Pharmacological study of a cannabinoid-containing eyedrop formulation in dogs and mice

• The cannabinoid-containing eyedrop reduced the intraocular pressure in healthy dogs.
• The cannabinoid-containing eyedrop has potential for the treatment of glaucoma in dogs.
• The cannabinoid-containing eyedrop induced psychotropic effects in mice only upon systemic administration.

Cannabinoids have been indicated for the treatment of glaucoma in humans. However, pharmacological studies in other species are lacking. Healthy Beagle dogs were treated with 0.1% cannabinoid eyedrops for 3 or 7 days. Intraocular pressure (IOP) and pupillary diameter (PD) were measured. To evaluate whether the topical cannabinoid formulation affects the motor and central nervous systems, a parallel study was performed. Male Swiss mice received ocular or intraperitoneal (i.p.) cannabinoid solution for 1 day (acute) or 7 days (subacute) and were tested in the open field (OF), elevated plus maze (EPM), open field habituation test (HT), and marble burying test (MBT). The treated dogs exhibited a significant reduction of IOP and PD. Acute i.p. cannabinoid administration reduced locomotion in mice in the OF and increased the number of entries into the open arms of the EPM. Subacute ocular cannabinoid administration increased the time spent on the closed arms and reduced the time spent on the open arms of the EPM. The cannabinoid i.p. and ocular did not exert anxiogenic effects in the MBT. These results indicate that the cannabinoid reduced IOP when used topically, and psychotropic effects occurred only with systemic administration.

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