**Question:** Constipation is a possible side effect of drugs taken by the oral route, but it is highly unlikely to occur with the use of

A. Insulin
B. Laxatives
C. Oral contraceptives
D. Antacids

**Core Concept:** Side effects of medications, particularly oral drugs, can include gastrointestinal issues such as constipation. These side effects depend on the specific medication, its mechanism of action, and the involved physiological pathways.

**Why the Correct Answer is Right:** Antacids are primarily used to neutralize excess stomach acid, treating conditions like gastroesophageal reflux disease (GERD) and peptic ulcers. Among the given options, they are the least likely to cause constipation because their primary action is not directly related to gastrointestinal motility or transit.

**Why Each Wrong Option is Incorrect:**

A. Insulin: Insulin is a hormone used to manage diabetes mellitus. While some patients may experience gastrointestinal side effects like bloating or diarrhea, constipation is not a common side effect.

B. Laxatives: Laxatives are medications specifically designed to stimulate bowel movements and relieve constipation. They are not the correct answer because they purposefully induce bowel movements, which contrasts with the desired outcome of constipation prevention.

C. Oral contraceptives: Oral contraceptives contain estrogen and progesterone, which can lead to gastrointestinal side effects like nausea, vomiting, and diarrhea. However, constipation is less likely due to their hormonal mechanism, not directly affecting gastrointestinal transit.

5. Clinical Pearl: To prevent or alleviate constipation, consider recommending lifestyle modifications, such as increasing fiber intake, engaging in regular physical activity, and maintaining adequate fluid intake. In some cases, over-the-counter laxatives or stool softeners may be prescribed. It is essential to individualize treatment based on patient-specific factors and the underlying cause of constipation.

**Correct Answer:** D. Antacids