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.
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.
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.
In the current study, treatment-emergent resistance was uncommon and all of the oseltamivir regimens were well tolerated in children and adults.