Dextropropoxyphene (Molecule of the Month for January 2007)
Co-proxamol, Darvon, Doloxene, Darvocet, CAPADEX
Dextropropoxyphene is an analgesic in the opioid category. It is used to treat mild to moderate pain and as an antitussive. It can be used to ease pain before, during and after an operation. Dextropropoxyphene, like codeine, is a "weak" opioid. Codeine is more commonly used, however some individuals (approximately 10-20% of the Caucasian population) are unable to metabolize it, so it is with these people dextropropoxyphene is particularly useful. In pure form, dextropropoxyphene is commonly used to ease the withdrawal symptoms in people addicted to opioids. Being very weak in comparison to the opioids that are commonly abused, dextropropoxyphene can only act as a "partial" substitute. It does not have much effect on mental cravings; however it can be effective in alleviating physical withdrawal effects, such as muscle cramps.
Darvon, a dextropropxyphene made by Eli Lilly, which had been on the market for 25 years, came under heavy fire in 1978 by consumer groups that said it was associated with suicide. Darvon was never withdrawn from the market, but Lilly has waged a sweeping, and largely successful, campaign among doctors, pharmacists and Darvon users to defend the drug as safe when it is used in proper doses and not mixed with alcohol.
Co-proxamol contains a combination of paracetamol and dextropropoxyphene. Co-proxamol is used by hundreds of thousands of patients but is to being withdrawn in the UK over reports linking about 400 deaths to overdoses of the drug. The UK Healthcare Products Regulatory Agency's (MHRA) claimed that taking 10 pills in a 24 hour period could lead to slowing of the respiratory system, abnormal heart rhythms and cardiac arrest. It is estimated that 1.7 million GP patients in the UK receive a prescription for the drug each year. A phased UK ban was introduced in 2005 but the painkiller will still be available on prescription until the end of 2007. This has been a somewhat controversial decision, since it has caused abusers to switch to the combined product and risk acetaminophen toxicity. Australia declined to follow suit and opted to allow pure dextropropoxyphene to remain available by prescription.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for January 2007 )