BETAXOLOL

Betaxolol is a β 1 -selective (cardioselective) adrenergic receptor blocking agent available as 10-mg and 20-mg tablets for oral administration. Betaxolol is chemically described as 2-propanol,1-[4-[2-(cyclopropylmethoxy)ethyl]phenoxy]-3-[(1-methylethyl)amino]-,hydrochloride,(±). It has the following chemical structure: Betaxolol hydrochloride is a water-soluble white crystalline powder with a molecular formula of C 18 H 29 NO 3 •HCl and a molecular weight of 343.9. It is freely soluble in water, ethanol, chloroform, and methanol, and has a pKa of 9.4. The inactive ingredients are anhydrous lactose, carnauba wax, hypromellose, microcrystalline cellulose, polyethylene glycol, polysorbate 80, pregeletanized starch (corn), sodium starch glycolate, stearic acid and titanium dioxide. Molecular Weight 343.9

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 (see Drug Interactions ). 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.

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. (see Warnings ).

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 (see Precautions ). 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

The following drugs have been coadministered with betaxolol and have not altered its pharmacokinetics: cimetidine, nifedipine, chlorthalidone, and hydrochlorothiazide. Concomitant administration of betaxolol with the oral anticoagulant warfarin has been shown not to potentiate the anticoagulant effect of warfarin. Catecholamine-depleting drugs (eg, reserpine) may have an additive effect when given with beta-blocking agents. Patients treated with a beta-adrenergic receptor blocking agent plus a catecholamine depletor should therefore be closely observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension. Should it be decided to discontinue therapy in patients receiving beta-blockers and clonidine concurrently, the beta-blocker should be discontinued slowly over several days before the gradual withdrawal of clonidine. Literature reports suggest that oral calcium antagonists may be used in combination with beta-adrenergic blocking agents when heart function is normal, but should be avoided in patients with impaired cardiac function. Hypotension, AV conduction disturbances, and left ventricular failure have been reported in some patients receiving beta-adrenergic blocking agents when an oral calcium antagonist was added to the treatment regimen. Hypotension was more likely to occur if the calcium antagonist were a dihydropyridine derivative, eg, nifedipine, while left ventricular failure and AV conduction disturbances, including complete heart block, were more likely to occur with either verapamil or diltiazem. Both digitalis glycosides and beta-blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia. Amiodarone is an antiarrhythmic agent with negative chronotropic properties that may be additive to those seen with beta blockers. Disopyramide is a Type I antiarrhythmic drug with potent negative inotropic and chronotropic effects. Disopyramide has been associated with severe bradycardia, asystole and heart failure when administered with beta blockers. Particular care should be taken when using anesthetic agents which depress the myocardium, such as ether, cyclopropane, and trichloroethylene (see Warnings, Major surgery ).