Does Omeprazole Decrease Intestinal Calcium Absorption?

Existing literature makes it unclear whether proton pump inhibitor therapy truly decreases intestinal calcium absorption. Up to 25 postmenopausal women will participate in this study. The primary study outcome is the change in intestinal calcium absorption following omeprazole therapy 40 mg daily for 30 days. The secondary outcomes include the change in urine n-telopeptide.

We will interview women and review their medical records to determine eligibility. Eligible subjects will undergo three calcium absorption studies. The first 2 studies will determine the monthly variation in calcium absorption, while the 3rd study will occur after taking 40 mg of omeprazole daily for 30 days. Women will present to the research unit in the early morning and receive an oral and intravenous calcium tracer with breakfast. Over the next 24 hours, we will collect all urine for measurement of its calcium content. During the first stay, we will measure each subject's gastric pH by collecting gastric fluid from a temporary nasogastric tube. In consenting subjects we will collect one tube of blood, isolate its DNA.

Inclusion criteria

• Women at least 5 years past menopause, defined as the last date of menses

Exclusion criteria

• Allergy/Intolerance to orange juice
• Allergy/Intolerance to omeprazole or other PPI therapy
• Use of drugs that interact with omeprazole including oral anti-fungal agents, coumadin, diazepam, phenytoin & tacrolimus
• Use of antacids, PPI or H2-blocker therapy within the past two months
• Intestinal conditions associated with malabsorption or low gastric acid levels including Crohn's Disease, ulcerative colitis, pernicious anemia, bacterial overgrowth, celiac sprue, chronic diarrhea or use of antibiotics within the past month
• Known Stage 4 or 5 Chronic Kidney Disease, defined as an estimated GFR <30 cc/minute
• Use of medications known to interfere with calcium metabolism, including oral steroids or anticonvulsants