Gastric pH, sevelamer hydrochloride and omeprazole

AIMS

Sevelamer hydrochloride is a polymer containing multiple amines (40% amine hydrochloride) separated by one carbon from the polymer backbone, and it is not absorbed by the intestine. These amines are partially protonated and interact with phosphate molecules through ionic and hydrogen bonding, therefore reducing phosphate absorption and lowering serum phosphate concentration. Alterations of gastric pH, in particular excessive alkalinization, could interfere with sevelamer phosphate binding capacity.

CASE HISTORY

A 30-year-old dialysis patient affected by secondary hyperparathyroidism started sevelamer treatment, 4.8 g/day, with a basal serum phosphate of 6.9 mg/dl. The patient was also treated with omeprazole (20 mg/day) because of chronic gastritis. Phosphate levels normalized (4.2 mg/dl), but after four months of follow-up serum phosphate unexpectedly increased to 7.2 mg/dl. We found out that in the same period she had autonomously increased the dosage of omeprazole to 80 mg/day, due to worsening of dyspepsia. Gastric pH measurement showed a median level of 4.1, rather than the normal values of 1 - 2, indicating excessive pharmacological alkalinization. When omeprazole was reduced to the correct dose of 20 mg/day, we observed a rapid decrease of phosphate levels.

CONCLUSION

This case report highlights the influence of gastric pH on sevelamer phosphate binding capacity. The high dose of omeprazole and the consequent excessive increase in gastric pH was probably responsible for a decreased phosphate binding capacity of sevelamer. When patients taking appropriate doses of sevelamer do not respond to treatment, a potential interaction with drugs determining an increase of gastric pH should be considered.

Double pylorus: report of two cases and review of the literature

Double pylorus is a rare condition consisting of a double communication between gastric antrum and duodenal bulb; in most cases it is a complication of penetrating ulcer, sometimes it is a congenital abnormality. The prevalence of this rare anomaly ranges from 0.02% to 0.13%; the male:female ratio is about 2:1. Two cases of acquired double pylorus are reported with a review of the literature. The first case represented an occasional report; in the other one the development of double pylorus from confluent prepiloric and bulbar ulcers was documented through serial endoscopies. Both patients were affected with chronic renal failure and referred previous treatment with diclofenac; however, their relationship with double pylorus onset remains unproven.