Phenytoin is prescribed for the management of generalized tonic-clonic (grand mal), complex partial seizures. It is also used for the prevention of seizures following head trauma/neurosurgery.
Phenytoin is an anti-seizure medication. It is used to prevent partial seizures, tonic-clonic seizures, but not absence seizures. It may also be used to treat certain heart arrhythmias or neuropathic pain. It can be taken intravenously or by mouth.
Common side effects include nausea, increased hair growth, stomach pain, poor coordination, loss of appetite, and enlargement of the gums. Potentially serious side effects include self harm, sleepiness, liver problems, low blood pressure, bone marrow suppression and toxic epidermal necrolysis.
Phenytoin should be used with caution in patients having low blood pressure, heart failure, liver disease, suicidal tendencies, kidney disorders, vitamin D deficiency, diabetes and porphyria. It should not be used in people having allergy towards Phenytoin or other ingredients in the medicine or people suffering from certain heart conditions. There is evidence that use during pregnancy results in abnormalities in the baby. It appears to be safe to use during breastfeeding.
Take this medication orally as per your doctor’s prescription, with plenty of water. Avoid consumption of alcohol during the treatment. If for some reason you cannot take the medicine orally, it may be administered by a healthcare professional as an injection into a muscle or a vein, or by diluting it and giving it as a drip into a vein.
The intravenous form generally begins working within 30 minutes and is effective for 24 hours. Blood levels of the patient can be measured to determine the suitable dose of the medicine.
Use Phenytoin cautiously in malnutrition (more free drug circulating), significant hepatic disease (adjust dose), or with other highly protein-bound drugs. Phenytoin is used cautiously in hypotension (I.V. form contains propylene glycol). I.V. form may cause hypotension.
This medicine is primarily used to treat the following conditions:
Generalized Tonic-Clonic Seizure
Is It safe with alcohol?Phenytoin may cause excessive drowsiness and calmness with alcohol.
Are there any pregnancy warnings?Phenytoin is unsafe to use during pregnancy.
There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk, for example in life-threatening situations. Please consult your doctor.
Are there any breast-feeding warnings?Phenytoin is safe to use during lactation. \nHuman studies have shown that either the drug does not pass into the breastmilk in significant amount or is not expected to cause toxicity to the baby.
Is it safe to drive while on this medicine?Phenytoin may make you feel dizzy, sleepy, tired, or decrease alertness. If this happens, do not drive.
Does this affect kidney function?Phenytoin is probably safe to use in patients with kidney disease. Limited data available suggests that dose adjustment of Phenytoin may not be needed in these patients. Please consult your doctor.
Does this affect liver function?Phenytoin should be used with caution in patients with liver disease. Dose adjustment of Phenytoin may be needed. Please consult your doctor.
What is the onset of action?The effect of this medicine will be initiated within 30 minutes to 1 hour after its administration.
How long is the duration of effect?The effect of this medicine will last for about 8 - 10 hours.
Missed Dose instructionsTake the missed dose as soon as you remember. If itâ€™s almost time for your next dose, skip the missed dose. Do not double your dose to make up for the missed dose.
Overdose instructionsSeek emergency medical treatment or contact the doctor if any symptoms of the overdose like uncontrolled body movements, slurred speech appear.
Below is the list of medicines, which contains Phenytoin as ingredient
Phenytoin is an anticonvulsant which is known to prevent seizures by causing a voltage-dependent block of voltage gated sodium channels. It acts by increasing sodium efflux from the neurons of the motor cortex which reduces the post-tetanic potentiation at synapses. This inhibits the cortical seizure foci from spreading to adjacent areas, thus stabilizing the threshold against hyperexcitability.
Whenever you take more than one medicine, or mix it with certain foods or beverages, you"re at risk of a drug interaction.
Interaction with Alcohol
- Alcohol: Additive CNS depression has been reported with hydantoins.
- Alcohol (acute use): Inhibits metabolism of phenytoin; avoid or limit use; watch for sedation.
- Alcohol (chronic use): Stimulates metabolism of phenytoin; avoid or limit use.
Interaction with Lab Test
Interaction with Medicine
- Phenytoin may decrease the effect of oral contraceptives, itraconazole, mebendazole, methadone, oral midazolam, valproic acid, cyclosporine, theophylline, doxycycline, quinidine, mexiletine, disopyramide.
- Amiodarone or disulfiram decreases metabolism of Phenytoin.
