Which of the following components is known to be effective in antacids for patients experiencing constipation?

Magnesium hydroxide is recognized for its effectiveness in antacids, particularly for patients experiencing constipation. This compound acts as an osmotic laxative, which increases water retention in the intestines, promoting bowel movement and alleviating constipation.

In contrast, other components, such as aluminium hydroxide, can actually contribute to constipation due to its binding effects in the gastrointestinal tract. Calcium carbonate can neutralize stomach acid and may also lead to constipation as a side effect. Sodium bicarbonate, while useful in neutralizing acid, does not have a notable laxative effect and can cause other gastrointestinal issues, such as gas or bloating. Thus, magnesium hydroxide stands out for its dual role in both neutralizing stomach acid and providing relief from constipation.