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Indications and Dosage
Ophthalmic
Ocular hypertension, Open-angle glaucoma Adult: As 0.25% or 0.5% drops: Instill 1 drop bid. Oral Hypertension Adult: Initially, 10 mg once daily, may increase to 20 mg/day after 1-2 wk if needed.
Elderly: Initially, 5 mg/day. |
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Renal Impairment
Oral:
Severe or on dialysis: Initially, 5 mg/day, may increase by increments of 5 mg every 2 wk. Max: 20 mg/day. |
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Administration
May be taken with or without food.
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Contraindications
Sick sinus syndrome, severe bradycardia, cardiogenic shock, uncontrolled cardiac failure, 2nd or 3rd degree AV block, severe bronchial asthma, severe COPD, metabolic acidosis, untreated phaeochromocytoma, severe peripheral arterial disease.
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Special Precautions
Patients w/ bronchospastic disease, DM, corneal disease. May mask signs of hyperthyroidism and acute hypoglycaemia. Avoid abrupt withdrawal as it may exacerbate angina, MI, ventricular arrhythmias and precipitate thyroid storm. Patients undergoing surgery involving general anaesth. Renal and hepatic impairment. Pregnancy and lactation.
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Adverse Reactions
Eye discomfort (stinging and burning), bradycardia, palpitation, chest pain, oedema, insomnia, fatigue, lethargy, nausea, dyspepsia, diarrhoea, arthralgia, paraesthesia, dyspnoea, pharyngitis, antinuclear antibody positive, cold extremities.
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Ophth/PO: C
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Monitoring Parameters
Monitor BP, pulse and baseline renal function.
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Overdosage
Symptoms: Symptomatic bradycardia, bronchospasm, hypotension and acute cardiac failure. Management: Perform gastric lavage. Administer IV atropine sulfate to induce vagal blockade; dopamine, dobutamine or norepinephrine for hypotension and glucagon for refractory cases; isoprenaline HCl and aminophylline for bronchospasm; conventional therapy w/ digitalis, diuretics and oxygen for acute cardiac failure.
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Drug Interactions
Increased risk of bradycardia w/ digitalis glycosides. May cause mydriasis w/ epinephrine. Potential additive effect w/ oral Ca channel blockers, β-adrenergic blockers, antiarrhythmics (including amiodarone), parasympathomimetics, guanethidine. Increased risk of myocardial depression and hypotension w/ peripheral muscle relaxants (e.g. tubocurarine).
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Food Interaction
May increase plasma levels w/ alcohol.
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Lab Interference
May interfere result w/ glaucoma screening test (oral).
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Action
Description:
Mechanism of Action: Betaxolol is a cardioselective β-blocker which has greater affinity for β1-receptors and has little or no effect on β2-receptors. It lacks intrinsic sympathomimetic but has little membrane-stabilising activity. It also causes the reduction of intraocular pressure by decreasing the production of aqueous humour. Onset: 1-1.5 hr (oral). Pharmacokinetics: Absorption: Completely absorbed from the GI tract. Oral bioavailability: Approx 90%. Distribution: Crosses the placenta and is distributed into the breast milk. Plasma protein binding: Approx 50%. Metabolism: Undergoes minimal first-pass metabolism. Excretion: Via urine (approx 15% as unchanged drug). Elimination half-life: 14-22 hr. |
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Storage
Store between 15-25°C.
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MIMS Class
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References
Anon. Betaxolol. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 04/12/2013. Batxolol tablet (Epic Pharma). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 04/12/2013. Buckingham R (ed). Betaxolol hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 04/12/2013. Kerlone Tablet. U.S. FDA. https://www.fda.gov/. Accessed 04/12/2013. McEvoy GK, Snow EK, Miller J et al (eds). Betaxolol hydrochloride (EENT). AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 04/12/2013.
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