Sibutramine (Meridia) increases metabolism. One study showed an average drop in weight of 11% in obese patients taking sibutramine for six months. Sibutramine does not appear to have the pulmonary hypertension and heart valve problems seen with phen-phen, but some have reported high blood pressure and irregular heartbeats.

Those with a history for stroke, heart disease, high blood pressure, and irregular heartbeat probably should not take sibutramine. People taking decongestants, bronchodilators for asthma, monoamine oxidase inhibitors, or serotonin reuptake inhibitors (like Prozac) should also avoid sibutramine.