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Transcript
Lecture 9 Chapter 39 Antihypertensive Drugs Antihypertensive Agents • Hypertension (HTN) - An inc. in BP such that systolic is > 140 mm/hg & diastolic > 90 mm/hg on 2 or more occasions after initial screening • Essential HTN = most common. About 90% of clients. * Exact Origin - unknown. Contributing Factors - family hx, hyperlipidemia, African American background, diabetes, obesity, aging, stress, excessive ETOH & smoking. • Secondary HTN is about 10% of HTN, related to endocrine or renal disorders Renin-angiotensin system Hypertension • Non-Pharmacological - Should be first line of treatment. If successful, no meds. may be needed. * Stress reduction techniques, exercise, salt restriction, dec. in ETOH intake, no smoking, wt. reduction • Systolic pressure >140 mm/hg = antihypertensive meds started • Pt. education & compliance very important as in a good history Hypertension • Pharmacological therapy - Individualized * Want to start at lowest possible doses of meds. * Reduce risk factors, even while on meds. - lifestyle changes may allow the client to decrease medications. * suggested after 1 yr. of therapy to dec. dose to determine if less drug dose possible • Step care hypertensive approach to treatment developed several years ago - Classified by 4 stages based on BP range. Pg. 695 table 39-1 • Individualized approach is also used - more modified to each client. Pg. 696 - Table 39-3 STEPPED – CARE APPROACH Antihypertensive Agents • Drugs used to treat Hypertension: • Diuretics * Promote Na depletion dec. in extra cellular fluid (ECF) * First line drug for Rx of mild HTN * Hydrochlorothiazide (HydroDIURIL) most frequently prescribed for first line Rx of mild HTN * Can be used alone or w/ other antiHTN agents ANTIHYPERTENSIVE AGENTS Antihypertensive Agents • 1) Beta-Adrenergic Blockers (Beta Blockers) Atenolol (Tenormin), Metoprolol (Lopressor) - Beta-1 cardio selective Nadolol (Corgard), Propranolol (Inderal) Nonselective Beta-1, Beta-2 - Step 1 or 2 Rx - may be combined w/ a diuretic - Reduces cardiac output (CO) by diminishing sympathetic nervous system response Antihypertensive Agents Beta Blockers - With continued use the vascular resistance diminished & BP lowered - Reduces HR & contractility - Reduces renin release from kidneys Nonselective = inhibits Beta-1 (heart) & Beta-2 (bronchial) receptors - HR slows & BP decreases - Bronchoconstriction occurs Cardio selective - Preferred - acts mainly on Beta-1 receptors & bronchospasms less likely - not absolute protection *Use cautiously in clients w/ pulmonary history* Antihypertensive Agents • 2) Centrally Acting Sympatholytics (Adrenergic Blockers) Clonidine HCL (Catapres), Methyldopa (Aldomet) - Stimulate Alpha-2 receptors dec. sympathetic activity dec. epi., norepi. & dec.renin release dec. peripheral vascular resistance - Can be used w/ other agents - Clonidine = a new transdermal preparation - provides a 7 day duration of action - Used w/ diuretics – to prevent NA+ and fluid retention - Do not D/C drug abruptly - HTN crisis possible Antihypertensive Agents • 3) Alpha - Adrenergic Blockers Prazosin HCL (Minipress) - Blocks alpha adrenergic receptors vasodilatation & a dec. in BP - Helps maintain renal blood flow - Useful in clients with lipid abnormalities - decs. VLDL & LDL - responsible for build-up of fatty plaques in arteries & incs. HDL (friendly) - Can cause Na & H2O retention - diuretics may be added ANTIHYPERTENSIVE AGENTS Antihypertensive Agents • 4) Adrenergic Neuron Blockers (Peripherally acting sympatholytics) * Potent drugs that block norepi. form sympathetic nerve endings a dec. in norepi. dec. in BP * Decrease in both cardiac output & peripheral vascular resistance Reserpine (Serpasil) & guanethidine (Ismelin) - Potent - used for severe HTN * Step IV drugs - alone or with diuretics to dec. peri. edema * Common SE = Orthostatic Hypotension* Antihypertensive Agents • 5) Alpha-1 & Beta-1 Adrenergic blockers Carteolol (Cartrol), Labetalol (Trandate) - Blocks both alpha-1 & beta-1 receptors - Block alpha-1 = dilation of arterioles & veins -Effect on alpha receptors stronger than on beta receptors so have a dec. BP & pulse rate - Block beta-1 lead to decreased HR & AV contractility - Large doses could block beta-2 receptors inc. in air way resistance - Do not give to severe asthmatics. AV block SE = Orthostatic Hypotension, GI, nervousness, dry mouth&fatigue Antihypertensive Agents • Direct - Acting Arteriolar Vasodilators - potent Hydralazine (Apresoline) - Mod. to severe HTN Sodium Nitroprusside (Nipride) - Very potent - for hypertensive Emergencies - Act by relaxing smooth muscles of bld. vessels - mainly arteries vasodilation - Inc. blood flow to brain & kidneys - With vasodilation the BP dec., Na & H2O retained peripheral edema. Diuretics used to counter this SE - SE = numerous - tachycardia, palpitations, edema, dizzy, GI bleeding Antihypertensive Agents • Angiotensin Antagonists - Angiotensin-Converting Enzyme Inhibitors (ACE inhibitors) Captopril (Capoten), Enalapril (Vasotec), Lisinopril (Zestril) - Prevents conversion of Angiotensin I to angiotensin II (vasoconstrictor) & blocks release of aldosterone. Aldosterone promotes Na retention & K excretion. Block aldosterone & Na excreted, but H2O & K retained - Used to treat HTN primarily, - but not a 1st line drug. Also used in heart failure. - SE = hyperkalemia & 1st dose hypotension (more common with comb. Diuretic & ACE inhibitor. Antihypertensive Agents • Angiotensin II receptor Antagonists (Blockers) - A - II Blockers Losartan (Cozaar) - Newer drugs similar to ACE inhibitors + prevent release of aldosterone (Na+ retaining hormone) - Act on renin - angiotensin system - Diff between ACE &AII is A-II blockers block angiotensin from angiotensin I receptors found in many tissues - blocks at receptor site. - A-II blockers cause vasodilation & dec. peripheral resistance Antihypertensive Agents • Calcium Channel Blockers Verapamil (Calan), Nifedipine (Procardia), Diltiazem (Cardizem) - Free calcium muscle contractility, peripheral resistance & BP . Calcium blockers - Dec. calcium levels & promote vasodilation - Drugs can be used w/ clients prone to asthma - SE. Flushing, HA, dizzyness, ankle edema, bradycardia, AV node block, So,