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Mechanism Of Action
Timolol maleate is a beta1 and beta2 (non-selective) adrenergic receptor blocking agent that does not have significant intrinsic sympathomimetic, direct myocardial depressant, or local anesthetic (membrane-stabilizing) activity.
Beta-adrenergic receptor blockade reduces cardiac output in both healthy subjects and patients with heart disease. In patients with severe impairment of myocardial function, beta-adrenergic receptor blockade may inhibit the stimulatory effect of the sympathetic nervous system necessary to maintain adequate cardiac function.
Beta-adrenergic receptor blockade in the bronchi and bronchioles results in increased airway resistance from unopposed parasympathetic activity. Such an effect in patients with asthma or other bronchospastic conditions is potentially dangerous.
TIMOPTIC Ophthalmic Solution, when applied topically on the eye, has the action of reducing elevated as well as normal intraocular pressure, whether or not accompanied by glaucoma. Elevated intraocular pressure is a major risk factor in the pathogenesis of glaucomatous visual field loss. The higher the level of intraocular pressure, the greater the likelihood of glaucomatous visual field loss and optic nerve damage.
The onset of reduction in intraocular pressure following administration of TIMOPTIC can usually be detected within one-half hour after a single dose. The maximum effect usually occurs in one to two hours and significant lowering of intraocular pressure can be maintained for periods as long as 24 hours with a single dose. Repeated observations over a period of one year indicate that the intraocular pressure-lowering effect of TIMOPTIC is well maintained.
The precise mechanism of the ocular hypotensive action of TIMOPTIC is not clearly established at this time. Tonography and fluorophotometry studies in man suggest that its predominant action may be related to reduced aqueous formation. However, in some studies a slight increase in outflow facility was also observed.
In a study of plasma drug concentration in six subjects, the systemic exposure to timolol was determined following twice daily administration of TIMOPTIC 0.5%. The mean peak plasma concentration following morning dosing was 0.46 ng/mL and following afternoon dosing was 0.35 ng/mL.
In controlled multiclinic studies in patients with untreated intraocular pressures of 22 mmHg or greater, TIMOPTIC 0.25% or 0.5% administered twice a day produced a greater reduction in intraocular pressure than 1, 2, 3, or 4% pilocarpine solution administered four times a day or 0.5, 1, or 2% epinephrine hydrochloride solution administered twice a day.
In these studies, TIMOPTIC was generally well tolerated and produced fewer and less severe side effects than either pilocarpine or epinephrine. A slight reduction of resting heart rate in some patients receiving TIMOPTIC (mean reduction 2.9 beats/minute standard deviation 10.2) was observed.
Last reviewed on RxList: 9/1/2016
This monograph has been modified to include the generic and brand name in many instances.
Additional Timoptic Information
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