Interaction of timolol and caffeine on intraocular pressure

The clinical interaction of 0.5% timolol maleate and 400 mg of oral caffeine on the intraocular pressure of 20 normotensive volunteers was studied. Caffeine administration did not significantly alter the reduction in intraocular pressure in timolol treated eyes. An antagonism, however, was observed in the fellow timolol untreated eyes with caffeine. The crossover reduction in intraocular pressure noted in the control group was significantly depressed in the caffeine group. A proposed mechanism for these observations is discussed.