Qsymia (Phentermine / Topiramate ER)

Qsymia is a once-daily extended-release combination of phentermine and topiramate, FDA-approved July 17, 2012, and the most effective non-GLP-1 prescription weight loss option. Extended to adolescents aged 12+. Generic versions are available, making it substantially more affordable than GLP-1 therapies. Phentermine stimulates hypothalamic norepinephrine release, suppressing appetite and increasing energy expenditure. Topiramate has multiple mechanisms including GABA modulation, carbonic anhydrase inhibition, and glutamate receptor effects, collectively reducing caloric intake. At low doses used in Qsymia, each drug stays below its therapeutic threshold for its primary indication -- reducing individual side effects while producing synergistic weight loss. In the EQUIP trial (N=1,267, 56 weeks, BMI 35+), patients on highest dose (15/92 mg) lost 10.9% body weight vs 1.6% placebo; 66% achieved 5%+ loss; 47% lost 10%+. CONQUER trial (N=2,487) showed 9.8% weight loss at 15/92 mg. Critical safety: Teratogenicity (oral cleft defects in infants) -- REMS program required, monthly pregnancy tests mandatory for women of childbearing potential. Black box warning. Also: cognitive impairment known as the Dopamax effect, increased heart rate, metabolic acidosis, kidney stones. Cost: Brand $200-$250/month; generics cheaper. Contraindicated with hyperthyroidism, glaucoma, MAOIs.