For information 410.787.4000
Diphenylhydantoin; DPH; Phenytoin Sodium; Phenytoin Sodium, Extended; Phenytoin Sodium, Prompt
Yes: Excludes chewable tablet, extended release capsule
Management of generalized tonic-clonic (grand mal), complex partial seizures; prevention of seizures following head trauma/neurosurgery
Ventricular arrhythmias, including those associated with digitalis intoxication, prolonged QT interval and surgical repair of congenital heart diseases in children; epidermolysis bullosa
Phenytoin crosses the placenta. Congenital malformations (including a pattern of malformations termed the "fetal hydantoin syndrome" or "fetal anticonvulsant syndrome") have been reported in infants. Isolated cases of malignancies (including neuroblastoma) and coagulation defects in the neonate following delivery have also been reported. Epilepsy itself, the number of medications, genetic factors, or a combination of these probably influence the teratogenicity of anticonvulsant therapy.
Total plasma concentrations of phenytoin are decreased by 56% in the mother during pregnancy; unbound plasma (free) concentrations are decreased by 31%. Because protein binding is decreased, monitoring of unbound plasma concentrations is recommended. Concentrations should be monitored through the 8th week postpartum. The use of folic acid throughout pregnancy and vitamin K during the last month of pregnancy is recommended.
A pregnancy registry is available for women exposed to antiepileptic drug (including phenytoin) at the Genetics and Teratology Unit Massachusetts General Hospital, 1-888-233-2334.
Enters breast milk/not recommended (AAP rates "compatible")
Hypersensitivity to phenytoin, other hydantoins, or any component of the formulation; pregnancy
May increase frequency of petit mal seizures; I.V. form may cause hypotension, skin necrosis at I.V. site; avoid I.V. administration in small veins; use with caution in patients with porphyria; discontinue if rash or lymphadenopathy occurs; use with caution in patients with hepatic dysfunction, sinus bradycardia, SA block, or AV block; use with caution in elderly or debilitated patients, or in any condition associated with low serum albumin levels, which will increase the free fraction of phenytoin in the serum and, therefore, the pharmacologic response. Sedation, confusional states, or cerebellar dysfunction (loss of motor coordination) may occur at higher total serum concentrations, or at lower total serum concentrations when the free fraction of phenytoin is increased. Abrupt withdrawal may precipitate status epilepticus.
I.V. effects: Hypotension, bradycardia, cardiac arrhythmia, cardiovascular collapse (especially with rapid I.V. use), venous irritation and pain, thrombophlebitis
Effects not related to plasma phenytoin concentrations: Hypertrichosis, gingival hypertrophy, thickening of facial features, carbohydrate intolerance, folic acid deficiency, peripheral neuropathy, vitamin D deficiency, osteomalacia, systemic lupus erythematosus
Concentration-related effects: Nystagmus, blurred vision, diplopia, ataxia, slurred speech, dizziness, drowsiness, lethargy, coma, rash, fever, nausea, vomiting, gum tenderness, confusion, mood changes, folic acid depletion, osteomalacia, hyperglycemia
Related to elevated concentrations:
>20 mcg/mL: Far lateral nystagmus
>30 mcg/mL: 45° lateral gaze nystagmus and ataxia
>40 mcg/mL: Decreased mentation
>100 mcg/mL: Death
Cardiovascular: Hypotension, bradycardia, cardiac arrhythmia, cardiovascular collapse
Central nervous system: Psychiatric changes, slurred speech, dizziness, drowsiness, headache, insomnia
Gastrointestinal: Constipation, nausea, vomiting, gingival hyperplasia, enlargement of lips
Hematologic: Leukopenia, thrombocytopenia, agranulocytosis
Neuromuscular & skeletal: Tremor, peripheral neuropathy, paresthesia
Ocular: Diplopia, nystagmus, blurred vision
Rarely seen effects: SLE-like syndrome, lymphadenopathy, hepatitis, Stevens-Johnson syndrome, blood dyscrasias, dyskinesias, pseudolymphoma, lymphoma, venous irritation and pain, coarsening of facial features, hypertrichosis
Symptoms of overdose include unsteady gait, slurred speech, confusion, nausea, hypothermia, fever, hypotension, respiratory depression, coma. Treatment is symptomatic.
