Drug Groups

approved

Description

A beta-adrenergic antagonist similar in action to propranolol. The levo-isomer is the more active. Timolol has been proposed as an antihypertensive, antiarrhythmic, antiangina, and antiglaucoma agent. It is also used in the treatment of migraine disorders and tremor. [PubChem]

Indication

In its oral form it is used to treat high blood pressure and prevent heart attacks, and occasionally to prevent migraine headaches. In its opthalmic form it is used to treat open-angle and occasionally secondary glaucoma.

Pharmacology

Similar to propranolol and nadolol, timolol is a non-selective, beta-adrenergic receptor antagonist. Timolol does not have significant intrinsic sympathomimetic, direct myocardial depressant, or local anesthetic (membrane-stabilizing) activity, but does possess a relatively high degree of lipid solubility. Timolol, when applied topically to 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 and optic nerve damage.

Toxicity

LD₅₀=1190 mg/kg (oral, mice), LD₅₀=900 mg/kg (oral, rat). Symptoms of overdose include drowsiness, vertigo, headache, and atriventricular block.

Affected Organisms

Biotransformation

Primarily hepatic (80%) via the cytochrome P450 2D6 isoenzyme.

Absorption

Bioavailability is about 60%

Half Life

2.5-5 hours

Protein Binding

~10%

Elimination

Timolol and its metabolites are primarily excreted in the urine.

References

External Links