SEATTLE — Side effects continue to limit pharmacologic treatments for obesity, Dr. Jonathan Purnell said at a meeting on drug therapy sponsored by the University of Washington.
Dr. Purnell, director of the weight regulation disorders clinic at Harborview Medical Center in Seattle, cited a lengthy list of potential side effects of phentermine (Fastin, Adipex, Ionamin) or sibutramine. These include primary pulmonary hypertension (associated with phenter-mine), dry mouth, constipation, insomnia, anxiety,. increased blood pressure, and palpitations and increased heart rate.
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Phentermine works by facilitating dopamine and norepinephrine release, while sibutramine facilitates serotonin release and norepinephrine release. The range of weight loss ascribed to these medications is 2-10 kg, he said.
In his opinion, contraindications for use of these drugs include age of less than 18 years, pregnancy or nursing, alcoholism, concomitant use of MAO inhibitors, personal or family history of pulmonary hypertension, glaucoma, untreated moderate to severe hypertension, coronary artery disease, peripheral vascular disease, seizure disorder, hyperthyroidism, and severe renal or liver disease.
Orlistat (Xenical) contains tetrahydrolipstatin, a nonabsorbed inhibitor of gastric and pancreatic lipase. This results in reduced absorption of fat and fat-soluble substances. The range of weight loss ascribed to this medication is 5-7.5 kg when combined with a hypocaloric diet.
Orlistat can cause gastrointestinal side effects that range from oily spotting and flatus to fecal incontinence (JAMA 281[3]:235-42, 1999). It also causes reductions in fat-soluble vitamins A, D, E, and [beta]-carotene, so Dr. Purnell recommends multivitamin supplement.
In his opinion, orlistat should not be used in patients with chronic malabsorption problems, cholestasis, or hypersensitivity to orlistat.
After prescribing a weight loss medication, Dr. Purnell sees patients 1 month later to assess tolerability and then every 3-4 months to check for side effects and assess the impact of regular aerobic exercise and other lifestyle measures. He discontinues medical therapy if patients have significant side effects or have lost less than 5%-10% of body weight after 6 months of drug therapy (See box.)
Above all, physicians should avoid using the one obesity therapy that clearly does not work: simple caloric restriction in the absence of any other lifestyle or pharmacologic treatments.
“Caloric restriction alone fails 95% of the time,” Dr. Purnell said.
Pharmacologic Tx Criteria
Dr. Purnell urged physicians to use specific criteria to determine whether a patient is eligible for pharmacologic treatment of obesity.
To qualify. the patient should meet one of the following conditions:
* Have a body mass index of at least 30 kg/[m.sup.2], or
* Have a body mass index Between 27 and 30 kg/[m.sup.2] and have one or more of the following conditions: type 2 diabetes, dyslipidemia, or hypertension.
If the patient does not experience a 5%-10% weight loss from baseline, the medication should be stopped, he said.