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: oral capsule extended release, oral suspension, oral tablet chewable.

Other dosage forms:

• injection solution

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 immediately if any of the following side effects occur while taking phenytoin:

More common side effects

• decreased coordination
• mental confusion
• nervousness
• slurred speech
• trouble with breathing, speaking, or swallowing
• unsteadiness, trembling, or other problems with muscle control or coordination

Rare side effects

• inability to move the eyes
• increased blinking or spasms of the eyelid
• shakiness and unsteady walk
• shakiness in the legs, arms, hands, or feet
• sticking out of the tongue
• trembling or shaking of the hands or feet
• twitching, twisting, or uncontrolled repetitive movements of the tongue, lips, face, arms, or legs
• uncontrolled twisting movements of the neck, trunk, arms, or legs
• unusual facial expressions

Incidence not known

• bleeding gums
• blistering, peeling, or loosening of the skin
• blisters, hives, itching, skin rash
• bloating of the abdomen or stomach
• blood in the urine or stools
• bloody, black, or tarry stools
• chest pain or discomfort
• chills
• cough
• dark urine
• diarrhea
• difficulty with moving
• fainting spells
• fever with or without chills
• general feeling of discomfort or illness
• hair loss
• headache
• high fever
• hoarseness
• irritation in the mouth
• joint or muscle pain
• light-colored stools
• lightheadedness or dizziness
• lower back or side pain
• muscle stiffness
• nausea
• numbness, tingling, or pain in the hands or feet
• painful or difficult urination
• pale skin
• pinpoint red spots on the skin
• red skin lesions, often with a purple center
• red, irritated eyes
• redness and swelling of the gums
• slow or irregular heartbeat
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• stomach pain
• swollen, painful, or tender lymph glands in the neck, armpit, or groin
• unusual bleeding or bruising
• unusual tiredness or weakness
• upper right abdominal or stomach pain
• vomiting
• weight loss
• yellow eyes or skin

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:

More common side effects

• trouble sleeping
• uncontrolled eye movements

Incidence not known

• difficulty having a bowel movement
• enlarged lips
• feeling of constant movement of self or surroundings
• increased hair growth on the forehead, back, arms, or 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