KETOTIFEN EYE DROPS

What is ketotifen?

Ketotifen is an antihistamine and mast cell stabilizer used as an eye drop to prevent and treat eye itching caused by allergies (also known as allergic conjunctivitis). An oral formulation of ketotifen is available to treat asthma and hives, but it is only available in the United States as an eye drop. It can be applied as one drop into the affected eye(s) twice daily every 8-12 hours and should not be used more than two applications daily.

How can ketotifen help alleviate certain long COVID symptoms?

Histamine is a chemical our immune system releases that causes allergy symptoms. Cells in our body called mast cells release histamine, and in some patients after COVID, they may release too much, leading to some of the symptoms of long COVID. Ketotifen prevents mast cells from releasing inflammatory mediators and blocks histamine in the body as a histamine type-1 blocker.

As an eye drop, ketotifen and similar products such as olopatadine (Pataday) can specifically relieve itchy eyes that certain COVID variants can cause. There have been some reports of the Omicron variant causing unusual symptoms such as itchy eyes or pink eye in some patients.¹ While this is rarely reported outpatient, there may be up to 31.6% of hospitalized COVID patients experiencing conjunctivitis.² If you are experiencing an isolated symptom of itchy eyes without other symptoms of COVID, however, it is likely not due to a COVID infection.

What evidence supports ketotifen’s use for long COVID?

The SARS-CoV-2 virus can cause extreme inflammatory outbreaks by activating mast cells in the respiratory tract and may cause an accumulation of mast cells. As a result, ketotifen has been studied to see if its mast cell stabilizer properties could be used for pulmonary inflammatory symptoms of COVID. Ketotifen has been found to reduce lung lesions in the early stages of an H5N1 infection and was studied to investigate its impact on a COVID infection.^{3, 4}

While ketotifen was found to be useful for its anti-inflammatory and mast cell-stabilizing effects, it is important to note that these effects would only be significant enough in ketotifen taken orally, which is not currently available in the US. As an ophthalmic formulation, it is reserved for relieving conjunctivitis or itchy eyes due to COVID. More studies need to be conducted specifically on the use of ketotifen eye drops for long COVID symptoms.

What are some things to watch out for with ketotifen?

Ketotifen can cause some eye irritation or eye pain. Otherwise, it has minimal systemic absorption and relatively few side effects. If symptoms worsen or do not improve within three days, you should inform your provider and consider other options.

Additionally, soft contact lenses should be removed before using ketotifen. Ketotifen should not be used for irritation related to contact lenses. If you wear contact lenses, you should wait at least 10 minutes after using ketotifen before reinserting them.

References:

1)      Korin M. Can Omicron cause itchy eyes? Experts explain. Prevention. Jan 20, 2022. Accessed October 31, 2023. https://www.prevention.com/health/a38830511/omicron-itchy-eyes/

2)      Napoli PE, Mangoni L, Gentile P, Braghiroli M, Fossarello M. A Panel of Broad-Spectrum Antivirals in Topical Ophthalmic Medications from the Drug Repurposing Approach during and after the Coronavirus Disease 2019 Era. J Clin Med. 2020 Jul 30;9(8):2441. doi: 10.3390/jcm9082441

3)      Hafezi B, Chan L, Knapp JP, Karimi N, Alizadeh K, Mehrani Y, Bridle BW, Karimi K. Cytokine Storm Syndrome in SARS-CoV-2 Infections: A Functional Role of Mast Cells. Cells. 2021 Jul 12;10(7):1761. doi: 10.3390/cells10071761

4)      Ruggiero V, Aquino RP, Del Gaudio P, Campiglia P, Russo P. Post-COVID Syndrome: The Research Progress in the Treatment of Pulmonary sequelae after COVID-19 Infection. Pharmaceutics. 2022 May 26;14(6):1135. doi: 10.3390/pharmaceutics14061135