Dihydrocodeine
Systematic (IUPAC) name
4,5-alpha-epoxy-3-methoxy-17-methyl-morphinan-6-ol
Identifiers
CAS number	125-28-0
ATC code	N02AA08
PubChem	6426647
Chemical data
Formula	C18H23NO3
Mol. mass	301.38 g/mol
Pharmacokinetic data
Bioavailability	20%[1]
Metabolism	Mainly hepatic, through CYP3A4 and CYP2D6
Half life	4 hours[1]
Excretion	?
Therapeutic considerations
Pregnancy cat.	C(US) Image File history File links Dihydrocodeine_skeletal. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The Anatomical Therapeutic Chemical Classification System is used for the classification of drugs. ... A section of the Anatomical Therapeutic Chemical Classification System. ... PubChem is a database of chemical molecules. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... For other uses, see Carbon (disambiguation). ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... The molecular mass (abbreviated Mr) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... In pharmacology, bioavailability is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. ... Drug metabolism is the metabolism of drugs, their biochemical modification or degradation, usually through specialized enzymatic systems. ... For the bird, see Liver bird. ... Cytochrome P450 3A4 (abbreviated CYP3A4) (EC 1. ... Cytochrome P450 2D6 (CYP2D6), a member of the cytochrome P450 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body. ... The biological half-life of a substance is the time required for half of that substance to be removed from an organism by either a physical or a chemical process. ... The kidneys are important excretory organs in vertebrates. ... The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from...
Legal status	Class B(UK) Schedule II(US) The regulation of therapeutic goods, that is drugs and therapeutic devices, varies by jurisdiction. ... The Misuse of Drugs Act 1971 is an Act of Parliament, by which the United Kingdom aims to control the possession and supply of numerous drugs and drug-like substances, as listed under the Act, and to enable international co-operation against illegal drug trafficking. ... The Controlled Substances Act (CSA) was enacted into law by the Congress of the United States as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from...
Routes	Oral, IV, subcutaneous, rectal

Dihydrocodeine, also called DHC, Drocode, Paracodeine and Parzone and by the brand names of Synalgos DC, Panlor DC, Panlor SS, SS Bron, Drocode, Paracodin, Codidol, Didor Continus, Dicogesic, Codhydrine, Dekacodin, DH-Codeine, Didrate, Dihydrin, Hydrocodin, Nadeine, Novicodin, Rapacodin, Fortuss, Dico, and DF-118 amongst others, is a semi-synthetic opioid analgesic developed in Germany in the first decade of the XX. Century and put on the market in 1911. It is prescribed for postoperative pain, severe dyspnea, or as an antitussive. Dihydrocodeine tartrate is also present in co-dydramol. In some countries, controlled-release dihydrocodeine and/or the immediate release forumulations are used as an alternative to methadone in treatment of opioid dependency and addiction. In pharmacology and toxicology, a route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body. ... An intravenous drip in a hospital Intravenous therapy or IV therapy is the administration of liquid substances directly into a vein. ... An opioid is a chemical substance that has a morphine-like action in the body. ... An analgesic (colloquially known as a painkiller) is any member of the diverse group of drugs used to relieve pain (achieve analgesia). ... Dyspnea (R06. ... A cough medicine is a drug used to treat coughing and related conditions. ... Co-dydramol (BAN) is a non-proprietary name used to denote a combination of dihydrocodeine tartrate and paracetamol. ...

Commonly available as tablets, solutions, elixirs, and other oral forms, dihydrocodeine is also available in some countries as an injectable solution for deep subcutaneous and intra-muscular administration. Intravenous administration could be dangerous due to pulmonary oedema and the potential of anaphylaxis as it is with codeine. At one time in the past and possibly now, dihydrocodeine suppositories also existed.

Dihydrocodeine is used as an alternative to or incrementation on codeine for the above mentioned spectrum of situations. It is available as the following salts, in rough descending order of frequency of use: bitartrate, phosphate, hydrochloride, tartrate, hydroiodide, methyliodide, hydrobromide, and sulphate. The salt to free base conversion factors are 0,67 for the bitartrate, 0,73 for the phosphate, and 0,89 for the hydrochloride.

