key: cord-1003812-egdmk8ke authors: Aslan Kayıran, Melek; Cebeci, Filiz; Erdemir, Vefa Aslı; Aksoy, Hasan; Akdeniz, Necmettin; Gürel, Mehmet Salih title: Fluorescence of nails and hair on Wood's lamp examination in Covid pandemic; undefined effect of Favipiravir in humans date: 2021-01-11 journal: Dermatol Ther DOI: 10.1111/dth.14740 sha: f53c94b7c6a30a3030c0d80fe63f07d9d0e0e6fd doc_id: 1003812 cord_uid: egdmk8ke nan Favipiravir selectively inhibits the RNA-dependent RNA polymerase by acting as a guanine analog. It transforms into active phosphoribosylated form in cells, causing chain termination, slowing viral RNA synthesis and lethal mutagenesis. 2 Despite the lack of doubleblind randomized controlled studies regarding its effects on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), favipiravir has been employed in patients in our country among with Russia, China and India. 3 It is prescribed to all patients with a positive Reverse Transcriptase Polymerase Chain Reaction (PCR) test. Favipiravir is effective on COVID-19 only at high doses. 4 Current treatment scheme consists of 1600 mg bid on the first day followed by 600 mg bid po reaching a total dose of 8000 mg in Turkey. Lungs, kidneys, spleen, and brain are main targets for Favipiravir. 5 No cutaneous side effect of favipiravir has been reported. 6 The main purpose of the Wood's lamp examination is to enhance the visibility of some substances by using their fluorescence properties. Fluorescence may occur due to certain substances like elastin, collagen, melanin precursors found naturally in the skin or external factors like drugs. Drug metabolites or excipients may accumulate in the skin and cause fluorescence. Yellow fluorescence is observed in both lunula and nails after oral tetracycline and yellow-green fluorescence on the nails is seen due to quinacrine hydrochloride. 7 (Figures 1-4) . This suggests that the fluorescence formation in the nails is due to favipiravir use. The fluorescence appearance seen in human hair and nails due to favipiravir use has not been reported. In fact, it is a mystery whether the fluorescent substance is mainly caused by the drug metabolites or by the ingredients such as titanium dioxide, yellow ferric oxide in the tablet. The drug's active phosphorylated metabolite was shown in human plasma and its concentration and fluorescence intensity had shown a linear relationship. 8 Systemically taken metals like titanium Considering that the substance accumulated in the tissues like hair and nails with a high dose of favipiravir, it may be necessary to be careful in accumulation in the other tissues. Since it is known that the drug distributes in the kidney, lungs, spleen and brain, and titanium dioxide in organs such as the liver and spleen more, caution should be taken in patients with comorbidities such as liver and kidney dysfunction. We would like to thank our patients, all of whom are health care workers. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. Melek Aslan Kayıran An effective drug against COVID-19: reality or dream? Expert Rev Respir Med. 2020;1-14 Favipiravir strikes the SARS-CoV-2 at its achilles heel, the RNA polymerase Favipiravir, an antiviral for COVID-19? Favipiravir at high doses has potent antiviral activity in SARS-CoV-2-infected hamsters, whereas hydroxychloroquine lacks activity Tissue distributions of antiviral drugs affect their capabilities of reducing viral loads in COVID-19 treatment Review of adverse cutaneous reactions of pharmacologic interventions for COVID-19: a guide for the dermatologist Yellow lunulae with fluorescence after tetracycline therapy Experimental design approach for development of spectrofluorimetric method for determination of favipiravir; a potential therapeutic agent against COVID-19 virus: application to spiked human plasma Titanium dioxide (rutile) particle uptake from the rat GI tract and translocation to systemic organs after oral administration Levels of heavy metals in human hair and nail samples from Maiduguri metropolis Melek Aslan Kayıran, MD, Istanbul Medeniyet University, Göztepe