Phenytoin Toxicity: A Case Report

Abstract

Background: Phenytoin is a commonly used sedative antiepileptic medication in many countries. It is used against tonic-clonic and complex partial seizures. Phenytoin is reported to cause a range of deleterious and erratic side effects at therapeutic and toxic doses. Case report: An eighteen year old female presented with ataxia, nystagmus, gingival hypertrophy, nodular skin lesions and hirsutism while she was on treatment with oral phenytoin at 200 mg once daily since the past five years for seizures. Based on the presenting signs and symptoms, her condition was diagnosed as phenytoin induced toxicity. The symptoms improved significantly after the offending drug was withdrawn. Alternatively she was started on oral carbamazepine. Naranjo and WHO causality assessment was done, indicating a probable relationship between the patient's symptoms and her use of phenytoin. Conclusion: This case report and review highlights the adverse drug reactions of phenytoin and the need of regular monitoring in patients on long term therapy.

Phenytoin induced Lyell’s syndrome: a case report

“…Phenytoin has a narrow therapeutic index of 10-20 mcg/ml. 2 At plasma concentrations below 10 mcg/ml, elimination follows first order. However, at higher concentrations, including those in the therapeutic range (10-20 mcg/ml), the metabolic pathway becomes saturated and elimination shifts to zero order.…”

“…The increased half-life due to zero order pharmacokinetics can also result in prolonged duration of toxic symptoms. 2 Currently TEN is considered as a clinically distinct disorder, earlier SJS was considered to be part of a spectrum of erythema multiform (EM) and is part of the SJS-toxic epidermal necrolysis (SJS-TEN) spectrum, characterized by heterogeneous cutaneous bullous eruptions which can result in sloughing of the epidermis. BSA with 10-30%, there is overlapping of SJS and TEN.…”

“…1 Phenytoin (5,5-diphenylhydantoin) is one of the most effective and widely prescribed drug for the treatment of epilepsy, which was found to cause toxic epidermal necrolysis (TEN) or Stevens-Johnson syndrome (SJS) more frequently. 2 Despite the inherited risk of dose related toxicity attributed to its zero-order pharmacokinetics, Phenytoin is still considered a first line drug therapy for some types of seizure disorder. 3 Adverse drug reactions (ADRs) are one of the most leading causes of death among hospitalized patients and occur in between 0.3 to 7 per cent of all hospital admissions.…”

Imaging in phenytoin induced neurotoxicity: a case series

“…7 Other side effects of phenytoin include hematological side effects like megaloblastic anemia, osteomalacia, hirsutism and gingival hyperplasia. 8 Phenytoin is known to cause a decrease in folate levels resulting in megaloblastic anemia. The mechanism of gum hypertrophy, though is more complex and is a resultant of a manipulation of extracellular matrix metabolism.…”

Ataxia, Manifestation of Phenytoin Toxicity: A Case Report

“…3 Non-CNS related ADR of phenytoin includes gum hypertrophy, decrease in haemoglobin count, hypersensitivity syndrome, reduced serum folic acid levels. 4 Phenytoin is categorized under the drugs which are having narrow therapeutic index due to wide variability in its pharmacokinetic profile. There are more chances of phenytoin toxicity with its overdose, symptoms of an overdose of phenytoin include coma, difficulty in pronouncing words correctly, involuntary eye movement, lack of muscle coordination, hypotension, nausea, sluggishness, slurred speech, tremors and vomiting.…”