CODEINE

CODEINE

Brand Names : Methylmorphine; Morphine 3-methyl ether; Codicept.

Codeine is an alkaloid which occurs naturally in opium from O.7 to 2.5 percent. Commercially codeine is prepared from morphine by methylating the phenolic hydroxyl with methyl iodine in the presence of potassium hydroxide.

Codeine, m.p. 154-156°, occurs as odourless laevorotatory, colourless crystals or white crystalline powder. It effloresces slowly in dry air and is affected by light. It is soluble in water (l in 120), alcohol (1 in 2), chloroform (l in 0.5) and ether; almost insoluble in petroleum ether or in solutions of alkali hydroxides. A 0.5% solutionin water has a pH of more than 9. It is kept in airtight containers and protected from light.

Codeine is a mono-acid tertiary base and dissolves readily in dilute acids with formation of salts. Its molecule does not contain a free phenolic hydroxyl group like morphine, therefore, it does not react with alkali hydroxides to form metallic derivatives. It does not give bluish-green colour with ferricyanide and ferric ions and yellow colour with nitrous acid and ammonia as observed in morphine. Generally codeine is used in the form of hydrochloride, sulphate or phosphate salt. The general pharmacological action of codeine is identical to that of morphine but it does not possesses the same degree of analgesic potency.

Codeine hydrochloride is prepared by neutralizing an aqueous solution of codeine with dilute hydrochloric acid and crystallizing the salt, m.p. about 280°. It occurs as small colourless crystals or a white crystalline powder. It is soluble in water, slightly soluble in alcohol; practically insoluble in chloroform and ether; stored in well-closed container and protected from light.

Codeine sulphate, prepared similarly to the hydrochloride salts, occurs as white crystals or white crystalline powder. It is soluble in water (l:3O), and alcohol (l:l 3OO); insoluble in ether or chloroform; Stored in airtight containers and protected from ight.

Codeine phosphate is prepared by neutralizing codeine with phosphoric acid and precipitating the salt from aqueous solution with alcohol. It occurs as odourless, colourless, crystals or a white crystalline powder; affected by light. It is soluble in water, slightly soluble in alcohol; practically insoluble in chloroform and ether. The pH of 2% aqueous solution is 4.6. It is kept well-closed and protected from light.

Uses

Codine  is a narcotic analgesic agent used for the symptomatic relief of pain, to alleviate the anxiety associated with pain; as general anaesthetic in high doses.

It is more potent as an analgesic and has mild sedative effects.

Codeine is also reputed as an antitussive, depressing the cough reflex and is used in cough preparations.

Side Effect

The common side effects of morphine are nausea, vomiting constipation, drowsiness, and confusion. Dry mouth, sweating. facial flushing, vertigo, bradycardia, palpitation, orthostatic hypotension, hypothermia, restlessness, changes in mood and miosis also occur. Abuse leads to habituation or addiction.