Life-threatening bradyarrhythmia with oral phenytoin overdose

Abstract

We report a case of a 41-year-old lady, who developed severe hypotension and sinus bradycardia, following oral consumption of 20 g of phenytoin and 500 mg of glibenclamide. She required high dose of inotropes and a temporary transvenous pacer for her hemodynamic instability. This life-threatening cardiotoxicity of phenytoin could have been due to its interaction with sulphonylurea. It is imperative to be aware of drug interactions, due to which, life-threatening cardiovascular manifestations following phenytoin toxicity can occur.

Persistent Bradycardia with the Long-term Use of Phenytoin and Oxycodone: First Case Report

“…However, phenytoin has almost no effect on interventricular conduction or the sinoatrial node [ 4 ]. Toxicity from phenytoin ingestion typically first manifests as neurological symptoms affecting the cerebellar and vestibular functions of the nervous system [ 1 ]. The neurological manifestations of phenytoin toxicity include altered mental status, ataxic gaits, and nystagmus [ 5 ].…”

“…The neurological manifestations of phenytoin toxicity include altered mental status, ataxic gaits, and nystagmus [ 5 ]. Phenytoin toxicity is typically the result of a suicidal attempt via an intentional overdose, drug interactions, or elevated dosage adjustments [ 1 ]. We had no reason to believe this patient was intentionally overdosing on his medications.…”

“…In addition to neurologic manifestations, some serious adverse cardiac manifestations have been observed that include arrhythmias, hypotension, and respiratory arrest. While cardiotoxic effects have been well-documented in the use of intravenous phenytoin administration, these effects are not commonly seen in oral phenytoin administration [ 1 , 3 ].…”

“…In one case, severe hypotension and sinus bradycardia developed following the consumption of 20 g of phenytoin and 500 mg of glibenclamide in a suicide attempt. The authors suggested that this cardiotoxicity of phenytoin could be due to the patient’s metabolic disorder or interactions with the sulfonylurea he was using [ 1 ]. In another case, sinus node arrest with symptomatic junctional bradycardia was observed in a patient who was managed with 150 mg of oral phenytoin.…”

“…Oxycodone and phenytoin are both well known for their cardiotoxic side-effect profile, especially at higher doses [ 1 - 2 ]. The oral administration of phenytoin is particularly prone to neurological manifestations [ 1 ]. A few studies have been reported to cause bradycardia following the toxicity of phenytoin.…”