- Isoniazid, chloramphenicol, or fluconazole may increase Phenytoin serum concentrations.
- Valproic acid may increase, decrease, or have no effect on Phenytoin serum concentrations.
- Dopamine: Phenytoin may increase the effect of dopamine (enhanced hypotension).
- Primidone: Increase the rate of conversion of to phenobarbital resulting in increased phenobarbital serum concentrations.
- Ticlopidine increases serum phenytoin concentrations to increase toxicity of Phenytoin.
- Acetaminophen: Phenytoinmay enhance the hepatotoxic potential.
- Acetazolamide: Concurrent use with Phenytoin may result in an increased risk of osteomalacia.
- Phenytoin may increase the metabolism of alprazolam, amiodarone, bromfenac, carbamazepine, clozapine, cyclosporine, diazepam, disopyramide, doxycycline, felbamate, furosemide, itraconazole, lamotrigine, mebendazole, meperidine, methadone, metyrapone, mexiletine, midazolam, oral contraceptives, quetiapine, quinidine, tacrolimus, teniposide, theophylline, thyroid hormones, triazolam, and valproic acid resulting in decreased levels/effect.
- Trimethoprim, sulfamethoxazole, valproic acid, sulfamethizole, sulfaphenazole, trimethoprim, nifedipine, omeprazole, phenylbutazone, phenobarbital, amiodarone, chloramphenicol, cimetidine, ciprofloxacin, disulfiram, enoxacin, norfloxacin, felbamate, fluconazole, fluoxetine, influenza vaccine, isoniazid, and metronidazole inhibit the metabolism of Phenytoin resulting in increased serum phenytoin concentrations/effects; monitor.
- Carbamazepine, cisplatin, diazoxide, ethanol (chronic), folic acid, phenobarbital, pyridoxine, and rifampin may enhance the metabolism of Phenytoin resulting in decreased serum concentrations.
- Concurrent use of I.V. Phenytoin with dopamine may result in an increased risk of hypotension.
- Phenytoin may inhibit the anti-Parkinson effect of levodopa.
- Concurrent use of Phenytoin and lithium has resulted in lithium intoxication.
- Phenytoin enhances the conversion of primidone to phenobarbital resulting in elevated phenobarbital serum concentrations.
- Sucralfate may reduce the GI absorption of Phenytoin.
- Valproic acid and sulfisoxazole may displace Phenytoin from binding sites.
- Vigabatrin and theophylline may reduce Phenytoin serum concentrations.
- Warfarin: Phenytoin transiently increased the hypothrombinemia response to warfarin initially; this is followed by an inhibition of the hypoprothombinemic response.
Interaction with Food
- Folic acid: Low erythrocyte and CSF folate concentrations. 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.
- Calcium: Hypocalcemia has been reported in patients taking prolonged high-dose therapy with an anticonvulsant. Phenytoin may decrease calcium absorption. Monitor calcium serum concentration and for bone disorders (eg, rickets, osteomalacia). Some clinicians have given an additional 4,000 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.
- Glucose: Hyperglycemia and glycosuria may occur in patients receiving high-dose therapy. Monitor blood glucose concentration, especially in patients with impaired renal function.
- Tube feedings: Tube feedings decrease phenytoin bioavailability; 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.
Ques: What is Phenytoin?
Ques: What are the uses of Phenytoin?
Ques: What are the Side Effects of Phenytoin?
Ques: What are the instructions for storage and disposal Phenytoin?
Ques: Should I use Phenytoin empty stomach, before food or after food?
Ques: How long do I need to use Phenytoin before I see improvement of my conditions?
Ques: Is there any food or drink I need to avoid?
Ques: Will Phenytoin be more effective if taken in more than the recommended dose?
Ques: Can I take Phenytoin with ibuprofen?
Ques: Does Phenytoin cause weight gain?
Ques: Does Phenytoin affect birth control?
Phenytoin-Drug Information Portal [Internet].druginfo.nlm.nih.gov 2022 [Cited 27 May 2022].Available from:https://druginfo.nlm.nih.gov/drugportal/name/phenytoin
Phenytoin-DrugBank Online [Internet].go.drugbank.com 2022 [Cited 27 May 2022].Available from:https://go.drugbank.com/drugs/DB00252
PHENYTOIN Tablet,solution-DailyMed [Internet].dailymed.nlm.nih.gov 2022 [Cited 27 May 2022].Available from:https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=PHENYTOIN
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