of CYP2C8/9 (major), 2C19 (major), 3A4 (minor); CYP2B6 (strong), 2C8/9 (strong), 2C19 (strong), 3A4 (strong)SubstrateInduces
Acetaminophen: Phenytoin may enhance the hepatotoxic potential of acetaminophen overdoses
Acetazolamide: Concurrent use with phenytoin may result in an increased risk of osteomalacia
Acyclovir: May decrease phenytoin serum levels; limited documentation; monitor
Allopurinol: May increase phenytoin serum concentrations; monitor
Antacids: May decrease absorption of phenytoin; separate oral doses by several hours
Antiarrhythmics: Phenytoin may increase the metabolism of antiarrhythmics, decreasing their clinical effect; includes disopyramide, propafenone, and quinidine; amiodarone also may increase phenytoin concentrations (see CYP inhibitors)
Anticonvulsants: Phenytoin may increase the metabolism of anticonvulsants; includes barbiturates, carbamazepine, ethosuximide, felbamate, lamotrigine, tiagabine, topiramate, and zonisamide; does not appear to affect gabapentin or levetiracetam; felbamate and gabapentin may increase phenytoin levels; monitor
Antineoplastics: Several chemotherapeutic agents have been associated with a decrease in serum phenytoin levels; includes cisplatin, bleomycin, carmustine, methotrexate, and vinblastine; monitor phenytoin serum levels. Limited evidence also suggest that enzyme-inducing anticonvulsant therapy may reduce the effectiveness of some chemotherapy regimens (specifically in ALL). Teniposide and methotrexate may be cleared more rapidly in these patients.
Antipsychotics: Phenytoin may enhance the metabolism (decrease the efficacy) of antipsychotics; monitor for altered response; dose adjustment may be needed; also see note on clozapine
Benzodiazepines: Phenytoin may decrease the serum concentrations of some benzodiazepines; monitor for decreased benzodiazepine effect
Beta-blockers: Metabolism of beta-blockers may be increased and clinical effect decreased; atenolol and nadolol are unlikely to interact given their renal elimination
Calcium channel blockers: Phenytoin may enhance the metabolism of calcium channel blockers, decreasing their clinical effect; calcium channel blockers (diltiazem, nifedipine) have been reported to increase phenytoin levels (case report); monitor.
Capecitabine: May increase the serum concentrations of phenytoin; monitor
Chloramphenicol: Phenytoin may increase the metabolism of chloramphenicol and chloramphenicol may inhibit phenytoin metabolism; monitor for altered response
Cimetidine: May increase the serum concentrations of phenytoin; monitor.
Ciprofloxacin: May decrease serum phenytoin concentrations; monitor.
Clozapine: Phenytoin may decrease levels/effects of clozapine; monitor.
CNS depressants: Sedative effects may be additive with other CNS depressants; monitor for increased effect; includes ethanol, barbiturates, sedatives, antidepressants, narcotic analgesics, and benzodiazepines
Corticosteroids: Phenytoin may increase the metabolism of corticosteroids, decreasing their clinical effect; also see dexamethasone
Cyclosporine and tacrolimus: Levels may be decreased by phenytoin; monitor
CYP2B6 substrates: Phenytoin may decrease the levels/effects of CYP2B6 substrates. Example substrates include bupropion, efavirenz, promethazine, selegiline, and sertraline.
CYP2C8/9 inducers: May decrease the levels/effects of phenytoin. Example inducers include carbamazepine, phenobarbital, rifampin, rifapentine, and secobarbital.
CYP2C8/9 inhibitors: May increase the levels/effects of phenytoin. Example inhibitors include delavirdine, fluconazole, gemfibrozil, ketoconazole, nicardipine, NSAIDs, pioglitazone, and sulfonamides.
CYP2C8/9 substrates: Phenytoin may decrease the levels/effects of CYP2C8/9 substrates. Example substrates include amiodarone, fluoxetine, glimepiride, glipizide, losartan, nateglinide, pioglitazone, rosiglitazone, sertraline, sulfonamides, warfarin, and zafirlukast.
CYP2C19 inducers: May decrease the levels/effects of phenytoin. Example inducers include aminoglutethimide, carbamazepine, phenytoin, and rifampin.
CYP2C19 inhibitors: May increase the levels/effects of phenytoin. Example inhibitors include delavirdine, fluconazole, fluvoxamine, gemfibrozil, isoniazid, omeprazole, and ticlopidine.
