By Brian Houlihan

Article in the Dublin Journal of Science

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In a previous blog I detailed the life and work of Sir. William Brooke O’Shaughnessy who helped introduce cannabis research into Western medicine. One of those to follow in O’Shaughnessy’s footsteps was his fellow Irishman Michael Donovan.

Michael Donovan (1790–1876) was an apothecarist and chemist from County Clare. An apothecarist was someone who prepared and sold medicines for physicians and the public. Donovan is widely regarded as an important figure in the development of medicine in Ireland. He produced numerous works which influenced the profession including The State of Pharmacy in Ireland which was published in 1829.

In 1820 he was appointed the Professor of Pharmacy, Chemistry and Materia Medica at the Apothecaries Hall in Dublin. The hall contained a mill and laboratory and was established to develop medicines of the purest quality. The Apothecaries Hall was the predecessor to the Pharmaceutical Society of Ireland which was founded in 1875.

After learning of O’Shaughnessy’s research Michael Donovan began cannabis experiments of his own. His patients were successfully treated for neck pain, toothaches, arthritis, migraines, sciatica and other ailments. In 1845 he published an article entitled ‘On the physical and medicinal qualities of Indian hemp’ in the Dublin Journal of Science.

Donovan begins his article by praising O’Shaughnessy, whom he believes the medical profession and wider society owes gratitude to. Donovan writes that O’Shaughnessy’s research “brought to light a medicine possessed of a kind of energy which belongs to no other known therapeutic agent, and which is capable of effecting cures hitherto deemed nearly hopeless or altogether impracticable”

In his article Donovan outlines the differences between European and Indian hemp. European varieties were typically grown for fibre and were what we now regard as ‘industrial hemp’. Indian hemp is more akin to modern day cannabis and was used for medicinal and recreational purposes in Asia and elsewhere.

As part of his investigations Donovan even grew his own hemp which he noted “ ripened in the beginning of October”. From the hemp he “made a tincture, four ounces to one pint of rectified spirit. The expressed tincture was allowed to evaporate spontaneously until very little remained, and this was dried by a gentle heat; it weighed 53 grains.”

Irish grown hemp (October 2017)

Donovan highlights the lack of resin on European hemp varieties and how tinctures made with it are much less psychoactive than Indian hemp tinctures. He writes “I therefore conceive that domestic hemp is thus proved to be destitute of the principle which renders the Indian plant so desirable an excitant to the voluptuous people of the East.”

He adds that “Were a system of classification founded on chemical constitution, the two plants would have good claims to distinction of species”. He believes the differences are “under the general law, that in hot climates all plants are more sapid, odorous, and resinous”.

As many of the cannabis samples he acquired (or grew) were so weak he eventually sourced cannabis directly from O’Shaughnessy in Calcutta for his experiments. Nonetheless he cautioned that potency might be lost during its transportation to Europe from India and encouraged local cultivation where possible.

Donovan (like O’Shaughnessy) was weary of the psychoactive effects his tinctures produced. He informed his patients upon dosing that they could experience hallucinations or as he termed it “bouts of insanity”. Many of his patients reported the tinctures induced hallucinations, palpitations, giddiness and other effects which indeed made them uncomfortable.

While many patients noted the unwanted side effects most appeared to benefit greatly from the medicine.One such case involved a watchmaker named Mr. Hanlon who was confined to bed for nine weeks with sciatica. He obtained pain relief and long term benefit from the treatment but only after a night of heavy sedation and having imagined a non-existent person in the room.

Donovan used his tinctures to treat personal ailments and was aware of such side effects. Following one instance where he treated leg pain he wrote that “There was this peculiarity of the relief obtained, that I walked without much consciousness of the motion of my legs, or indeed of having legs at all: I felt as if they did not belong to me.”

Donovan also noticed many of the patients found themselves with great appetites after ingestion. He writes that “I have witnessed this effect so often, that it suggests the idea of using it as a remedy worthy of trial in that most intractable symptom or disease, anorexia.”

Part of the appendix to Donovan’s article

What’s fascinating about his 1845 article is that some case studies come from physicians he is collaborating with. Donovan includes reports from at least four doctors who are using his tinctures to treat their patients. This shows there was genuine interest in cannabis as a medicine among the medical community.

He concludes by writing “ I have forborne to draw any general conclusions, concerning the therapeutic powers of this medicine, conceiving that the employment of it in this country has not been, as yet, sufficiently extensive.” However, he declares that “On a future occasion I may return to the subject” and a few years later he did.

In 1851 he published ‘Observations on the resin of Indian hemp’ which featured more patient cases and more personal experiences. In this work he also comments more on the remarkable differences in effect a similar dosage could have on two people.

Donovan wrote “The difficulty, or rather impossibility, of determining what would be an effective dose for a patient of whom the practitioner has had no experience, with reference to the intensity of the pain and the susceptibility of the patient, has greatly limited the employment of this important medicine.”

Like many of his colleagues he contemplated the potential of cannabis medicines. He declared that “I content myself with expressing my belief that Indian hemp will one day or another occupy one of the highest places amongst the means of combating disease.”

170 years after Michael Donovan’s experiments it now seems Irish society is ready to embrace cannabis as a medicine once again.

Brian Houlihan is the curator of the Dublin Hemp Museum and regularly writes about hemp. Follow him on Twitter at @dubhempmuseum and@houlihanbrian. You can also find us on Facebook.