@lvnl & @kathyjjb There are numerous protocols for treatment. Some use 2 drugs (often based on sensitivity testing), some adding Arikayce or another drug right away. The decision between 7-day and 3-day dosing may be made based on severity of the infection, or what strain of NTM is being treated.

The usual protocol for beginning antibiotic treatment for MAC has been 3 times weekly for many years. My personal observation is that some ID docs not working in conjunction with a MAC-knowledgeable pulmonologist are more likely prescribe daily meds. I'm not sure why this is the case, but sometimes when that person gets to an expert pulmonologist, the dosage is cut back to 3 times a week.

If you want to see the published protocol from 2020, look at the table on page 20 of this document:
https://ntminfo.org/wp-content/uploads/2020/07/NTMguidelines2020.pdf
New guidelines are coming, here is a preview that has not yet been published for the US:
https://www.atsjournals.org/doi/full/10.1513/AnnalsATS.202408-904FR
It says, in part, "For less severe noncavitary NB disease, a thrice-weekly regimen is often adopted for its effectiveness and better tolerability than daily treatment."