Dilantin Infatabs Side Effects Center

Last updated on RxList: 3/8/2022
Dilantin Infatabs Side Effects Center

What Are Dilantin Infatabs?

Dilantin Infatabs (phenytoin) is an anti-epileptic drug (anticonvulsant) used to control seizures.

What Are Side Effects of Dilantin Infatabs?

Common side effects of Dilantin Infatabs include:

  • headache,
  • nausea,
  • vomiting,
  • constipation,
  • dizziness,
  • spinning sensation,
  • drowsiness,
  • trouble sleeping (insomnia),
  • nervousness,
  • slurred speech,
  • loss of balance or coordination, or
  • swollen or tender gums

Dosage for Dilantin Infatabs?

The initial adult dose Dilantin Infatabs for patients who have received no previous treatment is two Infatabs three times daily. For most adults, the maintenance dosage is six to eight Infatabs daily. Pediatric dosing is determined by the child's weight.

What Drugs, Substances, or Supplements Interact with Dilantin Infatabs?

Dilantin Infatabs may interact with stomach acid reducers, sedatives, antidepressants, estrogen hormone replacement, phenothiazines, disulfiram, methylphenidate, sulfa drugs, carbamazepine, sucralfate, molindone, phenobarbital, valproic acid, divalproex sodium, steroids, antibiotics, digoxin, furosemide, or theophylline. Tell your doctor all medications and supplements you use.

Dilantin Infatabs During Pregnancy and Breastfeeding

During pregnancy, Dilantin Infatabs should be used only when prescribed. It may harm a fetus. Since untreated seizures are a serious condition that can harm both a pregnant woman and her fetus, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, talk to your doctor about using this medication during pregnancy. Since birth control pills, patches, implants, and injections may not work if taken with this medication, discuss birth control with your doctor. This drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Dilantin Infatabs (phenytoin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

QUESTION

If you have had a seizure, it means you have epilepsy. See Answer
Dilantin Infatabs Consumer Information

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Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include: skin rash, fever, swollen glands, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have:

  • slow or uneven heartbeats, chest pain, fluttering in your chest, and dizziness (like you might pass out);
  • any skin rash, no matter how mild;
  • fever, chills, sore throat, swollen glands;
  • red or swollen gums, mouth sores;
  • easy bruising, unusual bleeding, purple or red spots under your skin; or
  • liver problems--loss of appetite, upper stomach pain, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common side effects may include:

  • drowsiness, confusion;
  • slurred speech;
  • abnormal eye movement; or
  • problems with balance, coordination, or muscle movement.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

SLIDESHOW

What Is Epilepsy? Symptoms, Causes, and Treatments See Slideshow
Dilantin Infatabs Professional Information

SIDE EFFECTS

The following serious adverse reactions are described elsewhere in the labeling:

  • Withdrawal Precipitated Seizure, Status Epilepticus [see WARNINGS AND PRECAUTIONS]
  • Suicidal Behavior and Ideation [see WARNINGS AND PRECAUTIONS]
  • Serious Dermatologic Reactions [see WARNINGS AND PRECAUTIONS]
  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see WARNINGS AND PRECAUTIONS]
  • Hypersensitivity [see WARNINGS AND PRECAUTIONS]
  • Cardiac Effects [see WARNINGS AND PRECAUTIONS]
  • Angioedema [see WARNINGS AND PRECAUTIONS]
  • Hepatic Injury [see WARNINGS AND PRECAUTIONS]
  • Hematopoietic Complications [see WARNINGS AND PRECAUTIONS]
  • Effects on Vitamin D and Bone [see WARNINGS AND PRECAUTIONS]
  • Exacerbation of Porphyria [see WARNINGS AND PRECAUTIONS]
  • Teratogenicity and Other Harm to the Newborn [see WARNINGS AND PRECAUTIONS]
  • Hyperglycemia [see WARNINGS AND PRECAUTIONS]

The following adverse reactions associated with the use of DILANTIN were identified in clinical studies or postmarketing reports. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as a Whole: Allergic reactions in the form of rash and rarely more serious forms and DRESS have been observed, as has angioedema [see WARNINGS AND PRECAUTIONS]. Anaphylaxis has also been reported.

There have also been reports of coarsening of facial features, systemic lupus erythematosus, periarteritis nodosa, and immunoglobulin abnormalities.

Digestive System: Acute hepatic failure, toxic hepatitis, liver damage, nausea, vomiting, constipation, enlargement of the lips, and gingival hyperplasia.

Hematologic and Lymphatic System: Hematopoietic complications, some fatal, have occasionally been reported in association with administration of phenytoin. These have included thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia with or without bone marrow suppression. While macrocytosis and megaloblastic anemia have occurred, these conditions usually respond to folic acid therapy. Lymphadenopathy including benign lymph node hyperplasia, pseudolymphoma, lymphoma, and Hodgkin's disease have been reported [see WARNINGS AND PRECAUTIONS].

Laboratory Test Abnormality: Phenytoin may decrease serum concentrations of thyroid hormone (T4 and T3), sometimes with an accompanying increase in thyroid-stimulating hormone (TSH), but usually in the absence of clinical hypothyroidism. Phenytoin may also produce lower than normal values for dexamethasone or metyrapone tests. Phenytoin may cause increased serum levels of glucose [see WARNINGS AND PRECAUTIONS], alkaline phosphatase, and gamma glutamyl transpeptidase (GGT).

