Presentation Details
| No pressure: Does timing really matter for phentermine discontinuation? Maria Fernanda Acevedo-Kury, Zulma Sosa-Carcamo, Tachy Valentina Hernandez-Romero, Ridwan Ahmad, Adam Jacob, Joan Irizarry-Alvarado. Mayo Clinic, Jacksonville, FL, USA |
Abstract
BACKGROUND: Phentermine is a sympathomimetic amine commonly prescribed for weight loss. Due to its long half-life (~20 hours), current guidelines recommend discontinuing phentermine at least four days prior to surgery to minimize the risk of intraoperative hypotension. However, these recommendations are based on an outdated systematic review of a review article, two case reports and a letter. These studies involved phentermine with fluphenazine, rather than current formulations of phentermine alone or with topiramate. We hypothesized that intraoperative hypotension would not differ significantly between patients who continued phentermine through the day of surgery and those who discontinued it four or more days preoperatively.
METHODS: In this retrospective cohort study, we identified 1,362 adults (≥18 years) who underwent elective, non-cardiac surgery under general, neuraxial, or peripheral regional anesthesia at all Mayo Clinic locations (Rochester, Florida, Arizona) from 01/01/2019-12/31/2023, and were prescribed phentermine or phentermine-topiramate. We grouped patients by timing of last dose (≤1 day vs ≥4 days preoperatively). We collected baseline demographics, surgical and anesthetic factors, and intraoperative hemodynamic variables (i.e., MAP, use of pressors, colloids and crystalloids). Hypotension was defined as MAP <65 mmHg.
RESULTS: Patients who discontinued phentermine less than four days before surgery had a significant lower likelihood of experiencing intraoperative hypotension compared to those who discontinued it four or more days prior (p = 0.0035) (See figure 2). Similarly, discontinuation less than seven days before surgery was associated with lower vasopressor use (p = 0.0145). Intraoperative MAP was not statistically significant in patients who discontinued phentermine less than 7 days (See figure 1). Furthermore, the use of pressors was statistically more significant in those patients who held phentermine more than 7 days before surgery.
CONCLUSIONS: Findings suggest that phentermine is unlikely to be the sole cause of hypotension. Other underlying factors (e.g., comorbidities, physiological responses, intraoperative events) may contribute, thus warranting further investigation and clarity to current perioperative medication guidelines.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
METHODS: In this retrospective cohort study, we identified 1,362 adults (≥18 years) who underwent elective, non-cardiac surgery under general, neuraxial, or peripheral regional anesthesia at all Mayo Clinic locations (Rochester, Florida, Arizona) from 01/01/2019-12/31/2023, and were prescribed phentermine or phentermine-topiramate. We grouped patients by timing of last dose (≤1 day vs ≥4 days preoperatively). We collected baseline demographics, surgical and anesthetic factors, and intraoperative hemodynamic variables (i.e., MAP, use of pressors, colloids and crystalloids). Hypotension was defined as MAP <65 mmHg.
RESULTS: Patients who discontinued phentermine less than four days before surgery had a significant lower likelihood of experiencing intraoperative hypotension compared to those who discontinued it four or more days prior (p = 0.0035) (See figure 2). Similarly, discontinuation less than seven days before surgery was associated with lower vasopressor use (p = 0.0145). Intraoperative MAP was not statistically significant in patients who discontinued phentermine less than 7 days (See figure 1). Furthermore, the use of pressors was statistically more significant in those patients who held phentermine more than 7 days before surgery.
CONCLUSIONS: Findings suggest that phentermine is unlikely to be the sole cause of hypotension. Other underlying factors (e.g., comorbidities, physiological responses, intraoperative events) may contribute, thus warranting further investigation and clarity to current perioperative medication guidelines.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
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