Betaxolol (Dosing, Interaction, Side Effect, Administration, Etc..)

CLASS:
Antiglaucoma
Beta-Adrenergic Blocker, Cardioselective
Cardiovascular Agent

DOSING:

Adult Dose

:
Angina pectoris, chronic:
5 to 80 mg ORALLY once daily

Cardiac dysrhythmia:
20 mg orally once daily starting 2 days prior to CABG and continuing for not less than 10 days postoperatively was

used in

1 study (off-label dosage)

Hypertension:
Initial:
10 mg orally once daily; titration, may

double dose

after 7 to 14 days if required. Doses greater than 20 mg/day have not demonstrated additional efficacy

Concomitant medication:
May add a diuretic or other antihypertensive agent if monotherapy does not produce desired response

Withdrawal of therapy:
Decrease dosage gradually over a period of about 2 weeks

Ocular hypertension:
(0.25% suspension)
1 drop in the affected eye(s) twice daily

(0.5% solution)
1 to 2 drops in the affected eye(s) twice daily

Primary open angle glaucoma:
(0.25% suspension)
1 drop in the affected eye(s) twice daily

(0.5% solution) :
1 to 2 drops in the affected eye(s) twice daily

Pediatric Dose

:
General Dosage Information:
Safety and efficacy not established in children

Ocular hypertension:
(0.25% suspension)
1 drop in the affected eye(s) twice daily

Primary open angle glaucoma:
(0.25% suspension)
1 drop in the affected eye(s) twice daily

INDICATIONS:
FDA-LABELED INDICATIONS:
Hypertension
Ocular hypertension
Primary open angle glaucoma

NON-FDA LABELED INDICATIONS:
Angina pectoris, chronic
Cardiac dysrhythmia

MECHANISM OF ACTION:

Betaxolol hydrochloride

is a beta-adrenergic blocker with selective activity on beta(1) adrenergic receptors and with weak membrane-stabilizing activity and no intrinsic sympathomimetic activity. At

higher doses

, it may inhibit beta(2) receptors of bronchial and vascular musculature.

ADVERSE EFFECT:
Common:
Cardiovascular:
Bradyarrhythmia (5.8% to 8.1%)

Gastrointestinal:
Indigestion (3.9% to 4.7%)
Nausea (1.6% to 5.8%)

Musculoskeletal:
Arthralgia (3.1% to 5.2%)
Chest pain (2.4% to 7.1%)

Ophthalmic:
Burning sensation in eye (30%, ophthalmic)

Other:
Fatigue (2.9% to 9.7%)

Serious:
Cardiovascular:
Atrioventricular block
Myocardial infarction

CONTRAINDICATION:
Hypersensitivity to

betaxolol

or any component of the product
Sinus bradycardia or greater than first degree heart block
Cardiogenic shock or overt cardiac failure

INTERACTION:
The following drugs have been coadministered with Kerlone and have not altered its pharmacokinetics: cimetidine, nifedipine, chlorthalidone, and hydrochlorothiazide. Concomitant administration of Kerlone with the oral anticoagulant warfarin has been shown not to potentiate the anticoagulant effect of warfarin.

Catecholamine-depleting drugs (e.g., 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, e.g., 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).

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.

PHARMACOKINETICS:
Absorption:
Oral: Time For Maximum Plasma Concentration (Tmax): 3 hours (1.5 hours to 6 hours)
Bioavailability: 89% +/- 5%
Effect of food: no clinically relevant effects

Distribution:
Plasma Protein binding: approximately 50%

Metabolism:
Hepatic

Excretion:
Renal: greater than 80%, 15% unchanged
Dialyzable:
Hemodialysis: No
Peritoneal dialysis: No

Elimination:
About 14 hours to 22 hours
Patients with chronic renal failure undergoing dialysis: approximately doubled
Patients with severe renal impairment: increases by 24% compared to mildly impaired patients

PRECAUTION:
Administration:
Systemic adverse effects, including severe or fatal respiratory or cardiac reactions, have been reported with topical

use of beta-blockers

.

Cardiovascular:

Use with

caution in patients with a history of heart block or cardiac failure; discontinue use if suspected. New onset cardiac failure may occur in patients without history of cardiac failure; consider discontinuation if suspected. Potentially fatal worsening of heart failure may occur; use with caution patients with hypertension and congestive heart failure who are treated with digitalis and diuretics.
Use caution in patients with vascular insufficiency; consider alternative therapy if symptoms of reduced cerebral blood flow or Raynaud phenomenon develop

Concomitant use:
Hypotension, atrioventricular conduction disturbances, and left ventricular failure has been reported with concomitant

use of oral calcium channel antagonists

; avoid concomitant use in patients with impaired cardiac function. Concomitant

use of oral

and ophthalmic beta-adrenergic antagonists may result in additive effects on intraocular pressure or additive systemic effects; monitoring recommended.

