Do Medications Absorb Differently After Weight Loss Surgery?
Our patients often wonder if prescription drugs or medications are absorbed differently after weight loss surgery, and do they need to adjust their dosage.
The answer is no.
Patients who undergo a Lap – Band procedure will not have any of the small intestines bypassed, so they shouldn’t worry about medication absorption. Many will ask why we place them on supplemental vitamins and calcium if the upper portion of the small bowel is not bypassed like after the Roux-en-Y Gastric Bypass. The answer to that question is many patients don’t eat a balanced diet which is high in iron such as green leafy vegetables, or avoid some food groups such as milk products which are high in calcium. About one out of every three Weight Loss Surgery patients are found to have low iron, calcium or “B” vitamin on the pre-op labs we perform. In addition over 50% of women over age 50 who haven’t had weight loss surgery will develop osteoporosis in their lifetime, so taking supplements is a good idea.
Gastric Bypass patients do have around 20% of the small bowel bypassed along with the portion just beyond the stomach called the duodenum. This will decrease the absorption of iron, calcium and “B” vitamins, so they must take supplements to remain healthy. This bypassed intestine only represents around 20% of the bowel, so medications can be absorbed normally in the remaining 80% of the distal bowel. No medications, vitamins, or nutrients are absorbed in the stomach. It simply serves as a mixer to grind up the food particles into smaller pieces. This is why you must chew your food until it is almost liquid to make up for the bypassed stomach.
We are not aware of any medications that are absorbed better or worse after Gastric Bypass Surgery. We occasionally see a reduction in prescription thyroid medications, but we believe this is due to a change in the patient’s metabolism and weight loss, not a change in absorption. Requirements for other medications like for diabetes, high blood pressure or cholesterol may also decrease after Gastric Bypass due to weight loss and changes in the body’s metabolism, but it is not due to a change in absorption. Birth control pills are absorbed normally, but must be taken as prescribed. Fertility often increases with weight loss, so remember to be diligent with birth control methods the first 18 months. All methods of birth control including the pill have a known failure rate of at least 1%.
So remember, take your medication as prescribed and do not make adjustments or changes without clearance from either your Primary Care Provider or Dr. Champion. Please call our office if you have any questions.