When antibiotics are temporarily needed in the bloodstream, the injectable form is the only one that makes sense.
When the digestive tract has been invaded by a pathogen, it is usually because doctors have been destroying the balance in the patient’s ecosystem with oral antibiotics -when injectable or topical antibiotics made more sense- and because patients have self-prescribed medicines such as NSAIDs [weakens the protective coating of both the stomach and small intestine, making us feel stomach acid pain] and stomach acid blockers [reduces the bacteriocidal activity of stomach acid, reduces the efficiency of pre-digestion and thus nutrient status, and reduces the efficiency of vitamin B12 absorption]. Add to that the patient’s bad nutrition and we have a disaster waiting to happen.
In an emergency, oral antibiotics may be needed to save such a patient. How ironic!
Before it is an emergency, flooding the patient’s system from both ends if necessary with properly optimized beneficial competitors makes more sense. Temporary alterations in diet may strongly complement this by feeding the symbionts and starving or poisoning the parasites. Lots of options – but of course, there is negligible research being done in this area. No money in doing things properly. Never has been any money there. Not much effort put into antibiotics anymore either – also not enough money in it.