To the Editor.—
I read the letter from Stephen A. Shaivitz, MD (242:1612, 1979), in The Journal, titled "Timolol and Myasthenia Gravis." I was involved in some of the early clinical evaluation of timolol maleate,1 and we, like most investigators at the time, found few or no side effects. However, shortly after we submitted our article, several cases of abrupt cardiac failure were reported of patients who began receiving timolol. One patient required a pacemaker. Obviously, systemic absorption takes place and can affect systemic disorders such as cardiac insufficiency and asthma.Interestingly, while timolol is a β-adrenergic blocker and lowers intraocular pressure, epinephrine, the classic β-agonist, also is used clinically to lower intraocular pressure. Furthermore, there is evidence to show that the two drugs used together have an additive effect on lowering intraocular pressure.2 It is possible that the mechanisms of action of timolol are not solely as