Hypertension Drugs PDF

DRUGS ACTING ON THE CARDIOVASCULAR SYSTEM DRUGS AFFECTING BLOOD PRESSURE Introduction Hypertension (HTN) results from increased peripheral vascular arteriolar smooth muscle tone leading to increased arteriolar resistance and reduced capacitance of the venous system. The c...

DRUGS ACTING ON THE CARDIOVASCULAR SYSTEM DRUGS AFFECTING BLOOD PRESSURE Introduction Hypertension (HTN) results from increased peripheral vascular arteriolar smooth muscle tone leading to increased arteriolar resistance and reduced capacitance of the venous system. The cause of elevated vascular tone is unknown HTN is a risk factor for chronic kidney disease, MI, heart failure, stroke and blindness 2 Factors influencing blood pressure Blood Filling volume pressure Venous tone Cardiac Heart rate output Contractili Arterial ty Blood pressure Vascular structure Peripheral resistance Vascular function 3 Anti-HTN drugs Diuretics β-adrenoceptor blockers ACE-inhibitors Ang II receptor blockers (ARBs) Renin inhibitors Calcium channel blockers (CCB) α-adrenoceptor blockers α/β adrenoceptor blockers Centrally acting adrenergic drugs Vasodilators 5 Site of action of Anti-HTN drugs Site of action of Anti-HTN drugs ACE-inhibitors, ARBs, Renin inhibitors ACE-inhibitors : ARBs: - Captopril - Losartan - Enalapril - Valsartan - Ramipril 10 ANGIOTENSIN-CONVERTING-ENZYME INHIBITORS (ACE-I) Mechanism of action  ACE inhibitors act in the lungs  They prevent ACE from converting angiotensin I to angiotensin II  Ang II is a powerful vasoconstrictor and stimulator of aldosterone release  This action leads to a decrease in blood pressure and in aldosterone secretion  with a resultant slight increase in serum potassium and a loss of serum sodium and fluid Adverse effect of ACE-I Hypotension Hyperkalemia Elevated serum creatinine Dry cough (10%) Angioedema ANGIOTENSIN II–RECEPTOR BLOCKERS (ARBs) Mechanism of action: They selectively bind with the angiotensin II receptors in: Vascular smooth muscle: block vasoconstriction Adrenal cortex: inhibit the release of aldosterone. Adverse effects of ARBs Similar to that of ACE-I, except that the risk of dry cough and angioedema is significantly lower. ARBs can be used as alternative to ACE-I in patients suffering ACE-I induced dry cough. Indications of ACE-I and ARBs Treatment of hypertension, alone or in combination with other drugs Used in conjunction with digoxin and diuretics for the treatment of heart failure and left ventricular dysfunction To slow the progression of renal disease in patients with hypertension and type 2 diabetes CALCIUM CHANNEL BLOCKERS  Calcium Channel Blockers (CCB) Dihydropyridine Nondihydropyri s (DHP) dines (NDHP) Nifedipine Diltiazem Amlodipine Verapamil 18  Mechanism of action of CCBs CCBs inhibit the movement of calcium ions across the membranes of myocardial and arterial muscle cells This alters the action potential and block muscle cell contraction.  Effects of CCBs On the heart: depresses myocardial contractility, slows cardiac impulse formation in the conductive tissues, On blood vessels: relaxes and dilates arteries causing a fall in blood pressure and a decrease in venous return. Benefits of CCBs Decrease blood pressure Decrease cardiac workload Decrease myocardial oxygen consumption Clinical uses of CCBs Treatment of hypertension Treatment of angina Controlling arrhythmias Main adverse effects of CCBs - AV block and Constipation (more pronounced with Verapamil) - Dizziness, Headache and Fatigue (more with DHP) - Hypotension (more with DHP) - Peripheral edema CALCIUM CHANNEL BLOCKERS VASODILATORS Mechanism of action of vasodilators Act directly on vascular smooth muscle to cause muscle relaxation, leading to vasodilation and drop in blood pressure. They do not block the reflex tachycardia that occurs when blood pressure drops. Indications of vasodilators Reserved for use in severe hypertension or hypertensive emergencies Adverse effects of vasodilators Hydralazine: - Headache and nausea - Sweating - Tachycardia, arrhythmia, angina - Reversible lupus-like syndrome (with high doses) Nitroprusside: - Cyanide toxicity 29 DIURETIC AGENTS DIURETIC AGENTS Mechanism of action Diuretics are drugs that increase the excretion of sodium and water from the kidney. Thus, reducing blood volume and blood pressure. DIURETIC AGENTS Indications: Treatment of  Mild hypertension  Edemas Adverse Effects :  Increase urination  can disturb electrolyte and acid–base balances. DIURETIC AGENTS SYMPATHETIC NERVOUS SYSTEM BLOCKERS β-adrenoceptor blockers Studied before ANTIHYPOTENSIVE AGENTS Refer to the sympathomimetic agents in the previous chapters.