Comparison of Bioavailability of Single-Dose Extended-Release Venlafaxine Capsules in Obese Patients Before and After Gastric Bypass Surgery

Carrie A. Krieger, Julie L. Cunningham, Joel M Reid, Loralie J. Langman, Karen Grothe, Matthew M Clark, Ross A. Dierkhising

Research output: Contribution to journalArticle

10 Scopus citations


Study Objective: The extended-release (ER) form of venlafaxine is preferred because of improved patient adherence, but the immediate-release (IR) form is frequently used after Roux-en-Y gastric bypass (RYGB) surgery because of concerns for malabsorption. The objective of this study was to determine whether a statistically significant and predictable change in the bioavailability of venlafaxine ER capsules occurs after RYGB. Design: Prospective nonblinded single-dose pharmacokinetic study. Setting: Clinical research unit at a large tertiary care medical practice. Patients: Ten adult pre-bariatric surgery patients who met the criteria for noncomplicated RYGB were enrolled and served as their own controls. Interventions: Patients were administered one venlafaxine ER 75-mg capsule at two visits-the first visit at least 1 week before undergoing RYGB and the second visit 3-4 months after RYGB. Blood samples were collected at predetermined intervals over 48 hours after each dose, and the pharmacokinetics of venlafaxine were measured. Measurements and Main Results: Plasma levels of venlafaxine and its primary metabolite, O-desmethylvenlafaxine (ODV), were compared at baseline and 3-4 months after RYGB. The areas under the serum concentration-time curves from 0-24 hours (AUC0-24) for venlafaxine (mean ± SD 734 ± 602 vs 630 ± 553 ng·hr/ml, p=0.22) and ODV (mean ± SD 894 ± 899 vs 1083 ± 972 ng·hr/ml, p=0.07) were similar before and after RYGB. Using a bioequivalence approach, differences in pre-RYGB and post-RYGB values of AUC0-24, peak serum concentration, and time to peak serum concentration were not statistically significant for either venlafaxine or ODV. Conclusion: This study suggests that RYGB does not significantly alter the amount of venlafaxine or its active metabolite, ODV, absorbed from a venlafaxine ER capsule or the time over which it is absorbed.

Original languageEnglish (US)
StateAccepted/In press - 2017


  • Absorption
  • Bariatric surgery
  • Obesity
  • Pharmacokinetics
  • Roux-en-Y gastric bypass
  • Venlafaxine

ASJC Scopus subject areas

  • Pharmacology (medical)

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