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Tuesday 15 January 2008

How The FDA Has Done Nothing About An Unsafe Drug

By: Herb Denenberg, The Bulletin

When you get a dangerous, expensive prescription drug that can be toxic to the heart, has serious addiction problems, has a low margin of safety, is no more effective than taking two aspirin, doesn't belong on the market at all and is banned in the United Kingdom, what happens to it in the U.S. and before the FDA?

It becomes a best-seller. In 2006, 22 million prescriptions for this drug were filled in the U.S., where it is the 17th most prescribed generic drug.

I'm talking about a combination of propoxyphene and acetaminophen, also sold under the brand name Darvocet. It is a pain reliever related to Darvon (propoxyphene alone) and Darvon Compound (propoxyphene, aspirin and caffeine).

The focus of this story is on propoxyphene, not acetaminophen (best known under the brand name Tylenol). The latter is a perfectly sensible drug and is, for most people, the preferred over-the-counter pain reliever.

This Darvocet issue came to my attention by the newsletter Worst Pills, Best Pills (January 2008), which pointed out that the U.K. had banned Darvocet in 2005. (It is known in the U.K. as co-proxamol.) However, it was a phased-out ban as Darvocet has addictive qualities, and a patient should not abruptly stop taking it. Instead, it should be phased out under medical supervision. The complete ban became effective at the beginning of 2008.

The British health authorities say the drug was banned because "each year there are 300 to 400 fatalities following deliberate or accidental overdoses involving propoxyphene/acetaminophen in England and Wales alone. Approximately one-fifth (60 to 80) of these deaths are considered accidental." The British health authorities also said the drug's effectiveness "is poorly established and the risk of toxicity in overdose, both accidental and deliberate, is unacceptable. ... It has not been possible to identify any patient group in whom the risk benefits [ratio] may be positive." In other words, for all groups, the risks outweigh the benefits, and the drug doesn't even belong on the market.

The newsletter says that in the U.S. the death numbers are even higher. There have been 2,500 accidental deaths reported in association with propoxyphene in the U.S. since 1981. Note that figure is for accidental deaths only, not total deaths.

The drug can be very dangerous, but it usually delivers slight pain relief. That has been well established by clinical trials, considered the gold standard for evaluating the effectiveness and safety of drugs. What's more, almost 40 years ago a study in the Journal of the American Medical Association found propoxyphene to be no more effective than aspirin, which is readily available over-the-counter and costs less. A New England Journal of Medicine study in 1972 reached the same conclusion. In The New Handbook of Prescription Drugs (1976) the authors noted that most studies show that propoxyphene is no better than aspirin or acetaminophen, that there have been reports of death from it, and its most serious "side effect" is its expense - it's more than 10 times more expensive than aspirin.

In addition, Worst Pills, Best Pills points out that when broken down in the body, propoxyphene is converted into a compound that is toxic to the heart. In addition the drug has a small margin of safety. That means a dangerous dose is only slightly higher than a recommended dose, and the newsletter also says a dangerous dose may be the same as the recommended dose. This small margin of safety can become even riskier as some taking the drug may not get relief and may therefore up the dose.

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