Which of the following is NOT a class of laxatives?

The correct choice is D, H2 receptor antagonists, because they are not classified as laxatives. H2 receptor antagonists, such as ranitidine and famotidine, are used primarily to reduce stomach acid production, helping to treat conditions like gastroesophageal reflux disease (GERD) and peptic ulcers. They do not have a role in promoting bowel movements or treating constipation, which is the purpose of laxatives.

In contrast, osmotic agents, bulking agents, and stimulants are all recognized classes of laxatives. Osmotic agents work by drawing water into the intestines, which helps to soften the stool and increase bowel movement frequency. Bulking agents, such as psyllium, increase the bulk of the stool and stimulate the intestine, leading to improved stool passage. Stimulants, like senna, directly stimulate the intestinal walls to provoke bowel movements. Each of these classes serves a distinct function in managing constipation, underlining the important differences between laxatives and medications like H2 receptor antagonists.