Try famotidine 40 mg, also known as Pepcid. Research seems to indicate that it works on GI inflammation caused by covid. He may need a two week dose of the IBD antibiotic which helped me. Research also indicates that probiotic pills can be harmful. Try food with probiotics instead like yogurt, kombucha, kefir, etc. Pepcid is really helping me. I had months of intestinal cramps and terrible heartburn that were not helped by antacids or meds like Nexium, but famotidine works differently.