Dihydrocodeine was developed during the intense international search for more effective antitussives, especially to help reduce the airborne spread of tuberculosis, pertussis, pneumonia, and similar diseases, in the years from c.a. 1895 to 1915, and is similar in chemical structure to codeine. Depending on individual metabolism, dihydrocodeine is 100 to 150 percent as strong as codeine. Although dihydrocodeine does have extremely active metabolites, in the form of dihydromorphine and dihydromorphine-6-glucuronide (one hundred times more potent), these metabolites are produced in such small amount that they do not have clinically important effects.^[2] Codeine (INN) or methylmorphine is an opiate used for its analgesic, antitussive and antidiarrheal properties. ... Dihydromorphine is a semi-synthetic opioid invented in Germany in the first years of the twentieth century. ...

Indications

Approved indication for dihydrocodeine is the management of moderate to moderately severe pain as well as coughing and shortness of breath. As is the case with other drugs in this group, the antitussive dose tends to be less than the analgesic dose, and dihydrocodeine is a powerful cough suppressant like all other members of the immediate codeine family (see below) and their cousins hydrocodone, oxycodone and ethylmorphine (a.k.a. dionine and codethyline) “Hurting” redirects here. ... Hydrocodone or dihydrocodeinone (marketed as Vicodin, Anexsia, Dicodid, Hycodan (or generically Hydromet), Hycomine, Lorcet, Lortab, Norco, Novahistex, Hydroco, Tussionex, Vicoprofen, Xodol) is a semi-synthetic opioid derived from two of the naturally occurring opiates, codeine and thebaine. ... Not to be confused with oxytocin. ... Ethylmorphine is a drug in the class of both opiates (representing a minor synthetic change from morphine) and opioids (being effective in the CNSs opioid reception system) . Its effects in humans mainly stem from its metabolic conversion to morphine. ...

For use against pain, dihydrocodeine is usually formulated as tablets or capsules containing a quarter grain (15 or 16 mg) or a half grain (30 or 32 mg) with or without other active ingredients such as aspirin, paracetamol, ibuprofen, or others. The usual dose is one tablet taken every 4-6 hours when necessary. The milligram (symbol mg) is an SI unit of mass. ... This article is about the drug. ... Paracetamol (INN) (IPA: ) or acetaminophen (USAN), is the active metabolite of phenacetin, a so-called coal tar analgesic. ... Ibuprofen (INN) (IPA: ) (from the earlier nomenclature iso-butyl-propanoic-phenolic acid) is a non-steroidal anti-inflammatory drug (NSAID) originally marketed as Nurofen and since under various trademarks including Act-3, Advil, Brufen, Dorival, Herron Blue, Panafen, Motrin, Nuprin and Ipren or Ibumetin (Sweden), Ibuprom (Poland), IbuHEXAL, Moment (Italy...

Controlled-release dihydrocodeine is available for both pain and coughing as indicated below as waxy tablets containing 60 to 120 mg of the drug, and some formulations intended for use against coughing and the like have other active ingredients such as antihistamines, decongestants and others. Generally, the starting dose would be 60 mg every 12 hours.

Other oral formulations such as packets of effervescent powder, sublingual drops, elixirs and the like are also available in many places.

Injectable dihydrocodeine is most often given as a deep subcutaneous shot.

