Cosopt PF is administered for the purpose of treating eye and open-angle glaucoma in patients who respond negatively to other drugs. Cosopt PF drops contain a beta-blocker and carbonic anhydrase inhibitor combination. The drug works by decreasing the production of fluid and pressure in the human eye. Cosopt PF is a combination of two drugs (timolol maleate and dorzolamide hydrochloride). Dorzolamide belongs to carbonic anhydrase inhibitors class of drugs while timolol belongs to Beta-blockers.