Hi Qowpel, & welcome. No worries about dumb questions here. We're all living and learning all the time.
Regarding the persistence of IVM in tissues, I was surprised to learn this just the other day.
https://www.annualre...5.100191.002305
Apparently, for onchocerciasis a single dose once a year is all it takes.
"The investigators concluded that a dosage of 150 u/kg, given yearly, represented the best regimen in terms of efficacy and safety."
Don't know what the long term implications are, but IVM has been around for several decades, with over a billion doses given for parasitic disease in Africa. I'd think if there were issues with longevity, someone would have noticed.
MERCK's monograph on Stromectol (their brand name for ivermectin)...
https://www.merck.ca...MECTOL-PM_E.pdf
...doesn't have any ominous indicators I can find. Keep in mind, many of the side effects mentioned occur due to the parasitic die-off, and in these cases the drug itself is not what is causing the symptoms.
Personally, I feel the risk/reward ratio favors going with the IVM prophylaxis. I'm 64 and in good health. At my age, I no longer fear death like I once did, but chronic illness is now on the front burner for me. I really don't want to have to deal with pulmonary fibrosis or cardiomyopathy the last 10-20 years of my life. The brain fog is also a major concern, if this turns out to be chronic in some patients.
Can't advise others on this decision, but it's a no-brainer for me. I've been on IVM prophylaxis since November, without issues. Getting out from under the coronavirus black cloud has changed my entire outlook on life.
Best of Luck, & hope to see you posting again soon.