Betaxolol

Betaxolol is indicated in the management of hypertension. It may be used alone or concomitantly with other antihypertensive agents, particularly thiazide-type diuretics.

The initial dose of betaxolol in hypertension is ordinarily 10 mg once daily either alone or added to diuretic therapy. The full antihypertensive effect is usually seen within 7 to 14 days. If the desired response is not achieved the dose can be doubled after 7 to 14 days. Increasing the dose beyond 20 mg has not been shown to produce a statistically significant additional antihypertensive effect; but the 40-mg dose has been studied and is well tolerated.

An increased effect (reduction) on heart rate should be anticipated with increasing dosage. If monotherapy with betaxolol does not produce the desired response, the addition of a diuretic agent or other antihypertensive should be considered . Dosage Adjustments for Specific Patients Patients with renal failure In patients with renal impairment, clearance of betaxolol declines with decreasing renal function. In patients with severe renal impairment and those undergoing dialysis the initial dose of betaxolol is 5 mg once daily.

If the desired response is not achieved, dosage may be increased by 5 mg/day increments every 2 weeks to a maximum dose of 20 mg/day. Patients with hepatic disease Patients with hepatic disease do not have significantly altered clearance. Dosage adjustments are not routinely needed.

Elderly patients Consideration should be given to reduction in the starting dose to 5 mg in elderly patients. These patients are especially prone to beta-blocker-induced bradycardia, which appears to be dose related and sometimes responds to reductions in dose. Cessation of therapy If withdrawal of betaxolol therapy is planned, it should be achieved gradually over a period of about 2 weeks.

Patients should be carefully observed and advised to limit physical activity to a minimum.

Cardiac Failure Sympathetic stimulation may be a vital component supporting circulatory function in congestive heart failure, and beta-adrenergic receptor blockade carries the potential hazard of further depressing myocardial contractility and precipitating more severe heart failure. In hypertensive patients who have congestive heart failure controlled by digitalis and diuretics, beta-blockers should be administered cautiously. Both digitalis and beta-adrenergic receptor blocking agents slow AV conduction.

In Patients Without a History of Cardiac Failure Continued depression of the myocardium with beta-blocking agents over a period of time can, in some cases, lead to cardiac failure. Therefore at the first sign or symptom of cardiac failure, discontinuation of betaxolol should be considered. In some cases beta-blocker therapy can be continued while cardiac failure is treated with cardiac glycosides, diuretics, and other agents, as appropriate.

Exacerbation of Angina Pectoris Upon Withdrawal Abrupt cessation of therapy with certain beta-blocking agents in patients with coronary artery disease has been followed by exacerbations of angina pectoris and, in some cases, myocardial infarction has been reported. Therefore, such patients should be warned against interruption of therapy without the physician's advice. Even in the absence of overt angina pectoris, when discontinuation of betaxolol is planned, the patient should be carefully observed and therapy should be reinstituted, at least temporarily, if withdrawal symptoms occur.

Bronchospastic diseases PATIENTS WITH BRONCHOSPASTIC DISEASE SHOULD NOT IN GENERAL RECEIVE BETA-BLOCKERS. Because of its relative β 1 -selectivity (cardioselectivity), low doses of betaxolol may be used with caution in patients with bronchospastic disease who do not respond to or cannot tolerate alternative treatment. Since β 1 -selectivity is not absolute and is inversely related to dose, the lowest possible dose of betaxolol should be used (5 to 10 mg once daily) and a bronchodilator should be made available. If dosage must be increased, divided dosage should be considered to avoid the higher peak blood levels associated with once-daily dosing.

Major Surgery Chronically administered beta-blocking therapy should not be routinely withdrawn prior to major surgery, however the impaired ability of the heart to respond to reflex adrenergic stimuli may augment the risks of general anesthesia and surgical procedures . Titrate betaxolol dose to maintain effective heart rate control while avoiding frank hypotension and bradycardia. Diabetes and Hypoglycemia Beta-blockers should be used with caution in diabetic patients. Beta-blockers may mask tachycardia occurring with hypoglycemia (patients should be warned of this), although other manifestations such as dizziness and sweating may not be significantly affected.

