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About Beta Blockers - Part 1

Desmond | Lead Clinician

Jan-29-2022 | Physiology

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Beta blockers are a class of drugs, primarily used to treat cardiovascular diseases and other conditions. They are indicated for the management of abnormal heart rhythms, and to protect the heart from developing a second heart attack (myocardial infarction) after a first one. Other uses include treatment for: congestive heart failure, hypertension, essential tremor, glaucoma, migraine, hyperthyroidism and a lot more.

They work by blocking the effects of the hormones epinephrine and norepinephrine also known as adrenaline and noradrenaline respectively. This causes the heart to beat more slowly and with a lesser force, which lowers the blood pressure. Beta blockers also widen veins and arteries to improve blood flow.

Beta blockers classify as either non-selective or beta selective. They block the receptor sites for epinephrine and norepinephrine on these receptors. The non-selective beta-blockers block activation of all types of beta receptors (𝛃1, 𝛃2 and 𝛃3). 𝛃1 receptors are located mainly in the heart and in the kidneys. 𝛃2 receptors are located mainly in the lungs, gastrointestinal tract, vascular smooth muscle, and skeletal muscle, hence specifically targeted for treatment of diseases associated with the aforementioned organs. 𝝱3 receptors are found on both white and brown adipocytes and responsible for lipolysis.

Adverse reactions associated with the use of beta blockers include: bronchospasm, diarrhea, dyspnoea, bradycardia, hypotension, cold extremities, dizziness, hair loss, insomnia, nightmares, sexual dysfunction, alteration of glucose metabolism, hallucinations, and heart block.

Despite the wide indications of beta blockers, there are major contraindications that should be considered. 

The role of beta blockers on patients with a diagnosis of diabetes mellitus is controversial. They have been considered to reduce the blood glucose level (hypoglycemia) or, on the contrary, increase the blood glucose level (hyperglycemia). It’s important to check your blood sugar regularly if you have diabetes and you are taking a beta blocker.

Beta blockers generally aren’t used in people with asthma because of concerns that the medication may trigger severe asthma attacks. However, cardioselective beta blockers (𝝱1 blockers), if really required, can be used at a lower dose.

Beta blockers make the heart work less hard, in effect lowering the heart rate (pulse) and blood pressures. For this very reason, one should be very cautious with the use of beta-blockers.

Note: This article is for informational purposes only and is not intended as medical advice, or as the substitute for the medical advice of a physician.