Intraocular pressure-lowering effects of tetrahydrocannabinol drugs: a systematic review and meta-analysis.

PURPOSE: Within the past few decades, several studies have reported intraocular pressure (IOP)-lowering effects associated with tetrahydrocannabinol (THC) compounds as an alternative or complementary agent to conventional glaucoma therapies. The purpose of this study is to generate pooled estimates on the IOP-lowering effects of THC. METHODS: This systematic review and meta-analysis article was registered a priori on PROSPERO (CRD420251007916). MEDLINE, EMBASE, and Web of Science were searched for studies reporting IOP reduction following THC administration. Two reviewers independently performed screening, data extraction, and risk of bias assessments. A random-effects meta-analysis of mean differences was performed to estimate the overall pooled peak percentage reduction in IOP following THC administration, stratified by route of THC administration. RESULTS: Five studies were included, consisting of a total of 99 patients and 69 with THC exposure/intervention. Overall, the pooled peak percentage reduction in IOP after THC administration was 14.66% (95% CI: [3.38%, 25.93%]; p < 0.005). By route of THC delivery, the pooled peak percentage reduction in IOP was 33.27% (95% CI: [20.36%, 46.17%]; p < 0.0001) with the IV route. It was 10.65% (95% CI: [-7.60%, 28.89%]) with the oral route and 9.36% (95% CI: [-8.89%, 27.6%]) with the topical route. Four studies reported the peak percentage reduction in IOP after THC and control administration. From these studies, the pooled peak percentage reduction in IOP after THC was 6.88% (95% CI: [-9.56%, 23.33%]; p = 0.41) and nonsignificantly different from control. CONCLUSIONS: Our study generated literature-pooled estimates of the overall and route-stratified peak percentage reduction in IOP following THC administration. THC significantly reduced IOP, although comparatively less significant to the control group.