(4) Isoquinoline group. The opium alkaloids: morphine, codeine, thebaine, papaverine, narcotine, narceine, &c.; and the complicated substances hydrastine and berberine.
In the cough of phthisis minute doses are of service, but in this particular disease morphine is frequently better replaced by codeine or by heroin, which checks irritable coughs without the narcotism following upon the administration of morphine.
A small amount of morphine and codeine is also manufactured in India for medicinal use.
For the extraction of codeine, the Persian opium is preferred when Turkey opium is dear, as it contains on the average 22% of that alkaloid, whilst Turkey opium yields only 2-4%.
But codeine can also be made from morphine.
The greater proportion of the Persian opium imported into London is again exported, a comparatively small quantity being used, chiefly for the manufacture of codeine when Turkey opium is dear, and a little in veterinary practice.
The alkaloids fall into two chemical groups: (i) derivatives of isoquinoline, including papaverine, narcotine, gnoscopine (racemic narcotine), narceine, laudanosine, laudanine, cotarnine, hydrocotarnine (the last two do not occur in opium), and (2) derivatives of phenanthrene, including morphine, codeine, thebaine.
Cotarnine IV.Narceine The chemistry of morphine, codeine and thebaine is exceedingly complicated, and the literature enormous.
That these alkaloids are closely related may be suspected from their empirical formulae, viz.morphine = C17H19N03, codeine = C18H21N03, thebaine = C19H21N03.
As a matter of fact, Grimaux, in 1881, showed codeine to be a methylmorphine, and in 1903 Ach and L.
Thebenine and morphothebaine, from both codeine and thebaine, thereby establishing their connexion.
Codeine, or codeia, crystallizes in orthorhombic prisms with one molecule of water: it is readily soluble in alcohol, ether and chloroform.
- Of the opium alkaloids only morphine and codeine are used to any extent in medicine.
Of the other alkaloids narceine is hypnotic, like morphine and codeine, whilst thebaine, papaverine and narcotine have an action which resembles that of strychnine, and is, generally speaking, undesirable or dangerous if at all well marked.
Tannic acid, for instance, precipitates codeine as a tannate, salts of many of the heavy metals form precipitates of meconates and sulphates, whilst the various alkalis, alkaline carbonates and ammonia precipitate the important alkaloids.
The only alkaloids likely to remain in the prepared opium, and capable of producing well-marked physiological results, are morphine, codeine and narceine.
Morphine, in the pure state, can be sublimed, but codeine and narceine are said not to give a sublimate.