From the Research
Extended release (ER) medications should generally be avoided in patients who have undergone gastric bypass surgery and replaced with immediate-release formulations whenever possible. This recommendation stems from the altered gastrointestinal anatomy after bypass surgery, which significantly reduces the surface area available for drug absorption and shortens intestinal transit time. However, a study published in 2017 1 found that the bioavailability of extended-release venlafaxine capsules was not significantly altered after gastric bypass surgery, suggesting that some ER medications may still be effective in these patients.
When ER medications must be used, healthcare providers should monitor drug levels and clinical response closely, as absorption may be unpredictable. Specific medications of concern include extended-release formulations of metformin, antidepressants, antipsychotics, and pain medications. For example, instead of metformin ER, patients might use standard metformin in divided doses; rather than once-daily venlafaxine ER, immediate-release venlafaxine taken multiple times daily would be preferred. Crushing or splitting ER medications is not recommended as this can lead to dose-dumping and potential toxicity.
The fundamental issue is that gastric bypass creates a small gastric pouch and reroutes food directly to the small intestine, bypassing the areas where many ER medications are designed to be gradually released and absorbed. This altered anatomy can result in either reduced efficacy due to incomplete absorption or increased risk of side effects from inconsistent drug delivery. A study published in 2022 2 found that gastric bypass was associated with a slightly higher incidence of medication discontinuation and a slightly lower incidence of medication restart among patients who discontinued medication, highlighting the need for careful management of medications in these patients.
Key considerations for managing ER medications in patients who have undergone gastric bypass surgery include:
- Monitoring drug levels and clinical response closely
- Avoiding crushing or splitting ER medications
- Using immediate-release formulations whenever possible
- Selecting medications with a low risk of dose-dumping and toxicity
- Considering the altered gastrointestinal anatomy and its potential impact on drug absorption.
Overall, the management of ER medications in patients who have undergone gastric bypass surgery requires careful consideration of the potential risks and benefits, as well as close monitoring of drug levels and clinical response.