Introduction
This article aims at giving an overview of the ivermectin controversy, including current practices of research, publishing and governmental policy formation, by presenting a timeline of relevant events, compiled from peer-reviewed academic journals indexed in PubMed, preprint servers such as medRxiv, chemRxiv, SSRN, Research Square and ResearchGate, international clinical trials registers, international newspapers and medical news service providers as well as websites. As there have been a lot of sparsely documented events internationally, the search has not been systematic, the timeline is unavoidably incomplete, and there may naturally be some personal bias with regard to what has been selected. Also, the main focus of the article is on the last quarter of the 2020s and the first quarter of 2021. Despite these limitations the timeline may serve as a template for more detailed inquiries.
Due to the large number of studies and limited space, each study is mentioned only briefly, without a possibility to analyze methodologies or results in depth. Statistically significant endpoints are reported, with nonsignificant endpoints mostly left out. For consistency, results are in most cases formatted as they appear in a meta-analysis by the Covid Analysis research group, possibly reformulated in comparison to the original sources (e.g. odds ratios converted to relative risk or methodological errors corrected) [1];[2];[3].
Ivermectin was invented in Japan in 1975 by Kitasato University professor emeritus Satoshi ¯ Omura, for which he won the 2015 Nobel Prize in physiology or medicine [4]. The drug has proven effective in eradicating parasitic infections and it is therefore best known as an antiparasitic agent, with several billion doses having been administered since 1981. The patent for the product was owned by Merck & Co/MSD. In most countries the patent expired in 1996. Currently, ivermectin preparations are available internationally from many sources, with the production cost of a single dose estimated to be less than 0.1 US dollars [5].
For prophylaxis of onchocerciasis (river blindness) and strongyloidiasis ivermectin is administered as a single oral yearly dose of 0.15-0.20 mg/kg [6];[7]. For lymphatic filariasis, a once-yearly dose of 0.3-0.4 mg/kg or bi-yearly dose of 0.15–0.2 mg/kg is administered [6]. For classic scabies, two doses of 0.2 mg/kg approximately one week apart are recommended, and for crusted scabies three to seven doses of 0.2 mg/kg depending on the infection severity [8];[9]. With regard to malaria, repurposing ivermectin as a complement to current malaria vector control tools is currently being investigated, with a proposed dosing regime of 0.4 mg/kg repeated three times during the malaria season, and another proposed dosing regime of 0.3 mg/kg on three consecutive days in combination with two other pharmaceuticals also repeated three times during the season [10].
With regard to its in vitro antiviral action, ivermectin has shown robust antiviral action towards a range of RNA and DNA viruses, including HIV-1, dengue, Zika and West Nile Virus, Venezuelan equine encephalitis virus, Chikungunya, pseudorabies virus, adenovirus, and SARS-CoV-2 (COVID-19) [11]. For dengue virus, a combined phase II/III patient randomized controlled trial (RCT) has been completed[12].
Another recent line of research has been an investigation into ivermectin’s efficacy in cancer. A study found out that ivermectin at a very low dose drastically reversed the resistance of the tumor cells to the chemotherapeutic drugs both in vitro and in vivo [13]. Ivermectin could thus be used in combination with chemotherapeutic agents to treat drug-resistant cancers.
With regard to the mechanism of action of ivermectin as an antiparasitic medication, Chung et al. describe that ivermectin interacts with vertebrate and invertebrate γ-aminobutyric acid (GABA) receptor and invertebrate glutamate-gated chloride channels, increasing chloride ion influx with subsequent paralysis and death in the target organism [14]. Ivermectin is effective in killing nematodes and arthropods with a single dose of 0.1-0.3 mg/kg but has has a very wide margin of safety in mammals because in mammals GABA-mediated nerves occur only in the central nervous system and ivermectin does not readily cross the blood-brain barrier [14].
