I had the sam issue with the pulmonologist. When I saw the ID doc, he reduced the dosages if Rifampin and Ethambutol based on my weight, but not Azithromycin. He explained that some antibiotic dosages are computed by patient weight, but others are by what is effective on the specific bacteria.
This was confirmed again recently by another ID doc when I complained about massive doses Keflex - he said the culture required that much to knock down the specific staph bacteria the culture from my toe infection.

I dont tolerate drugs well so started with 400mg. My doctor also wanted me to take 3 Ethambutol MWF but started low.
If you are toleraring it, continue. It may wipe out MAC. I can only hope for keepig it at bay but not cured. Very sad about all this.7

I am sorry that you are having such a difficult time with the meds. I, too, have a very sensitive system. I am 5’1” and 100 pounds and have been that weight as long as I can remember, although I had lost some before I began treatment. From the start of treatment, I began very potent probiotics in addition to eating yogurt or drinking kefir - always in the morning on an empty stomach, far from my nightly meds. I also take a scoop of bovine colostrum in water with the probiotics to keep my gut integrity. I have had zero problems, other than fatigue from the meds.

The guidelines state that the 18 month countdown begins with the first negative culture. For example, I was started on 500 mg Azithromycin and 1200 mg Ethambutol three times weekly. My bacterial counts were sky high when I started. They dropped quickly with the meds, but at the six month mark, culture still showed a few colonies. Then my doctor added the liposomal Arikayce for nebulizing. In one month, I was smear and culture negative. That is when the 18 month countdown began. I believe this is necessary in order to eradicate the bug. If meds are stopped too soon, there is a higher risk of occurrence.

Nobody enjoys these meds, but by faithfully taking them, doing good airway clearance and nebulizing twice daily, eating well and exercising, you compound the likelihood of long term clearance of the bug and prevent progression of lung damage. You really need to be eating high quality protein and healthy fats along with plenty of vegetables and fruits. This will build your strength and help you to battle this bug. If you are able to meet with a dietitian, you can get good advice for dietary guidelines and helps to tolerate the meds.

There are so many on this site to encourage you and to offer their experiences and suggestions, so you are not alone. Please reach out with questions, and you will get lots of support. Don’t let the fear of the meds discourage you from treatment because the lung damage from this bug is real. The sooner you adjust to the meds and have any needed adjustments made with your doctor, the sooner you are on the road to recovery.

It also helps to take the meds right before bed, so you sleep through side effects. I always nebulize and do airway clearance at night before my meds and then go right to bed. I think that this helps many people. The probiotics are really essential and very helpful. You can do this!!

It is, admittedly frightening and overwhelming initially, but once you get into the pattern, it becomes just another part of your day