Ivermectin is a commonly used anti-parasitic in animals, and it’s also used in people to treat some parasitic diseases. Additionally, it’s still widely discussed in some internet circles for treatment or prevention of COVID-19. That’s based on mainly anecdotes, some in vitro study, and very poor quality “clinical trials”.
It’s led to stories of people using or even hoarding veterinary ivermectin products. I’ve had lots of questions from the general public and veterinarians as a result (including stories of people buying more heartworm meds for their dog than they’d ever need).
Bad idea. Here are some reasons why:
- There no evidence that it works. An in vitro study showed ivermectin inhibited SARS-CoV-2, but only at massive doses, well beyond what would be safe for use in people.
- Anecdotes aren’t data.
- I don’t dismiss clinical observation, as it is the starting point of many important discoveries. However, a lot of things I have thought I observed or initially appeared to “work” didn’t pan out to be true over time.
- Observations should lead us to take specific steps to figure out if something is real. They help raise questions, not answer them.
- Other factors may be involved that make the drug appear effective in some siutations, but those factors don’t apply broadly.
- One potential reason ivermectin may seem to work in some areas is because it’s an anti-parasitic. Strongyloides stercoralis is a human respiratory parasite that is common in some countries. People get infected and the parasite can lay dormant in the body, but when they are immunosuppressed, it can be re-activated.
- Dexamethasone is a common and effective treatment in people with moderate to severe signs of COVID-19. It reduces inflammation, but also impacts the function of the immune system (since that’s what triggers inflammation).
- If someone is infected with dormant Strongyloides stercoralis, dexamethasone treatment for COVID-19 might lead to re-activation of the parasite, and that would complicate respiratory disease.
- I don’t dismiss that potential, but it would mean that ivermectin might be effective in people with dormant Strongyloides stercoralis infection that are also receiving dexamethasone.
- That’s a lot different than “ivermectin works against SARS-CoV-2 and everyone, everywhere, who is infected should be on it.” They should not.
- Ivermectin isn’t a very commonly used drug in people, but it is important for treatment of certain parasitic infections.
- Diversion of the relatively small amount of human ivermectin products towards unnecessary use compromises the care of people that really need it. (I realize that isn’t associated with “don’t steal Fido’s stash” but it’s still an important point.)
- Your dog’s heartworm preventative is a low dose treatment.
- To get the levels used in the aforementioned in vitro study, a person would require a dose of about 3500 ug/kg. Heartworm prevention in dogs is dosed at about 6 ug/kg.
- So, my dog Merlin gets one 272 ug chewable a month. To get 3500 ug/kg, I’d need 965 tablets per dose. If I had a small dog, I’d need even more of his supply.
- If I wanted to self-treat for Strongyloides stercoralis (not sure why I would, but let’s pretend), I’d need 52 of my dog’s chewables – per day.
- Ivermectin also comes in more concentrated oral, injectable (don’t even think about it) and pour-on (topical) forms. While I have good confidence in mainstream veterinary pharmaceutical companies, I still don’t want people taking a product that is only intended for (studied in and approved for) use in animals.
Ivermectin is one of many so-called “miracle cures” that we’ve seen pushed on the internet. Like most others, there’s limited substance to the stories behind it. There’s no magic bullet for COVID-19. I’d love it if ivermectin was one, as it’s a drug we know how to use and how to produce. Production could be ramped up and it’s relatively cheap. While conspiracy theories abound, no one has come up with any plausible explanation why an effective drug would be suppressed. Dexamethasone is cheap, widely used and widely produced, and it’s standard of care for some patients. That’s because it works. Ivermectin fits all of those except the “works for COVID-19” which is the most important one.