Tamiflu Improves Flu Symptoms, Decreases Respiratory Infection Risk

Oseltamivir, aka Tamiflu, shortened the duration of symptoms by about one day and reduced the likelihood of having a respiratory infection by 44 percent, according to researchers from the University of Michigan, London School of Hygiene and Tropical Medicine, and University of Alabama.

A neuraminidase inhibitor, oseltamivir, blocks key enzymes used by Type A and B influenza viruses, a University of Michigan statement pointed out.

Published on Jan. 29 in The Lancet, the investigators analyzed available clinical trial data on the effects of a 75 mg dose of Oseltamivir administered twice daily to adults exhibiting flu-like symptoms. The authors included cases where patients were given the drug within 36 hours of experiencing two flu-like symptoms. The University of Michigan release also mentioned that the majority of studied patients had the H3N2 Influenza A strain — very common in the US currently.

Based on nine trials documenting effects of Oseltamivir on 4328 patients, the researchers determined when patients took the drug within 36 hours, their condition improved 21 percent faster (time ratio 0.79, 95% CI 0.74—0.85; p<0.0001), were not as likely to have respiratory tract complications (risk ratio [RR] 0.56, 95% CI 0.42–0.75; p=0.0001; 4.9% oseltamivir vs 8.7% placebo, risk difference −3.8%, 95% CI −5.0 to −2.2) and their hospitalization risk dropped 67 percent (RR 0.37, 95% CI 0.17—0.81; p=0.013; 0.6% oseltamivir, 1.7% placebo, risk difference −1.1%, 95% CI −1.4 to −0.3).

Though the team found no psychological or neurological risks, they reported that side effects such as nausea and vomiting were more common when taking Oseltamivr (RR 1.60, 95% CI 1.29—1.99; p<0.0001; 9.9% oseltamivir vs 6.2% placebo, risk difference 3.7%, 95% CI 1.8—6.1 and RR 2.43, 95% CI 1.83–3.23; p<0.0001; 8.0% oseltamivir vs 3.3% placebo, risk difference 4.7%, 95% CI 2.7—7.3, respectively).

“This is the first patient-level analysis of how well this drug works. Previous research has questioned its success and use in light of the side effects of nausea and vomiting, but the other studies combined those infected with influenza and those without, which diluted the positive effect in treatment," the Thomas Francis Jr. Collegiate Professor of Public Health at the University of Michigan School of Public Health and study’s co-author, Arnold Monto said.