Ivermectin and COVID-19 – A new use for an old and trusted drug?
THE COVID-19 pandemic has brought to the fore a drug that has been a core animal health medication for decades – ivermectin – a drug that is truly a multi-species medication. Jamaican vets and animal owners know some of its brand names well – Ivomec® and Ivocip®.
Ivermectin came into use in the late 1970s to the early ‘80s in the veterinary profession as an anthelminthic – a drug used to treat worm parasites. It belongs to a class of drug called macrocyclic lactones and is produced by a type fungus called Streptomyces avermitilis.
It could also kill external parasites, such as ticks, fleas, lice, flies and mange mites. It was, therefore, our very first ‘endectocide’ – able to eliminate both internal and external parasites, although it had no effect on tapeworms or flukes.
It had a wide safety margin in most animals, needing a very large overdose before any toxic effects occurred. The main exception was in certain breeds of dogs (Border collies) in which the drug could penetrate into the brain and do to the dog what it did to the parasites. Also, dogs that were heartworm-positive ran the risk of a shock reaction and death if they had large numbers of ‘baby’ heartworms, called microfilaria, circulating in their blood.
Its use became widespread as an injection for cattle and pigs, a drench for sheep and goats, an oral paste for horses, and tablets for heartworm prevention in dogs. Other related drugs soon emerged. Doramectin injection for cattle gave up to three weeks of protection from reinfestation. Eprinomectin was used in a pour-on applied to and absorbed through the skin for cattle. Selamectin was used in spot-on skin application for fleas and ticks in dogs. Moxidectin was used as an oral dewormer for sheep and goats. Milbemycin oxime was used for heartworm prevention in dogs.
It was only natural that human use followed. Ivermectin, in tablet form, was initially used in the treatment of the river blindness caused by a worm common in parts of Africa. This was soon extended to other parasites, such as scabies mites and screw-worm maggots. It proved to be safe and highly effective. Its main risk was to people in parts of Africa infested by another type of worm that produced microfilaria in the blood, who reacted similarly to dogs with heartworm.
With time, it was also found that ivermectin had antiviral capabilities. Researchers have been investigating its use against the Zika, chikungunya, and yellow fever viruses as well as HIV, but when it was tested against SARS-CoV-2, the cause of COVID-19, it was found to eliminate the virus within 48 hours in the laboratory. Since then, several controlled clinical trials and non-trial treatments have shown good results in both treating and preventing COVID-19 in people with the same dosage used for parasites. Several meta-analyses (studies evaluating various study results) have concluded that its use is extremely beneficial. Nevertheless, despite many medical proponents and successful outcomes, it still has not yet been officially sanctioned for COVID-19 treatment.