Effects of D-timolol on intraocular pressure, heart rate, cardiac contractility, and tracheal muscle function

Introduction of L-timolol maleate into the clinics for glaucoma treatment has been a great success as it produces relatively few side effects, such as miosis, ciliary spasm and headache, which are associated with the use of pilocarpine. Recent reports indicated, however, that L-timolol produces asthmatic attacks, cardiovascular suppression and central depression. D-Timolol was found to be as effective as L-timolol in lowering the intraocular pressure and aqueous humor production. However it was much less potent than L-timolol in inhibiting cardiac contractility and heart rate stimulated by isoproterenol and was less active in blocking beta-adrenergic receptors in tracheal muscle. It is suggested that the D-isomer of timolol could be used to treat glaucoma instead of L-isomer without producing untoward side effects in cardiovascular and bronchial tissues.