Phentermine and topiramate may aid in the efforts to reduce the occurrence of rapid weight regain after Roux-en-Y gastric bypass surgery (RYGB), according to study results published in Obesity.

Although bariatric surgery is an important treatment strategy for patients with severe obesity, weight regain is an important caveat. The goal of the current study was to assess the potential utility of topiramate and phentermine to prevent weight regain after RYGB.

The retrospective study included adult patients who underwent RYGB surgery at Boston Medical Center in Boston, Massachusetts, between 2004 and 2015. The researchers reviewed the electronic medical records of 1196 patients and after exclusion of 436 who had not achieved nadir weight, they calculated weight loss as the difference between presurgical weight and nadir weight for 760 individuals. Weight regain was evaluated by comparing each patient’s weight during subsequent postoperative office visits to nadir weight.

Use of anti-obesity medications was determined from the date of prescription of any of the following medications: phentermine, topiramate, lorcaserin (Belviq), phentermine/topiramate (Qsymia), and naltrexone/bupropion (Contrave). Patients who were prescribed anti-obesity medications and came to follow-up visits were classified as adherent users, whereas those who missed their follow-up visits were considered nonadherent given that prescriptions likely had to be refilled at these missed visits.


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Of the 760 patients in the cohort, 350 were treated with anti-obesity medications, including phentermine alone (119 patients), topiramate alone (74 patients), or combination of these medications (154 patients). Only 3 patients were prescribed lorcaserin.

The researchers classified weight regain as percentage of nadir weight by quartile, with cutoff points for the 25th, 50th, and 75th percentiles of weight regain of 1.49%, 6.25%, and 14.29% relative to the nadir, respectively. A total of 3 statistical models were used to evaluate the effect of anti-obesity medications on weight regain rates for each of the quartile cutoff values.

All models suggested that the use of anti-obesity medications, specifically topiramate and phentermine and adherence to these medications, was effective in mitigating weight regain after RYGB.

A Cox regression analysis showed a proportional hazard ratio of 0.729 (95% CI, 0.556-0.957; P =.023) for the adherent anti-obesity medications users compared with nonusers. In a binary logistic model adjusted for age, sex, race, and socioeconomic status, the odds ratio for occurrence of weight regain of ≥1.22% per month relative to nadir was 0.579 (95% CI, 0.371-0.877; P =.01) for patients adherent to anti-obesity medications compared with 0.872 (95% CI, 0.593-1.284; P =.5) for nonusers.

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The researchers acknowledged several limitations to the study, including the retrospective design, lack of unified protocol for use of anti-obesity medications, available data only on phentermine and topiramate, and the randomness of decisions made by providers and patients to use or abstain from anti-obesity medications.

“[P]hentermine and topiramate could play a role in the management of weight relapse after RYGB. However, the full potential of these agents and newer [anti-obesity medications] to counter weight recidivism and prevent the recurrence of obesity-related comorbidities needs to be further explored in prospective clinical trials,” concluded the researchers.

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Reference

Istfan NW, Anderson WA, Hess DT, Yu L, Carmine B, Apovian CM. The mitigating effect of phentermine and topiramate on weight regain after Roux-en-Y gastric bypass surgery. Obesity (Silver Spring). 2020;28(6):1023‐1030.