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Fosphenytoin Side Effects

Medically reviewed by Drugs.com. Last updated on Nov 25, 2023.

Applies to fosphenytoin: injection solution.

Warning

Injection route (Solution)

The rate of IV fosphenytoin sodium administration should not exceed 150 mg phenytoin sodium equivalents (PE) per minute in adults and 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) in pediatric patients because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering IV fosphenytoin sodium. Although the risk of cardiovascular toxicity increases with infusion rates above the recommended infusion rate, these events have also been reported at or below the recommended infusion rate. Reduction in rate of administration or discontinuation of dosing may be needed.

Serious side effects of Fosphenytoin

Along with its needed effects, fosphenytoin 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 fosphenytoin:

More common

Less common

Rare

Incidence not known

Other side effects of Fosphenytoin

Some side effects of fosphenytoin 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

Less common

Rare

For Healthcare Professionals

Applies to fosphenytoin: injectable solution, intravenous solution.

General

The more commonly reported adverse reactions have included pruritus, nystagmus, dizziness, somnolence, vomiting, and ataxia.

Cardiovascular

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[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]

Hypersensitivity

Frequency not reported: Hypersensitivity syndrome, periarteritis nodosa, SJS/TEN risk in patients of Asian ancestry who have HLA-B 1502

Postmarketing reports: Anaphylactoid reaction, anaphylaxis, angioedema[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]

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

Frequency not reported: Toxic hepatitis, hepatocellular damage[Ref]

Metabolic

Uncommon (0.1% to 1%): Generalized edema, cachexia, diabetes insipidus

Frequency not reported: Hyperglycemia, appetite disorder, hypokalemia[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]

Immunologic

Uncommon (0.1% to 1%): Sepsis, flu syndrome, cryptococcosis

Frequency not reported: Immunoglobulin abnormalities[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[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, taste loss,reflexes decreased, reflexes increased, migraine, speech disorder, 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)

Postmarketing reports: Dyskinesia[Ref]

Other

Common (1% to 10%): Asthenia, deafness, accidental injury, fever, face edema, hyperacusis, parosmia, ear pain

Uncommon (0.1% to 1%): Malaise[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]

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]

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]

Endocrine

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

References

1. Keegan MT, Bondy LR, Blackshear JL, Lanier WL. Hypocalcemia-like electrocardiographic changes after administration of intravenous fosphenytoin. Mayo Clin Proc. 2002;77:584-6.

2. Cerner Multum, Inc. UK Summary of Product Characteristics.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.