by saying "you are not a horse" in a tweet to draw attention to the issue. subsequent research failed to confirm the utility of ivermectin for covid-19, and in 2021 it emerged that many of the studies demonstrating benefit were faulty, misleading, or fraudulent. nevertheless, misinformation about ivermectin continued to be propagated on social media and the drug remained a cause célèbre for anti-vaccinationists and conspiracy theorists. economics the initial price proposed by merck in 1987 was us$6 per treatment, which was unaffordable for patients who most needed ivermectin. the company donated hundreds of millions of courses of treatments since 1988 in more than 30 countries. between 1995 and 2010, using donated ivermectin to prevent river blindness, the program is estimated to have prevented seven million years of disability at a cost of us$257 million. ivermectin is considered an inexpensive drug. as of 2019, ivermectin tablets (stromectol) in the united states were the least expensive treatment option for lice in children at approximately us$9.30, while sklice, an ivermectin lotion, cost around us$300 for 120 ml (4 us fl oz). as of 2019, the cost effectiveness of treating scabies and lice with ivermectin has not been studied. brand names it is sold under the brand names heartgard, sklice and stromectol in the united states, ivomec worldwide by merial animal health, mectizan in canada by merck, iver-dt in nepal by alive pharmaceutical and ivexterm in mexico by valeant pharmaceuticals international. in southeast asian countries, it is marketed by delta pharma ltd. under the trade name scabo 6. the formulation for rosacea treatment is sold under the brand name soolantra. while in development, it was assigned the code mk-933 by merck. research parasitic disease ivermectin has been researched in laboratory animals, as a potential treatment for trichinosis. tropical diseases as of 2016 ivermectin was studied as a potential antiviral agent against chikungunya and yellow fever. in chikungunya, ivermectin showed a wide in vitro safety margin as an antiviral. ivermectin is also of interest in the prevention of malaria, as it is toxic to both the malaria plasmodium itself and the mosquitos that carry it. a direct effect on malaria parasites could not be shown in an experimental infection of volunteers with plasmodium falciparum. use of ivermectin at higher doses necessary to control malaria is probably safe, though large clinical trials have not yet been done to definitively establish the efficacy or safety of ivermectin for prophylaxis or treatment of malaria. mass drug administration of a population with ivermectin to treat and prevent nematode infestation is effective for eliminating malaria-bearing mosquitos and thereby reducing infection with residual malaria parasites. one alternative to ivermectin is moxidectin, which has been approved by the food and drug administration for use in people with river blindness. moxidectin has a longer half-life than ivermectin and may eventually supplant ivermectin as it is a more potent microfilaricide, but there is a need for additional clinical trials, with long-term follow-up, to assess whether moxidectin is safe and effective for treatment of nematode infection in children and women of childbearing potential. there is tentative evidence that ivermectin kills bedbugs, as part of integrated pest management for bedbug infestations. however, such use may require a prolonged course of treatment which is of unclear safety. nafld in 2013, ivermectin was demonstrated as a novel ligand of the farnesoid x receptor, a therapeutic target for nonalcoholic fatty liver disease. covid-19 further information: ivermectin during the covid-19 pandemic § research during the covid-19 pandemic, ivermectin was researched for possible utility in preventing and treating covid-19, but no good evidence of benefit was found. veterinary use ivermectin is routinely used to control parasitic worms in the gastrointestinal tract of ruminant animals. these parasites normally enter the animal when it is grazing, pass the bowel, and set and mature in the intestines, after which they produce eggs that leave the animal via its droppings and can infest new pastures. ivermectin is only effective in killing some of these parasites, this is because of an increase in anthelmintic resistance. this resistance has arisen from the persistent use of the same anthelmintic drugs for the past 40 years. in dogs, ivermectin is routinely used as prophylaxis against heartworm. dogs with defects in the p-glycoprotein gene (mdr1), often collie-like herding dogs, can be severely poisoned by ivermectin. the mnemonic "white feet, don't treat" refers to scotch collies that are vulnerable to ivermectin. some other dog breeds (especially the rough collie, the smooth collie, the shetland sheepdog, and the australian shepherd), also have a high incidence of mutation within the mdr1 gene (coding for p-glycoprotein) and are sensitive to the toxic effects of ivermectin. clinical evidence suggests kittens are susceptible to ivermectin toxicity. a 0.01% ivermectin topical preparation for treating ear mites in cats is available. ivermectin is sometimes used as an acaricide in reptiles, both by injection and as a diluted spray. while this works well in some cases, care must be taken, as several species of reptiles are very sensitive to ivermectin. use in turtles is particularly contraindicated. a characteristic of the antinematodal action of ivermectin is its potency: for instance, to combat dirofilaria immitis in dogs, ivermectin is effective at 0.001 milligram per kilogram of body weight when administered orally. for dogs, the insecticide spinosad may have the effect of increasing the toxicity of ivermectin. notes this recommendation is not universal. the world health organization recommends ascariasis be treated with mebendazole or pyrantel pamoate, while the textbook parasitic diseases recommends albendazole or mebendazole. a 2020 cochrane review concluded that the three drugs are equally safe and effective for treating ascariasis. new drug application identifier: 50-742/s-022