With regard to safety of overdosing, in chickens and most dogs subcutaneous doses of approximately 5 mg/kg have been shown to cause mild symptoms and doses of approximately 15 mg/kg severe symptoms up to coma and death. In two described cases on humans, a 16-month-old child ingesting 6.7 to 8.72 mg/kg ivermectin resulted in frequent vomiting, somnolence, mild tachycardia, and hypotension, and a 61-year old woman became comatose three hours after ingesting 15.4 mg/kg agricultural ivermectin, requiring supportive intensive care but was discharged uneventfully on day 9 [14].
A double-blind, placebo-controlled dose escalation study with 68 healthy volunteers found no indication of central nervous system or general toxicity, or a difference in adverse effects between ivermectin and placebo groups for doses up to 2 mg/kg (ten times the highest FDA-approved dose of 0.2 mg/kg), in either single doses of 90 mg (1.0-1.5 mg/kg) or 120 mg (1.4-2.0 mg/kg), or in a repeated dosing regime with 30 mg (0.35-0.54 mg/kg) or 60 mg (0.71-1.1 mg/kg) on days 1, 4 and 7 (a total of three doses) [15]. Mean plasma concentrations were 2.6 times higher when administered with food.
The FDA-approved dosing for treatment of parasitic diseases is 0.2 mg/kg. The doses used in COVID-19 related clinical trials described in this article varied between 0.2-0.6 mg/kg. With regard to safety of ivermectin in general, a current World Health Organization (WHO) document on the treatment of onchocerciasis states that “ivermectin is safe and can be used on a wide scale” [16]. With regard to safety for children, a recent systematic review and and an individual patient data meta-analysis of ivermectin use in children weighing less than 15 kg concluded that existing limited data between January 1980 and October 2019 suggest that oral ivermectin in children weighing less than 15 kilograms is safe [17]. Overall a total of 1.4% (15/1,088) of children experienced 18 adverse events all of which were mild and self-limiting. No serious adverse events were reported.
With regard to safety of ivermectin during pregnancy, a document from 2004 published by the WHO titled “Mass treatment with ivermectin: an underutilized public health strategy” describes safety during pregnancy, noting that “a number of follow-up studies have found that inadvertent filariasis mass campaign use of ivermectin during pregnancy has not been associated with adverse pregnancy outcomes or negative effects on pregnant women or their offspring”, referring to a study by Gyapong et al. who concluded “there is no evidence of a higher risk of congenital malformation or abortions in those who are inadvertently exposed” [18];[19].
April 2020
On April 3, a Monash University of Australia in vitro ivermectin study by Caly et al. reported that ivermectin is an inhibitor of SARS-CoV-2 virus in vitro, that a single treatment effected approximately 5000-fold reduction in virus at 48 h in cell culture, and that ivermectin is FDA-approved for parasitic infections and included on the WHO model list of essential medicines, thus being widely available [20];[21];[22];[23].
On April 6, a French biotechnology company MedinCell which had been studying ivermectin for malaria announced an initiative to develop an injectable form of ivermectin for prophylaxis of COVID-19 [24];[25];[26].
On April 10, mentioning increased interest in ivermectin after the Australian in vitro study, US FDA issued a warning against using veterinary ivermectin as treatment for COVID-19 in humans, citing safety concerns [27]. It noted additional testing is needed to determine whether ivermectin might be safe or effective in COVID-19 in humans.
On April 13, two Florida, US pulmonologists Rajter and Cepelowicz-Rajter were said to be pioneering early treatments with ivermectin, reporting a nearly 100% response rate with early administration, adding that they were initiating clinical studies [28].
On April 13, a preprint by Patel et al. described an observational registry-based study from 169 hospitals claiming that a single dose of 0.15 mg/kg of ivermectin produced a significant mortality reduction (7.7% vs. 18.6%) in 1,970 patients requiring mechanical ventilation [29];[30].
On April 14, two medical doctors, Gustavo Elera Arévalo and Fernando Polanco Hinostroza in La Merced (Chanchamayo) in Peru, begun treating a COVID-19 outbreak in a prison with ivermectin, later also treating the local police [31].
... and hundreds more events to April 3 2021. Go to the source to read the full chronology.
