Timolol
Encyclopedia
Timolol maleate is a non-selective beta-adrenergic receptor blocker
.
In its ophthalmic
form (brand names Timoptol in Italy; Timoptic), it is used to treat open-angle and occasionally secondary glaucoma
by reducing aqueous humour production through blockage of the beta receptors on the ciliary epithelium. The pharmacological mechanism by which it actually does this is still unknown. First beta-blocker approved for topical use in treatment of glaucoma in the USA (1978). With monotherapy, depresses IOP 18-34% below baseline within first few treatments. However, there are short-term escape and long-term drift effects in some patients. That is, tolerance develops. May reduce extent of diurnal IOP curve up to 50%. IOP higher during sleep. 5-10x more potent beta-blocker than propranolol. Light sensitive; preserved with 0.01% benzalkonium Cl (and also comes BAC free). Can also be used in adjunctive therapy with pilocarpine or CAIs.
s. Timolol can also lead to fainting
, congestive heart failure
, depression
, confusion
, worsening of Raynaud's syndrome and impotence.
For ophthalmic use, timolol is also available combined with other medications:
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
.
Uses
In its oral form (Blocadren), it is used:- to treat high blood pressureHypertensionHypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
- to prevent heart attackMyocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
s - to prevent migraineMigraineMigraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
headaches
In its ophthalmic
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
form (brand names Timoptol in Italy; Timoptic), it is used to treat open-angle and occasionally secondary glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
by reducing aqueous humour production through blockage of the beta receptors on the ciliary epithelium. The pharmacological mechanism by which it actually does this is still unknown. First beta-blocker approved for topical use in treatment of glaucoma in the USA (1978). With monotherapy, depresses IOP 18-34% below baseline within first few treatments. However, there are short-term escape and long-term drift effects in some patients. That is, tolerance develops. May reduce extent of diurnal IOP curve up to 50%. IOP higher during sleep. 5-10x more potent beta-blocker than propranolol. Light sensitive; preserved with 0.01% benzalkonium Cl (and also comes BAC free). Can also be used in adjunctive therapy with pilocarpine or CAIs.
Side effects
The most serious possible side effects include cardiac arrhythmias and severe bronchospasmBronchospasm
Bronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release of substances from mast cells or basophils under the influence of anaphylatoxins...
s. Timolol can also lead to fainting
Syncope (medicine)
Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
, congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
, depression
Clinical depression
Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...
, confusion
ConFusion
ConFusion is an annual science fiction convention organized by the Stilyagi Air Corps and its parent organization, the Ann Arbor Science Fiction Association. Commonly, it is held the third weekend of January. It is the oldest science fiction convention in Michigan, a regional, general SF con...
, worsening of Raynaud's syndrome and impotence.
Usual dosage
- Children and Adults: Ophthalmic: Initial: 0.25% solution, instill 1 drop twice daily; increase to 0.5% solution if response not adequate; decrease to 1 drop/day if *controlled; do not exceed 2 drops twice daily of 0.5% solution Adults: Oral:
- Hypertension: Initial: 10 mg twice daily, increase gradually every 14 days, usual dosage: 20–40 mg/day in 2 divided doses; maximum: 60 mg/day
- Prevention of myocardial infarction: 10 mg twice daily initiated within 1–6 weeks after infarction
- Migraine headache: Initial: 10 mg twice daily, increase to maximum of 30 mg/day
Formulations
- Gel-forming solution, ophthalmic, as maleate (Timoptic-XE): 0.25% (2.5 mL, 5 mL); 0.5% (2.5 mL, 5 mL)
- Solution, ophthalmic, as hemihydrate (Betimol): 0.25% (5 mL, 10 mL, 15 mL); 0.5% (5 mL, 10 mL, 15 mL) [contains benzalkonium chlorideBenzalkonium chlorideBenzalkonium chloride, also known as alkyldimethylbenzylammonium chloride and ADBAC, is a mixture of alkylbenzyldimethylammonium chlorides of various even-numbered alkyl chain lengths. This product is a nitrogenous cationic surface-acting agent belonging to the quaternary ammonium group...
] - Solution, ophthalmic, as maleate: 0.25% (5 mL, 10 mL, 15 mL); 0.5% (5 mL, 10 mL, 15 mL) [contains benzalkonium chloride]
- Timoptic: 0.25% (5 mL, 10 mL); 0.5% (5 mL, 10 mL) [contains benzalkonium chloride]
- Solution, ophthalmic, as maleate [preservative free] (Timoptic OcuDose): 0.25% (0.2 mL);0.5% (0.2 mL) [single use]
- Tablet, as maleate (Blocadren): 5 mg, 10 mg, 20 mg
For ophthalmic use, timolol is also available combined with other medications:
- CombiganCombiganCombigan is a brand of eye drops indicated in the treatment of glaucoma. It is a combination of brimonidine and timolol, in concentrations of 0.2% and 0.5% respectively. Combigan is marketed and sold by Allergan....
- timolol and brimonidineBrimonidineBrimonidine is a drug used to treat open-angle glaucoma or ocular hypertension.It acts via decreasing synthesis of aqueous humor, and increasing the amount that drains from the eye through uveoscleral outflow.As a treatment for glaucoma, it is usually given in eyedrop form.Brimonidine is an... - CosoptCosoptDorzolamide/timolol eyedrops are used for lowering pressure in the eye to normal levels, and a treatment for glaucoma. The drug is a combination of two chemicals: dorzolamide hydrochloride and timolol maleate. It gained Food and Drug Administration approval in April 1998, and is supplied by...
- timolol maleate and dorzolamide hydrochlorideDorzolamideDorzolamide is a carbonic anhydrase inhibitor. It is an anti-glaucoma agent and topically applied in the form of eye drops. This drug, developed by Merck, was the first drug in human therapy which resulted from structure-based drug design... - DuoTrav - timolol and travoprostTravoprostTravoprost ophthalmic solution is a topical medication used for controlling the progression of glaucoma or ocular hypertension, by reducing intraocular pressure. It is a synthetic prostaglandin analog that works by increasing the outflow of aqueous fluid from the eyes...
- Xalacom (Pfizer) - timolol and latanoprost
Brand names
- In Canada: Apo-Timol, Apo-Timop, Gen-Timolol, Nu-Timolol, Phoxal-timolol, PMS-Timolol, Tim-AK, Timoptic, Timoptic-XE.
- In the United States: Betimol, Blocadren, Istalol, Timoptic, Timoptic-XE, Timoptic OcuDose.
External links
- http://dx.doi.org/10.1021/jo00881a011