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Medical Use of Marijuana for Glaucoma

Summary

The clinical utility of marijuana for the treatment of glaucoma is limited by the inability to separate the potential clinical action from the undesirable neuropsychological and behavioural effects.

The Canadian Ophthalmological Society does not support the medical use of marijuana for the treatment of glaucoma due to the short duration of action, the incidence of undesirable psychotropic and other systemic side effects and the absence of scientific evidence showing a beneficial effect on the course of the disease.

This is in contrast to other more effective and less harmful medical, laser and surgical modalities for the treatment of glaucoma.

Full policy statement

The marijuana plant Cannabis sativa has long been recognized to have medicinal properties.1 In 1964 the active component of marijuana, Δ9‐tetrahydrocannabinol (THC), was isolated and its structure defined.2

In addition to its psychotropic effects, THC also acts as an analgesic, appetite stimulant and nausea suppressant. The intraocular pressure lowering effects of marijuana were first reported in 1971.3

Since then other studies have confirmed the intraocular pressure lowering effect of THC by various modes of administration including inhalational,4 oral,5 intravenous,6 sublingual,7 and topical.8

Although topical application might seem to be an optimal route of administration, ocular penetration has been poor due to the high lipophilicity and low aqueous solubility of the cannabinoid extracts.

Topical preparations have also been noted to cause local irritation and corneal damage.

In addition some studies have failed to find a hypotensive effect of topical THC.9,10 The oral route has also been limited by variable absorption.5

The mechanism of intraocular pressure reduction is not well understood.11-13 The maximum hypotensive effect occurs between 60‐90 minutes and the duration of action of is brief at only 3‐4 hours.3,14

The main problems with inhaling the smoke of burning marijuana are the side effects which acutely include psychotropic effects (euphoria, dysphoria, decreased short‐term memory, cognitive impairment, time distortion, decreased co‐ordination, sleepiness),4,5 tachycardia, palpitations, systemic hypotension8 and conjunctival hyperaemia.

The long‐term effects of smoking marijuana include emphysema and possible lung cancer.15 There are also concerns about the potential addictive properties and the development of tolerance.16

The clinical utility of marijuana for the treatment of glaucoma is limited by the inability to separate the potential clinical action from the undesirable neuropsychological and behavioural effects.

The Canadian Ophthalmological Society does not support the medical use of marijuana for the treatment of glaucoma due to the short duration of action, the incidence of undesirable psychotropic and other systemic side effects and the absence of scientific evidence showing a beneficial effect on the course of the disease.

This is in contrast to other more effective and less harmful medical, laser and surgical modalities for the treatment of glaucoma.

Yvonne M Buys MD, FRCSC; Paul Rafuse MD, PhD, FRCSC (April 2010)

References

  1. Zias J, Stark H Sellgman J, et al. Early medical use of cannabis. Nature 1993;363:215.
  2. Gaoni Y, Mechoulam R. Isolation, structure and partial synthesis of the active constituent of hashish. J Am Chem Soc 1964;86:1646‐7.
  3. Hepler RS, Frank IR. Marihuana smoking and intraocular pressure. JAMA 1971;217:1392.
  4. Merritt JC, Crawford WJ, Alexander PC, Anduze AL, Gelbart SS. Effect of marihuana on intraocular and blood pressure in glaucoma. Ophthalmology 1980;87:222‐8.
  5. Merritt JC, McKinnon S, Armstrong JR, Hatem G, Reid LA. Oral delta 9‐tetrahydrocannabinol in heterogeneous glaucomas. Ann Ophthalmol 1980;12:947‐50.
  6. Purnell WD, Gregg JM. Delta(9)‐tetrahydrocannabinol, euphoria and intraocular pressure in man. Ann Ophthalmol 1975;7:921‐3.
  7. Tomida I, Azuara‐Blanco A, House H, Fling M, Pertwee RG, Robson PJ. Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study. J Glaucoma 2006;15:349‐53.
  8. Merritt JC, Olsen JL, Armstrong JR, McKinnon SM. Topical delta 9‐tetrahydrocannabinol in hypertensive glaucomas. J Pharm Pharmacol 1981;33:40‐1.
  9. Green K, Roth M. Ocular effects of topical administration of delta 9‐tetrahydrocannabinol in man. Arch Ophthalmol 1982;100:265‐7.
  10. Jay WM, Green K. Multiple‐drop study of topically applied 1% delta 9‐tetrahydrocannabinol in human eyes. Arch Ophthalmol 1983;101:591‐3.
  11. Green K, Podos SM. Antagonism of arachidonic acid‐induced ocular effects by D1‐tetrahydrocannabinol. Invest Ophthalmol. 1974;13:422–429.
  12. Porcella A, Casellas P, Gessa GL, et al. Cannabinoid receptor CB1 mRNA is highly expressed in the rat ciliary body: implications for the antiglaucoma properties of marihuana. Brain Res Mol Brain Res 1998;58:240–245.
  13. Zhan GL, Camras CB, Palmber PF, Toris CB. Effects of marijuana on aqueous humor dynamics in a glaucoma patient. J Glaucoma 2005;14:175‐7.
  14. Brown B, Adams AJ, Haegerstrom‐Portnoy G, et al. Pupil size after use of marijuana and alcohol. Am J Ophthalmol 1977;83:350–4.
  15. Hashibe M, Ford DE, Zhang ZF. Marijuana smoking and head and neck cancer. J Clin Pharmacol 2002;42(Suppl):103–7.
  16. Flom MC, Adams AJ, Jones RT. Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon? Invest Ophthalmol 1975;14:52–5.

Canadian Vision Care by the Numbers:

$15.8 billion: Cost of vision loss in Canada annually

$8.6 billion: Direct health care costs annually

$7.2 billion: Indirect costs (lost earnings, care & rehabilitation, special equipment, etc.)

$30.3 billion: Annual cost of vision loss in Canada by 2032

[Source: Vision Loss in Canada 2011]

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