Ivermectin, on the WHO’s List of Essential Medications, has been in clinical use since 1981 as an orally and topically active agent for treating a range of parasitic infections in humans, including river blindness and lymphatic filariasis. It is also widely used in veterinary practice.
Anecdotally, the use of the standard clinical dose of ivermectin, 9 mg once, has been associated with some cases of rapid clinical resolution in severe hospitalised COVID-19; clinical studies evaluating its utility in this regard are underway. Ivermectin is reported to inhibit the proliferation of SARS-CoV-2 in vitro, but the IC50 for this effect, 2 µM, has been noted to be 35-fold higher than the maximal concentration achieved after the administration of the approved clinical dose (9 mg) to humans, casting doubt on the utility of this agent as an antiviral drug in COVID-19 unless very markedly higher doses are used.1 2 However, drugs blocking viral replication would be expected to be of lesser utility in the context of the late, cytokine storm-associated phase of COVID-19 and anecdotes of ivermectin’s success in this disorder pertain to that phase. Hence, consideration should be given to the possibility that ivermectin is acting as an anti-inflammatory in these cases. This prompted us to search the research literature on ivermectin for anti-inflammatory actions.