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TABLE 4.6 Classes of Drugs Used to Treat Glaucoma

Cholinergic agonists

a2-Adrenergic agonists

Pilocarpine

Aproclonidine

 

Brimonidine

b2-Adrenergic agonists

Carbonic anhydrase inhibitors

Epinephrine

Acetazolamide

Dipivefrin

Dorzolamide (Trusopt)

b2-Adrenergic antagonists

Prostaglandin-F2a analogues

Timolol

Latanoprost

Betaxolol (Betoptic)

Unoprostone

of drugs.93 Surgical options are also available today to lower IOP, including laser trabeculoplasty, trabeculectomy/sclerostomy, drainage implantation, and cyclodestruction of fluid-forming tissues.73 Thus, there are now many effective options to slow the progression of glaucoma by reducing IOP.

One important factor in slowing the progression of glaucoma via medications that reduce IOP is patient compliance with dosing regimens. With respect to compliance, the ideal glaucoma drug is one that is applied at most twice a day (P. Kaufman, IOM workshop). If the dose must be repeated every three to four hours, patient compliance becomes a problem; for this reason, marijuana and the cannabinoids studied thus far would not be highly satisfactory treatments for glaucoma. Present therapies, especially combinations of approved topical drugs, can control IOP when administered once or twice a day, at a cost of about $60 per month.

Future Therapy

In all likelihood the next generation of glaucoma therapies will deal with neural protection, neural rescue, neural regeneration, or blood flow, and the optic nerve and neural retina will be treated directly rather than just by lowering IOP (P. Kaufman, IOM workshop). There is some evidence that a synthetic cannabinoid, HU-211, might have neuroprotective effects in vitro; this presents a potential approach that has nothing to do with IOP.197 HU-211 is commonly referred to as a cannabinoid because its chemical structure is similar to THC; however, it does not bind to cannabinoid receptor.

It is known that cannabinoids lower IOP fairly substantially but not how. No one has tested whether the effect is receptor mediated (B. Martin, IOM workshop). To do so, one could test whether a receptor antagonist



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