Does promethazine increase the percentage of codeine converted to morphine in the liver?

Question

If not, does potentiate or inhibit codeine?and by which mechanism?

Answer 1

Codeine (INN) or methylmorphine is an opiate used for its analgesic, antitussive and antidiarrheal properties. It is by far the most widely used opiate in the world and very likely most commonly used drug overall according to numerous reports over the years by organizations such as the World Health Organization and its League of Nations predecessor agency and others. It is one of the most effective orally-administered opioid analgesics and has a wide safety margin. It is from 8 to 12 percent of the strength of morphine in most people; differences in metabolism can change this figure as can other medications.

Codeine is an alkaloid found in opium and other poppy saps like Papaver bracteatum the Iranian poppy. It was first isolated in 1830 in France by Jean-Pierre Robiquet, in concentrations ranging from 0.3 to 3.0 percent. While codeine can be extracted from opium, most codeine is synthesized from morphine through the process of O-methylation.

Although it is a naturally-occurring opiate, codeine can also be made by complete synthesis as well. The effects of the Nixon War On Drugs by 1972 or so had caused across-the-board shortages of illicit and licit opiates because of a scarcity of natural opium, poppy straw and other sources of opium alkaloids, and the geopolitical situation was getting less helpful for the United States. After a large percentage of the opium and morphine in the US National Stockpile of Strategic & Critical Materials had to be tapped in order to ease severe shortages of medicinal opiates -- the codeine-based antitussives in particular -- in late 1973, researchers were tasked with and quickly succeeded in finding a way that codeine and its derivatives and precursors can be synthesised from scratch from petroleum or coal tar using a process developed at the United States' National Institutes of Health.

Codeine is marketed as the salts codeine sulphate and codeine phosphate in the United States and Canada. Codeine hydrochloride is more commonly marketed in continental Europe and other regions, and codeine hydroiodide and codeine bitartrate round out the top five most-used codeine salts worldwide. Codeine is usually present in raw opium as free alkaloid in addition to codeine meconate, codeine pectinate, and possibly other naturally-occurring codeine salts. Dozens of other salts of codeine have been developed over the last 175 years including some with special properties of other drug groups such as codeine salicylate and codeine-based salts of barbituric acid (barbiturates). Codeine citrate, nitrate, picrate, acetate, hydrobromide and others are occasionally encountered on the pharmaceutical market and in research.

Codeine is the starting material and prototype of a large class of mainly mild to moderately strong opioids such as hydrocodone, dihydrocodeine and its derivatives such as nicocodeine, oxycodone etc. Related to codeine in other ways are Codeine-N-Oxide (Genocodeine), related to the nitrogen morphine derivatives as is codeine methobromide, and heterocodeine which is a drug six times stronger than morphine and 72 times stronger than codeine due to a small re-arrangement of the molecule, viz. moving the methyl group from the 3 to the 6 position on the morphine carbon skeleton. Drugs bearing resemblance to codeine in effects due to close structural relationship are variations on the methyl groups at the 3 position including ethylmorphine a.k.a. codethyline (Dionine) and benzylmorphine (Peronine). While having no narcotic effects of its own, the important opioid precursor thebaine differs from codeine only slightly in structure. Pseudocodeine and some other similar alkaloids not currently used in medicine are found in trace amounts in opium as well.

Contents [hide]

1 Indications

2 Controlled substance

3 Pharmacokinetics

4 Pharmacology

5 Adverse effects

6 Recreational use

7 References



[edit] Indications

Approved indications for codeine include:

Cough, though its efficacy in low dose over the counter formulations has been disputed.[2]

Diarrhea

Mild to severe pain

Irritable bowel syndrome

Codeine is sometimes marketed in combination preparations with the analgesic, acetaminophen (paracetamol), as co-codamol, paracod, panadeine, or Tylenol 3, with the analgesic, acetylsalicylic acid (aspirin), as co-codaprin or with the NSAID (non-steroidal anti-inflammatory drug), ibuprofen, as Herron Blue or Nurofen Plus. These combinations provide greater pain relief than either agent alone (drug synergy). Codeine is also commonly compounded with other pain killers or muscle relaxers such as Fioricet with Codeine, Soma Compound/Codeine, etc. Codeine-only products can be obtained with a prescription as a time release tablet (eg. Codeine Contin(r) 100mg) and Perduretas (50 mg).

