The usual way to spray medicine up your nose may not be the best

Close one nostril, stick nozzle up the other, squeeze. The usual way to spray medicine into the nose is the obvious one, but it may not be the most effective, says Saikat Basu at South Dakota State University.

That’s according to his computer model of how aerosols enter the nose and reach the nasopharynx, the chamber at the beginning of the throat where the two airways in the nose come together. This is often the target for drugs preventing infections of the airway.

Instead, says Basu, pointing the nozzle towards your face, keeping it almost horizontal as you insert it into the nostril and slightly angled towards your cheek, may be the best approach.

To study what happens to an aerosol on its way to the nasopharynx, Basu obtained three-dimensional scans of noses and incorporated them in a computer model that simulates the airflow inside.

He found that spraying horizontally increases the number of aerosol droplets that land in the nasopharynx by at least a factor of 100. He presented the work at a meeting of the American Physical Society in November.

Basu’s explanation is that by spraying horizontally, the droplets escape the strong airflow of the person inhaling during or after administering the spray, which would otherwise rush the droplets past the nasopharynx into the throat and lungs. “If you’re targeting the upper airway sites, the airflow is not the best medium to transport the drugs,” he says.

He plans to validate his conclusions in physical models of noses and then in people. Such experiments might also lead to improvements in the design of nasal spray pumps, for instance by finding the optimal droplet size.

“Basu’s approach appears to provide a simple, low-cost solution to dramatically increase initial drug targeting to the nasopharyngeal region,” says Worth Longest at Virginia Commonwealth University.

Until experiments on actual noses confirm his numbers, Basu won’t give anyone the advice to disregard the instructions that come with nose sprays. “I don’t have that authority – but in my personal life, I do try to apply the sprays in this direction,” he says.

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