Medication Absorption in Gastric Bypass Surgery

I have been asked about medication absorption in gastric bypass surgery a fair number of times.  It can be a very challenging topic to navigate.  In patients who have had gastric bypass, there is definitely potential for drugs to be inadequately absorbed.  In addition, patients with gastric bypass may have nutritional absorption concerns and often need to have vitamins/minerals replaced like iron, B12, etc.

Probably the most challenging situation I come across is medications for mental health.  Antidepressants, potentially being the most challenging of those.  Venlafaxine extended release as well as duloxetine are medications that tend to be absorbed a little more slowly.  In patients with a shorter GI tract, are these medications being absorbed and/or being absorbed enough is always the $1,000,000 dollar question.

Here’s some things I think about when assess extended release medication following gastric bypass surgery.

  • Were they on these medications prior to the surgery? This might help you determine if the patient found them beneficial before the surgery.
  • Are drug levels a possibility/practical? Take something like lithium or valproic acid.  Doing drug levels before and after surgery can give you a sense of how much the gastric bypass surgery has impacted absorption of those type of medications.
  • Are we starting new medications post bypass surgery? If we are and if possible, we generally try to avoid initiating extended release medications because they may be less likely to be absorbed.
  • Clinical assessment. In clinically assessing the patient for medications that treat subjective symptoms, hopefully we can get a sense if the medications are still being absorbed and are beneficial for the patient.

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Written By Eric Christianson

March 7, 2018

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