CYP2C19 substrates: Phenytoin may decrease the levels/effects of CYP2C19 substrates. Example substrates include citalopram, diazepam, methsuximide, propranolol, proton pump inhibitors, sertraline, and voriconazole.
CYP3A4 substrates: Phenytoin may decrease the levels/effects of CYP3A4 substrates. Example substrates include benzodiazepines, calcium channel blockers, clarithromycin, cyclosporine, erythromycin, estrogens, mirtazapine, nateglinide, nefazodone, nevirapine, protease inhibitors, tacrolimus, and venlafaxine.
Digoxin: Effects and/or levels of digitalis glycosides may be decreased by phenytoin
Disulfiram: May increase serum phenytoin concentrations; monitor
Dopamine: Phenytoin (I.V.) may increase the effect of dopamine (enhanced hypotension)
Doxycycline: Phenytoin may enhance the metabolism of doxycycline, decreasing its clinical effect; higher dosages may be required
Estrogens: Phenytoin may increase the metabolism of estrogens, decreasing their clinical effect; monitor
Folic acid: Replacement of folic acid has been reported to increase the metabolism of phenytoin, decreasing its serum concentrations and/or increasing seizures
HMG-CoA reductase inhibitors: Phenytoin may increase the metabolism of these agents, reducing their clinical effect; monitor
Itraconazole: Phenytoin may decrease the effect of itraconazole
Levodopa: Phenytoin may inhibit the anti-Parkinson effect of levodopa
Lithium: Concurrent use of phenytoin and lithium has resulted in lithium intoxication
Methadone: Phenytoin may enhance the metabolism of methadone resulting in methadone withdrawal
Methylphenidate: May increase serum phenytoin concentrations; monitor
Metronidazole: May increase the serum concentrations of phenytoin; monitor.
Neuromuscular-blocking agents: Duration of effect may be decreased by phenytoin
Omeprazole: May increase serum phenytoin concentrations; monitor
Oral contraceptives: Phenytoin may enhance the metabolism of oral contraceptives, decreasing their clinical effect; an alternative method of contraception should be considered
Primidone: Phenytoin enhances the conversion of primidone to phenobarbital resulting in elevated phenobarbital serum concentrations
Quetiapine: Serum concentrations may be substantially reduced by phenytoin, potentially resulting in a loss of efficacy; limited documentation; monitor
SSRIs: May increase phenytoin serum concentrations; fluoxetine and fluvoxamine are known to inhibit metabolism via CYP enzymes; sertraline and paroxetine have also been shown to increase concentrations in some patients; monitor
Sucralfate: May reduce the GI absorption of phenytoin; monitor
Theophylline: Phenytoin may increase metabolism of theophylline derivatives and decrease their clinical effect; theophylline may also increase phenytoin concentrations
Thyroid hormones (including levothyroxine): Phenytoin may alter the metabolism of thyroid hormones, reducing its effect; there is limited documentation of this interaction, but monitoring should be considered
Ticlopidine: May increase serum phenytoin concentrations and/or toxicity; monitor
Tricyclic antidepressants: Phenytoin may increase metabolism of tricyclic antidepressants and decrease their clinical effect; sedative effects may be additive; tricyclics may also increase phenytoin concentrations
Topiramate: Phenytoin may decrease serum levels of topiramate; topiramate may increase the effect of phenytoin
Trazodone: Serum levels of phenytoin may be increased; limited documentation; monitor
Trimethoprim: May increase serum phenytoin concentrations; monitor
Valproic acid (and sulfisoxazole): May displace phenytoin from binding sites; valproic acid may increase, decrease, or have no effect on phenytoin serum concentrations
Vigabatrin: May reduce phenytoin serum concentrations; monitor
Warfarin: Phenytoin transiently increased the hypothrombinemia response to warfarin initially; this is followed by an inhibition of the hypoprothrombinemic response
Acute use: Avoid or limit ethanol (inhibits metabolism of phenytoin). Watch for sedation.
Chronic use: Avoid or limit ethanol (stimulates metabolism of phenytoin).
Food: Phenytoin serum concentrations may be altered if taken with food. If taken with enteral nutrition, phenytoin serum concentrations may be decreased. Tube feedings decrease bioavailability; hold tube feedings 2 hours before and 2 hours after phenytoin administration. May decrease calcium, folic acid, and vitamin D levels.
