882. Systematic Underdosing of Oseltamivir in Hospitalized Patients with Influenza


 
 
 Oseltamivir remains the primary treatment for seasonal influenza syndromes and early administration has been shown to increase the clinical benefit of treatment; we studied current practice and describe patient and system variables influencing dosing decisions.
 
 
 
 We reviewed oseltamivir dosing in 135 adult patients in our community hospital admitted with acute influenza over two northern Hemisphere influenza seasons (2016-2017 and 2017-2018) and for whom pharmacy dosing protocols were invoked. We reviewed admitting symptoms for factors suggesting possible dehydration, the timing of treatment in relation to testing for influenza, the estimated creatinine clearance at the time of dose determination for oseltamivir, the initial dose of drug, and dose-adjustment over time.
 
 
 
 Patients ranged in age from 27-96 years (mean 74), with 83 males and 52 females among the 135 patients over these two seasons. Testing results were available for 131 patients and 75 (57%) were positive, while 56 (43%) were negative, and therefore treated empirically based on presenting symptoms.
 Ninety patients (67%) received an initial dose of 30 mg of oseltamivir, while 45 patients (33%) received an initial dose of 75 mg. Of the 90 patients who were dose-adjusted by the pharmacist to 30 mg for the initial dose, 24 (27%) had a creatinine clearance > 60 mL/min, and it is not clear what factors influenced those decisions. Of the 90 patients with an initial creatinine clearance of < 60 mL/min, 22 (24%) showed a clinically significant improvement to > 60 mL/min within the first 24 hours of hospitalization yet only 8 patients had their dose adjusted. Presenting symptoms did not predict patients who had rapid improvement of creatinine clearance. Of the 45 patients receiving an initial dose of 75 mg of oseltamivir, 19 (42%) had creatinine clearance values of < 60mL/min, and were therefore given a loading dose, followed by dose adjustment.
 
 
 
 We found a significant percentage of patients were underdosed initially and dosing was not adjusted for changes in renal function. Reviewing and revising dosing protocols and guidelines may lead to more effective treatment for influenza and may serve as a model for future test-to-treat options for therapies for other acute viral respiratory infections in the future.
 
 
 
 All Authors: No reported disclosures.
