Background: A novel influenza A/H1N1 virus (H1N1pmd09) emerged in April 2009. To address concerns about the suitability of standard oseltamivir regimens for controlling the virus, a randomized trial was initiated to explore virologic responses to standard and nonstandard regimens in patients infected with H1N1pdm09.
Methods: Patients aged 1 year and older with influenza-like illness and a positive rapid test result for influenza A were eligible for enrollment. Adults received 75 mg or 150 mg of oseltamivir twice daily for 5 or 10 days; children received weight-based unit-dose equivalents. Assessments included viral shedding and resistance testing; symptoms were recorded in patients’ diaries and adverse events (AEs) were recorded during patient visits.
Results: When the pandemic was declared over, the study was closed prematurely and therefore did not meet its recruitment target. A total of 102 patients were enrolled, with 101 included in the safety population and 70 in the intent-to-treat infected population. The sample size prevented meaningful evaluation of virologic responses to the investigational regimens. No resistant viruses were isolated at baseline, and treatment-emergent resistance was detected in 2 (3.2%) of 63 patients with positive virology test results. All of the regimens were generally well tolerated, with most on-treatment AEs considered unrelated or remotely related to treatment. No serious AEs or deaths were reported.
Conclusions: In the current study, treatment-emergent resistance was uncommon and all of the oseltamivir regimens were well tolerated in children and adults.