Bariatric procedures: Managing patients after surgery
Changes in the gastrointestinal tract and body weight can alter drug absorption
Table
Weights of dissolved portions of antidepressants before and after simulated RYGB
| Simulated pre-RYGB environment | Simulated post-RYGB environment | ||||
|---|---|---|---|---|---|
| Drug | Median weight of dissolved portion (mg) | Percentage* | Median weight of dissolved portion (mg) | Percentage* | P† |
| Amitriptyline, 75 mg/d | 80 | 28% | 60 | 21% | <.04 |
| Fluoxetine, 20 mg/d | 110 | 30% | 40 | 11% | <.04 |
| Paroxetine, 20 mg/d | 30 | 9% | 10 | 3% | <.04 |
| Sertraline, 100 mg/d | 50 | 16% | 30 | 10% | <.04 |
| Bupropion, 100 mg/d | 320 | 52% | 450 | 73% | <.05 |
| Venlafaxine, 75 mg/d | 180 | 59% | 180 | 59% | Not significant |
| Citalopram, 20 mg/d | 70 | 27% | 80 | 31% | Not significant |
| *Relative to original pill weight †Mann-Whitney U test RYGB: Roux-en-Y gastric bypass Source: Adapted from reference 37 | |||||
Altering antidepressant doses
Current PK data are insufficient to make clinical recommendations regarding appropriate postsurgical adjustment of dose or alternate dosage formulations (liquid, extended-release, etc.). However, based on theoretical considerations, Miller and Smith suggest that patients avoid extended-release preparations whenever possible after bariatric surgery, citing the rationale that decreased intestinal length and surface area leads to reduced absorption.33 No data are available to advise clinicians regarding the appropriateness of switching patients from extended-release products to immediate-release or liquid preparations following surgery.
Presently, increased medication monitoring may be the most appropriate clinical approach. If appropriate doses have little or no effect, consider the possibility of decreased medication absorption.33 Monitoring plasma levels of medications that have therapeutic ranges also is advisable.
Areas for future research
Before specific clinical recommendations for managing antidepressants following RYGB can be proposed, the extent to which the absorption, volume of distribution, drug metabolism, and other measures change after surgery need to be quantified. It is also unclear whether changes in medication absorption are subject to inter-patient variability, whether predictive characteristics can be identified, and whether any observed changes remain stable over time. Similarly, the extent to which variability in surgical procedures (eg, surgeon preference regarding remnant intestinal length) affects medication absorption is unknown. Data regarding medication absorption following AGB and other bariatric procedures also will be needed.
- American Society for Metabolic and Bariatric Surgery. Fact sheet: Metabolic and bariatric surgery. www.asbs.org/Newsite07/media/asmbs_fs_surgery.pdf.
- American Society for Metabolic and Bariatric Surgery. Suggestions for the pre-surgical psychological assessment of bariatric surgery candidates. www.asmbs.org/html/pdf/PsychPreSurgicalAssessment.pdf.
Drug Brand Names
- Amitriptyline • Elavil
- Atorvastatin • Lipitor
- Bupropion • Wellbutrin
- Citalopram • Celexa
- Cyclosporine • Sandimmune
- Digoxin • Lanoxin
- Fluoxetine • Prozac
- Paroxetine • Paxil
- Sertraline • Zoloft
- Sulfisoxazole • Truxazole
- Tacrolimus • Prograf
- Venlafaxine • Effexor
Disclosures
Dr. Sarwer receives grant/research support from the National Institutes of Health, the American Society for Metabolic and Bariatric Surgery, and Ethicon Endo-Surgery, Inc., is consultant to Allergan, BAROnova, Inc., EnteroMedics, and Ethocon Endo-Surgery, Inc., and is on the board of directors of Surgical Review Corporation.
Dr. Roerig receives grant/research support from Eli Lilly and Company.
Drs. Faulconbridge, Steffen, and Mitchell report no financial relationships with any company whose products are mentioned in this article or with manufacturers of competing products.
