Obesity is a growing concern in the United States. There are three major types of bariatric surgery done in the United States to combat the obesity problem.
1. Vertical Banded (Stapled) Gastroplasty
2. Adjustable Gastric Banding
3. Roux-en-Y Gastric Bypass
Weight loss occurs by causing malabsorption or by restricting gastric volume or a combination of both. Banding procedures limit the amount of intake, whereas the Roux-en-Y procedure not only reduces the stomach size, it also changes the site of attachment of the small intestine. The Roux-en-Y procedure bypasses the lower portion of the stomach and a much smaller stomach pouch (15-30 mL capacity) is created, then the small intestine (the entire duodenum and part of the proximal jejunum) is removed from the lower stomach and attached to the newly formed stomach pouch. This procedure reduces the surface area that is available for absorption of nutrients and medications.
Different medications have different requirements for absorption and ultimately effectiveness. Medications in aqueous solution are more rapidly absorbed then those in oily solutions. Medications are soluble at different pH levels. Different medications that are more soluble at acidic pH are absorbed in the stomach, whereas medications that are more soluble at alkaline pH are absorbed in the small intestine. Intestinal enzymes are also necessary for the absorption of some medications. The Roux-en-Y Gastric Bypass can alter medication absorption.
Reducing the amount of time needed for absorption of the medication is essential for safe and effective use of medications. The formulation of the medication can be sufficient to reduce the amount of time needed in the stomach/small intestine for absorption. When possible the use of pills that can be crushed should be considered, as well as liquids, subcutaneous, intravenous, rectal, vaginal, intranasal and transdermal formulation and/or routes of administration should be considered. Avoid or use with caution any medication that has a long stomach absorptive phase.
Oral non-steroidal anti-inflammatory drugs (NSAIDs), salicylates and bisphosphonates should be avoided. These medications can cause or increase the potential of the patient to develop ulcers in the new much smaller stomach and/or reduced small intestines in all types of bariatric surgery. If the use of these medications are essential, then consider alternative routes of administration such as topical or injectable. Delayed release preparations of all medications such as CR, SR, XR, LA, EC, etc. should be avoided in Roux-en-Y Gastric Bypass.
Pain management in end of life care is essential. The use of MS Contin or morphine ER should be avoided in patients that have had a Roux-en-Y Gastric Bypass. Due to the reduced surface area of the gastrointestinal tract, the use of immediate release formulations would be a better alternative to extended release preparations. The use of immediate release formulations or non-extended release formulations may require a more frequent dosing schedule; however the Roux-en-Y bypass patient will be more apt to achieve more consistent pain management.
It is important to inform all healthcare providers of a patient’s bariatric surgical history if it exists as this will alter the medication therapy chosen for the patient. The length of time the patient is status post bariatric surgery has no impact to the medication therapy consideration. Once a patient has had bariatric surgery, medications will always need to be adjusted to take into account the changes made to the gastrointestinal tract through the bariatric surgery and how this will alter the absorption of medications. All medication therapies chosen for a bariatric surgery patient should be evaluated for effectiveness and for the increased potential for side effects if the proper monitoring is not done.
1. Vanhoose K. Medication Absorption after Gastric Bypass. Advance Healthcare Network for NPs and PAs. www.ADVANCEforNPs\&Pas\_PrinterFriendly.htm
2. Rogula T, Schauer P. Medications after Bariatric Surgery. www.Medicationsafterbariatricsurgery.htm
3. Miller AD, Smith KM. Medication and Nutrient Administration Considerations after Bariatric Surgery. AM J Health Syst Pharm.2006;63(19):1852-1857.
4. Lawrecki T. How is drug absorption altered by bariatric surgery? University of Illinois Chicago College of Pharmacy