Belviq is a serotonin receptor agonist that controls the appetite, notes WebMD. It is typically used in conjunction with a doctor-approved, reduced-calorie diet, exercise and behavior modification program.
Taken orally twice a day, Belviq should be effective within the first 12 weeks of treatment, explains WebMD. As it can be habit forming, it is important to consult regularly with one's physician while on the medication.
Common side effects include constipation, nausea, headache, dry mouth and dizziness. More serious side effects include enlarged breasts, easy bruising and bleeding, mental changes, unexplained fever, and twitching muscles. Belviq can also cause a painful or prolonged erection in men. Allergic reactions such as rash and difficulty breathing are rare.