For a few weeks, it looked like the number of cases of COVID-19 infection started to decrease around the world. Unfortunately, with new SARS-CoV-2 virus strains, the number of related infections and deaths started to grow again [1]. Vaccines are being distributed, but many people are still waiting for their turn. In the European Union alone (estimated population of 447 million people), only around 60 million doses were administered. This means that around 93% of the EU’s population is awaiting their vaccination against COVID-19 [2]. Therefore, complementary ways to fight the disease are still being investigated. One of the proposed treatments and/or prophylactics that recently received a lot of media and social media coverage is ivermectin [3].

In this article, we would like to explain what ivermectin is and what is known about its effect on the COVID-19 infection.

Ivermectin was originally discovered and described in the 1970s as a very potent anti-parasitic drug. It was shown to be effective on a wide variety of parasitic nematodes when treating domestic animals [4, 5]. Primarily, it was used in veterinary, but eventually it was also presented to be effective in humans [6]. Ivermectin was even proposed to be used to fight malaria, as research showed that it could be used to control the population of disease-spreading mosquitoes [7, 8]. Giving its wide spectrum of use, it was a promising candidate drug against the SARS-CoV-2 virus.

Indeed, early in vitro studies indicated that ivermectin can inhibit replication of the SARS-CoV-2 virus [9]. While on its own this is good news, there seemed to be a dosing problem. To achieve a similar amount of the drug in the human body as in the in vitro scenario, the dose would have to be 10 times higher than the highest dose tested in humans so far, and up to 100 times higher than what is commonly approved for use [9-11]. Nevertheless, in vitro studies do not necessarily predict the outcome in an in vivo context. Therefore, to assess the possible efficacy of ivermectin against COVID-19 in vivo, several clinical trials were initiated. Some of these trials showed shorter time required to clear the virus or lower mortality rates [12, 13]. However, other trials showed no benefits of using ivermectin during the COVID-19 therapy [14, 15]. Unfortunately, all of the aforementioned studies had a number of limitations, such as small sample size, patients receiving additional medications, or insufficient documentation about patients’ conditions prior to the treatment, and outcome post medication, just to mention a few.

The heterogeneity of these results and the circumstances around them prohibit any definitive answer at the moment. Indeed, organizations responsible for drug approval in the USA and EU advise against using ivermectin as a cure for COVID-19 outside of clinical trials, until reliable evidence for its efficacy is available [16, 17].

In conclusion, more clinical trials with a higher number of participants are needed to clearly state if ivermectin is truly an effective drug against COVID-19. In the meantime, it is important to only use properly tested medications approved for the purpose.