Dubbed "speed," amphetamines like Hydrin were the miracle drugs of a postwar US, used to treat everything from Parkinson's to hay fever. In 1947, Hydrin was also approved to treat obesity. True to its nickname, speed worked fast: Patients lost an average of 11 pounds in 30 days. Other amphetamine-based "diet pills" followed.
But: By the mid-1960s, amphetamines were the most prescribed and most abused drug in the US. Classified as a controlled substance in 1971, they were pulled from the market for weight loss in 1979.
In the 1990s, researchers discovered that a mixture of two amphetamine-like appetite suppressants phentermine and fenfluramine produced a highly effective combination for weight loss. Nearly two-thirds of patients lost at least 5 percent of their body weight after one year the FDA's benchmark for efficacy. The agency approved phen-fen for weight loss in 1996.
But: Phen-fen was a huge hit until the Mayo Clinic reported that the combination was associated with heart valve disease. In 1997, fenfluramine was pulled off the market.
Approved by the FDA in 1997, Meridia (known generically as sibutramine) boosts serotonin levels in the brain, making users feel satiated. In trials, 60 percent of patients lost 5 percent of their body weight after one year.
But: Meridia's most serious side effects are increased blood pressure and pulse rate, as well as an elevated risk of coronary artery disease. Since the obese are often already at great risk of heart disease, this has dampened enthusiasm for the drug.
Sold as Xenical, the obesity drug was approved in the US in 1999. It works by impeding the body's ability to absorb fat. Studies show weight-loss results are comparable to Meridia.
But: The fat has to go somewhere, and Xenical users report what's euphemistically called "oily discharge" flatulence and loose bowel movements making it unpopular among patients.
This Sanofi-Aventis drug is on the market in Europe as Acomplia but awaits FDA approval in the US. It packs a one-two punch: In the brain it diminishes cravings, while elsewhere in the body it improves fat metabolism.
But: Good results in four human trials, but some patients reported side effects including depression, anxiety, and irritability. The FDA delayed a decision on the drug earlier this year.
Published first at www.wired.com