The effect of H2-blockade on plasma gastrin concentration in patients with an achlorhydric stomach.

The mechanisms of hypergastrinaemia during H2-receptor antagonist therapy remain unclear. In addition, the effect of food stimulation in conditions of hypergastrinaemia is poorly understood. These effects may be important when considering long-term therapy with potent acid inhibitory agents. To investigate this we studied the effect of H2-receptor antagonist therapy on basal and meal-stimulated plasma gastrin concentrations in 9 patients with pentagastrin fast gastric achlorhydria associated with pernicious anaemia. The subjects received in double-blind randomized fashion 28-day courses of 300 mg ranitidine q.d.s. and placebo, with one-month wash-out between. The fasting and peptone meal-stimulated gastrin concentrations were studied on the final day of each course of treatment. The median fasting gastrin concentrations (ng/L) were similar following placebo (1100, range 25-2100), and 300 mg ranitidine q.d.s. (1075, range 15-2600) and both markedly elevated when compared with our laboratory's normal range of 0-100. Despite the elevated basal levels the pernicious anaemia patients still showed a further increase in response to the peptone meal. Their median peak percentage rise over basal in response to the meal was similar following placebo (96%, range 0-375) and 300 mg ranitidine q.d.s. (100%, range 25-425) (both P less than 0.02 c.f. basal). This study shows that: (a) in hypergastrinaemia in pernicious anaemia subjects, meal stimulation leads to a marked and prolonged increase in plasma gastrin concentrations; (b) H2-receptor antagonists have no effect on plasma gastrin in the neutral stomach and this is consistent with their gastrin effect being entirely secondary to acid inhibition.