Phentermine, Diethylproprion and related drugs
Drugs such as phenteramine and diethylproprion are the older drugs used in the treatment of obesity. They increase the amount of a substance norepineprine in the brain. They reduce appetite. They may also increase the energy utilization by the body. They are approved for short-term use for up to 3 months. Combination of phenteramine with fenfluramine (Fen - Phen) resulted in heart valve problems; hence this combination has been withdrawn. Phentermine and diethylproprion may cause adverse effects such as insomnia, palpitations, increased blood pressure, digestive system disorders and impotence. The patient may become dependent on these drugs or abuse them. Phenylpropanolamine, a drug from this class, was used earlier for weight loss. The FDA has withdrawn it due to increased risk of stroke.
Sibutramine
Sibutramine increases the amount of serotonin and noradrenaline in the brain. It increases satiety and reduces food intake. It may also reduce appetite. Additionally, it increases good cholesterol (HDL – cholesterol) levels. It is taken at a dose of 10 – 15 mg daily. It causes side effects such as dry mouth, headache, nausea, constipation and insomnia. It can cause changes in blood pressure and heart rate; hence patients should be monitored during treatment. Regular ECGs may be needed. It should not be used by patients with heart disease or stroke, or by patients over 65 years of age. Sibutramine is banned in Europe due to its heart-related side effects. It is now banned in the United States as well as in Australia.
Orlistat
Orlistat inhibits an enzyme called lipase in the digestive tract. Lipase breaks down fat into smaller particles that can be absorbed into the circulation. Orlistat thus prevents absorption of fat which is then excreted in the feces. Additionally, it helps to control cholesterol and blood glucose. It is also used in adolescent patients between 12 and 16 years of age. Since a large amount of undigested fat is excreted in the stool, the patient may suffer from side effects such as bloating, oily spotting and gas. Eating less fatty foods may reduce these side effects. Orlistat reduces the absorption of vitamins A, D, E and K that are absorbed along with fat, hence they have to be supplemented during treatment with orlistat.
Sibutramine and orlistat can reduce weight up to a maximum of 10%. Using the drugs together does not lead to additional weight loss, hence, combined use of these two drugs in obesity is not recommended.
Rimonabant
Rimonabant has been found to be very effective in causing weight loss. It reduces abdominal fat. It reduces the pleasure a person gets by eating tasty foods and consuming drinks, which are often rich in fat and calories. It inhibits the effects of certain substances called cannabinoids in the brain. It may benefit patients with altered cholesterol levels and liver diseases associated with obesity. However, it is known to cause adverse effects such as nausea, headache and vertigo. It has been withdrawn in most countries including India due to reports of depression and suicidal behavior as well as seizures.