Herb/Nutraceutical: Avoid evening primrose (seizure threshold decreased). Avoid valerian, St John's wort, kava kava, gotu kola (may increase CNS depression).
Capsule, tablet: Store below 30°C (86°F); protect from light and moisture
Oral suspension: Store at room temperature of 20°C to 25°C (68°F to 77°F); protect from freezing and light.
Solution for injection: Store at room temperature of 15°C to 30°C (59°F to 86°F); use only clear solutions free of precipitate and haziness, slightly yellow solutions may be used. Precipitation may occur if solution is refrigerated and may dissolve at room temperature.
Further dilution of the solution for I.V. infusion is controversial and no consensus exists as to the optimal concentration and length of stability. Stability is concentration and pH dependent. Based on limited clinical consensus, NS or LR are recommended diluents; dilutions of 1-10 mg/mL have been used and should be administered as soon as possible after preparation (some recommend to discard if not used within 4 hours). Do not refrigerate.
I.V. form is highly incompatible with many drugs and solutions. Mixing with other medications is not recommended.
in D5NS, D5W, fat emulsion 10%, /2NS; in NSIncompatible1variable stability (consult detailed reference)
Y-site administration: Compatible: Esmolol, famotidine, fluconazole, foscarnet, tacrolimus. Incompatible: Amphotericin B cholesteryl sulfate complex, ciprofloxacin, clarithromycin, diltiazem, enalaprilat, gatifloxacin, heparin, heparin with hydrocortisone sodium succinate, hydromorphone, linezolid, potassium chloride, propofol, sufentanil, theophylline, vitamin B complex with C. Variable (consult detailed reference): TPN
Compatibility in syringe: Incompatible: Hydromorphone, sufentanil
Compatibility when admixed: Compatible: Bleomycin, sodium bicarbonate, verapamil. Incompatible: Amikacin, aminophylline, bretylium, chloramphenicol, dimenhydrinate, diphenhydramine, dobutamine, hydroxyzine, insulin (regular), kanamycin, levorphanol, lidocaine, lincomycin, meperidine, metaraminol, morphine, nitroglycerin, norepinephrine, penicillin G potassium, pentobarbital, phenobarbital, phenylephrine, phytonadione, procainamide, procaine, prochlorperazine edisylate, promazine, promethazine, streptomycin, vancomycin, vitamin B complex with C
Stabilizes neuronal membranes and decreases seizure activity by increasing efflux or decreasing influx of sodium ions across cell membranes in the motor cortex during generation of nerve impulses; prolongs effective refractory period and suppresses ventricular pacemaker automaticity, shortens action potential in the heart
Onset of action: I.V.: ~0.5-1 hour
Absorption: Oral: Slow
Neonates: Premature: 1-1.2 L/kg; Full-term: 0.8-0.9 L/kg
Infants: 0.7-0.8 L/kg
Children: 0.7 L/kg
Adults: 0.6-0.7 L/kg
Adults: 90% to 95%
Others: Decreased protein binding
Disease states resulting in a decrease in serum albumin concentration: Burns, hepatic cirrhosis, nephrotic syndrome, pregnancy, cystic fibrosis
Disease states resulting in an apparent decrease in affinity of phenytoin for serum albumin: Renal failure, jaundice (severe), other drugs (displacers), hyperbilirubinemia (total bilirubin >15 mg/dL), Clcr<25 mL/minute (unbound fraction is increased two- to threefold in uremia)
Metabolism: Follows dose-dependent capacity-limited (Michaelis-Menten) pharmacokinetics with increased Vmax in infants >6 months of age and children versus adults; major metabolite (via oxidation), HPPA, undergoes enterohepatic recirculation
Bioavailability: Form dependent
Half-life elimination: Oral: 22 hours (range: 7-42 hours)
Time to peak, serum (form dependent): Oral: Extended-release capsule: 4-12 hours; Immediate release preparation: 2-3 hours
Excretion: Urine (<5% as unchanged drug); as glucuronides
Clearance: Highly variable, dependent upon intrinsic hepatic function and dose administered; increased clearance and decreased serum concentrations with febrile illness
Status epilepticus: I.V.:
Infants and Children: Loading dose: 15-20 mg/kg in a single or divided dose; maintenance dose: Initial: 5 mg/kg/day in 2 divided doses; usual doses:
6 months to 3 years: 8-10 mg/kg/day
4-6 years: 7.5-9 mg/kg/day
7-9 years: 7-8 mg/kg/day
10-16 years: 6-7 mg/kg/day, some patients may require every 8 hours dosing
Adults: Loading dose: Manufacturer recommends 10-15 mg/kg, however, 15-25 mg/kg has been used clinically; maintenance dose: 300 mg/day or 5-6 mg/kg/day in 3 divided doses or 1-2 divided doses using extended release
Anticonvulsant: Children and Adults: Oral:
Loading dose: 15-20 mg/kg; based on phenytoin serum concentrations and recent dosing history; administer oral loading dose in 3 divided doses given every 2-4 hours to decrease GI adverse effects and to ensure complete oral absorption; maintenance dose: same as I.V.
