Betaxolol: Pharmacology, Pharmacokinetics, Indications, Side effects, and Drug interactions

Betalocol, as well as metoprolol, bisoprolol, and atalol are severally commonly used β1 adrenergic receptor blockers, which is four times potent to block the β-receptor compared with propranolol. It has no intrinsic sympathetic activity, and is characterized with weak membrane stabilization, high bioavailability and long half-life. It mainly blocks the β1 receptor, but the selection for the β1 receptor is not absolute, and high dose of betalocol can block the bronchial and vascular β2 receptors.

Pharmacokinetics

Betalocol is fat soluble and almost completely absorbed after oral administration with Tmax of 2 ~ 4h. The peak plasma concentration was 43 to 47 μg/ml. F is 80% to 90%, and PBP is about 50%. The apparent distribution volume is 7.7 to 8.8 L/kg, and t1/12 is 16 to 20 hours. Betalocol can be secreted in the milk by going through the placental barrier. It is mainly metabolized in the liver. About 15% of the drug is excreted in the urine in its original form.

Indications

(1) Betalocol is used to treat primary hypertension, chronic open angle glaucoma with a similar efficacy to propranolol and atenolol. It can also be used in the treatment of angina with a similar effect to that of atenolol, which reduces the incidence and the dose of nitroglycerin. Generally po, 20mg, qd, (also starting from 10mg, qd), usually good effect could be reached within 7 to 14d. If necessary, the dose can also be increasedthe dose to 40mg, qd. The elderly patients should start with a reduced dose. 

(2) Used in the treatment of open-angle glaucoma:  0.25% to 1% eyedrops, recommended dose dropped into the affected eyes, bid. 

Side effects

Common: mild headaches and fatigue. A few people may have cold hands and feet, numbness and Raynaud. For patients who are elderly or take high dose, slow heartbeat may occur. The side effects may also include stomach upset, nausea, vomiting, and constipation.

Drug interactions

(1) Combination with non-steroidal anti-inflammatory analgesics not only weakens the antihypertensive effect, but also increases the toxicity.

(2) Combination with calcium antagonists enhances its the antihypertensive activities, but may cause slow heartbeat, conduction disorder and heart failure.

(3) Combination with amiodarone may cause slow heartbeat, sudden cardiac arrest, and ventricular fibrillation.

(4) Combination with theophylline drugs may increase the concentration of theophylline.

Precautions

Betalocol should be used with caution for patients with bronchial asthma, spasm, liver and kidney dysfunction. Betalocol is contraindicated in patients with slow heartbeat, cardiogenic shock, second or third degree atrioventricular block and uncontrolled congestive heart failure. Stop using if you have dry eyes, flushing when you take this drug. 

Reference

J. L. Wong and T. G. Wu, Speciation of airborne nickel in occupational exposure. Environ. Sci. Technol. 25, 306–309 (1991).
National Institute for Occupational Safety and Health (NIOSH), Manual of Analytical Methods, 4th ed., Method 8005, U. S. Department of Health and Human Services, Washington, DC, 1994.
13. National Institute for Occupational Safety and Health (NIOSH), Manual of Analytical Methods, 4th ed., Method 8310, U.S. Department of Health and Human Services, Washington, DC, 1994.