Azythro was tested for CFS in a 2006 trial with some benefits on 58% of patients (although no one was totally cured with a 6 weeks pulse treatment) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1562448/ I was not aware of this when I started to take Aythromycin 500mg/day for a bad bronchitis. I was not even aware that I may be ill with CFS.... I was still thinking my problem was rheumatologic, because it was very similar to Ankylosing Spondylarthritis or Spondylarthropathy for 15 years (had other symptoms for more than 30 years)...But my doctors were thinking another way: I didn't have the serologic/auto-antibodies profile expected in these kind of disease, and no radiographic evidence of it. So I was half dead with pain and fatigue in december, and that bronchitis was the ice on the cake when I started to take that drug to fight it. After 10 days, my joints/back pains were totally gone (I would say they were gone from day 1!), then I stopped azythro, and the pains were back 10 days later. I then looked which bacteria could have been targeted by this antibiotic, and found many could be involved, from Lyme (negative for me) to Chlamydia, Mycoplasma, Yersinia (all positive for me), and many others! I decided that I would follow the kind of protocol used for these intracellular bacteria, and kept the treatment for 4 months. I was taking tablets with food, and was doing welll, but soon I started to suffer from muscle pains (burning) and fasciculations/contractions, increased tiredness, and so had to stop. Then I had the feeling I had find a key to my disease but that I didn't know enough about it to use it properly. I had to know more, and to investigate more. At this time I started to investigate my blood lactates and to visit the phoenixrising forum that is a wonderful place for those who need to understand what is hapening and to find all the keys to escape from the trap we are in. I discover that my blood lactates were high after a meal, because I was suffering from abdominal postprandial vascular compression (thank you so much @kangaSue ) Then my joints pains came back again two days ago, after one and a half month after I stopped Azythro... So I decided to start it again, 250 mg with a meal two times a day (12h00 and 18h30) ...All the side effects were immediatly back again, muscle pains and increased fatigue/brain fog... But this time, I explored my blood lactates, and this told me that Azithro makes it to raise (with a pick one hour after), and that because of my post-prandial hyperlactatemia, it was a very big mistake to take the tablet with a meal (in my case). Today I took azythro with only a glass of water at 14h00 and 20h00, and wait 2 hours after taking it that my lactates lower again before I could eat anything. To be sure that I will not suffer from my post prandial compression, I ate only hydrolyzed amino-acid mixed with other nutritives powders and water during the whole day. It worked! no muscle pain, no fatigue, I was ok during my whole day, and it was a hard day at work for me, so I am really happy !! My lactates went to a pick of 3.6 mmmol/l at 15h00, and were beyond 2 mmol/l all the day, but I had no more than half an hour of brain fog, and little discomfort. Okay it's only a good day in a long time, but I wanted to share this victory with you, I wish many good days will follow, for me and for all the members as well.