The above doses are typical starting doses for "opioid naïve" patients. Existing tolerance to opioids and more severe pain (up to about 6 or 7 on a 1 to 10 scale perhaps) call for higher doses; dihydrocodeine may be more like hydrocodone and oxycodone than codeine and ethylmorphine in lacking a theoretical analgesic ceiling, but toxicity of other ingredients (especially aspirin and paracetamol) and/or the side effects of the opioid itself -- especially vasodilation, itching, and other effects of the large quantities of histamine released in the body -- generally supervene and thus limit dihydrocodeine to the middle range of painkillers, viz. between ethylmorphine and nicocodeine on the continuum. Controlled-release dihydrocodeine is often taken every 8 hours and even 6 especially when titrating the dose in chronic pain cases and similar situations. Different authorities list the maximum daily dose for dihydrocodeine as being anywhere from 240 mg to 720 mg, all other things being equal. Not to be confused with oxytocin. ... Vasodilation is where blood vessels in the body become wider following the relaxation of the smooth muscle in the vessel wall. ... Ethylmorphine is a drug in the class of both opiates (representing a minor synthetic change from morphine) and opioids (being effective in the CNSs opioid reception system) . Its effects in humans mainly stem from its metabolic conversion to morphine. ... Nicocodeine (Lyopect) is an opiate derivative developed as a cough suppressant and analgesic. ...

Dihydrocodeine products which can be purchased over the counter in many European and Pacific Rim countries generally contain from 2 to 20 mg of dihydrocodeine per dosing unit combined with one or more other active ingredients such as paracetamol, aspirin, ibuprofen, antihistamines, decongestants, vitamins, medicinal herb preparations and other such ingredients. In a subset of these countries and foreign possessions, 30 mg tablets and 60 mg controlled-release tablets are available over the counter and chemists may very well be able to dispense the 90 and 120 mg strengths at their discretion.

In the United States, the most common analgesic brands with DHC are: DHC Plus (16 and 32 mg), Panlor SS (32 mg), ZerLor (32 mg), Panlor DC (16 mg) and Synalgos DC (16 mg). These combination products also include paracetamol (acetaminophen) and caffeine. Aspirin is used in the case of Synalgos DC. Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans. ...

The Panlor series is manufactured by Pan-American Laboratories of Covington, Louisiana, and they also market several dihydrocodeine-based prescription cough syrups in the United States.

Dihydrocodeine is sometimes marketed in combination preparations with paracetamol as co-dydramol (BAN) to provide greater pain relief than either agent used singly (q.v. drug synergy). Co-dydramol (BAN) is a non-proprietary name used to denote a combination of dihydrocodeine tartrate and paracetamol. ... A British Approved Name (BAN) is the official non-proprietary or generic name given to a pharmaceutical substance, as defined in the British Pharmacopoeia (BP). ... Synergy (from the Greek synergos, συνεργός meaning working together, circa 1660) refers to the phenomenon in which two or more discrete influences or agents acting together create an effect greater than that predicted by knowing only the separate effects of the individual agents. ...

In the UK and other countries, 30-mg tablets containing only dihydrocodeine as the active ingredient (DF-118) are available.

The original dihydrocodeine product, Paracodin, is an elixir of dihydrocodeine hydroiodide also available as a Tussionex-style suspension in many European countries.

In many European countries and elsewhere in the world, the most commonly-found dihydrocodeine preparations are extended-release tablets made by encasing granules of the ingredient mixture, almost always using the bitartrate salt of dihydrocodeine, of four different sizes in a wax-based binder. The usual strengths are 60, 90, and 120 mg. These tablets are used in some countries, such as Austria, as an alternative to methadone (MS-Contin/MST-Continus type medications and buprenorphine are also used for this purpose) for management of opiate addiction. Common trade names for the extended-release tablets are Didor Continus, Codidol, Codi-Contin, Dicodin (made in France and the major product containing the tartrate salt) and DHC Continus. Methadone is a synthetic opioid, used medically as an analgesic and in the treatment of narcotic addiction. ... Buprenorphine, is an opioid drug with partial agonist and antagonist actions. ...

