Ivermectin is a commonly used anti-parasitic in animals, and it’s also used in people for some parasitic diseases. Additionally, it’s still widely discussed in some internet circles for treatment or prevention of COVID-19. That’s based on some in vitro study, poor quality ‘clinical trials’ and mainly anecdotes.

It’s led to stories of people hoarding or using animal ivermectin products for their own use. I’ve had lots of questions from the general public and vets (and stories of people buying more heartworm meds for their dog  than they’d ever need).

Not a good idea.

Here are some reasons why.

  1. There no evidence that it works. An in vitro study showed inhibition of SARS-CoV-2, but at massive doses, beyond what would be used in people.
  2. Anecdotes aren’t data.
    • I don’t dismiss clinical observation. That’s the foundation to many important discoveries. However, I realize that a lot of things I have thought I observed or that worked didn’t pan out to be true.
    • Observations lead us to try take specific measures to figure out if something is real.
    • They help raise questions, not answer
  3. Other factors may be involved and those 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 and it’s common in some countries. People get infected and the parasite can lay dormant in the body. However, when they are immunosuppressed, it can re-activate.
    • Dexamethasone is a common and effective treatment for COVID-19, and is widely used for people with moderate to severe disease.  It reduces inflammation but at the same time can impact the immune system (since that’s what triggers inflammation).
    • Therefore, if someone has this parasite laying dormant in their body, dexamethasone treatment might facilitate re-activation, and that would complicate respiratory disease.
    • I don’t dismiss that potential, but that would mean that ivermectin might be effective in people with dormant stercoralis infection that are also receiving dexamethasone.
    • That’s a lot different than “ivermectin works and everyone, everywhere, should be on it.”
  4. Ivermectin isn’t a very commonly used drug in people but it is used.
    • Diversion of the relatively small production in humans towards unnecessary use compromises the care of people that really need it. (Yes, that isn’t associated with ‘don’t steal Fido’s stash’ but it’s still a point to raise.
  5. Your dog’s heartworm prevention ivermectin is a low dose treatment.
    • To get the levels used in vitro in this in vitro study, a person would require a dose of ~3500 ug/kg. Heartworm prevention in dogs is done at 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 chewables….a day.
  6. Ivermectin also comes in more concentration oral, injectable (don’t even think about it) and pour on (topical) forms that are much more concentration. However, while I have good confidence in mainstream vet pharmaceutical companies, I still don’t want people taking an animal product.

Ivermectin is one of many ‘miracle cures’ that we’ve seen pushed on the internet. Like most others, there’s limited substance. There’s no magic bullet for COVID-19. I’d love it if ivermectin was one. It’s a drug that we know how to use and how to produce. Production could be ramped up and it’s 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’ aspect.