What it's like to have the terrible taste side effect of Paxlovid, a drug authorized to treat COVID-19

• Paxlovid, which is authorized to treat COVID-19, can lead to dysgeusia, or a bad taste.
• Paxlovid contains ritonavir, a part of some HIV treatments that's known to cause this side effect.

At first, Meghan Morris thought her slight cough was her asthma acting up. She'd just returned to New York from a friend's wedding in Chicago, and chalked it up to staying up late in a crowded bar for the afterparty. Plus, she'd tested negative for COVID, and was double-vaccinated and boosted.

But by the Tuesday after the wedding, Morris, a senior correspondent at Insider, experienced a worsened cough, trouble concentrating, headache and fatigue. This time, a COVID test turned up positive — just like it had for about 20 other wedding attendees.

Morris doesn't regret her trip, but as an asthma sufferer, she worried the illness could get serious.

So Morris asked her primary care physician for a prescription for Paxlovid, which the FDA authorized for emergency use in December. The antiviral drug can reduce the risk of hospitalization in high-risk patients. It consists of two medications packaged in three pills, which are taken twice a day for five days.

Morris swallowed her first dose that Wednesday night.

"I immediately thought something was wrong with my mouth because it tasted so bad," she said. "It felt like the back of my mouth was emitting a metallic tang."

Morris was experiencing dysgeusia, the medical term for a bad taste in the mouth. It's a known side effect of ritonavir, one of the two drugs that make up Paxlovid, but not one Morris was expecting — nor one she found any solutions for.

"In the grand scheme of things, of course, I would rather have a bad taste in my mouth than have the bad side effects of COVID for many more days," she said. "So the ends definitely justified the means, but it was not a pleasant experience."

Paxlovid's side effects may be more common than recorded in studies

In the clinical trial that led to Paxlovid's authorization, researchers found that 5.6% of the 1,120 patients who received the drug experienced dysgeusia. Pfizer's patient fact sheet notes the potential side effect, but the drug's packaging doesn't include it, The Atlantic's Rachel Guttman reported.

A Pfizer spokesperson told her "most events were mild" and "very few patients discontinued study as a result." (Pfizer did not respond to Insider's request for comment.)

But Morris's informal polling of friends and other anecdotes suggest it's more prevalent — and more than unpleasant.

"I imagine this is what grapefruit juice mixed with soap would taste like," Anna Valdez, a nursing professor in Sonoma Valley, California, told Guttman.

In the HIV world, where ritonavir was once used as a standalone treatment and is now used to support other medications' effectiveness, it's well-known as "a very common side effect," Dr. Melanie Thompson, an HIV researcher in Atlanta, said during an Infectious Diseases Society of America media briefing Friday.

"For people with HIV who may end up taking ritonavir every day for a very long period of time, this is a big problem," she said.

It's unclear what causes it, but Guttman laid out some theories. Our tongues are more primed to detect bitterness than other flavor profiles, and both substances in Paxlovid are bitter. The sensation could also be our bodies detecting chemicals, which is a different sensation than taste, experts told her.

Be prepared for side effects when taking the drug

Attempts at masking the sensation fall flat, Thompson said.

Morris, for one, tried brushing her teeth with baking soda and water right after her doses, and drinking all kinds of flavored water. She even tried taking the pills with a spoonful of chocolate syrup, thanks to a friend's suggestion.

The treat "was delicious," she said, "but I felt it did nothing for the taste." She found the sensation was even worse with dairy, so she made sure to eat her milk-containing breakfast before her first dose. "Ultimately I found I just had to suck it up," she said.

Thompson said the best thing clinicians can do is tell patients to expect dysgeusia when prescribing Paxlovid. "When you tell patients about a potential side effect and it happens, then they're more likely to say 'OK, I heard about that, I can get through this,' rather than thinking there's something terrible" going on, she said.

It's also important for patients to be aware of it so they don't mistake it for a side effect of COVID-19.

"We all know that COVID can lead to a change or loss to the sense of taste, therefore people are primed for that. Then they start taking Paxlovid and 'Oh no, it happened,'" Jason Gallagher, a doctor of pharmacy and clinical professor at Temple University, said during the briefing. "It's actually the medication, and it will go away."