• A randomized, double-blind clinical study was conducted on patients with primary open angle glaucoma to determine whether timolol and epinephrine have an additive effect in lowering intraocular pressure. Sixteen patients were randomly assigned to one of two treatment sequences (timolol alone, supplemented after two weeks with epinephrine, and vice versa). An initial additive effect in lowering IOP was found in both sequences. However, after several weeks of combined therapy, complete loss of additive effect was found. Patients who were treated first with epinephrine for two weeks and then supplemented with timolol had significantly lower IOPs, for at least two weeks, than patients in the reverse treatment sequence. Epinephrine treatment alone caused a significant increase in facility of outflow, but this effect did not occur with simultaneous timolol treatment. The results are discussed in terms of possible fundamental β- and α-adrenergic influences on aqueous dynamics and their potential clinical relevance.
Thomas JV, Epstein DL. Timolol and Epinephrine in Primary Open Angle GlaucomaTransient Additive Effect. Arch Ophthalmol. 1981;99(1):91-95. doi:10.1001/archopht.1981.03930010093010