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


METHODS
21 clinically normal dogs.


METHODS
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
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.
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37796, USA.
Kristin M
KM
Fischer
Daniel A
DA
Ward
Diane V H
DV
Hendrix
D060433:Administration, Ophthalmic; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001082:Aqueous Humor / Q000187:drug effects*; D003287:Contrast Media / Q000378:metabolism; D018592:Cross-Over Studies; D004285:Dogs / Q000502:physiology*; D013759:Dronabinol / Q000494:pharmacology*; D005260:Female; D019793:Fluorescein / Q000378:metabolism; D015590:Fluorophotometry / Q000662:veterinary; D007429:Intraocular Pressure / Q000187:drug effects*; D008137:Longitudinal Studies; D008297:Male; D014065:Tonometry, Ocular / Q000662:veterinary
D000959:Antihypertensive Agents; D003287:Contrast Media; D013759:Dronabinol; D019793:Fluorescein