Phenytek Side Effects

Generic name: phenytoin

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

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

Applies to phenytoin: injection solution.

Other dosage forms:

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

Serious side effects of Phenytek

Along with its needed effects, phenytoin (the active ingredient contained in Phenytek) 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:

More common side effects

• chest pain or discomfort
• cold, clammy, or pale skin
• decreased coordination
• difficulty with sleeping
• disorientation
• dizziness
• drowsiness to profound coma
• fainting
• fast, slow, or irregular heartbeat
• hallucination
• headache
• lightheadedness
• measles-like skin rash
• mood or other mental changes
• nausea
• nervousness
• pain in the shoulders, back, neck, or jaw
• shakiness and unsteady walk
• slow heart rate
• slurred speech
• sweating
• swelling of the feet and lower legs
• troubled breathing
• uncontrolled eye movements
• unsteadiness, trembling, or other problems with muscle control or coordination
• unusual tiredness or weakness

Rare side effects

• bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
• blistering, crusting, irritation, itching, peeling, or reddening of the skin
• cracked, dry, or scaly skin
• inability to move the eyes
• increased blinking or spasms of the eyelid
• shakiness in the legs, arms, hands, or feet
• sticking out of the tongue
• trouble with breathing, speaking, or swallowing
• twitching, uncontrolled movements of the tongue, lips, face, neck, trunk, arms, or legs
• unusual facial expressions

Incidence not known

• abdominal or stomach pain
• bleeding gums
• blisters, hives, or itching
• bloating of the abdomen or stomach
• blood in the urine or stools
• bloody, black, or tarry stools
• blurred vision
• break in the skin, especially associated with blue-black discoloration, swelling, or drainage of fluid
• burning, numbness, tingling, or painful sensations
• chills
• cough or hoarseness
• dark urine
• diarrhea
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• fainting spells
• fever with or without chills
• general feeling of discomfort or illness
• general feeling of tiredness or weakness
• hair loss
• high fever
• irritation in the mouth
• joint or muscle pain
• light-colored stools
• loss of appetite
• loss of heat from the body
• lower back or side pain
• muscle or joint pain
• painful or difficult urination
• pale skin
• pinpoint red spots on the skin
• red skin lesions, often with a purple center
• red, irritated eyes
• red, swollen skin
• redness and swelling of the gums
• skin rash
• sore throat
• soreness of the muscles
• sores, ulcers, or white spots on the lips or in the mouth
• stomach pain, continuing
• sweating
• swollen glands
• swollen, painful, or tender lymph glands in the neck, armpit, or groin
• unexplained bleeding or bruising
• unsteadiness or awkwardness
• unusual bleeding or bruising
• vomiting
• weakness in the arms, hands, legs, or feet
• weight loss
• yellow eyes or skin

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 of Phenytek

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:

Incidence not known

• difficulty having a bowel movement (stool)
• enlarged lips
• feeling of constant movement of self or surroundings
• increased hair growth on the forehead, back, arms, and legs
• pain of the penis on erection
• sensation of spinning

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

Phenytek 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.

Medical Disclaimer