"What are beta blockers and how do they work?
Beta blockers, also known as beta-adrenergic blocking agents, are a class of drugs that works by blocking the neurotransmitters norepinephrine and epinephrine from binding to receptors. "...
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.
Kerlone (betaxolol hydrochloride) , 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:
|Dose Range|| Betaxolol
5-40 mg q.d.*
40-160 mg b.i.d.
25-100 mg q.d.
|Body System/Adverse Reaction||(%)||(%)||(%)||(%)|
|Bradycardia (heart rate < 50 BPM)||8.1||4.1||12.0||0|
|Central Nervous System|
|Upper respiratory infection||2.6||0||0||5.5|
*Five patients received 80 mg q.d.
†N=336 males; impotence is a known possible adverse effect of this pharmacological class.
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- to 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:
|Dose range|| Betaxolol
20-40 mg q.d.
100 mg q.d.
|Body System/Adverse Reaction||(%)||(%)||(%)|
|Bradycardia (heartrate < 50 BPM)||5.8||5.0||0|
|Central Nervous System|
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.
Liver and biliary: increased AST, increased ALT.
Psychiatric:abnormal thinking, amnesia, impaired concentration, confusion, emotional lability, hallucinations, decreased libido.
Special senses: abnormal taste, taste loss.
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.
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 Kerlone (betaxolol hydrochloride) during investigational use and extensive foreign experience. However, dry eyes have been reported.
Read the Kerlone (betaxolol hydrochloride) Side Effects Center for a complete guide to possible side effects
The following drugs have been coadministered with Kerlone (betaxolol hydrochloride) and have not altered its pharmacokinetics: cimetidine, nifedipine, chlorthalidone, and hydrochlorothiazide. Concomitant administration of Kerlone (betaxolol hydrochloride) 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.
Risk of anaphylactic reaction: Although it is known that patients on beta-blockers may be refractory to epinephrine in the treatment of anaphylactic shock, beta-blockers can, in addition, interfere with the modulation of allergic reaction and lead to an increased severity and/or frequency of attacks. Severe allergic reactions including anaphylaxis have been reported in patients exposed to a variety of allergens either by repeated challenge, or accidental contact, and with diagnostic or therapeutic agents while receiving beta-blockers. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.
Read the Kerlone Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 7/28/2009
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