Bactrim is given as a prophylactic antibiotic to prevent serious lung infections. Please share your experience with this drug, concerning its side effects and the fact that it can do much damage to the gut biome. I understand there are alternative antibiotics offered in difficult cases, and I'd appreciate it if anyone can share their experiences if they've tried those alternatives. I've been taking Acyclovir, an antiviral is also given as a prophylactic, for years without problems. But I'm concerned about the side effects of Bactrim. How have patients here been able to maintain their Bactrim therapy? I've read that alternatives to Bactrim could be Pentamidine, Atovaquone or Dapsone. Pentamidine is given by nasal spray and both it and Atovaquone do not appear to be too damaging to the gut biome. Has anyone here tried these alternatives? Any comments would be appreciated.