Neurosurgery (prophylactic): 100-200 mg at approximately 4-hour intervals during surgery and during the immediate postoperative period
Dosing adjustment/comments in renal impairment or hepatic disease: Safe in usual doses in mild liver disease; clearance may be substantially reduced in cirrhosis and plasma level monitoring with dose adjustment advisable. Free phenytoin levels should be monitored closely.
Oral: Suspension: Shake well prior to use. Absorption is impaired when phenytoin suspension is given concurrently to patients who are receiving continuous nasogastric feedings. A method to resolve this interaction is to divide the daily dose of phenytoin and withhold the administration of nutritional supplements for 1-2 hours before and after each phenytoin dose.
I.M.: Although approved for I.M. use, I.M. administration is not recommended due to erratic absorption and pain on injection. Fosphenytoin may be considered.
I.V.: Vesicant. Fosphenytoin may be considered for loading in patients who are in status epilepticus, hemodynamically unstable, or develop hypotension/bradycardia with I.V. administration of phenytoin. Phenytoin may be administered by IVP or IVPB administration. The maximum rate of I.V. administration is 50 mg/minute. Highly sensitive patients (eg, elderly, patients with pre-existing cardiovascular conditions) should receive phenytoin more slowly (eg, 20 mg/minute). An in-line 0.22-5 micron filter is recommended for IVPB solutions due to the high potential for precipitation of the solution. Avoid extravasation. Following I.V. administration, NS should be injected through the same needle or I.V. catheter to prevent irritation.
SubQ: SubQ administration is not recommended because of the possibility of local tissue damage.
Blood pressure, vital signs (with I.V. use), plasma phenytoin level, CBC, liver function tests
Timing of serum samples: Because it is slowly absorbed, peak blood levels may occur 4-8 hours after ingestion of an oral dose. The serum half-life varies with the dosage and the drug follows Michaelis-Menten kinetics. The average adult half-life is about 24 hours. Steady-state concentrations are reached in 5-10 days.
Children and Adults: Toxicity is measured clinically, and some patients require levels outside the suggested therapeutic range
Total phenytoin: 10-20 mcg/mL (children and adults), 8-15 mcg/mL (neonates)
Concentrations of 5-10 mcg/mL may be therapeutic for some patients but concentrations <5 mcg/mL are not likely to be effective
50% of patients show decreased frequency of seizures at concentrations >10 mcg/mL
86% of patients show decreased frequency of seizures at concentrations >15 mcg/mL
Add another anticonvulsant if satisfactory therapeutic response is not achieved with a phenytoin concentration of 20 mcg/mL
Free phenytoin: 1-2.5 mcg/mL
Toxic: >30 mcg/mL (SI: <120-200
Lethal: >100 mcg/mL (SI: >400
When to draw levels: This is dependent on the disease state being treated and the clinical condition of the patient
Slow absorption of extended capsules and prolonged half-life minimize fluctuations between peak and trough concentrations, timing of sampling not crucial
Trough concentrations are generally recommended for routine monitoring. Daily levels are not necessary and may result in incorrect dosage adjustments. If it is determined essential to monitor free phenytoin concentrations, concomitant monitoring of total phenytoin concentrations is not necessary and expensive.
