Researchers in Hong Kong have warned against "natural" or "herbal" slimming products because undeclared and untested variants of banned and controlled drugs have been found in some of them.
At issue are "analogues," or close cousins of banned or controlled slimming drugs, which are slightly modified in their chemical structures in the hope that they might aid in weight loss but escape detection by regulators.
Writing in the latest issue of the Hong Kong Medical Journal, a group of pathologists said 42 patients were taken to hospital between September 2004 and December 2006 after consuming products that were described as containing only natural herbs.
A 53-year-old woman with a history of hyperthyroidism suffered a sudden cardiac arrest and died four days after she was taken to hospital. Another, a 33-year-old woman, suffered liver failure after consuming one of these products for six weeks and had to receive a liver transplant. She recovered.
Laboratory tests of these products found they contained N-nitrosofenfluramine, an analogue of fenfluramine, and N-desmethyl-sibutramine, an analogue of sibutramine.
Both fenfluramine and sibutramine are weight-loss drugs but fenfluramine was banned by the U.S. Food and Drug Administration in 1997 after studies linked it to heart-valve damage. Sibutramine is a prescription drug.
"These (analogues) are like new virus strains, they may be harmless or pathogenic (cause illness)," said Tony Mak, a member of the research team and a pathologist with the government-backed Hospital Authority Toxicology Reference Laboratory.
"People should know they are gambling with their lives if they use drugs they don't know about ... If you buy on the Internet or from overseas (from an unknown source), it will be very dangerous," Mak said in an interview.
Unlike approved drugs, which are put on the market after an average 10 years' research involving hundreds of millions of dollars and tests, many analogues are untested.
In the case of analogues of weight-loss drugs, industry sources say they are produced in underground laboratories and then added furtively into some slimming products that are freely available over the counter or on the Internet.
Asked why the direct copies of these banned or controlled drugs are not used, Mak said: "They won't do that because they can be arrested for it. But they won't just have pure herbal contents because there is no herb that can make anyone lose weight," Mak said.
"So they alter the chemical structure, but they don't find out whether it has any efficacy (or safety)."
Mak called for tighter regulation.
"In Taiwan, Japan and the U.S., they are now regulating not only drugs but drug analogues, but not in Hong Kong ... As a responsible government, you can't allow these products to be used as drugs without proper evidence," he said.
"There are other analogues out there in the market. So long as there is a market and demand out there, there will be such things in the market. They are chemists. They are underground. Whatever the source, they have to be controlled."
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