This document discusses various types of gastrointestinal agents including acidifying agents, antacids, protectives and absorbents, and saline cathartics. It provides details on specific agents such as hydrochloric acid, sodium bicarbonate, aluminum hydroxide, calcium carbonate, magnesium sulfate, and sodium potassium tartrate. The document also briefly introduces the roles of these agents and conditions they can help with such as achlorhydria.