This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Hemp was known to the ancient Greeks and Romans, who seem to have had some confused notion of its narcotic powers, though there is no reason to suppose that they ever employed it as a medicine. From time immemorial it has been used in India and Persia as a luxury, both internally and by smoking, in the same manner as opium. Its intoxicating and stupefying powers are spoken of by Linnaeus, Murray in his Apparatus Medicaminum, and other early modern writers on Materia Medica; but it was not employed as a remedy, to any extent at least, in Europe or America, until introduced to the notice of the profession, not many years since, by Dr. O'shaughnessy, of Calcutta, in the treatment of rheumatism, tetanus, cholera, etc.
The indications for the use of hemp, founded upon a knowledge of its physiological effects, are, 1. to allay pain, 2. to relieve spasm and various other nervous disorders, and 3. to promote sleep. In producing these effects, it probably operates in the same manner as opium; and it may be substituted for that medicine, for any of the purposes above mentioned, when opium has failed to act as desired, or is contraindicated by some idiosyncrasy of the patient, or when it is specially desirable to avoid its occasional nauseating influence on the stomach, its constipating effect on the bowels, and its tendency to restrain the secretions.
Another indication, derived from a supposed property of hemp not yet particularly noticed, is to produce uterine contraction. Attention, I believe, was first called to this property by Dr. Alexander Christison, of Edinburgh, who observed that, in several cases in which he had employed it during labor, it very much increased the intensity of the contractions.* The effect usually occurred, if at all, in two or three minutes after its administration, ceased after a few pains, and was not followed by any of the ordinary physiological results of its exhibition, as mental excitement, intoxication, or sleep; nor does the sense of pain appear to have been blunted. Indeed, the action took place much sooner than is required for its usual effects, and its powers seem to have been exhausted in the effort. Dr. Christison thinks the action of hemp more energetic, and perhaps more certain, than that of ergot. (See Am. Journ. of Med. Sci., N. S., xxiii. 2f>0.) Notwithstanding this supposed action of hemp, it has been found, in large doses, very promptly to suppress uterine pains in delivery. (Ed. Med. Journ., ii. 867).
With a view to the first indication, that, namely, of allaying pain, hemp has been used in different forms of neuralgia, in acute and sub-acute rheumatism, and in gout; and may be employed in these affections under the same circumstances as opium.
* Sir J. V. Simpson informed me. when in Edinburgh, that the idea of using hemp of India for its effects in causing uterine contractions orginated with him to the third edition).
To relieve pain and relax spasm jointly, it has been considerably used in tetanus, and with variable results. Dr. O'shaughnessy found it effectual on several occasions; a few successful cases have been reported by others; and, in some instances, where it has failed to cure, it has afforded relief. But the general result has not, I think, been favourable. As in the use of opium in this disease, it is necessary to increase the ordinary dose six or tenfold, or more, and to repeat the dose frequently. The medicine has been tried also in hydrophobia, but has proved quite powerless. In epidemic cholera it is said to have been found useful; but the property of checking alvine discharges, which renders opium so beneficial in that disease, is wanting in hemp, and it can act only by relieving pain and resolving spasm.
Hemp has also been used in various painless spasmodic affections, and nervous disorders, usually treated with the nervous stimulants and narcotics. In convulsions not connected with cerebral congestion, in chorea, hysteria, languid or depressed spirits, and insanity, it has been found more or less beneficial. For allaying cough, whether spasmodic, as in pertussis and hysteria, or dependent on bronchial irritation, as in different pulmonary affections, it may be resorted to as a substitute for opium, when this is contraindicated by its property of checking mucous secretion.
To promote sleep, it may be employed in any case of wakefulness, not associated with vascular irritation of the cerebral centres, and is said to have been used with special advantage in relieving the sleeplessness of drunkards.
In reference to its supposed property of promoting uterine contraction, it may be employed in protracted cases of delivery, in which it is preferable to ergot, if it be true, as may be inferred from the observations of Dr. Alexander Christison, that its operation is soon over, and not protracted like that of the medicine alluded to. It is thus free from the greatest objection to ergot, that, namely, of endangering the life of the foetus by the steady and prolonged contraction of the uterus. The same property of hemp would render it useful in expelling the retained placenta, and in checking uterine hemorrhage, when sustained by a relaxed condition of the organ.
But, if preferable to opium under the circumstances above mentioned, in which that medicine, though indicated by certain symptoms, is contraindicated by others,hemp cannot be brought into competition with it in any of the cases to which they are both applicable. It is not only less efficient than opium, but is much more uncertain on account of the inequality of strength in the preparations used, and probably also in consequence of the inequality of its operation upon different individuals, even when it may be of the due strength Dr. Fronmuller, who speaks of the practical use of hemp, with an authority based on the experience of a thousand cases, says that it pro-duces Bleep more like the natural than any other narcotic, causes considerable vascular excitement, does not disturb the secretory functions, and leaves behind no unpleasant sequelae, and, finally, that it may be employed as a substitute for opium in all the phlegmasiae, and all the typhous affections, without apprehension of evil result. It is, however, at the same time, less energetic and less certain than opium. (Arch. Gen., 5e ser., xv. 745).