As promised, I’ve read the study I mentioned yesterday, and I’m ready to report back. I am still very excited that this study was conducted, although it does have its limitations.
What was it important to look at the absorption of prescription medications after bariatric surgery?
Because of the changes to the gastrointestinal tract, the potential exists for clinically significant alterations in the absorption/bioavailability of ingested medications.
Gastric bypass alters both how we digest and how we absorb food and medications. In the small stomach pouch, there is a low concentration of stomach acid; gastric bypass patients are virtually achlorhydric—they do not produce much hydrochloric acid. Hydrochloric acid is necessary for many digestive processes, such as the conversion of pepsinogen to pepsin. As a result, digestion is altered. The surgery also induces malabsorption by bypassing the upper portion of the small intestine. This is a selective absorption site for many nutrients and medications.
While several studies have examined the effects of bariatric surgery on micronutritional status, the research on prescription medications has been severely limited:
A paucity of empiric data exploring these changes has been available, and what has been available has consisted of case reports and case studies.
Moreover, the malabsorption of prescription medications has important real world ramifications. What dose will be therapeutic for a gastric bypass patient? Currently, we have no way of knowing beyond experimentation:
Such changes in how drugs are absorbed and distributed can result in difficulty in prescribing the correct dose and in choosing the correct drug for patients after bariatric surgery.
The researchers in the present study chose to look at the absorption of a single 100 mg dose of the antidepressant sertraline (Zoloft). They compared serum levels for the drug in five postbariatric surgery subjects and five nonsurgical control subjects.
It was hypothesized that the AUC0-10.5 [plasma concentration/time curve] would be smaller in the postbariatric surgery (PBS) group than in the matched nonsurgical control (NSC) group.
Basically, they expected to see the effects of malabsorption in the serum sertraline levels of the postbariatric surgery group. Such a result “would suggest an altered exposure to the antidepressant.”
And that’s exactly what the results showed:
The mean value of the AUC0-10.5 of the PBS group was significantly smaller than that of the NSC group, just as we had postulated in our hypothesis.
For the weight loss surgery patients, there was a statistically significant decrease in the amount of the antidepressant that made it into their bloodstream, suggesting some degree of maldigestion and/or malabsorption.
So, why is this study significant?
The assumption has been that gastric bypass patients will experience some malabsorption of prescription medications, even though there has been little empirical research on the subject. This study contributes to a much-overlooked area of bariatric medicine. As the authors state,
preoperative depression continues to be a problem for many patients after bariatric surgery.
As a result,
it is imperative that patients who require antidepressant medications receive appropriate evidence-based dosing of the agents after surgery.
I could not agree more! While this small study does not develop evidence-based recommendations, it is a step in the right direction, and I commend its authors.
One thing I would like to see is an expansion of this study. Sertraline is available in a liquid concentrate, and the tablets can also be crushed. (In the current study, subjects swallowed a single 100 mg tablet whole.) Does the preparation of the medication have an effect on the patient’s serum levels? Looking at such a question could help determine whether maldigestion or malabsorption is at play.
Clearly, there are still many “interesting and important research questions” (to quote my Logic, Methodology, and Scope professor) surrounding prescription medications and bariatric surgery, but this is such an encouraging step in the right direction. This is the type of research that will truly affect patient care.
Source:
Roerig JL, Steffen K, Zimmerman C, Mitchell JE, et al. Preliminary comparison of sertraline levels in postbariatric sugery patients versus matched nonsurgical cohort. Surgery for Obesity and Related Diseases 2011.
This is why I wish I had a crystal ball. I am facing aortic valve replacement surgery with a mechanical valve. Mechanical valves require lifetime Coumadin therapy. I have no idea how I will adjust or absorb this medication and it will likely be a challenge all my life to get my INR just right.
This is a new issue in the post bypass world. It will likely bring on much more research in drug absorption in the post bypass patient.
It just means you have to be a very educated patient too. You have to tell your doctors you have had bypass and ask them if they think your medication absorption could be affected by your bypass. It pays to be educated!
Thank you for posting. Very timely for me.
Maggie
Excellent post! Most doctors don’t believe that a person with rerouted guts needs to take more of a dosage because of malabsorption. There are some drugs I take more of…don’t tell, though.
For depression, I have been taking a liquid called fluoxetine. I hope that it’s absorbing well. I am on the max dose my doctor allows, 60 mg. I don’t take more of that one since it is liquid. I would love to know how well it is absorbing though. I am better on the 60 than I was on the 40, but I am not great yet.
I hope there are more studies done!
Maggie I too am on coumadin and my bariatric docs are reluctant to give me a gastirct bypass. I had lap band surgery 4 years ago and it was a total failure. How are you doing with your inr levels?
jerry
I had Gastric Bypass Surgery 6 years ago. I have taken Zoloft for 15+years. I began having worse symptoms of depression this past fall. It is hard for me to understand why after 6 yrs I began having Major Depression. My Doctor has switched me to Prozac–I am felling alittle better.
I also have alot of trouble focusing on task at work and home. I would Love to see More Studies Gastric Bypass Patients and Malabsorption with Meds after the surgery..I think this would help
Not Only the People that have had GBS but the Doctors too… We all need to Understand this so we can be placed on the correct doseages of Meds/ or adjusting doseages for GBS patients
There are reference labs which can determine if you are getting a therapeutic blood level of almost any medication – information which could facilitate appropriate dosage/administration adjustments
Wow..I had gastric bypass 26 months ago, and once all the weight was off I started experiencing the worst depression of my life. I had always had issues with depression but had been well maintained on Zoloft 100 for a few years. My primary care switched me to Wellbutrin, which didn’t seem to change things much. I thought I was bipolar, my mood swings were so high and so low. I started experiencing insomnia, anxiety, agitation, and I thought it was just me. An extremely brilliant psychiatrist suggested I try a relatively new product called asenapine. It is a sublingual formulation, therefore bypasses first pass metabolism. It’s indications are for bipolar and schizophrenia, but this MD felt that the molecule might be extremely effective in treating major depression, although this is off label. He said that anyone who had bypass surgery or any abdominal surgery might have trouble absorbing anti-depressants. I was ready to try anything.
I have been on it for one week now, and I feel like I have my life back. I want to go to work everyday, I am not yelling at the kids, I am sleeping at night. It has been an amazing transformation. Maybe it is placebo effect, but I don’t think so because in reviewing the literature I have found that malabsorption of anti depressants post op is common. Any thoughts anyone?