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Phenytoin Toxicity

Phenytoin or Carbamazepine Toxicity


Presentation

  • (20% incidence when abnormal signs present v 3.5% incidence when absent, P .026).[ncbi.nlm.nih.gov]
Euthyroid
  • Normalisation of phenytoin levels was associated with return of euthyroidism. The interaction between phenytoin, thyroid function, and thyroid replacement therapy is discussed.[ncbi.nlm.nih.gov]
Noncompliance
  • Noncompliance can lead to accumulation of the drug-causing toxicity. We present a patient with acute alcohol intoxication who developed phenytoin toxicity due to noncompliance with the drug.[ncbi.nlm.nih.gov]
Absent Bowel Sounds
  • Multiple doses may also be given every 2-6 hours until there is a passage of charcoal stool, absent bowel sounds or improved condition of the patient.[overdoseinfo.com]
Pelvic Mass
  • A 64-year-old woman initially presented to her family physician with pelvic discomfort and, on ultrasonography, was found to have a pelvic mass.[current-oncology.com]
Skin Lesion
  • Key words: Ataxia, Gingival hypertrophy, Hirsutism, Nodular skin lesions, Nystagmus Phenytoin toxicity.[jyoungpharm.org]
Broad Nasal Bridge
  • Fetal hydantoin syndrome Intrauterine exposure to phenytoin may result in the following physical features: Broad nasal bridge Wide fontanelle Low hairline Cleft lip/palate Epicanthal folds Short neck Microcephaly Low-set ears Small or absent nails Hip[emedicine.medscape.com]
Withdrawn
  • The symptoms improved significantly after the offending drug was withdrawn. Alternatively she was started on oral carbamazepine.[jyoungpharm.org]
  • Phenytoin was withdrawn. Then patient then recovered eventually. Medication errors may produce severe toxicity resulting in hospitalization. It also increases morbidity and mortality. A prescribing fault is a failure in the prescribing process.[ijbcp.com]
Abnormal Gait
  • Symptoms of phenytoin toxicity include: confusion, nystagmus, agitation, abnormal gait and hallucinations. This case report describes phenytoin toxicity in a patient receiving phenytoin 300 mg three times a day for a number of weeks.[ncbi.nlm.nih.gov]
  • Neurologic The neurologic toxicity symptoms may include abnormal gait, confusion, irritability, agitation, respiratory distress, tremors, hallucinations, mental status alterations, peripheral neuropathy, dysphagia or difficulty in swallowing and the presence[overdoseinfo.com]
  • Neurologic findings in phenytoin toxicity may include the following: Hyperreflexia or hyporeflexia Abnormal gait (bradykinesia, truncal ataxia - Ataxia is very typical with elevated phenytoin levels, and may lead to falls and consequent trauma Encephalopathy[emedicine.medscape.com]
  • TABLE 4 Toxicity of Phenytoin Central nervous system - Dizziness, tremor (intention), visual disturbance (horizontal and vertical nystagmus), diplopia, miosis or mydriasis, ophthalmoplegia, abnormal gait (bradykinesia, truncal ataxia), choreoathetoid[emjournal.net]
Focal Neurologic Deficit
  • A possible mechanism for focal neurological deficit in brain-damaged patients on phenytoin therapy is discussed.[ncbi.nlm.nih.gov]
  • This paper reports a rare but recognizable complication in a patient in whom reversible monoplegia, a focal neurological deficit, developed during long-term phenytoin therapy for grand mal seizures.[mdedge.com]
  • She was confused with no focal neurologic deficits. A complete blood count revealed a normal white blood cell count, mild anemia, and a platelet count of 22,000. Liver function and PT/INR were normal.[shmabstracts.com]
Meningism
  • The past medical history was significant for neonatal Group B Strep meningitis with seizures. Among the child's discharge medications was a prescription for phenytoin (30 mg/5 mL) 2.5 cc by mouth three times daily.[ncbi.nlm.nih.gov]
  • Neurologic findings in phenytoin toxicity may include the following: Hyperreflexia or hyporeflexia Abnormal gait (bradykinesia, truncal ataxia - Ataxia is very typical with elevated phenytoin levels, and may lead to falls and consequent trauma Encephalopathy Meningeal[emedicine.medscape.com]
  • […] abnormal gait (bradykinesia, truncal ataxia), choreoathetoid movements, vomiting, dysphagia, respiratory distress, irritability, agitation, confusion, hallucinations, fatigue, coma, death (rare), encephalopathy, pseudodegenerative disease, dysarthria, meningeal[emjournal.net]
Cerebellar Ataxia
  • Its popularity however is in decline, partly because of perception of adverse effects that include gum hypertrophy, hirsutism, osteoporosis and cerebellar ataxia.[jnnp.bmj.com]

Workup

  • Further workup for thrombo‐cytopenia was negative. Platelet count increased as the phenytoin level decreased, and her mental status followed the same pattern.[shmabstracts.com]
HLA-DQ2
  • Eight out of 17 (47%) patients had the HLA DQ2/DQ8 type, strongly associated with autoimmune ataxias. Volumetric 3T MRI imaging and spectroscopy data were available in 6 of the 13 patients with ataxia.[jnnp.bmj.com]

Treatment

  • CASE REPORT: A 63-year-old man who was maintained with a stable dose of phenytoin for treatment of seizures began treatment with ticlopidine following percutaneous transluminal angioplasty and stent placement.[ncbi.nlm.nih.gov]

Prognosis

  • Early withdrawal is associated with a better prognosis. If the patient has developed SJS or TEN with the use of phenytoin, phenytoin must not be re-started in this patient at any time.[medicines.org.uk]

Etiology

  • Cardiovascular toxicity is extremely rare in oral overdose and should suggest other etiologies. Prolonged cardiac monitoring after oral ingestion is unnecessary.[emjournal.net]
  • Phenytoin 125mg TID had been added to this regimen one month prior to this presentation for the treatment of new onset seizures of undetermined etiology. There were no other recent medication changes reported by the group home staff.[ispub.com]

Epidemiology

  • Poisonings with Cardiotoxicants: Epidemiology, Features, Management, and Exceptional Therapies, 1st Edition. Springer UK. London UK 2013: 1-47. (Chapter).[emdocs.net]
Sex distribution
Age distribution

Pathophysiology

  • Phenytoin Toxicity Pathophysiology Stabilizes Na channels in the motor cortex increase seizure threshold Prolongs refractory period of vent. pacer, shortens action potential in heart Risk factors for toxicity Acute alcohol ingestion can increase levels[fprmed.com]
  • PATHOPHYSIOLOGY The toxic effects of phenytoin depend on the route of administration, the duration of exposure, and the dosage used. Of these determinants of toxicity, the most important is the route of administration.[emjournal.net]

Prevention

  • Further, established polymorphisms should be documented to prevent toxicity of drugs metabolized by similar pathways.[ncbi.nlm.nih.gov]
  • Prevention Those who are taking phenytoin may prevent toxicity by taking the medication according to the prescription of the physician.[overdoseinfo.com]
  • Once she could breathe on her own and regained consciousness, she started taking phenytoin to prevent seizures. After her time in the intensive care unit, Susan was admitted to a rehabilitation program due to loss of muscle function.[personalizedprescribing.com]
  • In this case instead of suddenly increasing the dose of phenytoin one should change the drug or add another drug to prevent toxicity or side effect.[ijbcp.com]

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