The following statements regarding H2 receptor antagonist are true except:

H2 receptor antagonists inhibit gastric acid secretion elicited by histamine and other H2 agonists in a dose dependent manner. They reduce the volume and the H+ ion concentration of gastric juice. They also reduce the secretion of intrinsic factor, however since this protein is normally secreted in great excess, absorption of vitamin B12 is usually adequate even during long-term therapy with them. They have no consistent effect on the pressure of lower esophageal sphincter or the gastric emptying time.