Abstract
Objective To identify expected pharmacokinetic changes and provide practical recommendations for the medication management of chronic disease states after bariatric surgery.
Sources of information MEDLINE, EMBASE, PubMed, Scopus, and the Cochrane Library were searched. The search was limited to studies in human adults. Search terms included obesity, obese, bariatric surgery, gastric bypass, gastrectomy, gastric band, RYGB, roux-en-y, gastrointestinal absorption, medication absorption, drug absorption, bioavailability, dose adjust, drug monitoring, medication adjust, drug change, medication change, medication management, and medication dosing. Reference lists of original studies and reviews were also hand searched. Included studies were entered into PubMed and articles under the “Similar articles” heading were also reviewed. Only studies relevant to bariatric surgery types currently available in Canada (ie, Roux-en-Y gastric bypass, sleeve gastrectomy, or gastric banding) were included.
Main message Pharmacokinetic changes anticipated after bariatric surgery vary by surgery type. There are several guiding principles that might be applied to medication management regimens after bariatric surgery. Practice tips are also presented for medication management of specific chronic disease states.
Conclusion Changes to long-term medication regimens after bariatric surgery should be anticipated and managed in an appropriate and timely manner. The provided clinical practice recommendations might be used in conjunction with a patient’s clinical picture to adjust chronic medication regimens in an appropriate and evidence-based manner after bariatric surgery.
Obesity is a progressive chronic health condition affecting more than 1 in 4 adult Canadians.1 Patients who are obese are at an increased risk of many other serious health conditions including type 2 diabetes, hypertension, cardiovascular disease, arthritis, and various types of cancer.2 Bariatric surgery structurally modifies the gastrointestinal tract to reduce caloric consumption or absorption. The number of bariatric surgeries performed annually in Canada has more than tripled since 2009.3
In addition to restricting caloric absorption, bariatric surgeries also have the unintended potential to restrict absorption of other enteral products, including vitamins, minerals, and medications. After surgery, patients typically experience rapid weight loss and might require adjustments to long-term medication regimens owing to changing medication distribution patterns and the effects of weight loss on chronic disease states.
Bariatric surgeries are classified as having restrictive or malabsorptive properties. Restrictive surgeries reduce the volume of food that can be consumed at one time, leading to reduced total caloric intake. Malabsorptive procedures create a diversion around substantial portions of the digestive tract causing reduced absorption of consumed products. Bariatric surgeries currently offered in Canada include Roux-en-Y gastric bypass (RYGB), in which a small functional pouch at the top of the stomach is isolated from the rest of the stomach and directly connected to the jejunum, allowing food to bypass most of the stomach and the entire duodenum; sleeve gastrectomy, in which approximately 80% of the stomach is removed, leaving a smaller sleevelike stomach; and gastric banding, in which an obstructive band is placed around the proximal stomach, physically restricting the rate at which food can pass into the stomach. Roux-en-Y gastric bypass has both restrictive and malabsorptive properties, while sleeve gastrectomy and gastric banding are primarily restrictive procedures.
Unfortunately, the current literature offers very few clear recommendations regarding specific medication management strategies in patients after bariatric surgery. The objective of this review is to identify expected pharmacokinetic changes and provide practical recommendations for the medication management of chronic disease states after bariatric surgery based on the current available evidence.
Case description
A 40-year-old woman is 2 weeks removed from an RYGB procedure and presents to a family medicine clinic with an elevated blood pressure of 158/96 mm Hg. All other vital signs are within normal limits. Her medical history is relevant for class III obesity and stage 1 hypertension, which had previously been well controlled with 10 mg of oral ramipril daily and 60 mg of oral extended-release nifedipine daily. The patient indicates she has adhered to and tolerated her prescribed regimen.
Sources of information
Search strategy.
