A needle-free option
Sometimes, the bloodstream is the main target. Because the nose’s middle and upper stretches are so vascular, drugs can be rapidly absorbed.
This is especially valuable for time-sensitive conditions. “If you give something nasally, you can have peak uptake in 15-30 minutes,” said Mr. Hoekman.
Take Narcan nasal spray, which delivers a burst of naloxone to quickly reverse the effects of opioid an overdose. Or Noctiva nasal spray. Taken just half an hour before bed, it can prevent frequent nighttime urination.
There’s also a group of seizure-stopping sprays, known as “rescue treatments.” One works by temporarily loosening the space between nasal cells, allowing the seizure drug to be quickly absorbed through the vessels.
This systemic access also has potential for drugs that would otherwise have to be injected, such as biologics.
The same goes for vaccines. Mucosal tissue inside the nasal cavity offers direct access to the infection-fighting lymphatic system, making the nose a prime target for inoculation against certain viruses.
Inhaling protection against viruses
Despite the recent surge of interest, nasal vaccines faced a rocky start. After the first nasal flu vaccine hit the market in 2001, it was pulled due to potential toxicity and reports of Bell’s palsy, a type of facial paralysis.
FluMist came in 2003 and has been plagued by problems ever since. Because it contains a weakened live virus, flu-like side effects can occur. And it doesn’t always work. During the 2016-2017 flu season, FluMist protected only 3% of kids, prompting the Centers for Disease Control and Prevention to advise against the nasal route that year.
Why FluMist can be so hit-or-miss is poorly understood. But generally, the nose can pose an effectiveness challenge. “The nose is highly cycling,” said Dr. Hindle. “Anything we deposit usually gets transported out within 15-20 minutes.”
For kids – big fans of not using needles – chronically runny noses can be an issue. “You squirt it in the nose, and it will probably just come back out in their snot,” said Jay Kolls, MD, a professor of medicine and pediatrics at Tulane University, New Orleans, who is developing an intranasal pneumonia vaccine.
Even so, nasal vaccines became a hot topic among researchers after the world was shut down by a virus that invades through the nose.
“We realized that intramuscular vaccines were effective at preventing severe disease, but they weren’t that effective at preventing transmission,” said Michael Diamond, MD, PhD, an immunologist at Washington University in St. Louis.
Nasal vaccines could solve that problem by putting an immune barrier at the point of entry, denying access to the rest of the body. “You squash the infection early enough that it not only prevents disease,” said Dr. Kolls, “but potentially prevents transmission.”
And yes, a nasal COVID vaccine is on the way
In March 2020, Dr. Diamond’s team began exploring a nasal COVID vaccine. Promising results in animals prompted a vaccine development company to license the technology. The resulting nasal vaccine – the first for COVID – has been approved in India, both as a primary vaccine and a booster.
It works by stimulating an influx of IgA, a type of antibody found in the nasal passages, and production of resident memory T cells, immune cells on standby just beneath the surface tissue in the nose.
By contrast, injected vaccines generate mostly IgG antibodies, which struggle to enter the respiratory tract. Only a tiny fraction – an estimated 1% – typically reach the nose.
Nasal vaccines could also be used along with shots. The latter could prime the whole body to fight back, while a nasal spritz could pull that immune protection to the mucosal surfaces.
Nasal technology could yield more effective vaccines for infections like tuberculosis or malaria, or even safeguard against new – sometimes surprising – conditions.
In a 2021 Nature study, an intranasal vaccine derived from fentanyl was better at preventing overdose than an injected vaccine. “Through some clever chemistry, the drug [in the vaccine] isn’t fentanyl anymore,” said study author Elizabeth Norton, PhD, an assistant professor of microbiology and immunology at Tulane University. “But the immune system still has an antibody response to it.”
Novel applications like this represent the future of nasal drug delivery.
“We’re not going to innovate in asthma or COPD. We’re not going to innovate in local delivery to the nose,” said Dr. Hindle. “Innovation will only come if we look to treat new conditions.”
A version of this article originally appeared on WebMD.com.