Peihua Jiang knows how difficult it can be to convince a child to take a sip of a bitter liquid medication.
When they were young, his kids sometimes balked at taking medicines because they didn’t like how they tasted. And as a neurobiologist, Jiang knew the medical issues at stake went beyond a minor inconvenience.
Swallowing pills can be difficult for many young children and elderly people. Liquid medications are easier to consume, but their taste is often so off-putting that some patients will avoid them entirely — a significant barrier to good health for those who need to take lifesaving medications.
“My kids would refuse to take medicine when they were young,” he said, laughing. “It’s evolution; it makes perfect sense. A bitter taste is a sign you’re not supposed to eat something. But with medicine, it’s a different story.”
That’s why Jiang and his colleagues at Philadelphia’s Monell Chemical Senses Center, have spent years taking on what they describe as one of the most enduring challenges in medicine — finding a “bitter blocker” substance that can prevent a patient from tasting anything bitter.
This month, Jiang and several colleagues announced a breakthrough: They identified a nerve inhibitor in liquid form that temporarily blocks all taste entirely. The center says it’s the first temporary taste blocker that works universally in humans, and a game-changer in a yearslong research journey.
“We are very pumped,” said Carol Christensen, a consultant to the director at Monell and a coauthor with Jiang of a paper on the compound recently published in British Journal of Pharmacology.
How bitter medication hurts health outcomes
Researchers at Monell, an independent research institution devoted to studying the senses of taste and smell, first began developing a bitter blocker in 2016 with a grant from the Bill and Melinda Gates Foundation. The foundation was concerned about bitter tastes preventing the uptake of medications in developing countries, where many people need to take regular medication for serious chronic illnesses such as HIV and tuberculosis.
Ninety percent of U.S. pediatricians cited “a drug’s taste and palatability” as the biggest barrier to getting their patients to complete a course of medication, according to a 2013 review of existing research on bitter medications for children.
The paper noted it’s also hard for young children to swallow pills, even in small sizes, and that people of all ages, especially elderly adults, can have issues taking pills.
For patients with serious conditions that require a long course of treatment, such as HIV, avoiding bitter medications can be dangerous.
‘It’s actually really wonderful’
At first, Monell researchers hoped to develop a bitter blocker by targeting the taste receptors on the tongue that handle bitter sensations. But that’s more complicated than it seems.
Sweet tastes are easier to block, because they affect only two taste receptors on the tongue. But at least 25 taste receptors are devoted to detecting bitter tastes. And a person’s reaction to a bitter taste can vary depending on their genetics.
“Some may have a strong response to one bitter receptor. Some people may not have any response at all,” Flammer said.
So the researchers pivoted to target the nerve receptor that receives signals from the taste buds, Jiang said. In their search, they identified clinical trials for medications that targeted the same nerve receptor to treat various health conditions.
In trials for one of those medications, designed to treat chronic cough, the researchers noticed a curious side effect. “People were taking these medications for chronic cough, but they were saying, ‘It messed up my taste,’ ” Jiang said. They theorized they might be able to adapt a nerve inhibitor used in the medication to intentionally target a person’s sense of taste.
They discovered that the compound in liquid form, swished around the mouth for less than a minute, blocks all taste for about an hour and a half. Then, taste returns to normal, allowing a patient to go about their lives without a bitter taste lingering in their mouths.
The researchers tested it on adult humans and on mice, and found that the inhibitor only blocks taste — not any other sensations, such as temperature or even the tingling felt from a sip of a carbonated beverage.
“It’s actually really wonderful. We’ve never seen that before,” Jiang said.
