Phentermine is the most frequently recommended prescription medication for weight loss as it is considerably cheaper than other weight loss medications such as Meridia and Xenical.

It accounts for approximately 50% of all prescribed weight loss drugs, with about 18 million prescriptions issued last year alone.

Presently, phentermine is sold in the U.S. under the brand names of Ionamin® and Adipex-P®. Ionamin® is produced by Medeva Pharmaceuticals, while Adipex-P® is made by Gate Pharmaceuticals.

Phentermine is also available in generic form under the same name. It was previously sold as Fastin® by SmithKline Beecham, who discontinued it from the market.

Currently no new trials of phentermine have been conducted. However trails were carried out on the combination usage of Phentermine and Fenfluramine together, commonly known as “Phen-fen” in the early 90's.

Phen-fen was marketed as a weight loss phenomenon, but was withdrawn from the market in 1997 by the FDA, after it was proved that this drug combination caused valvular heart disease.

Initially touted as a miracle pill to ‘melt fat away', phentermine like all like all appetite suppressants is not be substituted for a proper diet. For optimum results this drug should be use in conjunction with a healthy diet and a proper exercise program.

Phentermine is a sympathomimetic amine medication that is similar to an amphetamine. It is also identified as an "anorectic" or "anorexigenic" drug. Phentermine stimulates the central nervous system, which causes the heart rate and blood pressure to rise and in doing so decreases appetite.

Caution is advised however when using phentermine as it a ‘habit forming' drug. This means that with prolonged usage of this medication you can become physically and psychologically dependent on it, and experience withdrawal symptoms with its discontinuation. Use phentermine only under the observation of a qualified heath care professional or doctor.

This medication is known to cause dizziness, blurred vision and restlessness, caution is advised when driving or operating machinery.

It is important to remember not to take phentermine later in the day, as it can trigger insomnia. Phentermine should be taken ideally at breakfast.

If you experience any of the following serious side effects, stop taking phentermine and consult your doctor immediately.
- An allergic reaction such as breathing problems, swelling of face, tongue or lips or hives.
- An irregular heartbeat or extremely high blood pressure.
- Restlessness or tremors
- Nervousness or anxiety
- Headaches
- Insomnia
- Dry or unpleasant taste in the mouth
- Diarrhea or constipation
- Impotence or lack of sex drive.

Phentermine also has serious interaction with other medications such as MAO inhibitors like Nardil or Marplan; blood pressure medications like Ismelin or tricyclic antidepressants like Elavil, Pamelor or Asendin.

Phentermine should not be taken by patients who have glaucoma, hyperthyroidism, a history of drug or substance abuse, psychotic illness or heart problems. Patents with diabetes need to monitor their insulin levels, as phentermine affects the body's blood sugar. Avoid alcohol while on phentermine as it can cause a drug interaction.