Can cannabis be used for treatment in glaucoma?
In October 2017, Canadian investment firm LCG Capital signed an option with AAA Trichomes to acquire an interest in a new cannabis processing facility to be built in Quebec. Canadians who have been authorised by their healthcare practitioner are allowed purchase or produce limited amounts of cannabis for their own medical purposes. At present there are 69 producers licensed by Health Canada, and following investments in Australia and South Africa, LGC are hoping to make inroads into this growing market.
Several states worldwide have decriminalised cannabis use for medical reasons, without defining clearly what conditions warrant its use. Since the 1970s it has been suggested that cannabis use can help treat glaucoma. This has been disputed for almost as long, however. In short, smoking marijuana has proven to be effective for lowering intra-ocular pressure (IOP), a key element in glaucoma treatment. Its effects last for just three-to-four hours, and patients need a 24-hour reduction in pressure, so one would have to be smoking six-to-eight times per day.
In a study carried out to observe the effects of cannabis on IOP, researchers noted that seven of nine participants lost any beneficial effect of the drug due to tolerance. Furthermore, smoking can have negative effects, such as dizziness, sleepiness, distortion of perception and anxiety.
“Synthetic analogues of cannabinoid with more potency and longer duration of action, sensible utilization of novel drug delivery systems namely nanoparticle approaches, and combination of cannabinoids with other conventional drugs to control glaucoma could be alternative solutions,” write the authors of a detailed paper entitled The arguments for and against cannabinoids application in glaucomatous retinopathy.
In another study, entitled Cannabinoids and glaucoma, researchers pointed out the difficulties of attempting to administer cannabis via eye drops. “After instillation of an eye drop of any medication, loss of the instilled solution via the lacrimal drainage system and poor drug penetration results in only <5% of an applied dose reaching the intraocular tissues,” the authors write. As well as this, natural cannabinoid extracts “are highly lipophilic and have low aqueous solubility”, making effective application even more difficult.
While cannabis has proven effective as an appetite stimulant, a spasticity relief and pain relief for a variety of conditions, it remains the case that more traditional remedies such as eye drops or surgery, based on current research, may continue to be appropriate for the treatment of glaucoma.