The patient may have an unreliable response to oral therapy due to potential oral absorption issues such as: continuous tube feeding or NG suction, shortened gastrointestinal (GI) time (malabsorption syndrome, removal of part of GI tract, inflammatory bowel disease), ileus or GI obstruction, difficulty swallowing, severe diarrhea/nausea/vomiting, pancreatitis, shock, active GI bleeding, drug interactions that would limit oral antimicrobial absorption.