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See related phenytoin information
| | | Listed in Dosage. | | Adult: PO Epilepsy Initial: 3-4 mg/kg/day as single dose or in divided doses. Maintenance: 200-500 mg/day. IV Tonic-clonic status epilepticus As adjunct w/ a benzodiazepine: 10-15 mg/kg. Maintenance: 100 mg 6-8 hrly.
Click to view Dosage by Indications | | Should be taken with food. (When administering to patients on nasogastric or other enteral feeds, be consistent throughout therapy in relation to feed times. Do not switch dosage forms/ brands without prior consideration.)
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| | Pregnancy. IV admin in sinus bradycardia, heart block, or Stokes-Adams syndrome. | | Cardiovascular disease, e.g. sinus bradycardia, heart blocks; DM; hepatic impairment; hypoalbuminemia; porphyria; seizures (may increase frequency of petit mal seizures); debilitated patients; elderly. Caution in IV admin in hypotension, heart failure or MI, monitor BP and ECG during therapy. IV must be given slowly (too rapid admin may cause hypotension, CNS depression, cardiac arrhythmias and impaired heart conduction). Extravasation and intra-arterial admin must be avoided. Do not discontinue abruptly (may increase seizure frequency), unless safety concerns require a more rapid withdrawal. May impair ability to drive or operate machinery. | | Hypersensitivity, lack of appetite, headache, dizziness, tremor, transient nervousness, insomnia, GI disturbances (e.g. nausea, vomiting, constipation), tenderness and hyperplasia of the gums, acne, hirsutism, coarsening of the facial features, rashes, osteomalacia. Phenytoin toxicity as manifested as a syndrome of cerebellar, vestibular, ocular effects, notably nystagmus, diplopia, slurred speech, and ataxia; also with mental confusion, dyskinesias, exacerbations of seizure frequency, hyperglycaemia. Solutions for inj may cause local irritation or phlebitis. Prolonged use may produce subtle effects on mental function and cognition, especially in children.
Potentially Fatal: Toxic epidermal necrolysis, Stevens-Johnson syndrome. | | Effects with other sedative drugs or ethanol may be potentiated. Enhances toxic effects of paracetamol, lithium. Increased risk of osteomalacia with acetazolamide. Decreased serum levels/effects with acyclovir, antineoplastics, benzodiazeines, ciprofloxacin, CYP2C9 inducers (e.g. carbamazepine), CYP2C19 inducers (e.g. rifampin), folic acid, vigabatrin. Increased serum concentrations with allopurinol, capecitabine, cimetidine, CYP2C9 inhibitors (e.g. fluconazole), CYP2C19 inhibitors (e.g. delavirdine), disulfiram, methylphenidate, metronidazole, omeprazole, SSRI, trazodone, trimethoprim. Increases metabolism of antiarrhythmics, anticonvulsants, antipsychotics, beta-blockers, calcium channel blockers, chloramphenicol, corticosteroids, doxycycline, oestrogens, HMG-CoA reductase inhibitors, methadone, theophylline, TCAs. Decreases levels/effects of clozapine, ciclosporin, tacrolimus, CYP2B6 substrates (e.g. bupropion, selegiline), CYP2C8 substrates (e.g. amiodarone), CYP2C9 substrates (e.g. celecoxib), CYP2C19 substrates (e.g. citalopram), CYP3A4 substrates (e.g. benzodiazepines), digoxin, itraconazole, levodopa, neuromuscular-blocking agents, thyroid hormones, topiramate. Increases levels/effect of dopamine, ticlopidine. Valproic acid may displace phenytoin from binding sites; and affect phenytoin serum concentrations. Transiently increases the hypothrombinaemia response to warfarin initially, followed by an inhibition of the response.
Potentially Fatal: Enhances the hypotensive properties of dopamine and the cardiac depressant properties of lidocaine.
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| | | Category D: There is positive evidence of
human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed
in a life-threatening situation or for a serious disease for which safer drugs
cannot be used or are ineffective).
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For details of the mechanism of action, pharmacology and pharmacokinetics and toxicology ...
click to view | | Anticonvulsants | | N03AB02 - phenytoin; Belongs to the class of hydantoin derivatives antiepileptics. Used in the management of epilepsy.
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