Common side effects with the drops is irritation of the eye.[3] 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.[3] Use is not recommended in those with asthma, uncompensated heart failure, or COPD.[3] It is unclear if use during pregnancy is safe for the fetus.[6] Timolol is a non-selective beta blocker.[3]
In its eye drop form it is used to treat open-angle and, occasionally, secondary glaucoma.[3][14] The mechanism of action of timolol is probably the reduction of the formation of aqueous humor[3] 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]orprostaglandin analogs.[20]
ACochrane 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]
^ abcdefghijk"Timolol eent". The American Society of Health-System Pharmacists. Archived from the original on 28 December 2016. Retrieved 8 December 2016.
^Volotinen M, Turpeinen M, Tolonen A, Uusitalo J, Mäenpää J, Pelkonen O (July 2007). "Timolol metabolism in human liver microsomes is mediated principally by CYP2D6". Drug Metabolism and Disposition. 35 (7): 1135–1141. doi:10.1124/dmd.106.012906. PMID17431033. S2CID794764.
^ abc"Timolol Maleate". The American Society of Health-System Pharmacists. Archived from the original on 28 December 2016. Retrieved 8 December 2016.
^World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
^Liu JH, Kripke DF, Weinreb RN (September 2004). "Comparison of the nighttime effects of once-daily timolol and latanoprost on intraocular pressure". American Journal of Ophthalmology. 138 (3): 389–95. doi:10.1016/j.ajo.2004.04.022. PMID15364220.
^Liu JH, Medeiros FA, Slight JR, Weinreb RN (March 2009). "Comparing diurnal and nocturnal effects of brinzolamide and timolol on intraocular pressure in patients receiving latanoprost monotherapy". Ophthalmology. 116 (3): 449–54. doi:10.1016/j.ophtha.2008.09.054. PMID19157559.
^Strohmaier K, Snyder E, Adamsons I (July 1998). "A multicenter study comparing dorzolamide and pilocarpine as adjunctive therapy to timolol: patient preference and impact on daily life". Journal of the American Optometric Association. 69 (7): 441–51. PMID9697378.
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