This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
With respect to the liver and metabolism, opium is by far the most powerful drug known in reducing or removing sugar from the urine in diabetes, and therewith ameliorating the condition of the patient in most respects. Very large doses of solid opium, morphia, or better still, codeia, may be tolerated in this disease, their effect on the nervous system being remarkably absent whilst the diabetes is yielding. Acute inflammatory and febrile diseases are now less frequently treated with opium than formerly, when a combination with calomel was generally used, the opium preventing the purgative action of the mercurial, and the latter preventing constipation, whilst both drugs were believed to act specifically on the morbid process, reducing the local general circulation, alleviating pain and restlessness, and promoting healing. The combination is, however, very valuable in syphilis. In the specific fevers, such as typhoid, opium given with judgment relieves delirium, as we have seen, checks diarrhoea, and is invaluable in haemorrhage, perforation, or peritonitis. With quinia it is given in some cases of malaria. Phagedaena may call for its free exhibition.
Opium is employed in obstetrics to prevent abortion, in some varieties of difficult labour, and to relieve after-pains.
The excretion of morphia commences quickly, but may not be completed for forty-eight hours. It passes out of the body by most of the secretions, especially the urine, where it is found mainly unchanged. The quantity of urine is diminished; its evacuation sometimes disturbed or difficult, from the local action of morphia on the bladder; and sugar occasionally present. These facts, and the probability of the retention and accumulation of morphia in the system if the action of the kidneys be deficient, indicate the necessity to give it only with the greatest caution, in reduced doses, or not at all, in renal disorder or disease.
Opium in passing through the shin may cause itching, heat, and sometimes eruptions. The vessels are also dilated, as we have seen, and the sweat glands decidedly stimulated; both being effects of its central, not local, cutaneous action. Thus opium, especially in the form of Dover's powder, is a valuable diaphoretic, and is given with great success as a refrigerant apyretic in the outset of catarrh, influenza, and mild febrile or rheumatic attacks caused by cold. Under certain circumstances, Dover's powder actually checks the sweating of phthisis, probably by removing its cause. Being excreted in the milk, opium must be prescribed with caution to nursing females.
Morphia. The action of opium depends chiefly on morphia, and the description just given applies so nearly to the pure alkaloid, that only a few points of difference require to be noticed. These depend upon two principal circumstances: (1) Opium, being much less soluble than the pharmacopoeial preparations of morphia, is more slowly absorbed, and thus acts less quickly than morphia, whilst its effects are more lasting, and its immediate local action on the intestines decidedly more marked. (2) Several of the constituents of opium possess more or less convulsant action (thebain, codeia, narcotin), morphia none (in man); the latter has therefore a somewhat more sedative influence than the entire drug. The effect of opium on the skin is also less marked in morphia. Unless there be some special reason to the contrary, morphia is generally to be preferred to opium in practice, as being of definite composition (whilst the crude drug is very variable), more rapid in action, readily administered hypodermically, whilst the dyspeptic and constipating effects of the drug are less marked. Opium is to be preferred in intestinal and abdominal diseases such as diarrhoea, obstruction, peritonitis, hernia, because it reaches the bowel; in delirium tremens and mental disorder, because its action is more continued; in diabetes, because it contains codeia; for combinations with quinine or calomel, and as a diaphoretic, because it prevents purgation and lowers fever; in astringent enemata, from its action on the bowel; and for local applications, e.g. to the conjunctiva, because less irritant than the alkaloid. The relative strength of opium to morphia is about 20 or 30 to 100, \ or 1/3 to 1.
Codeia. This alkaloid appears to excite the cord more than morphia, and to depress the convolutions less, so that muscular tremors may follow and exceed the sedative influence. Codeia, in 1/2-gr. doses cautiously increased, markedly reduces the amount of sugar in diabetes, appearing to act as an alterative to the nervous system, and thus to cure (not simply relieve) the disease in some instances.
3. Narcotin, which is so large a constituent of opium, is probably often impure from an admixture of morphia. By some authorities it is considered to be hypnotic, by others convulsant. It is not used.
4. Narcein probably acts like morphia, and is not employed medicinally.
5. Thebain is a convulsant, almost like strychnia, but is not used.
6. Opianin, cryptopia, metamorphia, and possibly papa-verina, act like morphia. Porphyroxin and laudanin act like codeia.
The action of meconic acid is doubtful.
This subject will be best discussed from the point of view of the conditions calling for opium.
1. Severe pain, such as colic or neuralgia, is to be treated with the Hypodermic Injection of Morphia. Failing this, either of the Solutions of Morphia must be given by the mouth, or a fluid preparation of opium, such as the Tincture, or Liquid Extract (about 1/7 more active than the tincture). The Enema is a valuable anodyne in cases of abdominal pain. The Pilula Saponis Composita also acts rapidly, being more readily soluble in the stomach than solid opium.