7.1. ANTIHYPERTENSIVE DRUGS
Hypertension (HT) is a persistent increase in blood pressure (BP). According to state-of-the-art clinical recommendations, normal BP levels are as follows: systolic blood pressure (SBP) <120 mmHg and diastolic blood pressure (DBP) <80 mmHg. SBP elevated to 120129 mmHg is considered high BP.
HT is a highly common condition present in 15-25% of adult population in countries with developed economy and can be determined as either a standalone disease (essential hypertension) or as a symptom of other diseases (secondary hypertension). The etiology of hypertension is unclear; however, the risk factors for its occurrence are known. These are hereditary background, overweight, excessive cooking salt intake, sedentary lifestyle, smoking and alcohol abuse. Secondary hypertension occurs in renal, adrenal, vascular diseases, and as a response to intake of certain pharmaceutical drugs. HT consequences include cerebral apoplexy, myocardial infarction, chronic heart failure, and sudden death.
The main systemic factors supporting BP level in the body are as follows: blood vessel tone, cardiac function and circulating fluid volume. Cardiac function (cardiac output) defines SBP values. DBP values are determined by systemic vascular resistance (SVR) which, in its turn, is determined by the tone of arteri-oles (resistance vessels). Cardiac function and blood vessel tone are regulated by the sym-pathoadrenal system. Blood vessel tone and circulating fluid volume are regulated by re-nin-angiotensin-aldosterone system (RAAS).
The sympathetic nervous system stimulates the heart and vessels. The bodies of central neuronsare located in the vasomotor centers of the medulla oblongata (fig. 7.1). Their axons reach the sympathetic trunk where they form synaptic contacts with ganglionic neurons whose axons innervate the heart [through в1-adrenergic receptors (AR)] and vessels (through б1-AR). Stimulation of в1-AR leads to increased force of contractions and frequency of the heart rate (increased cardiac output) and an increase in conduction and automatism. б1-AR stimulation leads to increased tone of smooth muscles of resistance vessels and elevated peripheral vascular pressure. Thus, activation of the sympathoadrenal system cau-