The narcotic content number in the US names of codeine tablets and combination products like Tylenol With Codeine No. 3, Emprin With Codeine No. 4 are as follows: No. 1 - 7½ or 8 mg (1/8 grain), No. 2 - 15 or 16 mg (1/4 grain), No. 3 - 30 or 32 mg (1/2 grain), No. 4 - 60 or 64 mg (1 grain). The Canadian 222 series is identical to the above list 222=1/8 grain, 292=1/4 grain, 293=1/2 grain, and 294=1 grain of codeine.

Injectable codeine is available for subcutaneous or intramuscular injecton; intravenous injection can cause a serious reaction which can progress to anaphylaxis. Codeine suppositories are also marketed in some countries.

[edit] Controlled substance

In Australia, New Zealand, Romania, Canada and many other countries, codeine is regulated. In some countries it is available without prescription in combination preparations from licensed pharmacists in doses up to 15 mg/tablet in Australia, 8 mg/tablet in Canada , 20 mg/tablet in New Zealand, and 10mg/tablet in Israel.[citation needed]

In Canada, codeine can be sold over the counter only in combination with two or more ingredients, which has resulted in the prevalence of AC&C (aspirin, codeine, and caffeine), and similar combinations using acetaminophen (paracetamol) rather than aspirin. Caffeine, being a stimulant, tends to offset the sedative effects of codeine. It also can increase the effectiveness and absorption rate of analgesics in some circumstances.[3]

Codeine is listed under the Betäubungsmittelgesetz in Germany and the similarly-named narcotics & controlled substances law in Switzerland. In Austria, the drug is listed under the Suchtmittelgesetz in categories corresponding to their classification under the Single Convention on Narcotic Drugs. Dispensing of products containing codeine and similar drugs (dihydrocodeine, nicocodeine, benzylmorphine, ethylmorphine &c.) generally require a prescription order from a doctor or the discretion of the pharmacist. Municipal and provincial regulations may impact the range of products which can be dispensed in the latter case.

In Hong Kong, codeine is regulated under Schedule 1 of Hong Kong's Chapter 134 Dangerous Drugs Ordinance. It can be used legally only by health professionals and for university research purposes. The substance can be given by pharmacists under a prescription. Anyone who supplies the substance without prescription can be fined $10,000(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.

However, codeine is available without prescription from licensed pharmacists in doses up to 0.1% (5mg/5ml) according to Hong Kong "Dangerous Drugs Ordinance".[4]

In the United Kingdom, codeine tablets are prescription only medicines, with the exception of co-codamol 8/500 where 8mg of codeine phosphate is combined with 500mg paracetamol which is available as a pharmacy supervised medicine. This applies as well to Nurofen Plus, which contains 200mg Ibuprofen with 12.8mg Codeine per tablet. Intramuscular injection of codeine is a controlled drug under the Misuse of Drugs Act 1971.

In the United States, codeine is regulated by the Controlled Substances Act. It is a Schedule II controlled substance for pain-relief products containing codeine alone or more than 90 mg per dosage unit. In combination with aspirin or acetaminophen (paracetamol/Tylenol) it is listed as Schedule III or V, depending on formula. Preparations for cough or diarrhoea containing small amounts of codeine in combination with two or more other active ingredients are Schedule V in the US, and in some states may be dispensed in amounts up to 4 fl. oz. per 48 hours without a prescription. Schedule V specifically consigns the product to state and local regulation beyond certain required record-keeping requirements (a dispensary log must be maintained for two years in a ledger from which pages cannot easily be removed and/or are pre-numbered and the pharmacist must ask for a picture ID such as a driving licence) and also which maintain controlled substances in the closed system at the root of the régime intended by the Controlled Substances Act of 1970 -- e.g. the codeine in these products was a Schedule II substance when the company making the Schedule V product acquired it for mixing up the end product. In locales where dilute codeine preparations are non-prescription, anywhere from very few to perhaps a moderate percentage of pharmacists will sell these preparations without a prescription. However, many states have their own laws that do require a prescription for Schedule V drugs. Other drugs which are present in Schedule V narcotic preparations like the codeine syrups are ethylmorphine and dihydrocodeine. Paregoric and hydrocodone were transferred to Schedule III from Schedule V even if the preparation contains two or more other active ingredients, and diphenoxylate is usually covered by state prescription laws even though this relative of pethi