Final answer:
Medications like Omeprazole and H2 antagonists (e.g., ranitidine) decrease gastric pH by reducing stomach acid production, while calcium salts act as antacids and neutralize existing stomach acid. PGE2, on the other hand, protects the stomach lining and does not decrease gastric pH.
Step-by-step explanation:
The medications that decrease gastric pH are those that inhibit stomach acid production. Omeprazole, a proton-pump inhibitor, and H2 antagonists like ranitidine are both designed to reduce gastric acid secretion and therefore lower gastric pH. These medications are used in the treatment of conditions such as gastroesophageal reflux disease (GERD), peptic ulcers, and Zollinger-Ellison syndrome. Calcium salts, such as calcium carbonate, act as antacids by chemically neutralizing stomach acid, which may also indirectly reduce gastric pH but their primary function is neutralization rather than reducing acid secretion.By contrast, PGE2 has different roles including protective effects in the gastrointestinal tract by inhibiting acid secretion and stimulating mucus and bicarbonate secretion to protect the stomach lining. The use of PGE2 would therefore not decrease gastric pH, but rather help to protect the stomach lining from the effects of acid.