Discussion
A central question in the communications was whether more studies were needed. In October 2020, when the FLCCC Alliance recommendation on ivermectin was published, the decision to recommend it was assumedly largely based on the perceived consistent positivity of the effects: “seeing a ‘signal’ in the data”. This method could also be called reliance on “clinical experience” or even “intuition”. Comparing five Covid Analysis group’s meta-analyses from November 26 (n=21), December 29 (n=28),January 26 (n=35), February 27 (n=42), and March 31 (n=49) [438], calculated improvements in clinical indicators, with probabilities of an equal or greater percentage of positive results from an ineffective treatment, were as follows: improvements in prophylaxis (pre-exposure/post-exposure or total) we-re 98%/87% (p=0.063/0.25), 91%/90% (p=0.0078/0.25), 90% (p=0.00098), 89% (p=0.00049), and 89%(p=0.00024), respectively. In early treatment, the improvements were 91% (p=0.13), 87% (p=0.016), 84%(p=0.00098), 83% (p=0.00012), and 80% (p=0.0000076). In late treatment, the improvements were 60%(p=0.00024), 48% (p=0.00012), 39% (p=0.000031), 51% (p=0.0000038), and 50% (p=0.00000095). All together, the improvements were 75% (p=0.00000048), 78% (p=0.0000000037), 74% (p=0.000000000029),75% (p=0.00000000000023), and 72% (p=0.000000000000002). It appears that in 2021 the variation in estimated efficacy due to addition of more studies to the meta-analysis was too small to be clinically meaningful. Therefore, more studies provided little additional clinically relevant information, and the argument against the treatment was solely based on the assumed unreliability of all the existing data.The panel which prepared the WHO guideline of March 30, 2021 included in its meta-analysis only five studies that directly compared ivermectin with standard of care and reported mortality [428]. The result indicated 64% reduction in mortality (RR 0.36, 95% CI 0.17-0.75, no p value given, n=915,very low certainty evidence). The meta-analysis of six studies by Hill et al. indicated 75% reduction in mortality (RR 0.25, CI 0.12-0.52, p=0.0002, n=1,255) [275]. The March 31, 2021 meta-analysis of eight randomized controlled trials by the Covid Analysis group indicated 70% reduction in mortality (RR 0.31,95% CI 0.16-0.61, n=1,729, p<0.00032) [437]. The meta-analysis of thirteen trials by Bryant et al. devised using Cochrane standards indicated 68% reduction in mortality (RR 0.32, 95% CI 0.14-0.72, n=1,892,low to moderate-certainty evidence) [387]. The FLCCC group’s meta-analysis of four observational and six randomized controlled trials indicated an overall 69% reduction in mortality (RR 0.31, n=3,508,p<0.0001) [168];[214].
In addition to presenting the new meta-analysis, the guideline presented data from the WHO living guideline [439]. The living guideline analysis indicated 70 deaths per 1,000 patients (7%) for standard of care, and 14 (1.4%) for ivermectin, respectively, i.e. an absolute difference of 56 patients (5.6%) with a 95% confidence interval of 64 to 44 fewer deaths, and a relative mortality reduction of 80%. The odds ratio for mortality was 0.19 (OR 0.19, 95% CI 0.09-0.36) based on 1,419 patients in seven studies. The certainty of evidence was estimated to be very low due to serious risk of bias and very serious imprecision.
This imprecision was explained as follows: “for mortality there were only 31 deaths across all 915 patients randomised - an extremely small number of events on which to base conclusions” (referring to five studies instead of seven), suggesting unsuitability of the chosen methodology for evaluation of medicines that might significantly reduce mortality, as conclusions could then not be made.
As a reference for the above data the guideline cited Siemieniuk et al. [440] which did not contain theabove results but instead presented a third set of mortality results, indicating a mortality of 130 per1000 patients (13%) for stardard of care. For a combination of doxycycline and ivermectin, the estimated reduction in deaths was 130 (95% CI 130-123). For ivermectin alone, the reduction was 103 (95% CI117-78). For proxalutamide, the values were 130 (95% CI 130-118), for colchicine 78 (95% CI 110-9), and significantly less for other included options.
