Dextropropoxyphene is an analgesic in the opioid category, patented in 1955 and manufactured by Eli Lilly and Company. It is an optical isomer of levopropoxyphene. It is intended to treat mild pain and also has antitussive (cough suppressant) and local anaesthetic effects. The drug has been taken off the market in Europe and the US due to concerns of fatal overdoses and heart arrhythmias. It is still available in Australia, albeit with restrictions after an application by its manufacturer to review its proposed banning. Its onset of analgesia (pain relief) is said to be 20–30 minutes and peak effects are seen about 1.5–2.0 hours after oral administration. Dextropropoxyphene is sometimes combined with acetaminophen. Trade names include Darvocet-N, Di-Gesic, and Darvon with APAP (for dextropropoxyphene and paracetamol). The British approved name (i.e. the generic name of the active ingredient) of the paracetamol/dextropropoxyphene preparation is co-proxamol (sold under a variety of brand names); however, it has been withdrawn since 2007, and is no longer available to new patients, with exceptions. The paracetamol combination(s) are known as Capadex or Di-Gesic in Australia, Lentogesic in South Africa, and Di-Antalvic in France (unlike co-proxamol, which is an approved name, these are all brand names). Dextropropoxyphene is known under several synonyms, including: Alpha-d-4-dimethylamino-3-methyl-1,2-diphenyl-2-butanol propionate [(2S,3R)-4-(Dimethylamino)-3- methyl-1,2-diphenylbutan-2-yl] propanoate (+)-1,2-Diphenyl-2-propionoxy- 3-methyl-4-di-methylaminobutane Desoxypropiophen Uses Analgesia Dextropropoxyphene is generally considered a weak analgesic, with several studies finding its efficacy is no better than acetaminophen. Like codeine, is a weak opioid, however it has one-third to one-half its analgesic activity. Restless legs syndrome Dextropropoxyphene has been found to be helpful in relieving the symptoms of restless legs syndrome. Contraindications Dextropropoxyphene is contraindicated in patients allergic to paracetamol (acetaminophen) or dextropropoxyphene, and in alcoholics. It is not intended for use in patients who are prone to suicide, anxiety, panic, or addiction. Side effects Severe toxicity can occur with small increments above the therapeutic dose including cardiotoxicity, and fatal overdoses. This is especially true when the drug is combined with alcohol. Other side effects include: Constipation Itching Drowsiness Nausea Sensorineural deafness Pharmacology Dextropropoxyphene acts as a mu-opioid receptor agonist. It also acts as a potent, noncompetitive α3β4 neuronal nicotinic acetylcholine receptor antagonist, as well as a weak serotonin reuptake inhibitor. Toxicity Overdose is commonly broken into two categories - liver toxicity (from paracetamol poisoning) and dextropropoxyphene overdose. An overdose of dextropropoxyphene may lead to various systemic effects. Excessive opioid receptor stimulation is responsible