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Melissa M. Mitchell, PharmD, BCPS, BCPP, BCGP, Senior Clinical Pharmacist
PGY2 Psychiatric Pharmacy Residency Program Director
RUHS-Medical Center, Moreno Valley, CA

During the 2021 CPNP Virtual Annual Meeting, Dr. April Smith, PharmD, MA, BCPS spoke about the  utilization of medications after bariatric surgery and what considerations psychiatric and neurologic providers need to take into account for any patient who has had or will have bariatric surgery. Her presentation is filled with phenomenal figures, graphs and literature analysis that allows each of us to have a better understanding, and provide better care, to this patient population.

To begin, Dr. Smith discussed common bariatric procedures, breaking them down into categories of restrictive versus malabsorptive. Although we often think of bariatric surgery as Roux-en-Y gastric bypass (RYGB), the most common bariatric surgery performed today is the sleeve gastrectomy, performed in over 60% of patients receiving bariatric surgery. A sleeve gastrectomy is considered a restrictive bariatric surgery and will not affect absorption to the same extent a RYGB will. As such, much of the information and studies available are on the later.

In RYGB, the stomach is made smaller and a gastrojejunal anastomosis is created to decrease absorption and cause restriction. Because of this, the patient will need to make multiple changes to their daily life, including medications. After surgery, the gastrojejunal anastomosis is very small, often no more than 2-2.5 centimeters (or the size of a pencil eraser). As such, pill size has to be considered and may require the patient to crush many of their medications. Additionally, the patients are limited to the amount of fluids and foods they may intake over the first few weeks. Therefore, it is critical to monitor those medications that are fluid dependent and/or require food for better absorption. Post-surgery, some medications are completely avoided, and these include diuretics, oral antidiabetic agents (except metformin), and NSAIDs. Furthermore, the patient will begin on a regimen of bariatric vitamin supplements and calcium.

A RYGB can alter dissolution, metabolism, and absorption of medications. In a study by Seaman, et al., comparing the dissolution of multiple psychotropics either in a control solution or a RYGB solution, they were able to determine which medications were more likely to have a decreased absorption, increased absorption or no change. Medications used were only immediate release, which is the preferred formulation for RYGB patients.

Dr. Smith gave a very thorough literature analysis of multiple medication classes and their effects on absorption and metabolism. In a study by Marzinka et al., 4 RYGB patients saw a decrease in escitalopram concentrations up to 6 weeks post-operatively. Dr. Smith discussed how this can lead to SSRI discontinuation syndrome, as evidenced by a case report of a patient on paroxetine. Although many psychotropics can lead to a decrease in absorption and therapeutic efficacy, lithium levels have been increased to toxic levels in multiple cases.

In addition to psychotropics, substances with abuse potential were also reviewed. In a study of 25 RYGB patients on Morphine IR, a significant increase in Tmax and Cmax was seen at 2 weeks post-operatively which continued to increase at 6 months. In a study by Wallen, 2.1% of patients became high opioid users within 2 years post-surgery. Like opioids, alcohol also has significant changes. Patients had rapid and extensive absorption of alcohol due to increased gastric emptying, rapid absorption at the jejunum, and possible reduction in stomach alcohol dehydrogenase.

The key takeaways were related to the alteration of dissolution, absorption and metabolism of medications. If the issue is primarily issues related to dissolution, changing to a liquid formulation or crushing a tablet may resolve the patient’s issues. Non-oral formulations of medications may also be considered, such as patches. After RYGB, it is critical for patients to report any adverse effects from medications or exacerbations in symptoms. They can expect to have the greatest changes within the first 6 months post-surgery, which should then level off after the first year. For all patients on narrow therapeutic drugs, it is important to monitor them more closely within the first weeks or months post-surgery. For those drugs dependent on liquid or calorie consumption, it is vital to adjust the medications or doses according to their allowed daily consumption during that period of time of recovery.

The most important takeaway was that psychotropic medications are typically started again right after surgery. Often, surgeons may not adjust the patient’s medications, and it will be pertinent for the patient’s mental health provider to guide these decisions.

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