Effects of a topically applied 2% delta-9-tetrahydrocannabinol ophthalmic solution on intraocular pressure and aqueous humor flow rate in clinically normal dogs

Am J Vet Res. 2013 Feb;74(2):275-80. doi: 10.2460/ajvr.74.2.275.


Objective: To determine the effects of topically applied 2% delta-9-tetrahydrocannabinol (THC) ophthalmic solution on aqueous humor flow rate (AHFR) and intraocular pressure (IOP) in clinically normal dogs.

Animals: 21 clinically normal dogs.

Procedures: A randomized longitudinal crossover design was used. Following acquisition of baseline IOP (morning and evening) and AHFR (afternoon only) data, dogs were randomly assigned to 2 treatment groups and received 1 drop of either 2% THC solution or a control treatment (olive oil vehicle) to 1 randomly selected eye every 12 hours for 9 doses. The IOPs and AHFRs were reassessed after the final treatment. Following a washout period of ≥ 7 days, dogs were administered the alternate treatment in the same eye, and measurements were repeated.

Results: Mean ± SD IOPs in the morning were 15.86 ± 2.48 mm Hg at baseline, 12.54 ± 3.18 mm Hg after THC treatment, and 13.88 ± 3.28 mm Hg after control treatment. Mean ± SD IOPs in the evening were 13.69 ± 3.36 mm Hg at baseline, 11.69 ± 3.94 mm Hg after THC treatment, and 12.13 ± 2.99 mm Hg after control treatment. Mean IOPs were significantly decreased from baseline after administration of THC solution but not the control treatment. Changes in IOP varied substantially among individual dogs. Mean ± SD AHFRs were not significantly different from baseline for either treatment.

Conclusions and clinical relevance: Topical application of 2% THC ophthalmic solution resulted in moderate reduction of mean IOP in clinically normal dogs. Further research is needed to determine efficacy in dogs with glaucoma.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Ophthalmic
  • Animals
  • Antihypertensive Agents / pharmacology*
  • Aqueous Humor / drug effects*
  • Contrast Media / metabolism
  • Cross-Over Studies
  • Dogs / physiology*
  • Dronabinol / pharmacology*
  • Female
  • Fluorescein / metabolism
  • Fluorophotometry / veterinary
  • Intraocular Pressure / drug effects*
  • Longitudinal Studies
  • Male
  • Tonometry, Ocular / veterinary


  • Antihypertensive Agents
  • Contrast Media
  • Dronabinol
  • Fluorescein