We searched MEDLINE, EMBASE, PubMed, Scopus, and the Cochrane Library for studies examining the effects of bariatric surgery on either drug absorption or chronic medication management. Search terms included obesity, obese, bariatric surgery, gastric bypass, gastrectomy, gastric band, RYGB, roux-en-y, gastrointestinal absorption, medication absorption, drug absorption, bioavailability, dose adjust, drug monitoring, medication adjust, drug change, medication change, medication management, and medication dosing. A librarian from the University of Alberta in Edmonton assisted with identification of appropriate search terms. Reference lists of original studies and reviews were also hand searched. Included studies were entered into PubMed and articles under the “Similar articles” heading were also reviewed. The search was limited to studies in human adults and is considered up to date as of February 2019.
Eligibility criteria.
Human case reports, case series, cohort studies, and randomized controlled trials that evaluated or described drug absorption or chronic medication management in patients undergoing bariatric surgery types currently available in Canada (ie, RYGB, sleeve gastrectomy, or gastric banding) were included. We excluded studies examining nutritional supplements such as vitamins and iron preparations.
Study selection.
Based on the inclusion and exclusion criteria, we independently screened the titles and abstracts of each study to determine eligibility. Both authors independently assessed all full-text articles that were classified as included or unclear for final inclusion. Disagreements were discussed and resolved by consensus.
Data abstraction.
Using standardized data extraction forms, we independently extracted data on study characteristics (eg, design, country, inclusion and exclusion criteria, funding sources), participants’ clinical characteristics, interventions (eg, medication name, dosage type, dosage amount, surgery type), level of agreement among the evidence, and outcomes. Data not reported in the articles were extracted from supplementary texts where available. Authors were not contacted for missing data.
Main message
General practice tips.
As physiologic and pharmacokinetic changes develop in the days to months after bariatric surgery, it is typically the responsibility of family physicians to modify chronic disease medication regimens in a timely and appropriate fashion. General strategies are available to manage medication regimens after bariatric surgery (Table 1).4–6 Strategies to improve medication absorption are not required for all patients; the decision to proactively implement these strategies will depend on many factors, including surgery type and each patient’s long-term medication regimen. In many cases it will be reasonable to monitor patients after surgery and make adjustments if suboptimal medication absorption is suspected.
General approaches to medication management after bariatric surgery based on anticipated changes: Based on the anticipated medication and absorption changes after 3 specific procedures: 2 types of restrictive procedures (gastric banding and sleeve gastrectomy) and 1 type with both restrictive and malabsorptive properties (Roux-en-Y gastric bypass).
When reviewing general strategies for medication management after bariatric surgery, it is important to be mindful of these guiding principles:
Changes to absorption kinetics of drugs after bariatric surgery have high variability among individuals. No single algorithm or practice tool can accurately predict these changes for all patients after bariatric surgery.
Medication absorption issues might be temporary or permanent; therefore, medication modifications to counteract these issues might also be temporary or permanent.
Issues with medication absorption and dosage modifications are more likely to occur and persist after malabsorptive procedures.
When a medication adjustment is made, ensure appropriate monitoring and follow-up is implemented.
Ensure medication regimens that are dosed by weight are regularly reviewed and adjusted as patients experience weight loss.
Specific disease state management.
In addition to general management principles, we have identified a number of strategies to guide medication management for specific chronic disease states after bariatric surgery (Table 2).4–42 Specific medications for which recommendations are made are intended to represent the most commonly prescribed medications in Canada at the time of the literature review.
Medication management strategies for specific chronic disease states after bariatric surgery: Based on the anticipated medication and absorption changes after 3 specific procedures: 2 types of restrictive procedures (gastric banding and sleeve gastrectomy) and 1 type with both restrictive and malabsorptive properties (RYGB).
Underlying pharmacokinetic changes.
After bariatric surgery, there are multiple pharmacokinetic changes that might occur and that might also explain why patients are not achieving an adequate response to their medications (Table 3).6,43–45 The resultant pharmacokinetic changes might develop within days to months after surgery, vary from patient to patient, and depend on the type of bariatric surgery performed. The changes might either partially or fully reverse as the body heals and adapts to the alterations made from bariatric surgery.
