Phenytoin Sodium, Extended Release Side Effects

Generic name: phenytoin

Medically reviewed by Drugs.com. Last updated on Jun 30, 2024.

Note: This document provides detailed information about Phenytoin Sodium, Extended Release Side Effects associated with phenytoin. Some dosage forms listed on this page may not apply specifically to the brand name Phenytoin Sodium, Extended Release.

Applies to phenytoin: injection solution.

Other dosage forms:

• oral capsule extended release, oral suspension, oral tablet chewable

Precautions

It is very important that your doctor check your progress closely while you or your child are receiving this medicine. This is to see if it is working properly and to allow for a change in the dose. Blood tests may be needed to check for any unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.

Do not receive this medicine while you or your child are also taking delavirdine (Rescriptor®). Using these medicines together may cause unwanted effects.

This medicine may cause some people to become dizzy, lightheaded, faint, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert and able to see well.

Do not stop using this medicine without first checking with your doctor. Stopping the medicine suddenly may cause your seizures to return or to occur more often.

If you or your child develop a skin rash, hives, or any allergic reaction to this medicine, tell your doctor or nurse as soon as possible.

Tell your doctor right away if you or your child develop a fever, rash, swollen, painful, or tender lymph glands in the neck, armpit, or groin, unusual bleeding or bruising, or yellow eyes or skin after receiving this medicine. These may be symptoms of a serious and life-threatening condition called Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).

This medicine may cause liver damage. Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin.

This medicine may cause purple glove syndrome. Tell your doctor right away if you or your child have skin discoloration, pain, or swelling at the injection site after receiving this medicine.

This medicine may affect blood sugar levels. If you or your child notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor.

If you or your child develop any unusual or strange thoughts and behavior while receiving phenytoin (the active ingredient contained in Phenytoin Sodium, Extended Release) injection, be sure to discuss it with your doctor. Some changes that have occurred in people receiving this medicine are like those seen in people who drink too much alcohol. Other changes might be confusion, worsening of depression, hallucinations (seeing, hearing, or feeling things that are not there), suicidal thoughts, and unusual excitement, nervousness, or irritability.

Birth control pills may not work while you are using this medicine. To keep from getting pregnant, use another form of birth control along with your birth control pills. Other forms include a condom, a diaphragm, or a contraceptive foam or jelly.

Avoid drinking alcohol while you are receiving this medicine.

Before you have any medical tests, tell the medical doctor in charge that you or your child are taking this medicine. The results of some tests may be affected by this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects

Along with its needed effects, phenytoin may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking phenytoin:

Get emergency help immediately if any of the following symptoms of overdose occur while taking phenytoin:

Symptoms of overdose

• change in consciousness
• changes in patterns and rhythms of speech
• loss of consciousness
• pounding in the ears
• unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness

Other side effects

Some side effects of phenytoin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

See also:

For healthcare professionals

Applies to phenytoin: compounding powder, injectable solution, oral capsule, oral capsule extended release, oral suspension, oral tablet chewable.

Cardiovascular adverse events

• Common (1% to 10%): Hypotension, vasodilation, tachycardia
• Uncommon (0.1% to 1%): Shock, cardiac arrest, syncope, cerebral hemorrhage, palpitation, sinus bradycardia, atrial flutter, bundle branch block, cardiomegaly, cerebral infarct, postural hypotension, pulmonary embolus, QT interval prolongation, thrombophlebitis, ventricular extrasystoles, congestive heart failure
• Frequency not reported: Cardiovascular collapse, severe cardiotoxic reactions with atrial and ventricular conduction depression (including bradycardia and all degrees of heart block), asystole ventricular fibrillation, periarteritis nodosa^[Ref]

Dermatologic

• Very common (10% or more): Rash (more serious and rare forms have included bullous, exfoliative or purpuric dermatitis, lupus erythematosus, Stevens-Johnson syndrome and toxic epidermal necrolysis), pruritus
• Common (1% to 10%): Maculopapular rash, urticaria, sweating, skin discoloration, contact dermatitis, pustular rash, skin nodule, ecchymosis
• Frequency not reported: Hirsutism, hypertrichosis, coarsening of the facial features, enlargement of the lips, Peyronie's disease. Dupuytren's contracture and drug rash with eosinophilia and systemic symptoms (DRESS), erythema multiforme, SJS/TEN risk in patients of Asian ancestry who have HLA-B 1502^[Ref]

Endocrine

• Frequency not reported: Decreased serum T4 and FT4, increased serum estradiol levels, gynecomastia, alterations in vitamin D metabolism^[Ref]

