In reply to your inquiry regarding the need to possibly double the dose of Ivermectin for a Strongyloides infection - I know of several doctors who are using double to quadruple the dose of oral ivermectin for several reasons.
For many, they are seeing that more patients are not absorbing therapeutic doses for various reasons. The main reason involves a parasitic and/or pathogenic infection(s) in the stomach and/or intestinal tract which impedes absorption of nutrients and drugs.
This topic has even been discussed at several veterinarian conferences when many of the vets noticed ivermectin was not working in many animals. At first, they thought the drugs were not working. Though, upon testing, they discovered after oral ivermectin administration therapeutic drug levels were not appearing in the blood in about half of the tested groups.
I have read i several medical journals where they have administered ivermectin parenterally because the patients were not showing therapeutic levels in their blood after oral administration. They believed it was due to the fact that strongyloides burrows into the stomach and lining of the intestines which significantly impedes absorption, especially if the infection has been present for quite a while. Other co-infections ( parasite or pathogen) can also do this.
In these cases they gave ivermectin IM, subcutaneously or by IV.
Parenteral administration routes include: subcutaneous (SC, SQ), transdermally, IV, or intramuscularly (IM).
In a couple cases the patients were diagnosed with severe strongyloides infection and they cleared up after receiving ivermectin intravenously or IM, taking daily doses for 1 week and then repeating this regimen 1-2 weeks later.
Another reason involves the fact that many people are showing severe acidosis due to multiple parasitic and pathogenic infections all of which create a lot of acid byproduct. In addition, the drugs create an acidic byproduct. So, it is important to ensure the urine pH is 7.0 - 7.2, 7.4 if possible. Most drugs are absorbed better and are more effective in the human body at this pH range. Many enzyme systems in the body operate in a very narrow pH range.
My physician gave me a regimen in which I was taking 12 mg of ivermectin, four times a day, on an empty stomach, for 14 days. I had to repeat my entire regimen a week or two later.
Also, they are using Ivermectin for other medical conditions and have found higher doses are needed.