Other agents that did not achieve FDA approval for obesity treatment recently for safety reasons include rimonabant, a cannabinoid receptor antagonist; lorcaserin, a 5-hydroxytryptamine (serotonin) 2C receptor agonist; and the combination drugs topiramate/ phentermine and naltrexone/bupropion. Concerns about side effects were again the predominant reason for non-approval status, including anxiety and depression for rimonabant, breast tumors in rat models for lorcaserin, cardiovascular effects and teratogenicity for topiramate/phentermine, and elevations in blood pressure for naltrexone/ bupropion. These drugs did meet the FDA efficacy recommendations listed above. The approval bar for obesity agents in the United States is high because of the number of Americans who would be eligible for these agents (33.8% of the population was considered obese in the United States as of 2008).