Anticipated pharmacokinetic changes after bariatric surgery: Based on the anticipated medication and absorption changes after 3 specific procedures: 2 types of restrictive procedures (gastric banding and sleeve gastrectomy) and 1 type with both restrictive and malabsorptive properties (RYGB).
Case resolution
This patient’s hypertension has become poorly controlled after RYGB, most likely as a result of decreased absorption and efficacy of extended-release nifedipine. Extended-release oral nifedipine tablets use an osmotic gradient mechanism to control the release of medication; faster gastric transit time might result in incomplete emptying of tablets and thus incomplete absorption of medication. The family physician discontinues nifedipine and initiates 10 mg of oral amlodipine daily, while continuing ramipril as previously prescribed. Amlodipine and nifedipine have the same mechanism of action; however, amlodipine is available in a small immediate-release tablet and is less likely to be absorbed differently after bariatric surgery. The patient returns to the clinic 2 weeks later and presents with blood pressure at target, 136/84 mm Hg. In-clinic follow-up is planned for every 2 to 4 weeks until the patient’s weight loss stabilizes, and she is encouraged to monitor her blood pressure at home between appointments.
Conclusion
Owing to alterations in the gastrointestinal tract after bariatric surgery, there is an intuitive presumption that the absorption, and therefore effectiveness, of medications will change. This review describes changes to the absorption of medications that can be anticipated after bariatric surgery and provides clinical guidance for management of these changes. There is a paucity of previous high-quality literature to support medication management decisions after bariatric surgery. This review closes this gap and provides clinical guidance to practitioners by consolidating the best available evidence. Clinical guidance provided here must always be considered in conjunction with each patient’s clinical picture when adjusting medication regimens. To provide the best care to future bariatric surgery patients, further clinical studies are needed to reveal the effects of bariatric surgeries on drug absorption and to understand the underlying mechanisms. Awareness of this important issue must be stressed and it will be incumbent on prescribers to remain informed of new evidence in this area and adjust their practices accordingly.
Notes
Editor’s key points
▸ There is a paucity of high-quality literature to support medication management decisions after bariatric surgery. This review describes changes to the absorption of medications that can be anticipated after bariatric surgery and provides clinical guidance for the management of these changes. Clinical guidance must always be considered in conjunction with each patient’s clinical picture when adjusting medication regimens.
▸ General considerations include being aware of the high variability in absorption kinetics among patients; being aware that medication absorption issues might be temporary or permanent; knowing that issues with medication absorption and dosage modifications are more likely to occur and persist after malabsorptive procedures; and ensuring appropriate monitoring and follow-up is implemented.
▸ This review provides practical tips on managing specific disease states and anticipating pharmacokinetic changes. Anticipated pharmacokinetic changes after bariatric surgery include reduced ability of solid oral medications to dissolve and altered first-pass metabolism. Suggestions for management include switching solid-medication doses to liquids, dissolvable or crushable tablets, or capsules that can be opened; nonoral dose forms; and immediate-release formulations.
Footnotes
Contributors
Dr Lorico determined the initial search strategy, which was then modified after consultation with Mr Colton and a University of Alberta librarian. Dr Lorico identified all articles that met the search criteria. Dr Lorico and Mr Colton independently reviewed all titles and abstracts to determine which articles to include; discrepancies were resolved with discussion. Dr Lorico initially read the included articles and recorded pertinent results in a data collection spreadsheet; Mr Colton then read the articles to confirm the information and add to the data collection spreadsheet as required. Dr Lorico wrote most of the initial draft of the manuscript; Mr Colton proofread and edited it. All writing and editing was agreed upon by both authors. Consensus was achieved via discussion for all disputes.
Competing interests
None declared
This article is eligible for Mainpro+ certified Self-Learning credits. To earn credits, go to www.cfp.ca and click on the Mainpro link.
This article has been peer reviewed.
La traduction en français de cet article se trouve à www.cfp.ca dans la table des matières du numéro de juin 2020 à la page e171.
- Copyright© the College of Family Physicians of Canada
References
In this issue
Jump to section
Related Articles
Cited By...
- No citing articles found.