Two common allergy medications could cause a severe reaction in some people who stop using it.
The U.S. Food and Drug Administration (FDA) issued an alert related to cetirizine (Zyrtec) or levocetirizine (Xyzal), warning that patients who stop taking it after long-term use may experience "rare but severe itching," a condition called pruritus.
The itching was reported by people who used the medicines every day for months or years, and then stopped using them.
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In total, 209 cases were reported worldwide (197 in the U.S.) between April 25, 2017, and July 6, 2023.
"This number includes only reports submitted to FDA, so there may be additional cases of which we are unaware," the agency stated in the release.
"Reported cases were rare but sometimes serious, with patients experiencing widespread, severe itching that required medical intervention."
Many reports described a "significant and persistent impact on quality of life and ability to function," the FDA noted.
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In most cases (90%), restarting the medicine resolved the severe itching. Some (38%) had success with gradually tapering off after restarting.
The drugs are available in both prescription and over-the-counter versions.
The FDA said it will update the medications' prescribing information to include a warning of the itching risk, and will also ask the manufacturers to add the information to the drug facts label for over-the-counter versions.
Cetirizine and levocetirizine are antihistamines that are approved to treat seasonal allergies in adults and children 2 and up, according to the FDA.
The drugs are also approved as a treatment for year-round allergies and chronic hives in patients 6 months and older.
People who experience severe itching after the cessation of these medications should contact a healthcare professional, the FDA advised.
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"Individuals planning on long-term use of cetirizine or levocetirizine, especially for more than a few months, should discuss the benefits and risks with your healthcare professional, who can provide advice based on your personal needs," the agency stated.
Other common side effects of cetirizine and levocetirizine include fatigue, drowsiness, cough, dry mouth, fever, sore throat, nosebleed, diarrhea and vomiting, per the FDA.
Dr. Marc Siegel, clinical professor of medicine at NYU Langone Health and Fox News senior medical analyst, noted that these medications are "very effective" at alleviating allergy symptoms.
"The FDA is noting that in extremely rare circumstances after long-term use, stopping them can lead to severe itching, which is alleviated after restarting them," he reiterated to Fox News Digital.
"I suspect this might be due to accelerated histamine release once the blocker is stopped."
A spokesperson from the Consumer Healthcare Products Association provided the below statement to Fox News Digital.
"Consumer safety is the top priority for CHPA and our manufacturer members. The OTC industry supports FDA's ongoing commitment to notifying the public about safety signals, even when extremely rare, as in this case."
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"CHPA members will continue to comply with FDA guidelines, including any needed updates to Drug Facts labels, while also evaluating and monitoring the latest science and product profiles. Consumers who use these medicines daily for an extended period (months-years) should not stop taking their medication abruptly without first consulting with their healthcare provider."
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Opella, the manufacturer of Xyzal, shared the below statement with Fox News Digital.
"Xyzal has a strong track record of safety and efficacy backed by scientific research and user satisfaction. This is a rare reaction, and Opella stands by the safety of Xyzal when used as directed."