Unlike nonselective beta-blockers, betaxolol does not prolong insulin-induced hypoglycemia. Thyrotoxicosis Beta-adrenergic blockade may mask certain clinical signs of hyperthyroidism (eg, tachycardia). Abrupt withdrawal of beta-blockade might precipitate a thyroid storm; therefore, patients known or suspected of being thyrotoxic from whom betaxolol is to be withdrawn should be monitored closely . Betaxolol should not be given to patients with untreated pheochromocytoma.

Betaxolol is contraindicated in patients with known hypersensitivity to the drug. Betaxolol is contraindicated in patients with sinus bradycardia, heart block greater than first degree, cardiogenic shock, and overt cardiac failure. .

Pregnancy Pregnancy Category C In a study in which pregnant rats received betaxolol at doses of 4, 40, or 400 mg/kg/day, the highest dose (600 × MRHD) was associated with increased postimplantation loss, reduced litter size and weight, and an increased incidence of skeletal and visceral abnormalities, which may have been a consequence of drug-related maternal toxicity. Other than a possible increased incidence of incomplete descent of testes and sternebral reductions, betaxolol at 4 mg/kg/day and 40 mg/kg/day (6 × MRHD and 60 × MRHD) caused no fetal abnormalities. In a second study with a different strain of rat, 200 mg betaxolol/kg/day (300 × MRHD) was associated with maternal toxicity and an increase in resorptions, but no teratogenicity.

In a study in which pregnant rabbits received doses of 1, 4, 12, or 36 mg betaxolol/kg/day (54 × MRHD), a marked increase in post-implantation loss occurred at the highest dose, but no drug-related teratogenicity was observed. The rabbit is more sensitive to betaxolol than other species because of higher bioavailability resulting from saturation of the first-pass effect. In a peri- and postnatal study in rats at doses of 4, 32, and 256 mg betaxolol/kg/day (380 × MRHD), the highest dose was associated with a marked increase in total litter loss within 4 days postpartum.

In surviving offspring, growth and development were also affected. There are no adequate and well-controlled studies in pregnant women. Betaxolol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Beta-blockers reduce placental perfusion, which may result in intrauterine fetal death, immature and premature deliveries.

In addition, adverse effects (especially hypoglycemia and bradycardia) may occur in fetus.

Most adverse reactions have been mild and transient and are typical of beta-adrenergic blocking agents, eg, bradycardia, fatigue, dyspnea, and lethargy. Withdrawal of therapy in U.S. and European controlled clinical trials has been necessary in about 3.5% of patients, principally because of bradycardia, fatigue, dizziness, headache, and impotence. Frequency estimates of adverse events were derived from controlled studies in which adverse reactions were volunteered and elicited in U.S. studies and volunteered and/or elicited in European studies.

In the U.S., the placebo-controlled hypertension studies lasted for 4 weeks, while the active-controlled hypertension studies had a 22- to 24-week double-blind phase. The following doses were studied: betaxolol—5, 10, 20, and 40 mg once daily; atenolol—25, 50, and 100 mg once daily; and propranolol—40, 80, and 160 mg b.i.d. Betaxolol, like other beta-blockers, has been associated with the development of antinuclear antibodies (ANA) (e.g., lupus erythematosus).

In controlled clinical studies, conversion of ANA from negative to positive occurred in 5.3% of the patients treated with betaxolol, 6.3% of the patients treated with atenolol, 4.9% of the patients treated with propranolol, and 3.2% of the patients treated with placebo. Betaxolol adverse events reported with a 2% or greater frequency, and selected events with lower frequency, in U.S. controlled studies are: Of the above adverse reactions associated with the use of betaxolol, only bradycardia was clearly dose related, but there was a suggestion of dose relatedness for fatigue, lethargy, and dyspepsia. In Europe, the placebo-controlled study lasted for 4 weeks, while the comparative studies had a 4-52-week double-blind phase.

