Initial weight loss as a predictor of response to obesity drugs

BACKGROUND: Initial weight loss has been used as a predictor of long-term r esponse to obesity drugs. Discontinuation of drugs has been recommended if weight loss is not greater than or equal to 1.81 kg (4 lb) in the first mon th of treatment. OBJECTIVE: We compared the weight loss response at 6 months of patients los ing greater than or equal to 1.81 kg (responders) vs < 1.81 kg (non-respond ers) in the first month of treatment with the combination of fenfluramine a nd phentermine. DESIGN: Outcomes at 6 months in 975 patients treated in a comprehensive pro gram of phentermine (15 - 30 mg/d) d,l-fenfluramine (20 - 60 mg/d), were co mpared for responders vs non-responders. RESULTS: In the total population, first month weight loss highly correlated with % reduction in body mass index (BNI) after 6 months of treatment (P < 0.001). The reduction in baseline BMI after 6 months treatment was greater for the responders (15.9% vs 10%, P < 0.02). However, the North American A ssociation for the Study of Obesity (NAASO) guidelines for drug treatment o f obesity state that a 5% weight loss produces significant health benefits, and may be used as a criteria for success. At 6 months, 76%, 37% and 14% o f the non-respondents had lost greater than or equal to 5%, greater than or equal to 10% and greater than or equal to 15% of baseline BMI, respectivel y. After 6 months treatment the reductions in serum cholesterol, triglyceri des and LDL-cholesterol were 0.55, 0.31 and 0.42 mmol/L, respectively, (P l ess than or equal to 0.006), for the non-responders. Adverse effects after 6 months of treatment and the dropout rates after 1 y of treatment were not significantly different for the two groups. CONCLUSIONS: Although, the first month weight loss predicted the long-term response to phen-fen treatment, it was inadequate in identifying the non-re sponders and may unnecessarily preclude potential beneficiaries of the trea tment.