After a loading dose: Draw level within 48-96 hours
Rapid achievement: Draw within 2-3 days of therapy initiation to ensure that the patient's metabolism is not remarkably different from that which would be predicted by average literature-derived pharmacokinetic parameters; early levels should be used cautiously in design of new dosing regimens
Second concentration: Draw within 6-7 days with subsequent doses of phenytoin adjusted accordingly
If plasma concentrations have not changed over a 3- to 5-day period, monitoring interval may be increased to once weekly in the acute clinical setting
In stable patients requiring long-term therapy, generally monitor levels at 3- to 12-month intervals
Adjustment of serum concentration: See tables.
|Measured Total Phenytoin Concentration
|Patient's Serum Albumin
|Adjusted Total Phenytoin Concentration
|1Adjusted concentration = measured total concentration divided by [(0.2 x albumin) + 0.1].|
|Measured Total Phenytoin Concentration
|Patient's Serum Albumin
|Adjusted Total Phenytoin Concentration
|1Adjusted concentration = measured total concentration divided by [(0.1 x albumin) + 0.1].|
Folic acid: Phenytoin may decrease mucosal uptake of folic acid; to avoid folic acid deficiency and megaloblastic anemia, some clinicians recommend giving patients on anticonvulsants prophylactic doses of folic acid and cyanocobalamin. However, folate supplementation may increase seizures in some patients (dose dependent). Discuss with healthcare provider prior to using any supplements.
Calcium: Hypocalcemia has been reported in patients taking prolonged high-dose therapy with an anticonvulsant. Some clinicians have given an additional 4000 units/week of vitamin D (especially in those receiving poor nutrition and getting no sun exposure) to prevent hypocalcemia.
Vitamin D: Phenytoin interferes with vitamin D metabolism and osteomalacia may result; may need to supplement with vitamin D
Tube feedings: Tube feedings decrease phenytoin absorption. To avoid decreased serum levels with continuous NG feeds, hold feedings for 2 hours prior to and 2 hours after phenytoin administration, if possible. There is a variety of opinions on how to administer phenytoin with enteral feedings. Be consistent throughout therapy.
Sodium content of 1 g injection: 88 mg (3.8 mEq)
Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy without consulting prescriber. Take exactly as directed, preferably on an empty stomach. Do not alter dose or discontinue without consulting prescriber. Do not crush, break, or chew extended release capsules. Shake liquid suspension well before using. Follow recommended diet, avoid alcohol, and maintain adequate hydration (2-3 L/day of fluids) unless instructed to restrict fluid intake, May cause gum or mouth soreness (use good oral hygiene and have frequent dental exams); drowsiness, dizziness, nervousness, or headache (use caution when driving or engaging in tasks that require alertness until response to drug is known); or nausea or vomiting (small, frequent meals, frequent mouth care, chewing gum, or sucking lozenges may help). Report chest pain, irregular heartbeat, or palpitations; slurred speech, unsteady gait, coordination difficulties, or change in mentation; skin rash; unresolved nausea, vomiting, or constipation; swollen glands; swollen, sore, or bleeding gums; unusual bruising or bleeding; acute persistent fatigue; vision changes; or other persistent adverse effects. Do not get pregnant; use contraceptive measures to prevent possible harm to the fetus (effectiveness of oral contraceptives may be affected by phenytoin). Consult prescriber if breast-feeding.Pregnancy/breast-feeding precautions:
Because phenytoin induces the metabolism of many drugs, it may alter their effective blood concentration.
The vehicle which contains propylene glycol, ethanol, and sodium hydroxide, may cause hypotension, bradycardia, arrhythmias, or asystole refractory to defibrillation. Phenytoin 50 mg/mL contains propylene glycol 414.4 mg/mL (40% v/v).
Patients on chronic phenytoin therapy require larger and more frequent doses of nondepolarizing muscle relaxants to attain the same degree of muscle relaxation. This is probably due to increased levels of alpha1-acid glycoprotein released by the liver (which bind free phenytoin) during hepatic enzyme induction.
Rapid intravenous administration may cause hypotension. Infuse at a rate no greater than 50 mg/minute in adults and 25 mg/minute in the elderly.
