Absence of ivermectin-associated excess deaths

Repurposing Ivermectin for COVID-19: Molecular Aspects and Therapeutic Possibilities

As of January 2021, SARS-CoV-2 has killed over 2 million individuals across the world. As such, there is an urgent need for vaccines and therapeutics to reduce the burden of COVID-19. Several vaccines, including mRNA, vector-based vaccines, and inactivated vaccines, have been approved for emergency use in various countries. However, the slow roll-out of vaccines and insufficient global supply remains a challenge to turn the tide of the pandemic. Moreover, vaccines are important tools for preventing the disease but therapeutic tools to treat patients are also needed. As such, since the beginning of the pandemic, repurposed FDA-approved drugs have been sought as potential therapeutic options for COVID-19 due to their known safety profiles and potential anti-viral effects. One of these drugs is ivermectin (IVM), an antiparasitic drug created in the 1970s. IVM later exerted antiviral activity against various viruses including SARS-CoV-2. In this review, we delineate the story of how this antiparasitic drug was eventually identified as a potential treatment option for COVID-19. We review SARS-CoV-2 lifecycle, the role of the nucleocapsid protein, the turning points in past research that provided initial 'hints' for IVM's antiviral activity and its molecular mechanism of action- and finally, we culminate with the current clinical findings.

Macrocyclic Lactone Endectocides

The macrocyclic lactone endectocides such as ivermectin, abamectin, selamectin and moxidectin have revolutionized the treatment of parasitic diseases in animals, being active against internal and external parasites. Ivermectin was introduced into veterinary medicine in the 1980s and since that time a number of related compounds have been introduced. In the treatment of internal parasites they complement the use of levamisole and the benzimidazoles, but in recent years they have found utility in treating external insect parasites. These agents show very low levels of toxicity under most circumstances. However, they are neurotoxic particularly in subpopulations of animals with mutations in the MDR1 gene. Toxicity may be also seen during off-label use, possibly because the doses used have been extrapolated from use in other animals. Regardless of these considerations, the macrocyclic lactone endectocides are extremely effective and safe drugs in the treatment of parasitic diseases of animals.

Reduction in acute filariasis morbidity during a mass drug administration trial to eliminate lymphatic filariasis in Papua New Guinea

BACKGROUND

Acute painful swelling of the extremities and scrotum are debilitating clinical manifestations of Wuchereria bancrofti infection. The ongoing global program to eliminate filariasis using mass drug administration is expected to decrease this and other forms of filarial morbidity in the future by preventing establishment of new infections as a consequence of eliminating transmission by the mosquito vector. We examined whether mass treatment with anti-filarial drugs has a more immediate health benefit by monitoring acute filariasis morbidity in Papua New Guinean communities that participated in a 5-year mass drug administration trial.

METHODOLOGY/PRINCIPAL FINDINGS

Weekly active surveillance for acute filariasis morbidity defined by painful swelling of the extremities, scrotum and breast was performed 1 year before and each year after 4 annual mass administrations of anti-filarial drugs (16,480 person-years of observation). Acute morbidity events lasted <3 weeks in 92% of affected individuals and primarily involved the leg (74-79% of all annual events). The incidence for all communities considered together decreased from 0.39 per person-year in the pre-treatment year to 0.31, 0.15, 0.19 and 0.20 after each of 4 annual treatments (p<0.0001). Residents of communities with high pre-treatment transmission intensities (224-742 infective bites/person/year) experienced a greater reduction in acute morbidity (0.62 episodes per person-year pre-treatment vs. 0.30 in the 4(th) post-treatment year) than residents of communities with moderate pre-treatment transmission intensities (24-167 infective bites/person/year; 0.28 episodes per person-year pre-treatment vs. 0.16 in the 4(th) post-treatment year).

CONCLUSIONS

Mass administration of anti-filarial drugs results in immediate health benefit by decreasing the incidence of acute attacks of leg and arm swelling in people with pre-existing infection. Reduction in acute filariasis morbidity parallels decreased transmission intensity, suggesting that continuing exposure to infective mosquitoes is involved in the pathogenesis of acute filariasis morbidity.

The Scourge of Sarcoptes: Oral Ivermectin for Scabies

OBJECTIVE

To review the use of the oral antiparasitic ivermectin in the treatment of scabies, with an emphasis on its use in the elderly and in long-term care settings.

DATA SOURCE

A MEDLINE/PUBMED search was conducted to identify pertinent studies, case reports, letters, and reviews in the English language. All articles published from 1980 to October 2003 were reviewed. Additional references were obtained from the bibliographies of these articles.

