A 6-month-old's brown eyes turned deep blue after COVID-19 treatment with favipiravir, an unusual occurrence doctors have observed before. Favipiravir, known for inhibiting RNA-based virus replication, causes mutations as it integrates with growing RNA molecules.
Unusual Side Effects of COVID-19 Treatment Favipiravir
China approved the use of the antiviral favipiravir to treat COVID-19 in early 2020 due to the RNA-based nature of SARS-CoV-2, the virus causing the disease. Following China's lead, countries like India, Japan, and Thailand also authorized the drug for treating mild to severe COVID-19, with Thailand specifically using it as the primary antiviral for infected children.
Typical side effects of favipiravir include diarrhea, decreased white blood cell counts, and elevated uric acid levels in the blood, which, if left untreated, can lead to nausea and painful kidney stone formation. However, the reports of unexpected blue eyes have raised questions.
The peculiar effect was initially documented in December 2021 when a 20-year-old man with brown eyes experienced a day of blue corneas after taking Favipiravir. Corneas are the transparent front eye tissues covering the iris, the colored part around the pupil.
Before this report, during the preceding summer, another group of doctors encountered a patient who used a UV light to demonstrate a fluorescent eye surface after taking favipiravir. Furthermore, a 2022 case study detailed the emergence of fluorescent specks in the white part of three individuals' eyes, along with appearances in their nails and some teeth, following the drug's administration.
Baby's Brown Eyes Turn Into Blue
The most recent case of this peculiar side effect is a six-month-old baby boy. In a report published in April in the journal Frontiers in Pediatrics, doctors noted that the boy in Thailand was initially admitted to the hospital due to fever and cough but later tested positive for COVID-19.
The doctors gave him favipiravir tablets and syrup as treatment. However, just 18 hours after the baby took the medication, his dark brown eyes turned to a blue hue in the sunlight. Medical examination showed a blue pigment buildup in both corneas.
The child continued favipiravir treatment for three days, during which his COVID-19 symptoms improved. Concerned about the unusual eye color change, the doctor discontinued the treatment. Remarkably, the boy's eyes returned to their normal color five days after the medication was halted.
Dr. Vik Sharma, an eye surgeon at the LondonOC clinic in the U.K., not involved in the case, explained that eye color is typically determined by the iris and its inherent pigment levels, not the cornea.
The bluish eye color change linked to favipiravir may be attributed to the drug's breakdown process, potentially releasing fluorescent compounds that accumulate in the cornea, says Dr. Vik Sharma. This theory is supported by previous observations of the drug causing fluorescence in human hair and nails.
While an eye examination conducted two weeks after the boy recovered from COVID-19 revealed no vision issues, the report acknowledges the uncertainty surrounding the potential long-term effects of the transient eye color change.
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