Antihypertensive Agents Unit six

Lecture objectives At the end of this lecture the student well be able to: Describe how blood pressure control normally. List causes of hypertension. Give an example of drug that drugs which lower Bp through different mechanism. Discuss nursing implication.

Antihypertensive Agents Medications used to treat hypertension

Classification of Blood Pressure 1. Primary Hypertension Specific cause unknown, 90% of the cases, Also known as essential or idiopathic hypertension 2. Secondary Hypertension Cause is known (such as eclampsia of pregnancy, renal artery disease, pheochromocytoma) 10% of the cases

Blood Pressure = CO x SVR CO = Cardiac output SVR = Systemic vascular resistance

The blood pressure depend on Systemic vascular resistance (sympathetic) The output of blood from the heart (sympathetic pulse rate increase) The volume and viscosity of the blood.( ACE, diuretics

How drug can lowered blood pressure Lower the systematic vesicular resistance Lower COP. Reduce blood volume Act centrally (CNS)

Antihypertensive Agents: Categories Adrenergic agents (Sympathetic blocking agent) Angiotensin-converting enzyme inhibitors Calcium channel blockers Diuretics Vasodilators

Sympathetic blocking agent Drugs Lower the systematic vesicular resistance: Adrenergic Agents Alpha1 Blockers doxazosin (Cardura) prazosin (Minipress) terazosin (Hytrin)

Antihypertensive Agents: Mechanism of Action Adrenergic Agents Alpha1 Blockers (peripherally acting) Block the alpha1-adrenergic receptors Result: vasodilation , improve the flow of urine. Stimulation of alpha1-adrenergic receptors causes hypertension

Antihypertensive Agents: Adrenergic Agents Therapeutic Uses Alpha1 blockers (peripherally acting) Treatment of hypertension Relief of symptoms of BPH Management of of severe CHF when used with cardiac glycosides and diuretics

Side Effects Most common: dry mouth drowsiness sedation constipation Other: headaches sleep disturbances nausea rash cardiac disturbances (palpitations) HIGH INCIDENCE OF postural HYPOTENSION

Angiotensin-Converting Enzyme Inhibitors (ACE Inhibitors) Large group of safe and effective drugs Often used as first-line agents for CHF and hypertension May be combined with a thiazide diuretic or calcium channel blocker

Antihypertensive Agents: Mechanism of Action ACE Inhibitors RAAS: Renin Angiotensin-Aldosterone System When the enzyme angiotensin I is converted to angiotensin II, the result is potent vasoconstriction and stimulation of aldosterone Result of vasoconstriction: increased systemic vascular resistance and increased afterload Therefore, increased BP

Antihypertensive Agents: Mechanism of Action ACE Inhibitors ACE Inhibitors block the angiotensin-converting enzyme, thus preventing the formation of angiotensin II. Also prevent the breakdown of the vasodilating substance, bradykinin Result: decreased systemic vascular resistance (afterload), vasodilation, and therefore, decreased blood pressure

Examples ACE Inhibitors captopril (Capoten) Short half-life, must be dosed more frequently than others enalapril (Vasotec) The only ACE inhibitor available in oral and parenteral forms lisinopril (Prinivil and Zestril) and quinapril (Accupril) Newer agents, long half-lives, once-a-day dosing

Therapeutic Uses: ACE Inhibitors Hypertension CHF Slows progression of left ventricular hypertrophy after an MI Renal protective effects in patients with diabetes Drugs of choice in hypertensive patients with CHF

Side Effects: ACE Inhibitors Fatigue Dizziness Headache Mood changes Impaired taste Dry, nonproductive cough, reverses when therapy is stopped NOTE: first-dose hypotensive effect may occur!!