The following doses were studied: betaxolol 20 and 40 mg once daily and atenolol 100 mg once daily. From European controlled hypertension clinical trials, the following adverse events reported by 2% or more patients and selected events with lower frequency are presented: The only adverse event whose frequency clearly rose with increasing dose was bradycardia. Elderly patients were especially susceptible to bradycardia, which in some cases responded to dose-reduction . The following selected (potentially important) adverse events have been reported at an incidence of less than 2% in U.S. controlled and open, long-term clinical studies, European controlled clinical trials, or in marketing experience.

It is not known whether a causal relationship exists between betaxolol and these events; they are listed to alert the physician to a possible relationship: Autonomic: flushing, salivation, sweating. Body as a whole: allergy, fever, malaise, pain, rigors. Cardiovascular: angina pectoris, arrhythmia, atrioventricular block, heart failure, hypertension, hypotension, myocardial infarction, thrombosis, syncope.

Central and peripheral nervous system: ataxia, neuralgia, neuropathy, numbness, speech disorder, stupor, tremor, twitching. Gastrointestinal: anorexia, constipation, dry mouth, increased appetite, mouth ulceration, rectal disorders, vomiting, dysphagia. Hearing and Vestibular: earache, labyrinth disorders, tinnitus, deafness.

Hematologic: anemia, leucocytosis, lymphadenopathy, purpura, thrombocytopenia. Liver and biliary: increased AST, increased ALT. Metabolic and nutritional: acidosis, diabetes, hypercholesterolemia, hyperglycemia, hyperkalemia, hyperlipemia, hyperuricemia, hypokalemia, weight gain, weight loss, thirst, increased LDH. Musculoskeletal: arthropathy, neck pain, muscle cramps, tendonitis. Psychiatric: abnormal thinking, amnesia, impaired concentration, confusion, emotional lability, hallucinations, decreased libido.

Reproductive disorders: Female: breast pain, breast fibroadenosis, menstrual disorder; Male: Peyronie's disease, prostatitis. Respiratory: bronchitis, bronchospasm, cough, epistaxis, flu, pneumonia, sinusitis. Skin: alopecia, eczema, erythematous rash, hypertrichosis, pruritus, skin disorders.

Special senses: abnormal taste, taste loss. Urinary system: cystitis, dysuria, micturition disorder, oliguria, proteinuria, abnormal renal function, renal pain. Vascular: cerebrovascular disorder, intermittent claudication, leg cramps, peripheral ischemia, thrombophlebitis. Vision: abnormal lacrimation, abnormal vision, blepharitis, ocular hemorrhage, conjunctivitis, dry eyes, iritis, cataract, scotoma.

Potential Adverse Effects Although not reported in clinical studies with betaxolol, a variety of adverse effects have been reported with other beta-adrenergic blocking agents and may be considered potential adverse effects of betaxolol: Central nervous system: Reversible mental depression progressing to catatonia, an acute reversible syndrome characterized by disorientation for time and place, short-term memory loss, emotional lability with slightly clouded sensorium, and decreased performance on neuropsychometric tests. Allergic: Fever combined with aching and sore throat, laryngospasm, respiratory distress. Hematologic: Agranulocytosis, thrombocytopenic purpura, and nonthrombocytopenic purpura.

Gastrointestinal: Mesenteric arterial thrombosis, ischemic colitis. Metabolic: Hypoglycemia. Miscellaneous: Raynaud's phenomena. There have been reports of skin rashes and/or dry eyes associated with the use of beta-adrenergic blocking drugs. The reported incidence is small, and in most cases, the symptoms have cleared when treatment was withdrawn.

Discontinuation of the drug should be considered if any such reaction is not otherwise explicable. Patients should be closely monitored following cessation of therapy. The oculomucocutaneous syndrome associated with the beta-blocker practolol has not been reported with betaxolol during investigational use and extensive foreign experience.

However, dry eyes have been reported. table-1 table-2