Article: Dextropropoxyphene

Dextropropoxyphene
Systematic (IUPAC) name
[(2R,3R)-4-dimethylamino- 3-methyl-1,2-diphenyl-butan-2-yl] propanoate
Identifiers
CAS number	?
ATC code	N02AC04
PubChem	10100
Chemical data
Formula	C22H29NO2
Mol. weight	339.471
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	?
Excretion	?
Therapeutic considerations
Pregnancy cat.	?
Legal status
Routes	?

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. It is often combined with acetominophen in the preparation co-proxamol (Darvocet in the US).

It is an optical isomer of Levopropoxyphene. The racemic mixture is called Propoxyphene.

Some preparations that contain dextropoxyphene include: Distalgesic and Doloxene.

Indications

• Analgesia

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, due to poor functioning of the enzyme CYP2D6. It is in these people that dextropropoxyphene is particularly useful, as its metabolism does not require CYP2D6.

• Opioid withdrawal

In pure form, dextropropoxyphene is commonly used to ease the withdrawal symptoms in people addicted to opioids. Being very weak in comparison to those opioids which 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.

Dextropropoxyphene is subject to some controversy: while many physicians prescribe it for a wide range of mildly to moderately painful symptoms as well as in treatment of diarrhoea, many others refuse to prescribe it, citing its highly addictive nature and limited effectiveness (some studies show it to be no more effective as a painkiller than aspirin).

The therapeutic index of dextropoxyphene is relatively small. In the UK, dextropropoxyphene and co-proxamol are now discouraged from general use, and since 2004 preparations containing only dextropropoxyphene have been discontinued. This has been a somewhat controversial decision, since it has caused abusers to switch to the combined product and risk acetominophen toxicity. Australia declined to follow suit, and opted to allow pure dextropropoxyphene to remain available by prescription.

In the United States, dextropropoxyphene HCl is available as a prescription with acetaminophen in ratio anywhere from 30mg / 600mg to 60mg / 325mg, respectively. These are usually named "Darvocet," "Darvin," or "Darvon." In Australia, dextropropoxyphene is available on prescription, both as a combined product (32.5mg dextropropoxyphene per 325mg acetaminophen) known as either "Digesic", "capadex", or "paradex" and in pure form (100mg capsules) known as "Doloxene".

Adverse effects

Darvocet overdose is commonly broken into two categories: liver toxicity (from acetaminophen poisoning) and dextropropoxyphene overdose. Many users experience toxic effects from the acetaminophen in pursuit of the endlessly-increasing dose required to achieve euphoria. They suffer acute liver toxicity, which causes severe stomach pain, nausea, and vomiting (all of which are increased by light or stimulation of the sense of sight).

Recreational use

Recreational users tend to take anywhere from 240 to 420 milligrams of dextropropoxyphene (and the acetaminophen that goes with it). These users often suffer a persistent dry mouth, decreased appetite, urinary retention and constipation that may lead to diverticulitis.