STUDY SELECTION

All studies evaluating ivermectin in the context of scabies mite infestation.

DATA SYNTHESIS

The semisynthetic macrocyclic lactone ivermectin has been available since the early 1980s as a broad-spectrum antiparasitic agent in animals and humans. This agent, which works by suppressing motor nerve conduction leading to parasite paralysis and death, was first used in ectoparasitic diseases (i.e., those caused by lice and mites) shortly after commercial introduction. A large body of literature, mainly uncontrolled case reports and series, has since evolved. However, these reports and results of the small number of placebo- and/or active-controlled studies have demonstrated the favorable response of both classic and crusted scabies to single- and multiple-dose oral ivermectin. Adverse reactions to the drug are uncommon, with the exception of a transient, new onset, or mild increase in existing pruritus soon after drug ingestion, which is thought to be a hypersensitivity reaction to dead mites and/or their products.

CONCLUSION

Oral ivermectin may prove to be a time- and labor-saving alternative to topical scabicide treatments, especially in the institutional setting where labor shortages make the management of scabies outbreaks a true challenge. However, the use of this agent does not change the need to decontaminate the environment (clothing, bedding, bed clothes, and, in selected cases, floors and walls) in order to truncate an outbreak and prevent reinfestation.

[Systemic adverse reactions with ivermectin treatment of scabies]

BACKGROUND

Scabies is a common parasitic infestation and is very difficult to eradicate from institutions. Ivermectin is used extensively thanks to its efficacy and ease of use through oral administration; it was approved for the treatment of scabies in humans in 2001 in France. Most of the adverse effects noted with this drug have been seen during treatment of onchocerciasis and other filarial disease, but they are rare in the treatment of scabies. We report side effects with ivermectin in two elderly patients with scabies.

CASES REPORT

A 72-year-old man was referred for scabies and was treated with benzyl benzoate (Ascabiol) and ivermectin (200 microg/kg) in a single dose. Two days later, the patient presented abdominal pain and nausea. Laboratory tests revealed cytolysis tests for other causes of hepatitis were negative. Within two weeks, liver function had returned to normal. Hepatitis due to ivermectin was diagnosed. An 86-year-old woman hospitalised for scabies was treated with benzyl benzoate and a single dose of ivermectin (200 microg/kg). She developed sinus tachycardia and asthma 3 days later. Screening for embolic, cardiac and infectious origins was found. Toxicity of ivermectin was suspected.

DISCUSSION

Since the introduction of ivermectin for the treatment of scabies, reports of adverse events are rare although this drug can cause cardiac dysfunction and liver disease in other indications. In our cases, the causal relationship with ivermectin is probable and care must be taken, particularly in the elderly, the population in which this drug is probably most widely prescribed.

Scabies

Scabies is a neglected parasitic disease that is a major public health problem in many resource-poor regions. It causes substantial morbidity from secondary infections and post-infective complications such as acute post-streptococcal glomerulonephritis. Disease control requires treatment of the affected individual and all people they have been in contact with, but is often hampered by inappropriate or delayed diagnosis, poor treatment compliance, and improper use of topical compounds such as permethrin, lindane, or benzyl benzoate. In addition to concerns over toxicity with such compounds, parasite resistance seems to be increasing. Oral ivermectin is an alternative that has been used successfully in community control programmes. Plant derivatives such as turmeric, neem, and tea tree oil are also promising future treatments. The disease is strongly associated with poverty and overcrowding, and the associated stigma can ostracise affected individuals. Treatment of scabies in poor countries needs to integrate drug treatment programmes with efforts to improve the socioeconomic conditions and education programmes to reduce stigma. We expect the future to bring more sensitive and specific clinical and laboratory-based diagnostic methods, as well as new therapeutic strategies.

Ivermectin: pharmacology and application in dermatology

Ivermectin is a synthetic derivative of the antiparasitic class of compounds known as avermectins. It is a macrolide endectocide with activity against both endoparasites with cutaneous tropism (Strongyloides stercoralis, Ancylostoma braziliense, Cochliomyia hominivorax, Dermatobia hominis, Filaria bancrofti, Wucheria malayi, Onchocerca volvulus, Loa-loa) and ectoparasites such as Sarcoptes scabies, Pediculus humanus, Demodex folliculorum, and Cheyletiella sp. Ivermectin is of great interest in the treatment of patients with different forms of scabies, head lice, demodecidosis, cutaneous larva migrans, cutaneous larva currens, myiasis, and filariasis.

