IV fosphenytoin in obese patients: Dosing strategies, safety, and efficacy. Issue 1 (February 2017)

• Record Type: Journal Article
• Authors: Clark, Sarah L.; Leloux, Megan R.; Dierkhising, Ross A.; Cascino, Gregory D.; Hocker, Sara E.
• Is Part Of: Neurology. Volume 7:Issue 1(2017)
• Publication Date: 2017-02
• Subjects: Nervous system -- Diseases -- Periodicals; Neurology -- Periodicals; Neurology -- United States -- Periodicals; 616.8
• DOI: 10.1212/CPJ.0000000000000322
• Languages: English
• ISSNs: 2163-0402

Abstract

Abstract: Background: Previous studies evaluated the disposition of IV phenytoin loading doses and found that obese patients had increased drug distribution into excess body weight, larger volumes of distribution, and longer half-lives when compared to their nonobese counterparts. We assess the safety and efficacy of fosphenytoin loading doses in patients with different body mass indices (BMIs). Methods: A retrospective chart review was conducted in 410 patients who received fosphenytoin. Patients were divided into 2 groups: BMI <30 (nonobese) and BMI ≥30 (obese). Patient demographics, fosphenytoin dose administered in mg/kg body weight, renal and liver function tests, fosphenytoin drug levels, and pre- and post-fosphenytoin administration vital signs were collected to assess for adverse events. Necessity of additional antiepileptic loading doses was used as a surrogate for clinical efficacy. Results: The median dose of fosphenytoin administered was 19 mg/kg (interquartile range 15–20). The most frequently encountered adverse event was hypotension, which occurred in 39% of the cohort. Using a Bonferroni adjustment for multiple comparisons, there were no differences in adverse events between the 2 groups. The need for additional antiepileptic loading doses was not different between the 2 groups ( p = 0.07). Conclusions: The incidence of adverse events and the need for repeat loading antiepileptic medications was similar between the 2 groups. From our findings, the patients in our study did not receive empiric loading dose adjustments and the current method of loading fosphenytoin achieves similar outcomes, regardless of the patient's BMI.