Dihydrocodeine is available in Japan as tablets which contain 2½ mg of dihydrocodeine phosphate and caffeine, the decongestant d,l-methylephedrine HCl, and the antihistamine chlorpheniramine, and packets of granules which effervesce like Alka-Seltzer® with 10 mg of dihydrocodeine with lysozyme and chlorpheniramine, marketed for OTC sale as SS Bron. These two formulations may have once contained phenyltoloxamine citrate as the antihistamine component. The manufacturer of SS Bron, IsuIsu, also markets an ibuprofen with dihydrocodeine product called S.Tac EVE. Elsewhere in the Pacific Rim and elsewhere, Dicogesic in analogous to Glaxo/Smith-Kline's DF-118. Chlorphenamine (INN) or chlorpheniramine (USAN, former BAN), commonly marketed as its salt chlorphenamine maleate (CPM), is first-generation antihistamine used in the prevention of the symptoms of allergic conditions such as rhinitis and urticaria. ... Lysozyme single crystal. ... Phenyltoloxamine is an antihistamine with sedative and analgesic effects. ...

Dihydrocodeine is also the original member and chemical base of a number of similar semi-synthetic opiates such as acetyldihydrocodeine, dihydrocodeine enol acetate, dihydroisocodeine, nicocodeine, nicodicodeine, and thebacon. Scoring the poppy pod. ...

Side effects

As with other opioids, tolerance and physical and psychological dependence develop with repeated dihydrocodeine use. All opioids can impair the mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving or operating machinery if taken in large doses, but have the opposite effect in moderate doses.^[3] Drug addiction, or dependency is the compulsive use of drugs, to the point where the user has no effective choice but to continue use. ...

Itching and flushing and other effects of blood vessel dialation are also common side effects, due to histamine release in response to the drug using one or more types of receptors in the CNS and/or other responses elsewhere in the body. First-generation antihistamines such as tripelennamine (Pyrabenzamine®), clemastine (Tavist®), hydroxyzine (Atarax®), diphenhydramine (Benadryl®), cyproheptadine (Periactin®), brompheniramine (Dimetapp®), chlorpheniramine (Chlor-Trimeton®), doxylamine (NyQuil®) and phenyltoloxamine (Percogesic® Original Formula) not only combat the histamine-driven side effects, but are analgesic-sparing (potentiating) in various degrees. The antihistamine promethazine (Phenergan®) may also have a positive effect on hepatic metabolism of dihydrocodeine as it does with codeine. Higher doses of promethazine may interfere with most other opioids with the exception of the pethidine family (Demerol® and the like) by this and/or other unknown mechanisms.

Other side effects include giddiness and a sense of hyperactivity. Many patients and experts have pointed out that many opiates have the effect of generating empathy and improving interpersonal skills in a manner analogous to, but subjectively different from, MDMA, MDA, and many related amphetamine-variant entheogen/empathogen/hallucinogenics. Dihydrocodeine and hydrocodone seem to have this effect somewhat in excess of their theoretical analgesic potency as compared to other opioids.

As with all drugs, side effects depend on the person taking the medication. They can range in severity from mild to extreme, from headaches to difficulty breathing.

Constipation is the one side-effect of dihydrocodeine and almost all opioids which is near-universal. It results from the slowing of peristalsis in the gut and is a reason why dihydrocodeine, ethylmorphine, codeine, opium preparations, and morphine are used to stop diarrhoea and combat Irritable Bowel Syndrome (IBS) in its diarrhoeal and cyclical forms as well as other conditions causing hypermotility and/or intestinal cramping. The gut itself contains its own opioid receptors, which also allows opioids which do not enter the CNS at all or in appreciable quantites following oral administration such as the pethidine-related drugs loperamide, diphenoxylate, and difenoxin to work in the same fashion in a significant percentage of the population. These drugs also have direct anticholinergic effects which contribute to their action. The loperamide-like drugs, however, can exacerbate cyclical IBS and have little or no effect on the cramps associated with all major forms of IBS and exacerbate the constipation-predominant manifestation of this condition. As a result, the most effective opioids for this spectrum of GI complaints would be whole-opium preparations such as paregoric, laudanum, Dover's Powder, granulated opium, opium in pill form etc., with codeine and dihydrocodeine working very well also, especially on diarrhoeal and cyclical IBS. Whole opium contains not only morphine and codeine and other narcotic alkaloids but also the alkaloid papaverine, a smooth-muscle relaxant, and other alkaloids, oils, resins and waxes which can help with cramping and other symptoms. Preparations containing both paregoric and extract of belladonna were once available that were probably the strongest and most efficaceous of GI drugs.

