DESLORATADINE

What is desloratadine?

Desloratadine is a second-generation antihistamine that relieves seasonal or year-round allergy symptoms such as sneezing, runny nose, red, itchy eyes, hay fever, and hives. Unlike other first-generation antihistamines, it is non-drowsy and usually taken daily. Desloratadine is typically taken at 5 mg once daily. For people with liver or kidney impairment, it may be recommended to take 5 mg every other day.

Desloratadine is the active metabolite of the over-the-counter medication loratadine (Claritin). This allows the medication to have very similar effects to loratadine, but desloratadine is considered to be more potent.

How can desloratadine help alleviate certain long COVID symptoms? 

Histamine is a chemical our immune system releases that causes our allergy symptoms. Cells in our body called mast cells release histamine, and in some patients, after COVID, they may release too much and lead to a prolonged inflammatory response. Long COVID is believed to be caused by a persistent hyper-inflammatory state that results in symptoms such as fatigue, arthralgia, myalgia, shortness of breath, chest pain, and rash. Two types of drugs can block histamine in the body, which we call our H1- and H2-antihistamines.

Desloratadine is an H1-antihistamine that reduces the inflammatory symptoms caused by excess histamine. It is suggested that it has other functions outside of its effect on histamine, such as inhibiting the generation and release of inflammatory mediators.¹ With its anti-histamine and anti-inflammatory effects, it is believed to help relieve long-term COVID symptoms. 

What evidence supports desloratadine’s use for long COVID?

In vitro, desloratadine and loratadine were found to have the most potent antiviral activity out of eight tested agents against the SARS-CoV-2 virus in both monkey cells and human nasal epithelium cells.² Desloratadine has also been shown to have a stronger binding affinity to ACE2 receptors compared to loratadine, which can inhibit the virus from entering ACE2 cells.³ However, desloratadine should not be used to treat or prevent an acute COVID infection.

While there is currently a lack of studies investigating the use of desloratadine for long COVID, loratadine has been studied in combination with an H2-antihistamine with demonstrated beneficial effects in long COVID patients. A study with 49 long COVID patients found that a combination of an H1- and H2-antihistamine like loratadine 10 mg twice a day with famotidine 40 mg once daily taken for a minimum of 4 weeks showed an average reduction of about half of their symptoms. Symptoms that were most improved included neurologic symptoms such as brain fog and headaches, chest pain, and fatigue. Only the symptoms of postural tachycardia or an abnormal increase in heart rate when a person stands up were not improved.⁴  Because of its structural similarity to loratadine, desloratadine can be hypothesized to have similar effects on long COVID patients.

What should I be aware of when taking desloratadine?

Some side effects of desloratadine include dry mouth, headache, nausea, and dizziness.

References:

1)      Agrawal DK. Pharmacology and clinical efficacy of desloratadine as an anti-allergic and anti-inflammatory drug. Expert Opin Investig Drugs. 2001 Mar;10(3):547-60. doi: 10.1517/13543784.10.3.547

2)      Morin-Dewaele M, Bartier S, Berry F, et al. Desloratadine, an FDA-approved cationic amphiphilic drug, inhibits SARS-CoV-2 infection in cell culture and primary human nasal epithelial cells by blocking viral entry. Sci Rep. 2022 Dec 6;12(1):21053. doi: 10.1038/s41598-022-25399-5

3)      Hou Y, Ge S, Li X, Wang C, He H, He L. Testing of the inhibitory effects of loratadine and desloratadine on SARS-CoV-2 spike pseudotyped virus viropexis. Chem Biol Interact. 2021 Apr 1;338:109420. doi: 10.1016/j.cbi.2021.109420

4)      Glynne P, Tahmasebi N, Gant V, Gupta R. Long COVID following mild SARS-CoV-2 infection: characteristic T cell alterations and response to antihistamines. J Investig Med. 2022 Jan;70(1):61-67. doi: 10.1136/jim-2021-002051