Cannabis remains problematic for glaucoma
Despite the legalization of marijuana by several state governments, physicians should not recommend smoking it as a treatment for glaucoma, said Sunita Radhakrishnan, MD.
“It has been approved by public opinion rather than regulatory process,” said Dr. Radhakrishnan, research director of the Glaucoma Research and Education Group, San Francisco, in a talk at the 21st annual Glaucoma Symposium during the Glaucoma 360 annual meeting.
While cannabis lowers IOP for a 2 to 4 hours, few studies have examined its effects on glaucoma, she said.
In addition, it can cause adverse reactions, and is illegal under federal law and not subject to good quality control, she said.
Seven states and Washington, DC, have legalized cannabis for recreational use, and 21 have legalized it for medical use, she said, citing Business Insider.
However the U.S. Drug Enforcement Administration (DEA) continues to classify it on schedule I, “drugs with no currently accepted medical use and a high potential for abuse.”
The cannabis plant contains multiple cannabinoids including Delta 9 Tetra hydrocannabinol (THC), which is psychoactive, and cannabidiol (CBD), which is not.
Scientific exploration of its use for glaucoma dates back to 1971, when Hepler and Frank documented a 25% to 30% reduction in IOP for 3 to 4 hours in volunteers who smoked it. In 1980, Merritt et al. repeated the finding in a placebo-controlled trial.
Other researchers found that oral ingestion and sublingual administration of a whole plant extract of THC also reduced IOP for 2 to 4 hours. But topical THC administered in a light mineral oil had no effect compared with controls.
And one study found that taking THC daily resulted in only a transitory effect, with all patients electing to discontinue within 9 months.
There are no long-term studies for glaucoma, Dr. Radhakrishnan said.