Effect of dronabinol on ocular hemodynamics in glaucoma

With more than 10 million people affected in Europe, glaucoma is one of the most common reasons for irreversible vision loss in advanced age. The term glaucoma includes a number of different eye diseases, all of which are characterized by damage to the optic nerve head with characteristic deficits in the visual field. Although high intraocular pressure is the most important known risk factor for both the disease itself and its progression, low intraocular pressure does not rule out glaucoma. There is also evidence from the literature that glaucoma is associated with reduced ocular blood flow. Accordingly, pharmacological increase of ocular blood flow could represent a new therapeutic approach. Tetrahydrocannabinol (THC) has been used in some countries to treat glaucoma for several years because of its intraocular pressure lowering effects. Recent studies also suggest that THC improves blood flow to the eye. A recent study has found that administration of dronabinol (a synthetic cannabinoid) leads to an increase in optic nerve head blood flow. For this purpose only a low dose of dronabinol was used that did not cause any psychoactive side effects. The next step now is to investigate whether administration of dronabinol also increases ocular blood flow in patients with glaucoma. The aim of the present project is therefore to investigate whether the administration of dronabinol has an effect on ocular blood flow in patients with glaucoma and healthy control subjects. Optic nerve head and retinal blood flow as well as retinal oxygen saturation will be assessed before and after administration of dronabinol capsules or placebo. The results of the present study will help to gain more insight into the role of cannabinoids in glaucoma.

Glaucoma is a leading cause of irreversible blindness worldwide. Although lowering intraocular pressure is an effective therapy, there are still patients that progress despite optimal treatment. The aim of the present project was to investigate the impact of orally administered Dronabinol, a synthetic tetrahydrocannabinol (THC) derivative, on blood flow in the eye, which has been found to be reduced in patients with glaucoma. For participating glaucoma patients, two study days were scheduled. On one study day, patients received 5 or 10 mg Dronabinol and on the other study day they received placebo in a randomized order. Ocular blood flow parameters were measured before and after administration. While single administration of Dronabinol had no impact on intraocular pressure or systemic hemodynamics, a significant increase in ocular blood flow was found after administration of 10mg Dronabinol. This increase lasted more than four hours. This is the first study to show that even a single dose of Dronabinol increases ocular blood flow in patients with glaucoma without affecting systemic blood pressure. The next step will be to perform longitudinal studies to explore the long-term impact of Dronabinol on glaucoma progression and visual field preservation. If these studies show positive results, Dronabinol might be a valuable treatment option in the future.