Nervous System: The most common adverse reactions encountered with phenytoin therapy are nervous system reactions and are usually doserelated. Reactions include nystagmus, ataxia, slurred speech, decreased coordination, somnolence, and mental confusion. Dizziness, vertigo, insomnia, transient nervousness, motor twitchings, paresthesias, and headaches have also been observed. There have also been rare reports of phenytoin-induced dyskinesias, including chorea, dystonia, tremor and asterixis, similar to those induced by phenothiazine and other neuroleptic drugs. Cerebellar atrophy has been reported, and appears more likely in settings of elevated phenytoin levels and/or long-term phenytoin use [see WARNINGS AND PRECAUTIONS].

A predominantly sensory peripheral polyneuropathy has been observed in patients receiving long-term phenytoin therapy.

Skin and Appendages: Dermatological manifestations sometimes accompanied by fever have included scarlatiniform or morbilliform rashes. A morbilliform rash (measles-like) is the most common; other types of dermatitis are seen more rarely. Other more serious forms which may be fatal have included bullous, exfoliative or purpuric dermatitis, acute generalized exanthematous pustulosis, Stevens-Johnson syndrome, and toxic epidermal necrolysis [see WARNINGS AND PRECAUTIONS]. There have also been reports of hypertrichosis and urticaria.

Special Senses: Altered taste sensation including metallic taste.

Urogenital: Peyronie's disease

DRUG INTERACTIONS

Phenytoin is extensively bound to plasma proteins and is prone to competitive displacement. Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19, and is particularly susceptible to inhibitory drug interactions because it is subject to saturable metabolism. Inhibition of metabolism may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity. Monitoring of phenytoin serum levels is recommended when a drug interaction is suspected. Phenytoin is a potent inducer of hepatic drug-metabolizing enzymes.

Drugs That Affect Phenytoin Concentrations

Table 2 includes commonly occurring drug interactions that affect phenytoin concentrations. However, this list is not intended to be inclusive or comprehensive. Individual prescribing information from relevant drugs should be consulted.

The addition or withdrawal of these agents in patients on phenytoin therapy may require an adjustment of the phenytoin dose to achieve optimal clinical outcome.

Table 2: Drugs That Affect Phenytoin Concentrations

Interacting Agent Examples
Drugs that may increase phenytoin serum levels
Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate
Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole
Antineoplastic agents Capecitabine, fluorouracil
Antidepressants Fluoxetine, fluvoxamine, sertraline
Gastric acid reducing agents H2 antagonists (cimetidine), omeprazole
Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim
Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin
Drugs that may decrease phenytoin serum levels
Antacids* Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day
Antineoplastic agents usually in combination Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate
Antiviral agents Fosamprenavir, nelfinavir, ritonavir
Antiepileptic drugs Carbamazepine, vigabatrin
Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. John's wortt, sucralfate, theophylline
Drugs that may either increase or decrease phenytoin serum levels
Antiepileptic drugs Phenobarbital, valproate sodium, valproic acid
* Antacids may affect absorption of phenytoin.
† The induction potency of St. John's wort may vary widely based on preparation.

Drugs Affected By Phenytoin

Table 3 includes commonly occurring drug interactions affected by phenytoin. However, this list is not intended to be inclusive or comprehensive. Individual drug package inserts should be consulted. The addition or withdrawal of phenytoin during concomitant therapy with these agents may require adjustment of the dose of these agents to achieve optimal clinical outcome.

Table 3: Drugs Affected by Phenytoin

Interacting Agent Examples
Drugs whose efficacy is impaired by phenytoin
Azoles Fluconazole, ketoconazole, itraconazole, posaconazole, voriconazole
Antineoplastic agents Irinotecan, paclitaxel, teniposide
Delavirdine Phenytoin can substantially reduce the concentrations of delavirdine. This can lead to loss of virologic response and possible resistance [see CONTRAINDICATIONS].
Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. Whether or not phenytoin has the same effect on other nondepolarizing agents is unknown.
Prevention or Management: Patients should be monitored closely for more rapid recovery from neuromuscular blockade than expected, and infusion rate requirements may be higher.
Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin
Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D
Drugs whose level is decreased by phenytoin
Antiepileptic drugs* Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine,
Antilipidemic agents Atorvastatin, fluvastatin, simvastatin
Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir, the active metabolite. Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir
Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil
Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine
*The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable

Drug Enteral Feeding/Nutritional Preparations Interaction

Literature reports suggest that patients who have received enteral feeding preparations and/or related nutritional supplements have lower than expected phenytoin serum levels. It is therefore suggested that phenytoin not be administered concomitantly with an enteral feeding preparation. More frequent serum phenytoin level monitoring may be necessary in these patients.

Drug/Laboratory Test Interactions

Care should be taken when using immunoanalytical methods to measure serum phenytoin concentrations.

Read the entire FDA prescribing information for Dilantin Infatabs (Phenytoin Tablets)

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© Dilantin Infatabs Patient Information is supplied by Cerner Multum, Inc. and Dilantin Infatabs Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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