Status Epilepticus: A randomized, double-blind trial (Treiman D, 1998) evaluated the efficacy of four treatments in overt status epilepticus. Treatment arms were designed based upon accepted practices of North American neurologists. The treatments were: 1) lorazepam 0.1 mg/kg, 2) diazepam 0.15 mg/kg followed by phenytoin 18 mg/kg, 3) phenytoin 18 mg/kg alone, and 4) phenobarbital 15 mg/kg. Treatment was considered successful if the seizures were terminated (clinically and by EEG) within 20 minutes of start of therapy without seizure recurrence within 60 minutes from the start of therapy. Patients who failed the first treatment received a second and a third, if necessary. Patients did not receive randomized treatments after the first one but the treating physician remained blinded. Treatment success: Lorazepam 64.9%, phenobarbital 58.2%, diazepam/phenytoin 55.8%, and phenytoin alone 43.6%. Using an intention to treat analysis, there was no statistical difference between the groups. Results of subsequent treatments in patients who failed the first therapy indicated that response rate significantly dropped regardless of treatment. Aggregate response rate to the second treatment was 7.0% and third treatment 2.3%.
Rapid intravenous administration may cause hypotension. Infuse at a rate no greater than 50 mg/minute in adults and 25 mg/minute in the elderly. Phenytoin has antiarrhythmic properties (Class Ib) which are not often clinically relevant at standard doses.
Gingival hyperplasia is a common problem observed during the first 6 months of phenytoin therapy appearing as gingivitis or gum inflammation. To minimize severity and growth rate of gingival tissue begin a program of professional cleaning and patient plaque control within 10 days of starting anticonvulsant therapy.
No information available to require special precautions
Capsule, extended release, as sodium:
Dilantin®: 30 mg [contains sodium benzoate], 100 mg
Phenytek™: 200 mg, 300 mg
Capsule, prompt release, as sodium: 100 mg
Injection, solution, as sodium: 50 mg/mL (2 mL, 5 mL) [contains alcohol]
Suspension, oral (Dilantin®): 125 mg/5 mL (240 mL) [contains alcohol <0.6%, sodium benzoate; orange-vanilla flavor]
Tablet, chewable (Dilantin®): 50 mg
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Aleviatin® (JP); Aurantin® (IT); Dantoin® (IL); Difetoin® (HR, SI); Di-Hydan® (FR, LU); Dilantin® (AU, CA, FR, HK, ID, IL, IN, NZ, SG, TH); Dintoina® (IT); Diphantoine® (BE, NL); Diphantoine Z® (NL); Diphedan® (BD, HU); Ditomed® (TH); Epamin® (AR, CL, CO, MX); Epanutin® (AT, BE, CH, CY, CZ, DE, EG, ES, GB, HU, IE, IL, JO, KW, LB, LU, NL, PL, SE, TR, ZA); Epdantoin® (TR); Epelin® (BR); Epilan-D-Gerot® (AT, CZ); Epinat® (NO); Etoina® (AR); Fenantoin Recip® (SE); Fenidantoin® [tabs] (MX); Fenigramon® (AR); Fenital® (BR); Fenitenk® (AR); Fenitoina Biocrom® (AR); Fenitoina® (BR); Fenitoina Denver Farma® (AR); Fenitoina Richmond® (AR); Fenitoina Rubio® (CR, DO, ES, GT, PA, SV, TH); Fenitoina Sodica® (CL); Fenitoina Sodica Prompt L.CH.® (CL); Fenitoin® (RO); Fenitron® [tabs] (MX); Fenytoin Dak® (DK); Fenytoin® (NO); Garoin® (IN); Hidantal® (BR); Hidantina® (PT); Hidantin® (TR); Hidantoina® (MX); Hydantin® (FI); Hydantol® (JP); Idantoin® (IL); Lehydan® (SE); Lotoquis simple® (AR); Neosidantoina® (ES); Norstan-Phenytoin Sodium® (ZA); Opliphon® (AR); Pepsytoin-100® (TH); Phenhydan® (CH, DE, LU); Phenhydan® [inj.] (AT, CH, DE, HU, TR); Phenhydantin® (PL); Phenilep® (ID); Phenydan® (RO); Phenytoin Antigen® (TR); Phenytoin AWD® (DE); Phenytoin® (GB); Phenytoin-Gerot® (CH); Phenytoin Ikapharmindo® (ID); Phenytoin Injection BP® (AU, GB); Phenytoin Injection DBL® (SG); Phenytoin Sodium® (IL, ZA); Phenytoinum® (PL); Pyoredol® (AR); Sinergina® (ES); Sodanton® (CZ, SK); Zentropil® (DE)