Gastrointestinal disturbances such as constipation, increased stomach acidity, nausea and vomiting are commonplace occurrences. Medications effective for these conditions are frequently obtained ‘over-the-counter’ (OTC). Use of these medications is, however, associated with several inherent risks. This chapter examines the basic mechanism of action of commonly used medications used for constipation, gastric acidity and nausea and vomiting. This discussion is related to clinical practice and the adverse reactions that may occur.