Ivermectin

Ivermectin is a potent antiparasitic drug and the first commercially available member of a new class of drugs (macrocyclic lactones) that has been approved for human use. Ivermectin has already proven to be highly effective in the elimination of river blindness as a public health burden. Side effects have been minor, and patient acceptance is good. Promising results in off-label applications for ectoparasitic infestations are increasingly important as resistance to topical therapy becomes more prevalent Ivermectin represents an advance in the therapeutic armamentarium and should be considered in appropriate cases.

Ivermectin in scabies

The standard treatment for scabies has long been based on topical scabicides. Ivermectin, a broad-spectrum anti-parasitic agent, was first used in veterinary medicine. This drug, active against nematodes and arthropods, is used in humans for the treatment of filariasis. For the past few years worldwide reports on the use of ivermectin in human scabies have suggested that this drug could be an alternative oral therapy.

[New indications of ivermectin]

INTRODUCTION

Ivermectin is a semi-synthetic derivative of a family of macrocyclic lactones. This drug has a broad-spectrum anti-parasitic effect against various nematodes and ectoparasites. CURRENT KNOWLEDGE AND KEY-POINTS: Onchocerciasis and lymphatic filariasis are common indications. More recently ivermectin has been recommended in the treatment of strongyloidiasis and scabies.

FUTURE PROSPECTS AND PROJECTS

Promising results have been shown in the treatment of ascariasis, cutaneous larva migrans, loiasis and head lice.

Factors affecting adverse event reporting during mass ivermectin treatment for onchocerciasis

This study examines the effect of age, sex, dosing round, time of day, and distance from the nurse monitor on adverse event reporting during mass ivermectin administration at Achi, south-east Nigeria. There was a significant increase in adverse event reporting with age but no significant difference between the sexes. Both compliance and the incidence of reported adverse events were less during the second dosing round than during the first. Only three (2%) out of 144 subjects interviewed gave adverse events as a reason for non-compliance. Significantly fewer adverse events were reported as starting at night (22:00-06:00 h) than by day. The effect of distance on adverse event reporting was not statistically significant for distances up to 1 km.

Single-dose treatment of Wuchereria bancrofti infections with ivermectin and albendazole alone or in combination: evaluation of the potential for control at 12 months after treatment

The effect of single-dose ivermectin (150-200 micrograms/kg) and albendazole (400 mg) treatment alone and in combination on Wuchereria bancrofti microfilaraemia, antigenaemia and clinical manifestations was compared 12 months after treatment in a double-blind placebo-controlled field trial carried out in Ghana in 1996-98, to evaluate the potential of these treatments for control. Both ivermectin and combination treatments resulted in pronounced reductions in microfilaraemia among individuals who were microfilaria positive before treatment. Among individuals who were positive for circulating filarial antigen before treatment, antigen levels increased considerably over the 1-year period after treatment in the placebo group, whereas they decreased in the ivermectin and combination groups. However, the post-treatment difference reached statistical significance in neither microfilaraemia nor antigenaemia between the ivermectin and the combination groups. Albendazole treatment alone showed only a minor effect on microfilaraemia and antigenaemia. No effect of the treatments on the incidence of new cases of microfilaraemia or antigenaemia, or on clinical manifestations, was observed. Both ivermectin and combination treatment thus appeared effective for control of W. bancrofti infections, but the difference in efficacy between the 2 treatments after 12 months appeared to be minimal.

Ivermectin alone or in combination with benzyl benzoate in the treatment of human immunodeficiency virus-associated scabies

In order to establish a safe and reliable treatment for human immunodeficiency virus (HIV)-associated scabies, we have treated 60 episodes of scabies in this setting, occurring in 39 patients, with one of the following regimens: (i) topical treatment with benzyl benzoate solution; (ii) single-dose oral treatment with ivermectin alone; and (iii) combination therapy with benzyl benzoate solution and oral ivermectin, employing the same regimens as single-agent therapy. Patients were stratified according to the severity score of the disease and the outcome (eradication, relapse, failure). We found that both benzyl benzoate and ivermectin alone were quite effective in mild to moderate scabies, but they were both associated with an unacceptable rate of relapse and failure in severe or crusted scabies. In contrast, combined treatment produced an optimal rate of success, without significant treatment-related side-effects. Therefore, we consider that combination treatment with benzyl benzoate solution and oral ivermectin is preferable to single-agent therapy in crusted scabies occurring in HIV/acquired immune deficiency syndrome patients.