTS: IV Loading dose of 10 to 15 mg/kg via slow IV. Then PO/IV 100 mg q 6 to 8 hr. CHILDREN: IV Loading dose of 15 to 20 mg/kg at rate not exceeding 1 to 3 mg/kg/min.

Neurosurgery Prophylaxis

ADULTS: IM 100 to 200 mg at 4-hr intervals during surgery and postoperatively.

 

Interactions

Acetaminophen: May increase hepatotoxicity potential with chronic phenytoin use. Amiodarone, chloramphenicol, disulfiram, estrogens, felbamate, fluconazole, isoniazid, cimetidine, trimethoprim, phenylbutazone, oxyphenbutazone, phenacemide, sulfonamides: May increase phenytoin serum levels. Carbamazepine, sucralfate, antineoplastic agents, rifampin, rifabutin: May decrease phenytoin serum levels. Corticosteroids, coumarin anticoagulants, doxycycline, estrogens, levodopa, felodipine, methadone, loop diuretics, oral contraceptives, quinidine, rifampin, rifabutin: May impair effects of these agents. Cyclosporine: May reduce cyclosporine levels. Disopyramide: May cause decreased disopyramide levels and bioavailability and may enhance anticholinergic actions. Enteral nutritional therapy: May reduce phenytoin concentrations. Folic acid: May cause folic acid deficiency. Metyrapone: Phenytoin may cause subnormal response to metyrapone. Mexiletine: May decrease mexiletine levels and effects. Nondepolarizing muscle relaxants: May cause these agents to have shorter duration or decreased effects. Phenobarbital, sodium valproate, valproic acid: May increase or decrease phenytoin levels. Phenytoin may increase phenobarbital and decrease valproic acid levels. Primidone: May increase concentrations of primidone and metabolites. Sympathomimetics (eg, dopamine): May cause profound hypotension and possibly cardiac arrest. Theophyllines: Effects of either agent may be decreased.

 

Lab Test Interferences Phenytoin may interfere with metapyrone and dexamethasone tests, causing inaccurate results because of increased metabolism of these agents. Drug may cause decreases in serum levels of protein-bound iodine. It may cause increased levels of glucose, alkaline phosphatase and gamma glutamyl transpeptidase. Incompatibilities: Do not mix with other drugs in syringe.

 

Adverse Reactions

CV: (IV use): CV collapse; hypotension; atrial and ventricular conduction depression; ventricular fibrillation. CNS: Nystagmus; ataxia; dysarthria; slurred speech; mental confusion; dizziness; insomnia; transient nervousness; motor twitching; diplopia; fatigue; irritability; drowsiness; depression; numbness; tremor; headache; choreoathetosis (IV use). DERM: Rashes, sometimes accompanied by fever; bullous, exfoliative or purpuric dermatitis; lupus erythematosus; Stevens-Johnson syndrome; toxic epidermal necrolysis; hirsutism; alopecia. EENT: Conjunctivitis. GI: Nausea; vomiting; diarrhea; constipation. HEMA: Thrombocytopenia; leukopenia; granulocytopenia; agranulocytosis; pancytopenia; macrocytosis; megaloblastic anemia; eosinophilia; monocytosis; leukocytosis; simple anemia; hemolytic anemia; aplastic anemia. HEPA: Toxic hepatitis and liver damage; hepatocellular degeneration and necrosis; hepatitis; jaundice; nephrosis. OTHER: Gingival hyperplasia; coarsening of facial features; lip enlargement; Peyronie’s disease; polyarthropathy; hyperglycemia; weight gain; chest pain; IgA depression; fever; photophobia; gynecomastia; periarteritis nodosa; pulmonary fibrosis; tissue injury at injection site; lymph node hyperplasia; hypothyroidism.

 

Precautions

Pregnancy: Pregnancy category undetermined. Consult physician. Possible risk of birth defects must be considered along with risk of seizures to fetus in untreated epileptic mothers. Lactation: Excreted in breast milk. Special-risk patients: Use drug with caution with hepatic impairment, acute intermittent poryphria, alcohol abuse, hypotension, and severe myocardial insufficiency. Bioavailability: Because products vary in bioavailability; brand interchange is not recommended. Hypersensitivity reactions: Rapid substitution of alternate therapy may be necessary. Seizures: Drug should not be given to treat seizures due to hypoglycemia or other metabolic causes or petit mal (absence) epilepsy. Withdrawal: Abrupt withdrawal may precipitate status epilepticus. Dosage must be reduced or other anticonvulsant medicine substituted gradually.

PATIENT CARE CONSIDERATIONS

 

Administration/Storage

• Shake oral suspension well.
• Do not administer discolored capsules.
• Administer oral forms with food.
• Only extended-release capsules are recommended for once-a-day dosage. before any surgical, emergency, or dental procedure.
• Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.

Drugs Class ::

Action Appears to act at motor cortex in inhibiting spread of seizure activity. Possibly works by promoting sodium efflux from neurons, thereby stabilizing threshold against hyperexcitability. Also decreases post-tetanic potentiation at synapse.