Dermatologic:
Aggravation of psoriasis has been reported

Endocrine and metabolic:
Use may mask clinical signs of hyperthyroidism; avoid abrupt withdrawal if thyrotoxicosis suspected.
Use may mask symptoms of hypoglycemia; use with caution in patients with diabetes or patients who are prone to spontaneous hypoglycemia. Use is not recommended in untreated pheochromocytoma.

Immunologic:
An increase in the frequency or severity of allergic reactions, including anaphylaxis, has been reported during allergen exposure in patients receiving beta adrenergic antagonist therapy; patients with a history of atopy or anaphylaxis may become more reactive. Patients may become unresponsive to epinephrine treatment for anaphylactic reactions.

Musculoskeletal:
Potentiation of muscle weakness, consistent with myasthenic symptoms, has been reported.

Ophthalmic:

Oral use

may interfere with the glaucoma screening test; withdrawal may lead to the return of increased intraocular pressure.
Use is recommended only in combination with a miotic agent for elevated intraocular pressure in patients with angle-closure glaucoma.
Avoid using as sole treatment of angle-closure glaucoma
Bacterial keratitis may occur with

use of multiple-dose

containers due to inadvertent contamination
Choroidal detachment has been reported.
Preservative may be absorbed through soft contact lenses; remove prior to instillation and wait 15 minutes before reinserting.

Respiratory:

Use of beta blockers

is not recommended in bronchospastic disease or excessive restriction in pulmonary function; severe or fatal bronchospasm in asthmatic patients and pulmonary distress have been reported; if use is necessary, use caution, minimize dosing to

lowest effective dose

and bronchodilator therapy should be made available.

Special populations:
Elderly patients are at an increased risk for bradycardia; initial dosage adjustment recommended.

Surgery:
Use with caution with anesthesia and major surgery; chronic beta blocker therapy should not routinely be withdrawn prior to surgical procedures; dosage adjustment may be necessary prior to anesthesia.

Withdrawal:
Exacerbation angina pectoris or myocardial infarction have been reported during abrupt cessation of therapy in patients with coronary artery disease; close monitoring of withdrawal in all patients recommended.
Abrupt withdrawal may precipitate a thyroid storm; monitor withdrawal closely in patients with known or suspected thyrotoxicosis.

PREGNANCY CATEGORY:
C (FDA)
C (AUS)

BREAST FEEDING:
Infant risk cannot be ruled out.

MONITORING:
Intraocular hypertension or chronic open-angle glaucoma: Reduction of intraocular pressure may indicate efficacy; responses may require a few weeks to stabilize.

Hypertension:
Reduction in blood pressure may indicate efficacy; full antihypertensive effect is usually seen within 7 to 14 days

Oral:
Toxicity in patients with hepatic impairment

Oral:
All patients closely upon cessation of therapy, especially those known or suspected of being thyrotoxic

HOW TO TAKE OR ADMINISTRATION:
Ophthalmic:
(Suspension) shake well before using

DOSAGE FORM:
Ophthalmic Solution:
0.5 %

Oral Tablet:
10 MG
20 MG

Ophthalmic Suspension:
0.25 %

TREATMENTS:
MANAGEMENT OF MILD TO MODERATE TOXICITY:
Place patient on a cardiac monitor, give fluids for hypotension, and atropine for bradycardia.

MANAGEMENT OF SEVERE TOXICITY:
Perform early orotracheal intubation for airway protection if the patient has altered mental status. Initially manage hypotension with intravenous fluids (500 mL boluses up to 2L) and atropine for symptomatic bradycardia. Glucagon should be considered if the patient does not respond appropriately to intravenous fluids. Give catecholamines to those who do not respond to intravenous fluids and glucagon. No one catecholamine has been shown to be consistently effective; dopamine, norepinephrine and epinephrine may be considered.

High doses

may be required. If catecholamines are required despite glucagon and intravenous fluids, high-dose insulin euglycemia should be considered. Catecholamines should be titrated down when high-dose insulin euglycemia therapy starts to take effect. Intravenous lipid emulsion should be considered in patients with refractory hypotension. Other non-pharmacological therapies include: cardiac pacing, placement of an intraaortic balloon pump, cardiopulmonary bypass, and extracorporeal membrane oxygenation (ECMO). Seizures (rarely progress to status epilepticus) may require aggressive

use of benzodiazepines

(e.g. 1 to 2 mg lorazepam IV and increase as needed) and/or propofol. Monitor for dysrhythmias and treat accordingly.

TOXICOLOGY:
TOXICITY: The

toxic dose

is variable depending on the particular agent.

PATIENT COUNSELING OR CLINICAL TEACHING:
Warn patient to avoid driving or other activities requiring clear vision until drug effects are realized due to potential for blurred vision.
Instruct patient to report upcoming ocular surgery or intercurrent ocular conditions.
Side effects may include transient ocular discomfort, corneal punctate keratitis, foreign body sensation, photophobia, tearing, itching, or dryness of eyes.
Advise patient to remove contact lenses prior to instilling drug. Lenses may be reinserted 15 minutes following instillation.



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