Regulation

In Hong Kong, Dihydrocodeine is regulated under Schedule 1 of Hong Kong's Chapter 134 Dangerous Drugs Ordinance. It can only be used legally by health professionals and for university research purporses. The substance can be given by pharmacists under a prescription. Anyone who supply the substance without prescription can be fined $10000 (HKD). The penalty for trafficking or manufacturing the substance is a $5,000,000 (HKD) fine and life imprisonment. Possession of the substance for consumption without license from the Department of Health is illegal with a $1,000,000 (HKD) fine and/or 7 years of jail time. ISO 4217 Code HKD User(s) Hong Kong Inflation 2. ...

In the United Kingdom dihydrocodeine is a Class B drug; however, it is available over-the-counter in small amounts (less than 8 mg), when combined with paracetamol (see co-dydramol). Illegal possession of dihydrocodeine can result in up to 5 years in prison and/or an unlimited fine. The Misuse of Drugs Act 1971 is an Act of Parliament, by which the United Kingdom aims to control the possession and supply of numerous drugs and drug-like substances, as listed under the Act, and to enable international co-operation against illegal drug trafficking. ... Paracetamol (INN) (IPA: ) or acetaminophen (USAN), is the active metabolite of phenacetin, a so-called coal tar analgesic. ... Co-dydramol (BAN) is a non-proprietary name used to denote a combination of dihydrocodeine tartrate and paracetamol. ...

In the USA, it is a DEA Schedule II substance, although preparations containing small amounts of dihydrocodeine are classified as Schedule III or Schedule V, depending on the concentration of dihydrocodeine relative to other active constituents, such as paracetamol (acetaminophen). This scheduling is similar to codeine's. The DEA's Drug Code for dihydrocodeine free base and all salts is 9120. The DEAs enforcement activities may take agents anywhere from distant countries to suburban U.S. homes. ... The Controlled Substances Act (CSA) was enacted into law by the Congress of the United States as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. ... The Controlled Substances Act (CSA) was enacted into law by the Congress of the United States as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. ... The Controlled Substances Act (CSA) was enacted into law by the Congress of the United States as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. ... Codeine (INN) or methylmorphine is an opiate used for its analgesic, antitussive and antidiarrheal properties. ...

International treaties and the controlled-substances laws of most countries, such as the German Betäubungsmittelgesetz, regulate dihydrocodeine at the same level as codeine. Dihydrocodeine-based pharmaceuticals are especially used where chronic pain patients are able to have essentially OTC access to them provided they are registered with the provincial or national government as such a patient.

Controlled-release dihydrocodeine is a non-prescription item in some places, especially the 60 mg strength. A report by the Ivo Šandor Organisation in 2004 listed Andorra, Spain, Gibraltar, and Austria as having varying degrees of access to these and other dihydrocodeine, nicocodeine, and codeine products.

Chemistry

Dihydrocodeine is the parent drug of a series of moderately strong narcotics including hydrocodone, nicocodeine, nicodicodeine, thebacon, acetyldihydrocodeine and others. Hydrocodone or dihydrocodeinone (marketed as Vicodin, Anexsia, Dicodid, Hycodan (or generically Hydromet), Hycomine, Lorcet, Lortab, Norco, Novahistex, Hydroco, Tussionex, Vicoprofen, Xodol) is a semi-synthetic opioid derived from two of the naturally occurring opiates, codeine and thebaine. ... Nicocodeine (Lyopect) is an opiate derivative developed as a cough suppressant and analgesic. ... Nicodicodeine is an opiate derivative developed as a cough suppressant and analgesic. ... The chemical structure of dihydrocodeinone enol acetate Dihydrocodeinone Enol Acetate, or Thebacon, formerly marketed as its hydrochloride salt under the trade name Acedicon, is a semisynthetic opioid once used as an antitussive, primarily in Europe. ... Acetyldihydrocodeine is an opiate derivative developed as a cough suppressant and analgesic. ...

