Interaction between delta-9-tetrahydrocannabinol and indomethacin

Area of Science:

• Ophthalmology
• Pharmacology
• Cannabinoid Research

Background:

• Delta9-tetrahydrocannabinol (Delta9-THC) is known to lower intraocular pressure (IOP).
• The precise mechanisms underlying Delta9-THC's ocular effects are not fully understood.
• Prostaglandins are implicated in various ocular functions and inflammatory processes.

Purpose of the Study:

• To investigate the effect of indomethacin, a prostaglandin synthesis inhibitor, on Delta9-THC-induced changes in rabbit IOP.
• To explore the potential role of prostaglandins in mediating the ocular hypotensive effects of Delta9-THC.

Main Methods:

• Rabbits received topical indomethacin 1 hour prior to intravenous Delta9-THC administration.
• Intraocular pressure (IOP) was measured hourly in both control (Delta9-THC alone) and experimental (Delta9-THC plus indomethacin) groups.
• Statistical comparison of IOP changes between the groups was performed.

Main Results:

• Indomethacin administration substantially attenuated the decrease in IOP typically induced by Delta9-THC.
• A significant difference in IOP response was observed between rabbits treated with Delta9-THC alone versus those treated with Delta9-THC and indomethacin.

Conclusions:

• The findings suggest that Delta9-THC influences intraocular pressure, at least in part, via a prostaglandin-mediated pathway.
• Inhibition of the cyclooxygenase pathway by indomethacin interferes with Delta9-THC's hypotensive effect on IOP.
• This implicates the cyclooxygenase pathway in mediating various ocular cannabinoid effects, including IOP reduction, conjunctival hyperemia, and minor inflammation.