Flu antivirals ranked: zanamivir speeds relief, baloxavir cuts complications

When influenza circulates alongside SARS-CoV-2, treating influenza-like illness with antivirals is recommended, yet several drugs compete for that job and clinicians have lacked a clear ranking. The neuraminidase inhibitors, oseltamivir, peramivir, zanamivir and laninamivir, sit alongside baloxavir, an endonuclease inhibitor that attacks the virus differently. Most individual trials compare a single drug against placebo, which leaves the practical questions open: which agent eases symptoms fastest, which best prevents complications, and which causes the fewest side effects? This review set out to compare all of them in healthy adults and children.

The authors searched Medline, Embase and the Cochrane register of clinical trials from inception, with the final update in October 2020, for randomised clinical trials in patients of all ages with influenza treated with neuraminidase inhibitors or baloxavir against other active agents or placebo. Two investigators independently identified studies and extracted the data, then combined everything in a network meta-analysis, an approach that ranks treatments even where they were never tested head to head. The outcomes were time to alleviation of influenza symptoms, influenza complications and adverse events, including nausea and vomiting. Twenty-six trials with 11,897 participants were included; 52.9% were men and the mean age was 32.5 years.

Compared with placebo, all four antiviral agents assessed were associated with shorter time to symptom alleviation. Zanamivir came out fastest on high quality evidence, while baloxavir was associated with the lowest risk of influenza-related complications, roughly half the risk seen with placebo, on moderate quality evidence. Baloxavir was also associated with the lowest risk of total adverse events compared with placebo. Nausea and vomiting did not differ strongly across most comparisons, with one clear exception: oseltamivir at 75 mg was associated with more nausea and more vomiting than placebo.

Direct head to head trials between flu antivirals are scarce, so a network analysis of this kind is the closest thing available to a fair ranking of the field. It broadly confirms that these drugs shorten illness rather than curing it outright, and adds useful texture: different agents lead on different outcomes, with zanamivir strongest on speed of relief and baloxavir on complications and tolerability. The complications finding rests on moderate quality evidence, and the underlying trials were gathered up to October 2020, so how these rankings play out in seasons where influenza and SARS-CoV-2 circulate together remains an open question.

For a generally healthy adult, the practical message is that flu antivirals are not interchangeable. If a clinician offers one, it is reasonable to know that in this analysis zanamivir was linked to the quickest symptom relief, baloxavir to the fewest complications and total side effects, and standard dose oseltamivir to more nausea and vomiting. Which drug suits a given person remains a clinical decision shaped by availability and circumstances, and nothing here speaks to whether treatment is worthwhile for any particular bout of illness.