Codeine actions

Nonnarcotic Antitussives. The most centrally active, noimarcotic antitussive is dextromethorphan [125-71-3] (39). It is similar to codeine in terms of potency and mechanism of action, ie, it is a direct depressant of the cough center. It is unique in that even though it is stmcturaHy related to codeine, it is not addictive. 

When a-methylmoi phimethine, CjgHjjOjN, resulting from the action of boiling sodium hydroxide solution on codeine methiodide, is boiled with acetic anhydride, it is partly converted into the j3-isomeride and partly decomposed into ethanoldimethylamine and methylmorphol, thus —... 

A characteristic feature of the action of the opium alkaloids is their simultaneous depressing and exciting action on the central nervous system. In this respect there is no clear line of demarcation between the morphine group—morphine, codeine and thebaine—and the papaverine-narcotine group, and as the series is ascended in the order, morphine, papaverine, codeine, narcotine, thebaine, narcotic action diminishes and power of rellex stimulation increases until in thebaine a strychnine-like effect is exhibited. 

Codeine (morphine methyl ether) resembles morphine in its general effect, but is less toxic and its depressant action less marked and less prolonged, whilst its stimulating action involves not only the spinal cord, but also the lower parts of the brain. In small doses in man it induces sleep, which is not so deep as that caused by morphine, and in large doses it causes restlessness and increased reflex excitability rather than sleep. The respiration is slowed less than by morphine (cf. table, p. 261). Cases of addiction for codeine can occur but according to Wolff they are rare. The best known ethers of morphine are ethylmorphine and benzyl-morphine [cf., table, p. 261), both used to replace morphine or codeine for special purposes. 

According to Eddy, as quoted by Small, the analgesic action of neopine, n omorphine, 6-acetylneomorphine or 3 6-diacetylneomorphine (p. 218) is definitely less than that of morphine and its corresponding analogues. The first two are about half as toxic as codeine and morphine respectively, and the second pair are more toxic than their morphine analogues. None of the four shows the Straub reaction and the convulsant action is less marked. 

In the strict sense, opiates are drugs which are derived from opium and include the natural products morphine, codeine, thebaine and many semi-synthetic congeners derived from them. In the wider sense, opiates are morphine-like drugs with non-peptidic structures. The old term opiates is now more and more replaced by the term opioids which applies to any substance, whether endogenous or synthetic, pqrtidic or non-peptidic, that produces morphine-like effects through an action on opioid receptors. 

Tramadol is a pain reliever (analgesic). Its action is similar to opioid narcotics such as codeine and morphine, but it does not depress breathing the way the others can, and less often leads to abuse and addiction. 

The term opioid refers to any exogenous substance that acts as an agonist at any of several receptors. Opioid antagonists are drugs that bind to a receptor but produce no actions. The poppy plant, Papaver somniferum, from which opium is obtained, is grown in many areas of the world. Morphine constitutes 10% of opium, and codeine can be obtained direcdy from opium. Semisynthetic opioids such as heroin and oxycodone are obtained directly or indirectly from morphine. There are other distinct chemical classes of drugs with opioid actions, including the methadones. 

R. C., et al., Quantitative, non-invasive assessment of antidiarrheal actions of codeine using an experi-mental model of diarrhea in man, Dig. Dis. Sci. 1993, 38, 996-1003. 

Meanwhile, the Graphic Arts people were arranging their photographic equipment. Several 35 mm cameras stood just outside sliding panels in the walls. The camera operators would open them periodically to record a few minutes of Technicolor volunteer action. Lloyd Matter was making last-minute adjustments of his TV cameras and the monitors that would help us keep track of what the men were doing. My bed and traction equipment were in place. Aspirin, codeine and faithful nurses would get me through the weekend. 

Codeine, dextromethorphan and pholcodine are opioid cough suppressants indicated for dry cough. Sedating antihistamines, such as diphenhydramine, tend to have an antitussive action as well. Vitamin C is not used in the management of cough but may be used as a prophylaxis against colds. 

Dextromethorphan is an opioid antitussive similar in action to codeine and pholcodine. Codeine and pholcodine are considered to be more potent than dextromethorphan. Dextromethorphan tends to cause less constipation and dependence than codeine. Cough suppressants are not usually recommended in children under 2 years. 

A clue to possible treatments for pain was discovered in the 1970s when scientists found specialized receptor cells in neurons called opiate receptors. These receptors appeared to he well suited for accepting natural painkillers that occur in the body, such as the enkephalins and endorphins. Enkephalins and endorphins are naturally occurring painkillers similar in their action to opium, morphine, and codeine. 

Codeine and morphine are found to have reciprocal synergistic actions in the rat [30]. When a low (non-analgesic) dose of codeine is given with an analgesic dose of morphine, the mean hot-plate reaction times are found to be significantly longer than after morphine alone. A similar but more persistent effect is noted after codeine plus a low dose of morphine. 

CftHii), had tail-flick activities in the codeine-dextropropoxyphene potency range (oral and intraperitoneal routes in rats) and nalorphine antagonized the actions of both codeine and (XLIV) (R = C H,) in this test [132]. 

Pharmacology Dextromethorphan is the d-isomer of the codeine analog of levorphanol. Its cough suppressant action is due to a central action on the cough center in the medulla. Dextromethorphan 15 to 30 mg equals 8 to 15 mg codeine as an antitussive. 

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