Hypertensive drugs

• Blood pressure


  The pressure the blood exerts against the inner walls of the blood vessels, and it is the force that keeps blood circulating continuously even between heartbeats

  
• Measuring Blood Pressure

  1. The heart alternately contracts and relaxes, the off-and-on flow of blood into the arteries causes the blood pressure to rise and fall during each beat

  2. Systolic pressure: the pressure in the arteries at the peak of ventricular (discharging) contraction

  3. Diastolic pressure: the pressure when the ventricles are relaxing

  
• Blood flow

  1. Deoxygenated blood enters the superior and inferior vena cava through the right atrium, then the right ventricle and it will go to the lungs for gas exchange

  2. Afterwards it will go through the pulmonary vein going through the left atrium and then left ventricle to aorta

  
• Blood pressure measurement

  Reported in millimeters of mercury (mm Hg), with the higher systolic pressure written first—120/80 (120 over 80) translates to a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg

  
• Hydraulic equation of blood pressure

  BP = CO x PR

  
• Cardiac Output (CO)


  The amount of blood pumped out of the left ventricle per minute

  
• Cardiac Output


  Determined by Stroke Volume (SV) and Heart Rate (HR)<|>CO = HR X SV

  
• Peripheral resistance (PR)


  The amount of friction the blood encounters as it flows through the blood vessels

  
• If PR increases

  BP also increases
• Heart Rate (HR)


  The number of beats by each side of the heart in one minute
• Stroke Volume (SV)


  The volume of blood pumped by each ventricle in one contraction

  
• Autonomic Nervous System


  • The parasympathetic division has little or no effect on blood pressure, but the sympathetic division is important
  • The major action of the sympathetic nerves on the vascular system is to cause vasoconstriction, which increases the blood pressure

  
• Increase heart rate

  Increases cardiac output, which increases BP
• β-blockers


  Adrenergic antagonist, lowers BP
• Baroreceptors


  Pressoreceptors in the large arteries of the neck and chest send warning signals that result in reflexive vasoconstriction, increasing blood pressure back to homeostatic levels

  
• Sudden decrease in blood volume


  Blood pressure drops, and the heart begins to beat more rapidly as it tries to compensate

  
• Sympathetic nervous system activity

  During exercise or fear, there is a generalized vasoconstriction except in the skeletal muscles
• Kidneys


  • Play a major role in regulating arterial blood pressure by altering blood volume
  • If blood volume is too high, doctors will give the patient diuretics to decrease blood volume and thus decreasing blood pressure
  • When arterial blood pressure falls, the kidneys retain body water, increasing blood volume, stroke volume cardiac output, and blood pressure rises

  
• Renin-angiotensin-aldosterone system


  1. Renin triggers a series of chemical reactions that result in the formation of angiotensin II, a potent vasoconstrictor

  2. Angiotensin also stimulates the adrenal cortex to release aldosterone, which enhances sodium ion reabsorption by the kidneys, causing water to follow and increasing blood volume and pressure

  
• Cold


  Has a vasoconstricting effect
• Heat


  Has a vasodilating effect
• Epinephrine


  Increases both heart rate and blood pressure
• Nicotine


  Increases blood pressure by causing vasoconstriction
• Alcohol and Histamine


  Cause vasodilation and decrease blood pressure

  
• A diet low in salt, saturated fats, and cholesterol helps to prevent hypertension or high blood pressure

  
• Diuretics


  Affect stroke volume
• β-blockers


  Affect heart rate

  
• Vasodilators


  Affect peripheral resistance
• Baroreflex


  • Acts by changing the activity of the sympathetic nervous system
  • Responsible for the rapid, moment-to-moment regulation of blood pressure
  • A fall in blood pressure causes pressure-sensitive neurons (baroreceptors) to send fewer impulses to cardiovascular centers, prompting a reflex response of increased sympathetic and decreased parasympathetic output to the heart and vasculature, resulting in vasoconstriction and increased cardiac output

  
• Renin-angiotensin-aldosterone system (RAAS)


  1. Baroreceptors in the kidney respond to reduced arterial pressure by releasing the enzyme renin

  2. Renin converts angiotensinogen to angiotensin I, which is converted to angiotensin II, a potent circulating vasoconstrictor

  3. Angiotensin II causes vasoconstriction, and where sodium goes, water follows, increasing blood pressure

  
• JNC 7 Classification of Hypertension

  Normal: SBP<120 and DBP<80<|>Prehypertension: SBP 120-139 or DBP 80-89<|>Stage 1 Hypertension: SBP 140-159 or DBP 90-99<|>Stage 2 Hypertension: SBP≥160 or DBP≥100
• Different Classes of Antihypertensive Drugs

  • Diuretics
  • β-Adrenoreceptor Blockers
  • ACE (Angiotensin Converting Enzyme) Inhibitors
  • Angiotensin II Receptor Blockers (ARB)
  • Renin Inhibitor
  • Calcium Channel Blockers
  • α-Adrenoceptor Blocking Agents
  • α-/β-Adrenoceptor Blocking Agents
  • Centrally Acting Adrenergic Drugs
  • Vasodilators
• Diuretics


  Lower blood pressure primarily by depleting body sodium stores<|>Act on stroke volume, decreasing cardiac output and blood pressure

  
• Classes of Diuretics

  • Thiazide Diuretics
  • Loop Diuretics
  • Potassium-Sparing Diuretics

  
• Thiazide Diuretics


  Lower blood pressure by increasing sodium and water excretion by blocking Na/Cl transporter in the renal distal convoluted tubule

  
• Loop Diuretics


  Act promptly by blocking sodium and chloride reabsorption in the kidneys, even in patients with poor renal function or those who have not responded to thiazide diuretics

  
• Potassium-Sparing Diuretics


  Reduce potassium loss in the urine<|>Aldosterone antagonists that promote sodium reabsorption

  
• β-Adrenoreceptor Blockers


  Reduce blood pressure primarily by decreasing cardiac output<|>May also decrease sympathetic outflow from the CNS and inhibit renin release, decreasing angiotensin II and aldosterone

  
• Diuretics


  • Thiazide Diuretics
  • Loop Diuretic
  • Potassium-sparing Diuretics

  
• Thiazide Diuretics


  Block Na/Cl transporter in renal distal convoluted tubule