I took mepron/zith for several months (along with artemesia) and found that I hit a plateau..the artemesia combo worked for awhile but then I stopped taking art due to some blood tests. My LLMD wanted to continue with mepron/zith but by the 5 mos, I decided to go elsewhere. With a new LLMD and new treatment of mainly herbs, I am actually seeing lots of improvement regarding the babesia. So it may work for some and others not....I also have/had some other issues that may have blocked treatment. So each person I think has individual different reactions to such. your husband just has to find the right treatment for him.
Babesia target the RBCs so the treatment needs to go through the complete cycle of creating all new RBCs in the body and this may take at least 4 mos or more hence the longer treatment. If the treatment is cut short, there may be some babesia parasites not treated and can replicate and then relapse may occur. This is one tough disease.
I do know some folks pulse but you want to be sure to discuss this with his LLMD. What is most important is that he support his liver, spleen and kidneys through this treatment. Milk thistle, dandelion and other herbs help with this. When the meds target the parasite in the RBC the blood fragments are difficult to filter through the spleen and liver and detox. So support these three organs is so important.