(a) Appetite Stimulants: These include alkaloids having a bitter taste. They stimulate appetite mainly by reflex vagal stimulation. They include strychnine, nux vomica, and alcoholic beverages.
(b) Anorexiants: These agents depress the appetite. They may be used as an adjunct in the management of obesity. They act mainly through the following mechanisms by:
- They increase the levels of plasma-free fatty acids resulting in depression of appetite centers in the lateral hypothalamus.
- Inhibiting impulses reaching the appetite centers.
- Stimulating satiety center present in the medial hypothalamus.
Below mentioned are some common examples of anorexiants:
(i) Diethylpropion hydrochloride: It is a sympathomimetic agent having properties similar to amphetamine. Adverse effects include nausea, diarrhea, constipation, dry mouth, mydriasis, restlessness, insomnia, tremors, increased blood pressure, and tachycardia. It is used as an anorexiant in the management of obesity.
(ii) Fenfluramine hydrochloride: Chemically it is a trifluoromethyl derivative of amphetamine and is a sympathomimetic appetite suppressant agent. It has a plasma half-life of 13 – 30 hours. Inactive metabolites are excreted in the urine along with 10 – 20% unchanged drug. Adverse effects include vomiting, diarrhea, abdominal pain, dry mouth, alopecia, impotence, and pulmonary hypertension.
It is used as a weight-reducing agent for obesity. The adult oral dose is 20 – 40 mg three times a day. Treatment may be continued for up to 3 months and then the therapy can be gradually terminated.
(iii) Phendimetrazine tartrate: It is an orally active sympathomimetic agent having appetite suppressant activity. Upon hepatic inactivation, metabolites are excreted in the urine. The adult oral dose is 85 mg two to three times a day.
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