The nurse is caring for a client prescribed a proton pump inhibitor (PPI). Which client finding indicates a therapeutic effect of the drug?

A. Decreased abdominal pain with eating: PPIs suppress gastric acid secretion by irreversibly inhibiting the H+/K+ ATPase pump in parietal cells. Reduction in acid production alleviates symptoms of gastroesophageal reflux disease, peptic ulcer disease, and gastritis, leading to less abdominal discomfort, especially related to food intake. B. Increase in vitamin B12 level: Long-term PPI use can impair absorption of vitamin B12 by reducing gastric acidity needed to release B12 from food proteins. An increase in B12 is not an expected therapeutic effect and may indicate supplementation rather than drug action. C. Decreased bowel movements: PPIs do not directly affect intestinal motility. Constipation or bowel changes are not considered a therapeutic outcome of acid suppression. D. Increase in serum magnesium level: PPIs have been associated with hypomagnesemia in rare cases with prolonged use, not an increase in magnesium. Electrolyte alterations are an adverse effect rather than an intended therapeutic result.