A Doctor Explains Why Cannabis-Infused Eyedrops Are a Bad Idea

When Canada rolled out its list of proposed regulations for cannabis edibles, extracts and topicals back in December, the government specifically prohibited products that could be considered dangerous to human health. In those regulations, they made it clear that no product can be developed for “use in the eyes.”

So, cannabis eyedrops are out.
But why would someone want to put cannabis-infused drops in their eyes, anyway? 

“Presumably with an eyedrop, what you hope for is that you get absorption locally, and so the dose would be tiny, and not pose any risk of intoxication,” physician and cannabis researcher Dr. Ethan Russo told Civilized. “This could be a consideration for those who face problems with glaucoma, or another ocular disease."

This is in no way an endorsement. Dr. Russo says that just because there’s “a logic” behind an idea doesn’t mean it's a good one. Any potential benefits of cannabis eyedrops would be vastly outweighed by the risks, he said, adding,  “Besides, it just isn’t practical.” 

“A major question is how long is it going to last? It’s not pleasant to put in eyedrops, and if it has to be done multiple times a day, which is likely, it’s just very inconvenient.”

The Risks

The health risks that a cannabinoid-infused eyedrop could pose don't actually stem from the cannabis itself. It’s the method of delivery that creates the biggest problems. 

“Cannabinoids are oily substances," Dr. Russo explained. "They’re not water soluble, and so they have to generally be in an oily vehicle. So, there’s no way around it. If you’re going to administer a cannabis-based medicine into the eye, you’re going to have this oily substance that will blur the vision, and be irritating to the eye.”

So, if this were ever to work, finding the best delivery method would be of primary concern. Today, the most common way to dissolve cannabis is in ethanol, which, as Dr. Russo noted, “you certainly don’t want to get it in the eye.”

“These are things that have been examined in the past, but largely abandoned because of these issues.”

Is it Effective?

Just because cannabis eyedrops are impractical right now doesn’t mean researchers are ignoring eyedrops as a potential treatment option. In 2018, a clinical study tried to determine if cannabis eyedrops could relieve ocular tension in patients. The cannabinoids were, as Dr. Russo suggested, delivered via an oily solution. In the first month, patients were administered a non-intoxicating CBD-heavy drop. Then, after a washout period, they were treated with a drop that primarily contained THC.

Neither eyedrop had any great soothing effect. In fact, the treatment actually aggravated ocular tension in one patient by 20 percent.  

This doesn’t altogether surprise Dr. Russo, who is doubtful that cannabis eyedrops could ever truly become an effective treatment for ocular diseases. Even if they do, he feels there are much simpler and less inconvenient ways to achieve the same effect.

“A better solution for treating glaucoma, or any other eye disease, really, is to develop a preparation by mouth,” he said. “That’s going to deal with the problem just as well, and would be much longer lasting.”

The Future Of Cannabis Eyedrops

With huge demand for new products in the fast-growing marijuana industry, it's possible that companies looking to capitalize on rising trends might try to create cannabis eyedrops. And that worries Dr. Russo.

“I hope we don’t see artisanal products being sold in dispensaries, especially those that that have not gone through the many, many, important steps for showing safety and ethnicity.”

If cannabis eyedrops ever do hit the market, Dr. Russo thinks they should be subjected to rigorous safety tests, and, better still, used only in a medical setting.

“If this sort of thing is ever going to work, it’s going to have to be an approved drug that has gone through the regulatory process. But overall, I just don’t think it’s practical to approach things that way. There are just too many overriding concerns.”

And that cannabis eyedrops should “never” be considered for recreational use.

“Personally, I don’t think it’s a wise path to follow at all.”

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