The prescription diet drug phentermine has been around for nearly fifty years. The FDA first approved phentermine in 1959 for use as an appetite suppressant in the U.S. Then in the early 1970’s, phentermine hydrochloride was introduced to the weight loss market. King Pharmeceuticals sold Phentermine for Smith Kline Beecham under the name Fastin® until 1998, when the company stopped making the drug.
Phentermine is currently sold under a number of different brand names by several pharmaceutical companies. For example, Medeva Pharmaceuticals sells phentermine under the brand name Ionamin® and Gate Pharmaceuticals sells it as Adipex-P®.
Few tests were conducted on phentermine between 1959, when it was first approved, and the 1990’s. In the 1990’s, studies were conducted on a combination of phentermine and the drug fenfluramine, a combination that came to be known as Fen-Phen.
A 1992 study claimed that Phen-Fen produced better results than diet and exercise and that it had few side effects. But the safety of Fen-Phen came into question in 1997 when 24 people who had used Fen-Phen developed heart valve problems that were linked to the drug combination. As a result, the FDA requested the removal of Fen-Phen from the market. It was later determined that 30% of fenfluramine users had heart valve problems.
Phentermine alone was not believed to put people at risk, and the FDA has never requested that phentermine be removed from the market. The product remains available for use in many countries.
Because phentermine is similar in function to amphetamines, it is considered a controlled substance in many countries. Phentermine is classified as a schedule IV drug, meaning that it is relatively unlikely that anyone will abuse or become addicted to it.