Antiviral Drug May Shorten COVID-19-Induced Loss of Taste and Smell

Taste and smell loss are two symptoms of COVID-19, sometimes lasting years post-infection. New research indicates one drug may reduce duration of such symptoms.

Kateryna Kon/Shutterstock

New data suggest scientists have discovered a medication first designed to treat COVID-19 may also lessen the time it takes for two common symptoms of the disease: loss of taste and smell—to disappear.

The oral antiviral drug ensitrelvir (brand name Xocova) was granted a Fast Track designation by the U.S. Food and Drug Administration (FDA) to be investigated as a potential treatment for COVID-19 in April. Soon after, results from randomized clinical trials published in Clinical Infectious Diseases showed ensitrelvir was safe, effective, and successful in suppressing viral replication in patients with mild to moderate COVID-19.

Ensitrelvir is now gaining traction as a potential solution to address COVID-19’s symptoms of loss of taste and smell—two sensory problems that can linger for up to years after the acute infection has subsided. The drug’s multipurpose use is based on the results of a study by researchers from the drug’s co-developer, pharmaceutical giant Shionogi Inc., a United States subsidiary of Shionogi & Co. Ltd. based in Osaka, Japan.

Ensitrelvir Improves Taste and Smell Symptoms

In a poster presentation, Shionogi presented data demonstrating that patients given ensitrelvir within three days of the onset of symptoms may have benefited from the medication by preventing or reducing the loss of taste and smell. Researchers also presented their analysis of the phase 2/3 clinical study results, showing a “significantly smaller proportion of patients had taste disorder or smell disorder on Day 7 when treated with 125 [milligrams] of ensitrelvir versus a placebo,” according to a news release.

Story continues below advertisement

“As an investigator who has evaluated both clinical data and real-world experience with ensitrelvir, I am optimistic about its potential to become an important tool in managing the unpredictability of COVID-19,” said Dr. Yohei Doi, a professor of medicine at Fujita Health University in Japan, said in the news release. “The new data ... offer another reason to have confidence in this investigational agent and its potential to be a meaningful treatment option for patients.”

The findings were presented in Boston at the October 2023 IDWeek meeting, an annual conference that brings together infectious disease specialists and epidemiologists from around the globe.

Ensitrelvir remains an investigational drug, having received emergency approval in Japan in November 2022 to treat COVID-19. It has not been approved for use outside of Japan. However, Takeki Uehara, senior vice president of drug development and regulatory science at Shionogi, hopes this will change.

“The data we are seeing in Japan are promising as we work to meet unmet medical needs of COVID-19 and make ensitrelvir available worldwide, pending regulatory approvals,” he said in the same news release.

Loss of Taste and Smell in US Adults

A 2023 paper published in Laryngoscope showed 35.8 million U.S. adults—or 14 percent of the population—were diagnosed with COVID-19 in 2021. Among those, an estimated 60.5 percent reported losing their sense of smell, while 58.2 percent reported loss of taste.

Story continues below advertisement

Most patients (over 72 percent) completely recovered their sense of smell post-infection. However, about 1 in 4 people affected recovered only partially. Approximately 4 percent said their sense of smell had not yet returned.

Taste function recovery was similar, with most (about 77 percent) regaining their sense of taste, while 1 in 5 reported partial recovery. Under 3 percent reported no recovery.

“The majority of adults infected with COVID-19 in 2021 experienced olfactory or gustatory dysfunction with a non-negligible population reporting incomplete or no near-term sensory recovery,” the authors wrote in the 2023 paper. “Our results are useful for providers counseling patients and suggest that interventions lessening overall COVID-19 symptom burden may prevent prolonged sensory dysfunction.”

Other Treatments

COVID-related loss of smell can negatively affect people in several ways, including significantly altering a person’s overall quality of life and leading to poor nutrition. Mental health issues like depression, anxiety, and low self-esteem have also been linked to loss of taste and smell.

Fortunately, smell recovery is possible through smell retraining therapy (SRT). The treatment involves repeated exposure to smells to elicit memories of familiar scents like flowers, fruits, spices, and essential oils.

Ear, Nose, and Throat (ENT) Health, an organization powered by the American Academy of  Otolaryngology–Head and Neck Surgery, recommends patients sniff individual scents for at least 10 to 20 seconds once or twice a day. The four best scents are rose, lemon, cloves, and eucalyptus. Being entirely focused on the task is critical to stimulating memories of each smell. This should be followed by a few deep breaths before moving on to the next scent. Perform this exercise for at least three months.

Regaining taste is also possible. Experts at the University of Texas MD Anderson Center recommend the following:

• Introduce lemon into your diet because the tart flavor stimulates saliva and taste buds.
• Integrate sweet, salty, spicy, and sour foods like pickles, olives, hot sauces, and a variety of salad dressings.
• Play around with foods that provide texture, like apples, celery, or sticky peanut butter.
• Alternate between hot and cold foods.