Does Oral Isotretinoin Increase the Risk of Developing Infection With and Complications From Covid-19, Compared to an Age-matched Background Population

Isotretinoin is a drug used commonly in dermatology, usually for management of acne and occasionally for management of other dermatological diseases. The most common side effect of oral isotretinoin is mucocutaneous dryness, which can lead to nasal dryness and crusting. Isotretinoin is derived from vitamin A and produces this side effect by arresting the cell cycle of mucus secreting cells in the nasal cavity. The mucus usually secreted moisturises the nasal cavity and provides a protective, lubricating layer overlying the cilia.

Cilia and nasal mucous are both believed to have roles in defence against infection and immunity. Hence it was postulated at the start of the pandemic that the effect this medication has on the nasal environment may increase the likelihood of contracting a disease spread by droplet or aerosol particles, such as Covid-19.

In March 2020 the investigators established a departmental database of our patients on oral retinoid medications in order to track those currently receiving treatment. The database includes people taking isotretinoin, alitretinoin and acitretin. The greatest number of patients in this database are in the isotretinoin group and patients taking isotretinoin tend to be a relatively young and fit population. Acitretin on the other hand is often used in an older population who may have other underlying disease comorbidities. There were only a very small number of patients taking alitretinoin in the database.

In order to limit confounding variables and provide as clear a result as possible, it was decided to limit this study to comparing the group of patients taking isotretinoin, aged 16-40years, and compare their rates per 100000 of infection and deterioration with the age-matched local population from NHS Grampian & Moray catchment.

This study would examine the electronic patient record of patients aged 16-40years, taking isotretinoin between March and October 2020 and compare their rates of Covid-19 infection, hospitalisation and complications with the rates of the local age-matched background population. In initial protocols, prior to data being obtained, persons taking isotretinoin in the time period were to be excluded from the background population - unfortunately on obtaining the data, which could only be achieved after this protocol was originally written, it was not possible to exclude those taking isotretinoin, therefore the isotretinoin population's rates were to be compared against the age-matched local population as a whole.