Timolol
Chemical compound
From Wikipedia, the free encyclopedia
Timolol is a beta blocker medication used either by mouth or as eye drops.[4][5] As eye drops it is used to treat increased pressure inside the eye such as in ocular hypertension and glaucoma.[4] By mouth it is used for high blood pressure, chest pain due to insufficient blood flow to the heart, to prevent further complications after a heart attack, and to prevent migraines.[5]
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| Trade names | Timoptic, others[1] |
| AHFS/Drugs.com | Maleate Monograph eent Monograph |
| MedlinePlus | a684029 |
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| Routes of administration | By mouth, topical (eye drop) |
| Drug class | Beta blocker |
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| Pharmacokinetic data | |
| Bioavailability | 60% |
| Metabolism | Liver (80%, mainly CYP2D6[3]) |
| Onset of action | 15–30 min[4] |
| Elimination half-life | 2.5–5 hours |
| Duration of action | 24 hours[4] |
| Excretion | Kidney |
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| ECHA InfoCard | 100.043.651 |
| Chemical and physical data | |
| Formula | C13H24N4O3S |
| Molar mass | 316.42 g·mol−1 |
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Common side effects with the drops is irritation of the eye.[4] Common side effects by mouth include tiredness, slow heart beat, itchiness, and shortness of breath.[5] Other side effects include masking the symptoms of low blood sugar in those with diabetes.[4] Use is not recommended in those with asthma, uncompensated heart failure, or chronic obstructive pulmonary disease (COPD).[4] It is unclear if use during pregnancy is safe for the fetus.[6] Timolol is a non-selective beta blocker.[4]
Timolol was patented in 1968, and came into medical use in 1978.[7] It is on the World Health Organization's List of Essential Medicines.[8] Timolol is available as a generic medication.[4][9] In 2023, it was the 173rd most commonly prescribed medication in the United States, with more than 2 million prescriptions.[10][11]
Medical uses
By mouth
In its by mouth or oral form, it is used:
- to treat high blood pressure
- to prevent heart attacks
- to prevent migraine headaches[12]
The combination of timolol and the alpha-1 blocker prazosin has sedative effects.[13]
Eye drops
In its eye drop form it is used to treat open-angle and, occasionally, secondary glaucoma.[4][14] The mechanism of action of timolol is probably the reduction of the formation of aqueous humor[4] in the ciliary body in the eye. It was the first beta blocker approved for topical use in treatment of glaucoma in the United States (1978).[15] When used by itself, it depresses intraocular pressure (IOP) 18–34% below baseline within first few treatments. However, there are short-term escape and long-term drift effects in some people. That is, tolerance develops. It may reduce the extent of the daytime IOP curve up to 50%. The IOP is higher during sleep. Efficacy of timolol in lowering IOP during the sleep period may be limited.[16][17][18] It is a 5–10× more potent beta blocker than propranolol. Timolol is light-sensitive; it is usually preserved with 0.01% benzalkonium chloride (BAC), but also comes BAC-free. It can also be used in combination with pilocarpine, carbonic anhydrase inhibitors[19] or prostaglandin analogs.[20]
A Cochrane review compared the effect of timolol versus brimonidine in slowing the progression of open angle glaucoma in adults but found insufficient evidence to come to conclusions.[21]
On the skin
In its gel form it is used on the skin to treat infantile hemangiomas.[22]
Available forms
It is available in tablet and liquid formulations.[23][24]
For ophthalmic use, timolol is also available combined:
- with carbonic anhydrase inhibitors:
- timolol and brinzolamide
- timolol and dorzolamide
- with α2 agonists:
- with prostaglandin analogs:
- timolol and latanoprost
- timolol and travoprost
Contraindications
The medication should not be taken by individuals with:[23]
- An allergy to timolol or any other beta-blockers
- Asthma or severe chronic obstructive bronchitis
- A slow heart rate (bradycardia), or a heart block
- Heart failure[25]
Side effects
The most serious possible side effects include cardiac arrhythmias and severe bronchospasms.[23] Timolol can also lead to fainting, congestive heart failure, depression, confusion, worsening of Raynaud's syndrome and impotence.[23]
Side effects when given in the eye include: burning sensation, eye redness, superficial punctate keratopathy, corneal numbness.[24][14]
Chemistry
Society and culture
Brand names
Timolol is sold under many brand names worldwide.[1] Timolol eye drops are sold under the brand names Timoptic and Istalol among others.[29][30]
