There are three known types of adrenergic beta receptors, called beta1 (β1, found mainly in your heart and kidneys), beta2 (β2, found mainly in your liver, lungs, skeletal muscles, vascular smooth muscle, gastrointestinal tract, parts of your eye, and various other locations in your body) and beta3 (β3, found mainly in fat cells). One of the differences between different beta-blockers is the receptors they block. Beta-blockers are usually grouped into three subcategories: First-Generation Beta-Blockers
First-generation beta-blockers are ‘non-selective’ β1 and β2 blockers, which means they affect your heart, kidneys, liver, lungs, skeletal muscles, vascular smooth muscle, and gastrointestinal tract, among other parts of your body. First-generation beta-blockers include: Propranolol Timolol Sotalol Second-Generation Beta-Blockers
Second-generation blockers are ‘selective’ and act primarily upon β1 receptors. This means they predominantly affect your heart and, to a lesser extent, your kidneys. Because they do not affect other parts of your body, second-generation beta-blockers may be safer for certain people, such as those living with lung disease. Second-generation beta-blockers include: Metoprolol Atenolol Bisoprolol Third-Generation Beta-Blockers
Carvedilol and nebivolol are third-generation beta-blockers. Like first-generation beta-blockers, they are ‘non-selective’ β1 and β2 blockers. However, they have additional characteristics that set them apart from first-generation beta-blockers. For example, they have also been found to have vasodilating effects, which means they widen blood vessels. This can provide extra therapeutic benefits. Additionally, they tend to cause fewer metabolic side effects and do not decrease nocturnal melatonin release, which is believed to be a cause of sleep disturbance associated with first- and second-generation beta-blockers. Third-generation beta-blockers include: Carvedilol Nebivolol Other Differences
There are several other differences between beta-blockers. Some have a curious ability to both block beta receptors and partially stimulate (agonize) them, a phenomenon known as ‘intrinsic sympathomimetic activity’ (ISA), which gives them unique characteristics compared to regular beta-blockers. Other differences between beta-blockers include their solubility in water and the part of the body in which they are metabolized and excreted. These variabilities give each type of beta-blocker a unique set of characteristics. There is, therefore, no ‘best’ beta-blocker for everyone; rather, it depends on the exact nature of the treatment required. Your doctor will take your personal situation into account when deciding whether to prescribe a beta-blocker and, if so, which one. If you have any concerns or questions regarding your treatment, you should speak to your doctor or pharmacist.