Favipiravir therapy for Covid-19 infection and tacrolimus toxicity in a kidney transplant patient on chronic eculizumab therapy.

Although the latest data show that complement activation has an essential role in the pathogenesis and severity of Covid-19, the data on the prognosis of patients using complement inhibitors during Covid-19 infection are scarce. There is no specific treatment for Covid-19 yet. The introduction of novel agents such as favipiravir may affect metabolism of immunosuppressive drugs. We report the clinical course of Covid-19 in a kidney transplant patient with atypical haemolytic uraemic syndrome on chronic eculizumab therapy. The patient had mild Covid-19 but had severe tacrolimus toxicity, which may be associated with favipiravir and eculizumab. The mild course of Covid-19 in our patient is encouraging for eculizumab use; on the other hand, unusually high levels of tacrolimus that we observed underlines the importance of frequent drug level monitoring in transplanted patients who are receiving new drugs.