Timolol

Ophthalmic
Open-angle glaucoma, Ocular hypertension

Oral
Post-myocardial infarction

Oral
Hypertension

Oral
Prophylaxis of migraine

Oral
Angina pectoris

Oral:
Dose reduction may be needed.

Oral:
Dose reduction may be needed.

Should be taken with food.

Present or history of bronchial asthma, severe COPD, allergic bronchospasm, sinus bradycardia, sick sinus syndrome, 2nd and 3rd degree heart block, overt heart failure, cardiogenic shock, severe peripheral vascular disease, untreated phaeochromocytoma, metabolic acidosis.

Patients w/ inadequate cardiac function, DM, myasthenia gravis, cerebrovascular insufficiency, history of atopy. Avoid abrupt withdrawal as it may exacerbate angina symptoms or precipitate MI in patients w/ coronary artery disease, or precipitate thyroid crisis in patients w/ thyrotoxicosis. Patients undergoing major surgery. May mask signs of hyperthyroidism and hypoglycaemia. Ophth soln should not be used as monotherapy for angle-closure glaucoma. Renal and hepatic impairment. Pregnancy and lactation.

Burning and stinging sensation of the eyes, bradycardia, hypotension, arrhythmia and AV or SA nodal block, CHF, pulmonary oedema, Raynaud's phenomenon, headache, dizziness, fatigue, asthenia, abdominal discomfort, nausea, constipation, hypoglycaemia.

Ophth/PO: C

Monitor BP, heart rate.

Symptoms: Symptomatic bradycardia, hypotension, bronchospasm and acute heart failure. Management: Symptomatic and supportive treatment. Stomach should be emptied immediately by gastric lavage. IV atropine sulfate may be given for symptomatic bradycardia, if it persists, admin IV isoproterenol HCl cautiously. For severe hypotension, a vasopressor (e.g. dobutamine, dopamine, norepinephrine) may be given, for bronchospasm, a β-adrenergic agonist and/or IV aminophylline. An IV cardiac glycoside, diuretic and oxygen should be used for cardiac failure. IV glucagon may also be useful.

Concomitant admin w/ reserpine may increase hypotension and bradycardia. Additive effects w/ other antihypertensives (e.g. hydralazine, methyldopa). Increased β-adrenergic blockade (e.g. decreased heart rate) w/ quinidine. Rebound HTN due to abrupt withdrawal of clonidine. Hypotensive effect may be antagonised by NSAIDs (e.g. indomethacin, ibuprofen).

Description: Timolol is a non-selective β-adrenergic receptor blocker. It does not have significant intrinsic sympathomimetic activity, direct myocardial depressant activity or local anaesth activity. Exact mechanism of ocular hypotensive effect is unclear, but it is thought to be related to reduction of aqueous humour formation. β-blockade also causes lowering of BP.
Onset: Ophth: 30 min. Oral: 15-45 min.
Duration: Ophth: 24 hr. Oral: Approx 4 hr.
Pharmacokinetics:
Absorption: Oral: Almost completely absorbed from the GI tract (approx 90%). Oral bioavailability: 50%. Time to peak plasma concentration: Approx 1-2 hr. Ophth: Found in plasma at low concentrations.
Distribution: Crosses the placenta and enters breast milk. Volume of distribution: 1.7 L/kg. Plasma protein binding: 60%.
Metabolism: Extensively metabolised via CYP2D6 isoenzyme.
Excretion: Via urine (as metabolites and unchanged drug). Plasma half-life: 4 hr.

Store between 15-30°C. Avoid freezing and protect from light.

Antiglaucoma Preparations / Beta-Blockers

Anon. Timolol (Ophthalmic). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 02/12/2013.

Anon. Timolol (Systemic). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 02/12/2013.

Buckingham R (ed). Timolol Maleate. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 02/12/2013.

McEvoy GK, Snow EK, Miller J et al (eds). Timolol Maleate. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 02/12/2013.

Timolol Maleate Solution/Drops (Bausch & Lomb Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 02/12/2013.

Wickersham RM. Timolol maleate. Facts and Comparisons [online]. St. Louis, MO. Wolters Kluwer Clinical Drug Information, Inc. https://www.wolterskluwercdi.com/facts-comparisons-online/. Accessed 02/12/2013.