Calcium Channel Blockers Cause smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction This causes decreased peripheral smooth muscle tone, decreased systemic vascular resistance Result: decreased blood pressure

Calcium Channel Blockers Benzothiazepines: diltiazem (Cardizem, Dilacor) Phenylalkamines: verapamil (Calan, Isoptin) Dihydropyridines: amlodipine (Norvasc), bepridil (Vascor), nicardipine (Cardene) nifedipine (Procardia), nimodipine (Nimotop)

Therapeutic Uses Calcium Channel Blockers Angina Hypertension Dysrhythmias

Side Effects Calcium Channel Blockers Cardiovascular hypotension, palpitations, tachycardia Gastrointestinal constipation, nausea Other rash, flushing, peripheral edema, dermatitis

Diuretics Decrease the plasma and extracellular fluid volumes Results: decreased preload decreased cardiac output decreased total peripheral resistance Overall effect: decreased workload of the heart, and decreased blood pressure

B blockers By interfering SNS they certainly prevent the rise in COP, the ultimate goal of fall in blood pressure. Decrease renin relase kidney. Uses: Lowering BP.

Examples B blockers Selective B blockers: Atenolol Esmolol Non selective: Propranolol Oxprenolol Combind alpha, B blockers Labetalol

Side effect Asthma Heart failure Diabetes Hallucination

Antihypertensive Agents: Mechanism of Action Vasodilators Directly relaxes arteriolar smooth muscle Result: decreased systemic vascular response, decreased afterload, and PERIPHERAL VASODILATION

Antihypertensive Agents Vasodilators diazoxide (Hyperstat) hydralazine HCl (Apresoline) minoxidil (Loniten, Rogaine) sodium nitroprusside (Nipride, Nitropress)

Antihypertensive Agents: Therapeutic Uses Vasodilators Treatment of hypertension May be used in combination with other agents Sodium nitroprusside and diazoxide IV are reserved for the management of hypertensive emergencies

Antihypertensive Agents: Side Effects Vasodilators Hydralazine: dizziness, headache, anxiety, tachycardia, nausea and vomiting, diarrhea, anemia, dyspnea, edema, nasal congestion Sodium nitroprusside: bradycardia, hypotension, possible cyanide toxicity

Antihypertensive Agents: Nursing Implications Before beginning therapy, obtain a thorough health history and head-to-toe physical examination. Assess for contraindications to specific antihypertensive agents. Assess for conditions that require cautious use of these agents.

Antihypertensive Agents: Nursing Implications Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed. Patients should never double up on doses if a dose is missed; check with physician for instructions on what to do if a dose is missed. Monitor BP during therapy. Instruct patients to keep a journal of regular BP checks.

Antihypertensive Agents: Nursing Implications Instruct patients that these drugs should not be stopped abruptly, as this may cause a rebound hypertensive crisis, and perhaps lead to CVA. Oral forms should be given with meals so that absorption is more gradual and effective. Administer IV forms with extreme caution and use an IV pump.

Antihypertensive Agents: Nursing Implications Remind patients that medications is only part of therapy. Encourage patients to watch their diet, stress level, weight, and alcohol intake. Patients should avoid smoking and eating foods high in sodium. Encourage supervised exercise.

Antihypertensive Agents: Nursing Implications Instruct patients to change positions slowly to avoid syncope from postural hypotension. Patients should report unusual shortness of breath; difficulty breathing; swelling of the feet, ankles, face, or around the eyes; weight gain or loss; chest pain; palpitations; or excessive fatigue.

Antihypertensive Agents: Nursing Implications Men taking these agents may not be aware that impotence is an expected effect. This may influence compliance with drug therapy. If patients are experiencing serious side effects, or believe that the dose or medication needs to be changed, they should contact their physician immediately.

Antihypertensive Agents: Nursing Implications Hot tubs, showers, or baths; hot weather; prolonged sitting or standing; physical exercise; and alcohol ingestion may aggravate low blood pressure, leading to fainting and injury. Patients should sit or lie down until symptoms subside. Patients should not take any other medications, including OTC drugs, without first getting the approval of their physician.

Antihypertensive Agents: Nursing Implications Monitor for side/adverse effects (dizziness, orthostatic hypotension, fatigue) and for toxic effects. Monitor for therapeutic effects Blood pressure should be maintained at less than 140/90 mm Hg