Which of the following is the most common adverse effect of omeprazole?
A. Black stools
 Ranitidine inhibits which of the following?
A. Gastrin binding to parietal cells
B. Histamine binding to parietal cells
C. H+, K+-ATPase
D. Parietal cell prostaglandin receptors
 Which of the following is true of cimetidine?
A. It is a prostaglandin analog of PGE1
C. It is associated with confusion and hallucinations in elderly patients
D. It reduces the duration of action of other drugs
 C. The most common adverse effect of omeprazole is headache. Diarrhea, not constipation, is another common adverse effect. Black stools are associated with use of bismuth subsalicylate. Vomiting is not a typical effect.
 B. Ranitidine is a histamine H2-receptor antagonist that inhibits histamine binding to parietal cells and reduces acid secretion. It indirectly inhibits the synergistic acid secretion stimulated by gastrin binding to parietal cell gastrin receptors. PPIs inhibit parietal cell H+, K+-ATPase.
 C. Cimetidine is a histamine H2-receptor antagonist that uniquely causes confusion and hallucinations, particularly in elderly patients. It also inhibits hepatic microsomal enzymes to increase, not decrease, the duration of action of other drugs. proton pump inhibitors are prodrugs.
Histamine H2-receptor antagonists cross the blood-brain barrier and placenta, are secreted into breast milk, and therefore should be used judiciously during pregnancy and in nursing mothers.
Three to four days of PPI administration is necessary to achieve maximal inhibition of acid secretion (up to 98%). Likewise, 3-4 days are needed for acid secretion to return to normal after discontinuation of therapy.
Proton pump inhibitors are considered first-line agents for peptic ulcer disease and gastroesophageal reflux disease.