From the point of view of the organic chemist, the removal of the double bond makes the structure much more stable. It is more resistant to metabolic attack (hence a duration of action of 6 hours rather than 4 for codeine). It is also more stable in acidic, high-temperature environments. Whereas converting codeine to morphine is a difficult and unrewarding task, dihydrocodeine can be converted to dihydromorphine with very high yields (over 95%). Dihydromorphine is widely used in Japan. The dihydromorphine can be quantitatively converted to hydromorphone using potassium tert butoxide. Codeine (INN) or methylmorphine is an opiate used for its analgesic, antitussive and antidiarrheal properties. ... This article is about the drug. ... Dihydromorphine is a semi-synthetic opioid invented in Germany in the first years of the twentieth century. ... Dihydromorphine is a semi-synthetic opioid invented in Germany in the first years of the twentieth century. ... Hydromorphone is a drug developed in Germany in the 1920s and introduced to the mass market beginning in 1926. ...

Recreational Use

Due to dihydrocodeine providing a relaxing and euphoric high when taken in higher than therapeutic doses it is quite commonly used recreationally. As mentioned above, dihydrocodeine and its related drugs dihydromorphine and hydrocodone have a tendency to create subjective effects similar to those reported with MDMA such as enhanced empathy, euphoria, talkativeness and ability ro suspend or dissolve hang-ups and excessive defence mechanisms. Other opioids may also produce similar effects, hut compared to their analgesic strength the dihydrocodeine and hydrocodone series stand out as especially strong.

The onset of action of dihydrocodeine and the subsequent effects are often sufficient to satisfy and pleasantly surprise even heroin users; the article "Dihydrocodeine Information" quotes a heroin user as saying "[chewing Codidol extended-release tablets]...it's just like gear [i.e. heroin]!"

A typical recreational dose amongst those with low tolerance will be between 150mg-240mg, however it should be made clear not to go too high over this dosage as there has been one instance of death with as low as 400mg with a person without any opiate tolerance.

In both clinical and recreational respects, dihydrocodeine shares with hydrocodone the ability to be significantly boosted by the muscle relaxant Carisoprodol (Soma^®, Sanoma^® &c). The doses of both should be reduced and those who carlessly take these two drugs at the same time seriously endanger their health. None the less, this kind of mixture has a legitimate place in medicine and can he very helpful if undertaken properly: some proprietary Carisprodol preparations and doctors' orders for prescription compounding are mixtures of that drug with an NSAID, other ingredients like caffeine, dextromethorphan, vitamin C, cimetidine, paracetamol, antacids, antihistamines, all on top of a weak to moderately weak opioid such as codeine or dihydrocodeine. A common example is the three strengths of Soma Compound With Codeine^® No. 1, 2 or 3 -- i.e. with 8, 16 and 32 mg of codeine phosphate. Carisoprodol is a centrally-acting skeletal muscle relaxant whose active metabolite is meprobamate. ...

Footnotes

1. ^ ^{a b} Rowell F, Seymour R, Rawlins M (1983). "Pharmacokinetics of intravenous and oral dihydrocodeine and its acid metabolites.". Eur J Clin Pharmacol 25 (3): 419-24. PMID 6628531. 
2. ^ Schmidt H, Vormfelde S, Walchner-Bonjean M, Klinder K, Freudenthaler S, Gleiter C, Gundert-Remy U, Skopp G, Aderjan R, Fuhr U (2003). "The role of active metabolites in dihydrocodeine effects.". Int J Clin Pharmacol Ther 41 (3): 95-106. PMID 12665158. 
3. ^ O'Neill W, Hanks G, Simpson P, Fallon M, Jenkins E, Wesnes K (2000). "The cognitive and psychomotor effects of morphine in healthy subjects: a randomized controlled trial of repeated (four) oral doses of dextropropoxyphene, morphine, lorazepam and placebo.". Pain 85 (1-2): 209-15. PMID 10692620. 

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