Beta blockers are a class of medications used for the treatment of high blood pressure and congestive heart failure. When an individual has had a heart attack, beta blockers also are used to prevent future hospitalizations and death. Beta blockers block the binding of chemicals to beta receptors (molecules) found on the heart. This leads to a decrease in heart rate and in the force of the heartbeat. The heart does not have to work as hard to pump the blood. Common beta blockers include atenolol (Tenormin), propanolol (Inderal), timolol (Blocadren), metoprolol (Lopressor), metoprolol extended release (Toprol XL), and carvedilol (Coreg). Like all medications, beta blockers have warnings you should be aware of before initiating therapy.
Hypoglycemia
Hypoglycemia, or low blood sugar, can occur in individuals taking diabetes medications. Diabetics are instructed to carry around hard candy to quickly raise their blood sugar level in case it drops too low. Signs and symptoms of dangerously low blood sugar include sweating, nervousness, shakiness, dizziness and hunger. Beta blockers can mask all these symptoms other than sweating. This can be dangerous because you may be unaware that your blood sugar is dropping. It may lead to a coma and eventual death if left unattended.
Respiratory Depression
Beta receptors are not only located on the heart but are also located in other areas including the lungs, pancreas, liver, and kidneys. Some beta blockers only affect the heart; they are called cardioselective. Atenolol and metoprolol are cardioselective. Those that are not cardioselective affect on the lungs, as well. Timolol and propanolol are two examples of non-selective beta-blockers. "Pharmacotherapy: A Pathophysiologic Approach" states that these medications will result in narrowing of the arteries and narrowing of the walls of the airways. Also, higher dose of cardioselective beta blockers can potentially have the same effects. For this reason, beta-blockers are not given to individuals who have asthma or other respiratory diseases.
Heart Failure
Beta blockers can worsen preexisting heart conditions. According to the "Drug Information Handbook," a beta blocker must be administered with caution, and individuals must be monitored for possible worsening of symptoms of congestive heart failure. Adjustments of the dose may be necessary in these people.
Rebound Hypertension
Beta blockers should not be discontinued suddenly without gradually tapering off the dose. This means that the dose should be decreased slowly to avoid adverse effects. Stopping abruptly could cause tachycardia, or increased heart rate, and lack of oxygen to the heart. It may also lead to rebound hypertension, which is described as an increase in blood pressure to the the value it was before drug therapy. The blood pressure may even increase to a dangerous level and may require medical intervention. Always consult a physician before stopping any medication.
References
- "Drug Information Handbook 15th Edition"; Charles F. Lacy, RPh, PharmD, FCSHP, Lora L. Armstrong, RPh, PharmD, BCPS. et al; 2007
- "Pharmacotherapy: A Pathophysiologic Approach"; Joseph T. Dipiro, Robert L. Talbert, et al; 2008
