Evaluation of the frequency and intensity of favipiravir‐associated yellow‐green fluorescence in lunulae, hair, and face

Background We detected yellow‐green fluorescence in the face, hair and lunulae of patients using favipiravir. Aim We evaluated the frequency and intensity of favipiravir‐associated fluorescence. Patients/Methods. The participants comprised patients who had taken at least a single dose of favipiravir and been examined no later than 30 days after the last dose. The gender, age, body mass index (BMI), Fitzpatrick's skin‐type, hair color, N‐acetylcysteine use, presence and the intensity of fluorescent reflection under Wood's light in the lunulae of the fingernails, hair, and the face were recorded. Results There were 275 patients, 144 (52.4%) of whom were women. 165 (57.9%) had used treatment for a maximum of 5 days, 99 (34.7%) for 6–10 days, and 21 (7.4%) for more than ten days. Using more than 22 tablets of favipiravir increased the probability of detecting fluorescence in the lunulae by 6.72 (2.61–17.23) times. Using more than 28 tablets increased the risk of fluorescence in hair and the T‐zone by 5.92 (2.43–14.71) and 2.88 (1.11–7.47) times, respectively. No relationship was found between the fluorescence intensity in any localization and the total dose. However, we determined a negative correlation between the elapsed time after the last dose and the fluorescence intensity in the lunulae and the T‐zone (p=0.036; p=0.031; respectively). It was noted that BMI negatively correlated with the fluorescence intensity in the lunulae (p=0.001). Skin type was related to intensity for all localizations (p