Propranolol is a beta-blocker. The drug is used to treat heart disease and high blood pressure.
What is propranolol?
Propranolol is a beta-blocker. The drug is used for the therapy of heart disease and high blood pressure. Propranolol belongs to the group of drugs called beta-blockers. The drug has the property of lowering blood pressure. It also normalizes the heart rhythm. Propranolol was one of the first beta-blockers. It was developed in the early 1960s by James Whyte Black (1924-2010), a British pharmacologist and winner of the Nobel Prize in Medicine. The drug finally reached the market in 1964. Because propranolol lowers the heart rate and counteracts physiological tremor, the active ingredient is sometimes used as a doping agent, particularly in shooting sports. Since 1990, propranolol has been included in the WHO (World Health Organization) list of essential medicines.
Pharmacological action
Propranolol is classified as a beta-receptor blocker. Therefore, the drug has the ability to affect the autonomic nervous system. This is responsible for controlling heart activity and blood pressure. These two functions are regulated by special neurotransmitters (nerve messengers), the most important of which is adrenaline. This hormone is produced within the adrenal medulla and has the property of binding to beta receptors, which are special docking sites. In this way, a signal is given to accelerate the heartbeat. The beta blocker propranolol competes with adrenaline for the beta receptors near the heart. Ultimately, it causes the neurotransmitter to be displaced, so that the adrenaline is no longer able to increase the heartbeat. As a result, there is a slowing of the heartbeat and a drop in blood pressure. Furthermore, the heart reduces its consumption of oxygen. As a fat-soluble non-selective beta-blocker, propranolol has the property of exerting its effect at beta-1 receptors and beta-2 receptors. To lower blood pressure, the drug has a depressant effect on the release of the hormone renin, which exerts a blood pressure-increasing effect, at the beta-1 receptors of the kidneys. Blood vessels have both beta-1 and beta-2 receptors. As a result, propranolol can achieve the narrowing of the vessel diameter. In the case of a migraine, for example, in which the vessels dilate too much, the special effect of propranolol can restore them to their normal size. Propranolol is absorbed into the intestine relatively quickly and almost completely. However, two-thirds of the active ingredient is already broken down in the liver before it can be distributed within the organism via the bloodstream. After metabolization in the liver, most of the propranolol is excreted from the body via the kidneys. If the patient suffers from liver or kidney dysfunction, a prolonged effect of the substance is possible, which in turn requires an adjustment of the dosage.
Medical application and use
Propranolol is one of the most important drugs for the therapy of cardiovascular diseases. The active ingredient is used primarily for arterial hypertension (excessively high blood pressure), coronary artery disease (CAD), seizure-like chest pain such as angina pectoris, and functional cardiovascular complaints that are not organically caused, such as increased blood pressure or accelerated cardiac activity. In addition, the beta blocker is used to prevent another heart attack. In addition to treating cardiovascular diseases, propranolol is also suitable for preventing migraine attacks and counteracting severe tremors, the causes of which are unknown. It can also be used to support the treatment of hyperthyroidism (overactive thyroid gland) or to relieve simple anxiety states such as fear of exams or stress. Propranolol is usually administered in tablet form. The dose varies from patient to patient and is determined by the attending physician. For some patients, it can also be useful to administer the beta-blocker intravenously. In this case, the physician injects the medication directly into a vein.
Risks and side effects
In some patients, the use of propranolol causes unwanted side effects.In most cases, these are headaches, drowsiness, fatigue, nervousness, dizziness, insomnia, sweating, paresthesias, diarrhea, constipation, nausea, vomiting, cardiac conduction disorders, drop in blood pressure, skin reactions such as redness and itching. Even hair loss, nightmares, depression or hallucinations are within the realm of possibility. Occasionally, dry mouth, skin bleeding, changes in blood count, muscle weakness and breathing difficulties may also occur. In case of hypersensitivity to propranolol or other beta-blockers, if the blood pressure is too low or if the heartbeat slows down, it is necessary to refrain from taking the active substance. The same applies if the patient suffers from bronchial asthma, diseases of the cardiac conduction system, cardiovascular shock or pronounced circulatory disorders of the limbs. Special caution in the use of the drug is also advisable after prolonged fasting, diabetes mellitus or severe fluctuations in blood glucose levels. During pregnancy, propranolol should be taken only if absolutely required by the pregnant woman’s state of health. For example, there is a risk of premature labor or growth retardation in the baby. Since the drug passes into breast milk, medical monitoring of the infant during breastfeeding is recommended. Doctors advise against the use of beta-blockers in children. Interactions with other drugs administered at the same time as propranolol are also conceivable. For example, the effect of insulin or other diabetes medications is intensified by the beta blocker. The simultaneous use of propranolol and MAO inhibitors for depression should be avoided altogether. There is also a negative effect on the drug from calcium antagonists such as diltiazem, antiarrhythmics, antihypertensives such as clonidine, epinephrine, cardiac glycosides, and anesthetics.