Gastrointestinal

• Very common (10% or more): Nausea (13%)
• Common (1% to 10%): Tongue disorder, dry mouth, vomiting, constipation
• Uncommon (0.1% to 1%): Dyspepsia, diarrhea, anorexia, GI hemorrhage, increased salivation, tenesmus, tongue edema, dysphagia, flatulence, gastritis, ileus
• Frequency not reported: Hypoesthesia of the tongue, gingival hyperplasia^[Ref]

Genitourinary

• Uncommon (0.1% to 1%): Urinary retention, oliguria, dysuria, vaginitis, albuminuria, genital edema, polyuria, urethral pain, urinary incontinence, vaginal moniliasis
• Frequency not reported: Feeling of warmth or tingling in the groin, Peyronie's disease^[Ref]

Hematologic

• Common (1% to 10%): Ecchymosis
• Uncommon (0.1% to 1%): Thrombocytopenia, anemia, leukocytosis, cyanosis, hypochromic anemia, leukopenia, lymphadenopathy, petechia
• Frequency not reported: Granulocytopenia, agranulocytosis, pancytopenia (with or without bone marrow suppression), aplastic anemia^[Ref]

Hepatic

• Uncommon (0.1% to 1%): Liver function tests abnormal, kidney failure
• Frequency not reported: Toxic hepatitis, hepatocellular damage^[Ref]

Hypersensitivity

• Frequency not reported: Hypersensitivity syndrome, periarteritis nodosa
• Postmarketing reports: Anaphylactoid reaction, anaphylaxis^[Ref]

Immunologic

• Uncommon (0.1% to 1%): Sepsis, flu syndrome, cryptococcosis
• Frequency not reported: Immunoglobulin abnormalities^[Ref]

Local

• Common (1% to 10%): Injection site reaction, injection site pain
• Uncommon (0.1% to 1%): Injection site inflammation, injection site edema, injection site hemorrhage^[Ref]

Metabolic

• Uncommon (0.1% to 1%): Generalized edema, cachexia, diabetes insipidus
• Frequency not reported: Hyperglycemia, appetite disorder, hypokalemia^[Ref]

Musculoskeletal

• Common (1% to 10%): Back pain, chills, myasthenia
• Uncommon (0.1% to 1%): Myopathy, leg cramps, arthralgia, myalgia, muscular weakness, muscle twitching, muscle spasms
• Frequency not reported: Systemic lupus erythematosus, polyarthritis, Purple Glove Syndrome^[Ref]

Nervous system

• Very common (10% or more): Nystagmus (59%), dizziness (31%), somnolence (27%), ataxia (18%)
• Common (1% to 10%): Headache, stupor, incoordination, paresthesia, extrapyramidal syndrome, tremor, vertigo, brain edema, tinnitus, taste perversion (including metallic taste), taste loss, reflexes decreased, reflexes increased, migraine, slurred speech, dysarthria, intracranial hypertension, hyperesthesia, hyporeflexia
• Uncommon (0.1% to 1%): Twitching, Babinski sign positive, circumoral paresthesia, hemiplegia, hypotonia, convulsion, meningitis, CNS depression, hypokinesia, hyperkinesia, brain edema, paralysis, aphasia, coma, myoclonus, acute brain syndrome, encephalitis, subdural hematoma, encephalopathy, akathisia
• Frequency not reported: CNS depression, dyskinesia (including chorea), dystonia and asterixis similar to those induced by phenothiazines or other neuroleptic drugs, drowsiness, motor twitching, tonic seizures, sensory peripheral polyneuropathy (in patients receiving long-term therapy)^[Ref]

Ocular

• Common (1% to 10%): Diplopia, amblyopia, blurred vision, visual impairment
• Uncommon (0.1% to 1%): Photosensitivity reaction, photophobia, eye pain, mydriasis, visual field defect^[Ref]

Other

• Common (1% to 10%): Asthenia, deafness, accidental injury, fever, face edema, hyperacusis, parosmia, ear pain
• Uncommon (0.1% to 1%): Malaise^[Ref]

Renal

• Common (1% to 10%): Pelvic pain
• Uncommon (0.1% to 1%): Kidney failure^[Ref]

Respiratory

• Common (1% to 10%): Pneumonia
• Uncommon (0.1% to 1%): Pharyngitis, sinusitis, hyperventilation, rhinitis, apnea, aspiration pneumonia, asthma, dyspnea, atelectasis, cough increased, sputum increased, epistaxis, hypoxia, pneumothorax, hemoptysis, bronchitis
• Postmarketing reports: Respiratory arrest (sometimes fatal)^[Ref]

Psychiatric

• Common (1% to 10%): Agitation, thinking abnormal, nervousness, depression
• Uncommon (0.1% to 1%): Confusion, insomnia, depersonalization, psychosis, emotional lability, personality disorder, hostility, amnesia, neurosis, euphoric mood^[Ref]

Further information

Phenytoin Sodium, Extended Release side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

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