These two additional sets of results indicated larger reductions in mortality (approximately 80%) than the meta-analysis. With regard to the earlier meta-analysis by Hill et al. [275], Siemieniuk et al. stated that “several of these trials could not be included in the analysis . . . ten trials that reported no outcomesof interest”, citing the Hill et al. meta-analysis among the trials reporting no outcomes of interest. Thenew meta-analysis was presented in Rochwerg et al. [441]. This article mentioned neither the meta-analysis by Hill et al. nor the mortality results of Siemieniuk et al. Rochwerg et al. also noted that “we currently lack persuasive evidence of a mechanism of action for ivermectin in covid-19; any observed clinical benefit would be unexplained”, possibly suggesting that not even an effective intervention could be utilized unless the mechanism of action was “explainable”.
Based on their meta-analyses the other groups (FLCCC, CovidAnalysis, BIRD) recommended treatment, the WHO panel did not, referring to “the strong likelihood that chance may be playing a role in the observed findings” [441]. None of the authors of the WHO-funded meta-analysis by Hill et al. were included in the panel. The low cost and wide availability of ivermectin did not, in the panel’s view, mandate the use of a drug with uncertain benefits and possible harms. Resource considerations, accessibility,feasibility and impact on health equity “did not alter the recommendation”. The panel worried about drug shortages in helminth control and elimination programmes [441];[428]. The panel listed the risk of severe adverse events leading to drug discontinuation as a reason for non-adoption, apparently suggesting that a pharmaceutical should not be adopted at all if a small subset of patients might stop using it. For some reason the panel “inferred that almost all well-informed patients would want to receive ivermectin only in the context of a randomized trial, given that the evidence left a very high degree of uncertainty . . . the panel anticipated little variation in values and preferences between patients when it came to this intervention”, giving an impression of dictating patients’ preferences without asking them or giving them a choice.
The panel “raised concerns about diverting attention and resources away from care likely to provide a benefit such as corticosteroids in patients with severe COVID-19 and other supportive care interventions”. Considering that in the majority of countries, no prophylaxis or early treatment method was officiallyavailable, that corticosteroids were to be avoided in prophylaxis and early treatment, and that the useof corticosteroids in late treatment practically necessitated use of ivermectin to prevent strongyloidiasis-related hyperinflammation, this rationale appeared particularly illogical. The panel did note, however,that “ivermectin may still be considered in strongyloidiasis endemic areas, at the discretion of clinicians overseeing treatment, albeit not for treatment of COVID-19 itself”.
Considering the attitudes towards ivermectin in the industrialized countries in general, one of the main obstacles for reception of the idea of repurposed medicines may have been the Surgisphere scandal and the widespread controversy regarding hydroxychloroquine in early 2020, leading to a generalized distrust of research among the politicians, governmental administrative personnel and the public, especially in the more developed countries which appeared to put more importance on the research. This distrust, in turn, possibly opened new avenues for various kinds of societal manipulation.
The distrust appeared to have also lead to, for example, social media and video streaming platforms actively but inconsistently and indiscriminately censoring many subjects and groups, including ivermectin research groups and their results, regardless of their level of academic merit. These practices often appeared similar to censorship practices in authoritarian countries. Mainstream media appeared to maintain an inverted understanding on the process of science in which scientific knowledge was apparently assumed to flow down from the NIH and WHO to the researchers, not the other way around. Financial newspapers (Wall Street Journal, Financial Times) may have possessed a more realistic view on medical research and ivermectin than generalist press conventionally considered high quality (e.g. The New York Times, Associated Press, The Guardian), with some practically accusing researchers of not adhering to the guidelines given by the NIH, for example. The open encyclopedia Wikipedia took pains to only mention negative studies about ivermectin, listing it among the COVID-19 misinformation, even citing a commentator saying that “the narrative of ivermectin as a ‘miracle cure’ for COVID-19 is a ‘metastasized’ version of a similar conspiracy theory around the drug hydroxychloroquine, in which unspecified powers are thought to be suppressing news of the drug’s effectiveness for their own malign purposes” [442];[443];[444].
