**Core Concept**
Acid peptic disease, including conditions like peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD), involves an imbalance between gastric acid production and protective mechanisms. Misoprostol, H2 blockers, and proton pump inhibitors (PPIs) like omeprazole are commonly used medications to manage acid peptic disease.

**Why the Correct Answer is Right**
Misoprostol is a prostaglandin E1 analog that is used to prevent NSAID-induced gastric ulcers by reducing gastric acid secretion. In patients taking NSAIDs, misoprostol is a recommended prophylactic measure to prevent NSAID-related gastric mucosal damage. Option c is also correct as omeprazole, a PPI, is effective in healing ulcers refractory to H2 blockers due to its potent acid-suppressive properties. Option b is true as single nighttime H2 blockers can help prevent duodenal ulcers by reducing nocturnal acid secretion.

**Why Each Wrong Option is Incorrect**
**Option A:** Misoprostol is not the drug of choice in pregnant patients. In fact, prostaglandins like misoprostol are contraindicated in pregnancy due to their potential to induce uterine contractions and abortion.

**Option B:** This option is incorrect as it is too absolute. While H2 blockers can prevent duodenal ulcers, they do so only in a subset of patients and do not prevent ulcers in all individuals.

**Option C:** This option is incorrect as it is too broad. While omeprazole may help ulcers refractory to H2 blockers, it does not necessarily mean that all ulcers refractory to H2 blockers will heal with omeprazole.

**Clinical Pearl / High-Yield Fact**
It's essential to consider the specific pathophysiology and clinical context when selecting a medication for acid peptic disease. For example, in patients taking NSAIDs, misoprostol is a preferred choice for prophylaxis, while in patients with refractory ulcers, a PPI like omeprazole may be more effective.

**Correct Answer: D. Misoprostol is not the drug of choice in pregnant patients.**