The disclosure relates to a dosage forms and combinations of dosage forms useful for effective oral administration of drugs which are otherwise unsuitable for oral administration, owing to acid- and/or protease-mediated degradation. The dosage forms include a self-microemulsifying drug delivery system (SMEDDS) with which the drug is combined and an antacid. When co-administered to a mammal, the dosage form(s) can prevent drug degradation by the strong acid and digestive enzymes normally present in the gastric environment, and can improve water-soluble drug absorption in gastrointestinal (GI) tract. The dosage forms can be used to effectively administer insulin by an oral route, for example, such as in the form of a powder that can be stored for long periods and reconstituted with water or another fluid shortly before administration.