As noted by Wall Street Journal quite early on in the ivermectin saga, the majority of the medical establishment appeared to require almost absolute certainty, resulting in “too much caution killing patients”, both health-wise and financially [183]. This approach seemed to only take into account quite theoretical health risks, disregarding not only the very probable societal harms of not taking any action but also the possible health benefits of taking an action under uncertainty. Thus, the process appeared largely a failure of a relatively simple risk-benefit analysis.
The more medically oriented arguments against the adoption of ivermectin were usually based on the hypothesis that the required (as indicated by the Caly et al. in vitro study [22]) plasma and lung tissue concentrations for an antiviral effect would likely not be achievable. Another argument was based on the host-directedness and the assumed toxicity of larger doses.
An additional disagreement concerned the use of placebo in clinical trials. This disagreement may havebeen at least partly related to a long-standing divide of the research community into active-control and placebo orthodox proponents [445]. Vagueness of the Helsinki Declaration of 2013 may easily lead into opposite interpretations of what should be done [446]. For example, the sentence to allow the use of placebo “where no proven intervention exists” left open who should decide what is a “proven intervention”, easily leading to a circular reasoning according to which a proven intervention cannot exist without a placebo-controlled randomized trial, thus the use of placebo must be allowed to prove the efficacy of the intervention. Similar vagueness plagues the whole section about placebo controls. The parties involved in the ivermectin trial controversies appeared unable to find any common ground with regard to this issue.During the period there appeared to be somewhat scarce interest in treatments research, with the wealthy societies’ focus on vaccinations and lockdowns, despite vaccinations being largely unavailable and lockdowns harmful for the economy. These countries appeared to pursue expensive, narrow-spectrum vaccination and new pharmaceuticals based strategies, ignoring cheaper options, whereas developing countries put more emphasis on affordable, broad-spectrum antivirals. One factor may have been the developing nations’ clinicians’ familiarity with ivermectin and its easy availability, whereas it has been a rarely prescribed medicine in most industrialized countries. In addition, prejudices and a bias against ideas originating outside of familiar organizations or one’s own country may have played a part in the industrialized countries ignoring ivermectin research carried out in the developing countries [447]. Cost-effectiveness of government funding for development of new medications and vaccines is an important issue. The US government invested USD 356 million in 60,000-100,000 doses of MK-7110, indicating aunit price between USD 5,933.00 and USD 3,560.00, with the initial results of efficacy indicating the same or slightly smaller efficacy as that of ivermectin. A 2015 article about mass treatment of onchocerciasisin Africa stated that Merck & Co/MSD had offered ivermectin at USD 1.51 per treatment, indicating a2300 to 3900-fold difference between the prices of ivermectin and MK-7110 [448];[222]. In this example,allocation of US government funding appeared inefficient with respect to investment in an experimental product with the unit costs in thousands of dollars, versus the option to use an existing medication with similar efficacy proven at least on a similar level of evidence and the unit costs in single digits.
There was a widespread disagreement on the fundamentals: which methods were appropriate as a basis for decision making, what counted as evidence, and what was ethical. In a broader view, the appropriateness and usefulness of the evidence based medicine paradigm as it was understood and applied during the period appeared questionable. US and European governmental bodies appeared to reject or ignore most of the ivermectin-related data, referring to insufficient evidence. In the US, the paradigm appeared inconsistently applied; more specifically, not applied to US Food and Drug Administration Emergency Use Authorization of remdesivir, whereas strictly applied to other medications including ivermectin. In addition, a strict requirement to compare a significantly more effective treatment to placebo may be considered unethical with regard to high mortality of patients in control groups. These indicate a clear need for a new methodology better than the current understanding and application of evidence-based medicine.
