just to be aware - rifabutin and rifampicin are 2 quite different drugs in the same family (Rifamycins )
doses, half lifes, contra-indications etc are different
antibiotic dosing by almost all LLMD's follows general antibiotic dosing guidelines for each drug
they are after all medically trained and registered doctors - so do not like to stray far from what is known
dosing info on all antibiotics can be found - here
https://www.drugs.com/mtm/rifabutin.htmlthere are also sites like Dr MR's
https://www.treatlyme.net/ which outlines the protocols he suggests
i hope its some help