With the prevalence of obesity worldwide topping 650 million people1 and nearly 40% of U.S. adults having obesity,2 bariatric surgery is increasingly used to treat this disease and its associated comorbidities.
Dr. Jennifer C. Kerns
The American Society for Metabolic & Bariatric Surgery estimates that 228,000 bariatric procedures were performed on Americans in 2017, up from 158,000 in 2011.3 Despite lowering the risks of diabetes, stroke, myocardial infarction, cancer, and all-cause mortality,4 bariatric surgery is associated with increased health care use. Neovius et al. found that people who underwent bariatric surgery used 54 mean cumulative hospital days in the 20 years following their procedures, compared with just 40 inpatient days used by controls.5
Although hospitalists are caring for increasing numbers of patients who have undergone bariatric surgery, many of us may not be aware of some of the things that can lead to hospitalization or otherwise affect inpatient medical care. Here are a few points to keep in mind the next time you care for an inpatient with prior bariatric surgery.
Pharmacokinetics change after surgery
Gastrointestinal anatomy necessarily changes after bariatric surgery and can affect the oral absorption of drugs. Because gastric motility may be impaired and the pH in the stomach is increased after bariatric surgery, the disintegration and dissolution of immediate-release solid pills or caps may be compromised.
It is therefore prudent to crush solid forms or switch to liquid or chewable formulations of immediate-release drugs for the first few weeks to months after surgery. Enteric-coated or long-acting drug formulations should not be crushed and should generally be avoided in patients who have undergone bypass procedures such as Roux-en-Y gastric bypass (RYGB) or biliopancreatic diversion with duodenal switch (BPD/DS), as they can demonstrate either enhanced or diminished absorption (depending on the drug).
Reduced intestinal transit times and changes in intestinal pH can alter the absorption of certain drugs as well, and the expression of some drug transporter proteins and enzymes such as the CYP3A4 variant of cytochrome P450 – which is estimated to metabolize up to half of currently available drugs – varies between the upper and the lower small intestine, potentially leading to increased bioavailability of medications metabolized by this enzyme in patients who have undergone bypass surgeries.
Interestingly, longer-term studies have reexamined drug absorption in patients 2-4 years after RYGB and found that initially-increased drug plasma levels often return to preoperative levels or even lower over time,6 likely because of adaptive changes in the GI tract. Because research on the pharmacokinetics of individual drugs after bariatric surgery is lacking, the hospitalist should be aware that the bioavailability of oral drugs is often altered and should monitor patients for the desired therapeutic effect as well as potential toxicities for any drug administered to postbariatric surgery patients.
Finally, note that nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, and corticosteroids should be avoided after bariatric surgery unless the benefit clearly outweighs the risk, as they increase the risk of ulcers even in patients without underlying surgical disruptions to the gastric mucosa.
