Efficacy of phentermine/topiramate extended release in weight management and metabolic profiles: A multicentre study in South Korea

Aims: Clinical trials have demonstrated the effectiveness of the phentermine and topiramate combination in weight management. This research evaluated the efficacy and safety of phentermine/topiramate extended release (ER) for weight management, focusing on alterations in body weight and metabolic parameters in routine clinical practice. Materials and Methods: We retrospectively included people with obesity who initiated phentermine/topiramate ER between January 2020 and April 2023 at 10 tertiary hospitals in South Korea. The study assessed body weight changes at 5–6 months and for those who continued, at 12 months, along with metabolic parameters. Total body weight was measured using calibrated electronic scales with participants in light indoor clothing. Results: The cohort included 1839 patients (540 men and 1299 women), with a 5–6-month continuation rate of 48%. At 5–6 months, the mean weight reduction was 7.9%, with sex-specific losses of 7.1% in men and 8.2% in women. Over 56% of participants achieved more than 5% weight loss, with 23% exceeding a 10% reduction. Younger participants, women and those with moderate to severe obesity exhibited more pronounced weight loss compared to older men and individuals with mild obesity, respectively. Concurrently, phentermine/topiramate ER treatment improved glucose regulation, lipid profiles and decreased blood pressure: the HbA1c decreased by 0.4 ± 0.9%, low-density lipoprotein (LDL) cholesterol by 10 ± 32 mg/dL and systolic blood pressure by 6 ± 15 mmHg (all p < 0.001). Treatment was well-tolerated, with a 15% incidence of mild adverse events like paresthesia, dry mouth and insomnia. At 12 months, patients who persisted in treatment (21%) experienced an average weight loss of 9.6%, with 65% surpassing a 5% weight loss. Conclusion: The study suggests phentermine/topiramate ER is an effective option for obesity management in a South Korean population, though long-term adherence remains a challenge.