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Obesity drugs

Obesity drugs result in additional weight loss relative to placebo

Medications also resulted in greater improvements in many cardiometabolic risk factors than placebo

Obesity medications approved for long term use in conjunction with a healthy lifestyle result in additional weight loss relative to placebo ranging from approximately 3% of initial weight to 9%, according to a systematic review of medications currently approved in the US for obesity treatment in adults. The researchers from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institutes of Health.

The study, published in JAMA, concluded that orlistat, Belviq and Qnexa increase the likelihood that a patient will achieve clinically meaningful weight loss when used as an adjunct to lifestyle intervention.

Dr Susan Z Yanovski,  from the Division of Digestive Diseases and Nutrition, National Institute of Diabetes and Digestive and Kidney Diseases, and Dr Jack A Yanovski, Chief of the Section on Growth and Obesity in the Program on Developmental Endocrinology and Genetics, of the National Institutes of Health conducted a PubMed search from inception through September 2013 to find meta-analyses, systematic reviews, and randomised, placebo-controlled trials for currently approved obesity medications lasting at least one year that had a primary or secondary outcome of body weight change, included at least 50 participants per group, reported at least 50% retention, and reported results on an intention-to-treat basis.

Studies of medications approved for other purposes but tested for obesity treatment were also reviewed.

Overall all the systematic review included 21 studies; 15 on orlistat (Xenical, alli), four on lorcaserin (Belviq) and two on Qnexa (phentermine and topiramate).

The findings showed that obesity medications approved for long term use in conjunction with a healthy lifestyle result in additional weight loss relative to placebo ranging from approximately 3% of initial weight for orlistat and lorcaserin to 9% for top-dose (15/92mg) phentermine plus topiramate–extended release at one year.

The percentage of patients losing clinically meaningful weight loss (at least 5% of body weight) ranged from, 37% to 47% for lorcaserin, 35% to 73% for orlistat, and 67% to 70% for top-dose phentermine plus topiramate–extended release.

All three medications also resulted in greater improvements in many cardiometabolic risk factors than placebo. However, no obesity medication had reduced cardiovascular morbidity or mortality.

Most prescriptions are for noradrenergic medications, despite their approval only for short-term use and limited data for their long-term safety and efficacy. Noradrenergic agents are medications that regulate levels of a neurotransmitter called noradrenaline in the body. Noradrenergic agents used to treat people with autism include antidepressants, medications for high blood pressure, and medications to improve attention.

Yanovskis notes that each medication has its own cautions such as orlistat that produce changes in bowl function due to the unabsorbed fat. Fatty/oily stool, oily spotting, intestinal gas with discharge, a feeling of needing to have a bowel movement right away, increased number of bowel movements, or poor bowel control may occur.

Qnexa came with a risk evaluation and mitigation strategy (REMS) because of topiramate's links to potential birth defects. The neurological agent has been known to increase the risk of oral clefts in babies born to mothers who become pregnant while taking the drug. Also another concern raised was a small increase in heart rate due to using the drug.

Belviq does not currently have REMS, (a Risk Evaluation and Mitigation Strategy from manufacturers to ensure that the benefits of a drug or biological product outweigh its risks). However, the FDA required post marketing studies on the drug due to the drugs similarities to fenfluramine, the harmful component of Fen-Phen that was tied to heart valve problems.

The new agent more selectively targets the 5HT2C receptor, which is not found in heart muscle, as was the 5HT2B receptor that was the target of fenfluramine.

The researchers also examined other noradrenergic medications (including phentermine, diethylpropion, phendimetrazine, and benzphetamine) that had limited data on long-term safety and efficacy because they were developed many years ago.

The researchers noted that phentermine is currently the most widely prescribed drug in the US, with 25.3 million prescriptions for 6.2 million users written between 2008 and 2011.

Other medications that are being examined for weight loss benefits include liraglutide (Victoza), an injectable prescription medicine that may improve blood sugar (glucose) in adults with type 2 diabetes when used along with diet and exercise and Contrave, a fixed-dose combination of bupropion sustained-release (SR) and Orexigen´s proprietary SR version of naltrexone, designed to improve drug tolerability.

Contrave is believed to reduce appetite, help control cravings, increase metabolism and improve control over eating behaviours.

“Medications approved for long-term obesity treatment, when used as an adjunct to lifestyle intervention, lead to greater mean weight loss and an increased likelihood of achieving clinically meaningful one-year weight loss relative to placebo,” the authors conclude. “By discontinuing medication in patients, who do not respond with weight loss of at least 5%, clinicians can decrease their patients’ exposure to the risks and costs of drug treatment when there is little prospect of long-term benefit.”

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