Side effects of prescription weight loss medications

By Weight Loss Consultant • Related • Filed Under

Weight loss in overweight or obese humans can be achieved by diet, exercise and behavior modification or by treatment with drugs. During the past decades many weight loss medications have been tried with patients to reduce weight. Such drugs are generally anorexiants or appetite suppressants. Anorexiant drugs affect neurotransmitters in the brain. They may be further classified into those that affect catecholamines, such as dopamine and norepinephrine; those that affect serotonin; and those that affect more than one neurotransmitter. These weight loss drugs work by increasing the secretion of dopamine, norepinephrine, or serotonin into the synaptic neural cleft, by inhibiting the reuptake of these neurotransmitters into the neuron. Existing pharmacutical approaches to weight loss involve the use of amphetamine-based agents such as amphetamine, diethylpropion, mazindol and fenfluramine which act directly on the central nervous system to lower food intake by modulating dopaminergic, adrenergic and/or serotonergic mechanisms.

In general, weight loss drugs have limited efficacy and some clinically significant side effects. Although weight loss can be achieved with weight loss medications, their use is restricted due to CNS side-effects, potential addiction liability and the production of tolerance to their actions, with chronic administration leading to potential depression, vestibular disturbances, hallucinations and addiction, as well as interference with the actions of other drugs such as MAO inhibitors and antihypertensives. Adrenergic agents’ side effects include insomnia, irritability, nervousness, headache, nausea, and constipation. Some can even increase blood pressure and precipitate angina. Sibutramine can cause headache, insomnia, constipation, and dry mouth. Increases in blood pressure and pulse rate may also occur. Lipase inhibitors’ side effects include nausea, vomiting, oily spotting, abdominal pain, fatty oily stool, flatus, increased defecation, fecal urgency, and fecal incontinence. The gastrointestinal side effects could be worse if dietary fat is not reduced. Agents that increase energy expenditure such as ephedrine, theophylline, and thyroid hormone carry the risk of cardiac complications from hypertension, increased heart rate, and etc.

Sibutramine is a serotonin and norepinephrine reuptake inhibitor and reduces body weight by suppressing appetite. However, sibutramine inhibits the reuptake of norepinephrine and this may increase blood pressure. Therefore sibutramine is contraindicated for use in some overweight patients. Other side effects of sibutramine include increased heart rate, insomnia, constipation, headache, abdominal pain etc. Amphetamines, which are direct agents and readily cross the blood-brain barrier, mainly cause CNS stimulation, while ephedrine, and particularly pseudoephedrine, are indirect agents which do not cross the blood-brain barrier so readily, and thus are mainly seen to exert peripheral effects. The once popular appetite suppressant drug, the combination of fenfluramine and phentermine, was clinically determined to have significantly increased the risk of heart valve damage. Fenfluramine is known to be associated with primary pulmonary hypertension (PPH), a rare, often fatal disorder in which the blood vessels of the lungs are destroyed. Consequently, most of the drugs containing fenfluramine have been recalled and withdrawn. Orilistat acts by inhibiting the absorption of fat in the small intestine. This weight loss medication has as side effects oily stool, increased flatus, and occasional stool incontinence.

Manizidol is another CNS active drug which activates the central nervous system. Each of these agents have potential for addiction and induce significant CNS side effects, such as nervousness, loss of concentration, and insomnia. Dexfenfluramine was withdrawn from the market because of suspected heart valvulopathy; orlistat is limited by gastrointestinal side effects; the use of topiramate is limited by CNS effects; and the use of sibutramine is limited by its cardiovascular side effects which have led to reports of deaths and its withdrawal from the market. The phentermines are members of a class of drugs known as the sympathomimetics for their ability to mimic stimulation of the central nervous system. The phentermines act on the hypothalamus, an appetite control center of the brain. However, thIS drug loses effectiveness after about two weeks. It is not approved by the FDA for use beyond six weeks. Moreover, weight loss with this drug treatment may be temperary, in particular after the use of this drug is discontinued. Phentermine drug treatment is also associated with side effects including nervousness, irritability, headache, sweating, dry-mouth, nausea, and constipation.

Related information

Post a Response