Drugs used for weight loss are called anorexiants. Obesity is a complex disorder, and the therapies and drugs (prescription, over-the-counter supplements, herbs, medicines, etc.) discussed here are to be taken only under the supervision of a qualified physician, and as part of an overall weight loss program that includes diet, exercise, and psychological and lifestyle supportive counseling. Our discussion of diet pills addresses the following five categories:
- Over-the-counter diet pills: Preparations containing phenylpropanolamine (e.g., Acutrim, Dexatrim) in dosages of 75 mg or higher have been known to increase blood pressure to dangerous levels and even cause stroke. Herbal preparations such as Phen-Fen, Phen-Cal, or PhenTrim contain ephedrine, derived from the ephedra (also known as Ma Huang) herb, which can increase heart rate and blood pressure to dangerous levels, possibly leading to psychotic behavior, Seizures, heart
attack, stroke, and death.
- Supplements, laxatives, and dietary teas: Preparations containing "plantain" may adversely affect heart rate and cause dangerous abnormalities in heart rate and rhythm. As a result of their actions, these substances may cause excess fluid loss and loss of important Electrolytes (e.g., Potassium), which in certain individuals (e.g., elderly, those with kidney or heart disease) may be very dangerous and even fatal. Overuse and abuse of these agents may be addictive and lead to gastrointestinal problems such as Constipation and
chronic abdominal pain.
- Prescription diet pills (standard): Such drugs are available only through a doctor's prescription, and work in a variety of ways. Some work by increasing the availability of serotonin, a chemical neurotransmitter in the brain that affects mood (prevents Depression) and
reduces Calorie consumption, and
imparts a sense of "well being." In addition,
serotonin reduces cravings for complex carbohydrates and
curbs the appetite. The best-known examples of
prescription medicines used to control obesity are:
- Dexfenfluramine (Redux)
- Fenfluramine (Pondimin),
combined with another anti-obesity drug called
phentermine (Phentrol, Fastin, Ionamin, Adipex),
prevents the body from absorbing dopamine and
norepinephrine, resulting in the sensation of being
energized, while reducing the craving for sugar.
Most of these drugs have been removed from the market
(however, Fastin, Ionamin, Adipex, are still available)
because of reports of heart problems (damage to the
valves of the heart) and lung problems (i.e., pulmonary
hypertension). Studies are under way to determine
whether these valvular abnormalities will eventually
reverse after the drug is withdrawn. The risks are
highest in patients taking the drugs for long periods,
or in high doses. Consumption for
two to three months appears to do no harm. Patients treated with Pondimin, Redux, or phen-fenfluramine for more than three months may need to have a complete examination of the heart and lungs (including an Echocardiogram),
recommended by their primary physician, or if they have signs and symptoms of heart or lung disease. Patients on an antidepressant from the family of Selective Serotonin Reuptake Inhibitors (SSRIs) such as Prozac, or
antidepressants from the monoamine oxidase inhibitors
(MOIs) may be at increased risk for dangerous side
effects if they take these antidepressant with the diet
drugs mentioned above.
- Newer prescription drugs:
- Sibutramine (Meridia), which works by keeping brain chemicals (neurotransmitters) such as serotonin and norepinephrine in balance, increases metabolism and has been shown to result in significant weight loss. Sibutramine also causes an increase in energy levels and a feeling of fullness. Side effects include dry mouth and Insomnia, High Blood Pressure, and some abnormal heart rhythms. Experts recommend that those with High Blood Pressure, heart disease or stroke, and those on medications such as decongestants, Asthma drugs (bronchodilators), monoamine oxidase inhibitors, or SSRI antidepressants, should avoid Sibutramine.
- Orlistat (Xenical) is related to Olestra, a fat substitute (introduced in some food products such as potato chips), and acts by slowing down the production of Lipase, an enzyme
in the stomach that breaks down fat. Orlistat does not suppress the appetite, but instead blocks absorption of about one-third of the fat consumed. A recent study indicated that when 892 obese adults were put on weight-loss diets, counseled on exercise, and assigned to one of two groups for a year, the group given Orlistat lost an average of 19 pounds, compared with about 12 pounds among those given a placebo (dummy pills). Furthermore, during the second year, patients who continued on Orlistat gained back half as much weight as the patients who switched to a dummy pill. The drug can cause gastrointestinal problems (gas, oily loose stools, and cramping) and may interfere with absorption of vitamins A, D, and E, so vitamin supplements are recommended.
- In the past, amphetamines such as Methamphetamine (Desoxyn), Dextroamphetamine (Dexedrine), and phenmetrazine (Pleudin) were
used for weight loss, but they are no longer prescribed
due to serious side effects and risk of addiction.
Less addictive and possibly safer derivatives of these
drugs include benzphetamine (Didrex), diethylpropion,
and phendimetrazine (Adipost, Botril, Melfiat, Plegine,
Prelu-2, Statobex), and mazindol (Mazanor,
- Experimental Therapies:
- The drug naltrexone (Trexan) blocks the euphoria experienced by drug abusers, and is being tested for people who binge-eat. Preliminary results from an early study examining the genetically-engineered drug leptin reported that patients on the highest dose lost 8% of their body weight after six months, and that the drug was well-tolerated.
- A steroid known as dexamethasone can double the concentration of leptin in the blood, suggesting that it may prove to be an effective drug in the treatment of obesity.
- In a recent study, treatment with a combination of growth hormone and an Insulin-like
substance was shown to improve fat loss when added to diet and exercise in postmenopausal obese women. The drug is administered via self-injection, and can cause water retention and swelling (edema). Further studies need to be conducted before safe recommendations can be made.
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