Shortterm "escape" and longterm "drift." The dissipation effects of the beta adrenergic blocking agents.

The dissipation phenomena associated with timolol have important implications in the clinical management of glaucoma patients. Shortterm "escape" and longterm "drift" are clinical terms which describe the reduction of timolol's efficacy over a few days and over months and years, respectively. Recent physiological studies suggest a cellular explanation for these readjustments in tissue responsiveness to continued administration of timolol. While the precise location of the physiologically responding cells and the interactions of the various adrenergic responsive elements remain unclear, subsensitivity and supersensitivity may prove to be the most accurate designations for alterations in tissue responsiveness to adrenergic stimulation following "down regulation" or "up regulation" of beta receptor density on cell membranes.