With regard to conflicts of interest, the US Food and Drug Administration (FDA) issued an EmergencyUse Authorization (EUA) for the use of remdesivir in patients with severe disease on May 1, even before the initial results of an ongoing trial were published and despite remdesivir being an investigational drug not approved for any indication. The 1,063-patient randomized controlled trial of remdesivir publishedon May 22 only indicated that remdesivir shortened the time to recovery (11 days vs 15 days, p<0.001)[449]. There wasn’t an obvious difference in mortality rates (8% vs. 11.6%, p=0.059) and the endpoints were changed mid-study which was deemed a questionable practice [450]. The final results were published on October 8. On August 28 the EUA was extended to “no longer require a severe disease”.
The adoption of corticosteroids as a consequence of the WHO-initiated 2,000-patient RECOVERY trial results was relatively swift. Also the emergency use authorization of remdesivir in the US was swift,based on initial and conflicting evidence. Twenty randomized clinical trial results on ivermectin’s efficacy for COVID-19 were available in February 2021. These trials were predominantly carried out outside the US and the EU, and did not lead to emergency use authorizations in the US or the EU. US FDA document “Emergency Use Authorization of Medical Products and Related Authorities – Gui-dance for Industry and Other Stakeholders” section “1. Criteria for Issuance” subsection “d. No Alternatives” states that “For FDA to issue an EUA, there must be no adequate, approved, and available alternative to the candidate product for diagnosing, preventing, or treating the disease or condition. A potential alternative product may be considered ‘unavailable’ if there are insufficient supplies of the approved alternative to fully meet the emergency need. A potential alternative product may be considered ‘inadequate’ if, for example, there are contraindicating data for special circumstances or populations (e.g., children, immunocompromised individuals, or individuals with a drug allergy), if a dosage form of an approved product is inappropriate for use in a special population (e.g., a tablet for individuals who cannot swallow pills), or if the agent is or may be resistant to approved and available alternative products” [451].
It may thus be derived that licensing of repurposed medicines such as ivermectin for outpatient treatment and prophylaxis of COVID-19 would have prevented emergency use authorizations of new pharmaceuticals in development. In the case of prophylaxis, such licensing might even have affected vaccines. Thus,there appeared to exist substantial financial conflicts of interest against licensing of repurposed medicines.
Considering the total net utility of a society it is unlikely that unilateral support to only the investments of the pharmaceutical industry could ever offset the harms to other industries and the population. The society thus has a strong incentive to abolish the financial incentive structures of the pharmaceutical industry and the government that led to the current situation, in order to prevent a similar outcome in the future.
Considering the estimated efficacy of ivermectin around 90% in prophylaxis and the option of an early outpatient treatment with an estimated efficacy around 75%, an early introduction of ivermectin might have prevented a large part of COVID-19 infections post first wave in many European Union countries and in the United States.
Administrative issues, inconsistent requirements of evidence related to the evidence-based medicine paradigm, and possibly conflicts of interest with patentable, commercial products in development prevented introduction of early outpatient ivermectin treatments in the last quarter of 2020 and the first quarter of 2021. This lack of response is likely to have caused unnecessary deaths and difficult-to-repair financial and health consequences in the affected societies.
The culture of medical litigation prevalent in the United States may have created patterns of behavior that have also spread to countries with less actual litigation, yet leading to mental paradigms favoring extreme caution and non-action, in turn leading to stagnation. One of the features of a paradigm is an inability of the involved people to transcend it or even see that it is just one possible paradigm out of many options, some of which may be more optimal in a given situation.
Conclusion
The period appeared conflicted, with researchers, clinicians, governmental agencies and commercial entities holding deeply conflicting views on fundamental issues, including which methods were considered appropriate as a basis for decision making, what could be considered as sufficient evidence, and what was ethical. In a broader historical perspective, the timeline of events depicts rather dysfunctional societies unable to properly communicate and organize themselves, leading to misallocation of resources and decisions that may have conflicted with elementary ethical considerations, with this behavior rationalized by claiming adherence to mental paradigms that may have poorly matched the situation. In summary, the pandemic response especially in the United States and the European union appeared severely lacking.Further research on the details of these processes is warranted.