Medication Absorption Post-Bariatric Surgery with Emphasis on Management of Vitamin Deficiencies
Pp. 265-282 (18)
Susan Jacob, Nhu Nguyen, Christian S. Jackson and Stewart Rendon
The increased prevalence of obesity worldwide has led to a rise in bariatric surgeries
performed each year. Bariatric surgery is currently one of the most effective interventions for
weight loss. The most common procedures include gastric bypass, adjustable gastric band, jejunoileal
bypass, vertical banded gastroplasty, and biliopancreatic diversion with duodenal switch.
Bariatric surgery can improve various medical conditions including but not limited to diabetes,
hypertension, dyslipidemia, reflux, and obstructive sleep apnea. Patients with type 2 diabetes
develop increased insulin sensitivity and improvements in glucose metabolism within days after
surgery. As weight loss occurs, blood pressure and cholesterol levels may improve post operatively,
allowing discontinuation of medications. Due to the possible achlorhydric nature of the
gastrointestinal tract, post surgery patients often do not require acid suppressing agents for reflux.
Medication absorption is highly affected by post gastric bypass surgery, specifically drug solubility
and surface area for absorption. These changes warrant manipulation in drug route or dose to ensure
adequate delivery. As weight loss occurs, medication adjustments are essential to provide optimal
bioavailability for various health related conditions. Consideration should be made for certain
medications that depend on absorption site and pH of the gastrointestinal tract for solubility and
proper absorption. Non-steroidal anti-inflammatory drugs, aspirin, and bisphosphonates, should be
discontinued as these can cause an increased risk of stomach ulcerations if continued post surgery.
Long acting and enteric coated formulations will not be absorbed as they require an extended period
of time in the intestines for drug dissolution and metabolism. Patients undergoing bariatric surgery
have alterations in the digestive anatomy resulting in micronutrient and mineral deficiencies
requiring immediate postoperative vitamin supplementations. Nutrient deficiencies include calcium,
fat soluble vitamins (A, D, E, K), thiamine, iron, folic acid, and cyanocobalamin. Calcium and
vitamin D deficiencies may cause secondary hyperparathyroidism and bone softening diseases.
Cyanocobalamin deficiency may lead to irreversible peripheral neuropathy. Wernicke’s
encephalopathy is common in patients with thiamine deficiency. Anemia may develop in patients
with iron deficiency. Due to rapid weight loss and physiological changes, patient monitoring for
therapeutic effects is crucial. Recent developments in anti-obesity therapies such as bariatric
surgery have revealed improvements or complete remission of multiple chronic diseases.
Manipulation of the gastrointestinal tract post bariatric surgery requires medication adjustments and
vitamin supplementation for optimal patient care.
Bariatric surgery, vitamin deficiency, medication adjustments.
Department of Veterans Affairs Loma Linda, Western University of Health Sciences, Pomona, CA, USA.