Medication and Nutrient Administration Considerations After Bariatric Surgery

April D. Miller; Kelly M. Smith


Am J Health Syst Pharm. 2006;63(19):1852-1857. 

In This Article

Considerations for Nutrient Replacement

Nutrient deficiencies in patients who have had restrictive procedures have been reported[7]; the exact prevalence is unknown. Because restrictive procedures retain the use of the entire gastrointestinal tract, nutrient deficiencies are less common than in patients who have had gastric bypass procedures. After gastric bypass procedures, patients are prone to deficiencies of the fat-soluble vitamins (A, D, E, and K) and calcium.[7,8] In addition, these patients have an increased risk of developing anemia secondary to potentially inadequate amounts of iron, vitamin B12, and folate. Because of these deficits, all patients should receive a daily multivitamin and calcium supplementation indefinitely.[7,8] In patients with anemia, additional supplementation with iron, vitamin B12, and folate may be necessary. The specifics of these deficiencies have been discussed elsewhere.[8]

The partitioning of the stomach during bariatric surgery results in a dramatic decrease in the production of hydrochloric acid, affecting the absorption of calcium and iron. However, absorption can be increased by using different salt forms or manipulating gastric pH.[7,8,17] Calcium carbonate depends on acid for its absorption; calcium citrate does not. One study comparing the bioavailability of both products in achlorhydric patients found the bioavailability of calcium carbonate and calcium citrate to be 4% and 45%, respectively. [18] While calcium citrate is more expensive than calcium carbonate, it is logical to specifically recommend calcium supplementation with the citrate salt in this patient population. Decreased calcium absorption can increase the risk of osteoporosis.[19] While specific guidelines to monitor bone density do not exist for these patients, early bone densiometry testing would be prudent.

The duodenum is the primary site for absorption of iron and is bypassed in the Roux-en-Y procedure, creating the potential for nutrient deficiencies. To be absorbed, iron must be in the ferrous state (Fe2+). However, most consumed iron is in the ferric form (Fe3+) and reduced to the ferrous state in the acidic environment of the stomach. The ferrous form is then absorbed in the duodenum. In patients who have had gastric bypass surgery, iron salts can be combined with ascorbic acid (vitamin C) to acidify the stomach environment and facilitate absorption.[17,20] There are commercially available products that combine these two nutrients.

Vitamin B12 absorption is dependent on the presence of intrinsic factor, which is produced in the parietal cells of the stomach. In addition, hydrochloric acid is necessary to cleave vitamin B12 from protein in the stomach. These variations can lead to deficiencies in patients after gastric bypass surgery.[21] Monthly B12 injections are effective in this population; however, appropriate supplementation can also be achieved by using the oral formulation (1000 µg daily). [22] This helps these patients avoid the inconvenience of frequent health care visits and the pain associated with injections.


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