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Pharm S2015 > Lecture 17: Antihypertensives > Flashcards

Lecture 17: Antihypertensives Flashcards

1
Q

Current Treatments

A
  • First-line agents: ACE-inhibitors, ARBs, calcium channel blockers, thiazide diuretics
  • Second-line agents: Beta-blockers, aldosterone antagonists
  • Other agents: Loop diuretics, alpha-blockers, direct vasodilators, central alpha2-agonists, renin inhibitors
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2
Q

Antihypertensives classes

A
  • Inhibitors of angiotensin (ACE-inhibitors / ARBs / renin inhibitors)
  • Calcium-channel blockers
  • Diuretics
  • Beta-adrenoceptor antagonists
  • alpha-adrenoceptor antagonists
  • Central alpha2 agonists
  • Direct vasodilators
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3
Q

ACE Inhibitors

A
  • Captopril, Enalapril, Lisinopril
  • First-line agents (in particular for diabetics and patients w chronic kidney disease)
  • decr BP by decr peripheral vascular resistance
  • INHIBIT ACE (angiotensin converting enzyme) that cleaves angiotensin I to form angiotensin II
  • DECREASE Na+ & H20 retention
  • INCREASE BRADYKININ levels
  • DO NOT reflexively increase cardiac output, rate or contractility

Use

  • Hypertension (most effective in white and/or young patients) + diuretic = effectiveness similar in white and black
  • Preserve renal function in patients with either diabetic or non-diabetic nephropathy
  • Effective in treatment of chronic HF
  • Standard of care for patients following MI (started 24h after end of infarction)

Adverse

  • Hyperkalemia
  • Hypotension
  • Persistent Dry cough
  • Teratogenic
  • Angioedema (rare but life-threatening)
  • Acute renal failure (patients with bilateral renal artery stenosis RAS); However, ACE inhibitor is the drug of choice for unilateral
  • Rash, fever, altered taste
  • ABSOULTE contraindication in pregnancy
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4
Q

Angiotensin Receptor Blockers (ARB)

A
  • Block angiotensin-2 type 1 receptors
  • BP by causing arteriolar & venous dilation
  • Block aldosterone secretion -> decrease Na+ & H20 retention
  • diabetic nephrotoxicity
  • DO NOT INCREASE BRADYKININ levels
  • Antagonism of aldosterone receptor -> inhibition of Na+ and H20 retention -> inhibition of vasoconstriction
  • Reduces K+ excretion -> risk of hyperkalemia (more prominent in patients with chronic kidney disease or in patients taking concurrent ACEI, ARB or other K+-sparing diuretics)
  • Used in the treatment of hypertension & heart failure
  • Can be used as part of first-line therapy in patients with hypertension & severe left ventricular dysfunction

Adverse

  • Similar to those of ACE inhibitors
  • Dry cough does not occur (due to no effect on bradykinin levels)
  • Angioedema risk is significantly lower than with ACEI’s
  • contraindicated in pregnancy
  • contraindicated in Pt w bialteral RAS
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5
Q

Renin Inhibitor

A
  • Ex. Aliskerin
  • MOA: Inhibits enzyme activity of renin and prevents conversion of angiotensinogen into angiotensin I
  • End result: Inhibits production of both angiotensin II and aldosterone

Adverse

  • Similar to those of ACE inhibitors
    • hyperkalemia
  • Dry cough does not occur (due to no effect on bradykinin levels)
  • Angioedema risk is significantly lower than with ACEI’s
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6
Q

Ca2+ Channel Blockers (CCB)

A
  • Verapamil, Diltiazem, Nifedipine, Amlodipine
  • First-line agents
  • Ca2+ CHANNEL CLASSES
  • Non-dihydropyridines
    • Verapamil
    • Diltiazem
  • Dihydropyridines
    • Nifedipine, Amlodipine

Uses

  • HPT
  • have intrinsic natriuretic effect
  • Useful in patients with asthma, diabetes, peripheral vascular disease

PK

  • High-doses of short-acting dihydropyridine Ca2+- channel blockers can increase risk of MI (excessive vasodilation & reflex cardiac stimulation)
  • Sustained release preparations are preferred

Adverse

  • Verapamil: Constipation (~7 %), should be avoided in patients with CHF (-ve inotropic effects)
  • Dihydropyridines: Hypotension, peripheral edema (esp. feet & ankles), dizziness, headache, fatigue, bradycardia, heart block, reflex tachycardia can occur, especially in short-acting preparations
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7
Q

Verapamil

A
  • Least selective of any Ca2+-blocker
  • Significant effects in cardiac & vascular smooth muscle
  • Used to treat angina, supraventricular tachyarrythmias, hypertension & migraine
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8
Q

Dilitiazem

A
  • Effects in both cardiac & vascular smooth muscle (less pronounced effect on heart than verapamil)
  • Good side-effect profile
  • Used to treat angina, hypertension & supraventricular tachyarrythmias
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9
Q

Dihydropyridines

A
  • 1st gen: Nifedipine
  • 2nd gen: Amlodipine
  • Greater affinity for vascular Ca2+-channels than for cardiac Ca2+-channels
  • Reduce Ca2+ entry into smooth muscles to cause coronary & peripheral vasodilatation & lower BP
  • Primarily used in treating hypertension
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10
Q

Diuretics: Thiazides

A
  • First-line agents (particularly black and/or elderly patients)
  • Effective in lowering BP by 10-15 mmHg

MOA

  • Lower BP by incr Na+ and H20 excretion -> decr in extracellular volume -> decr in cardiac output & renal blood flow.
  • Long-term treatment = normal plasma volume but decreased peripheral resistance

Uses

  • Counteract Na+ & H20 retention caused by other antihypertensive drugs -> useful in combination therapy
  • Particularly useful in black & elderly (with normal renal & cardiac function)

Adverse

  • Hypokalemia
  • Hyperuricemia
  • Hyperglycemia
  • Hypomagnesemia
  • Hypercholesterolemia
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11
Q

Loop diuretics

A
  • Act promptly in patients with poor renal function or heart failure
  • More potent at inducing diuresis & can cause more side effects
  • Used primarily in patients who do not respond to thiazide therapy adequately
  • Cause decr renal vascular resistance & incr renal blood flow
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12
Q

Potassium-Sparing

A
  • decr K+ loss in urine caused by thiazide or loop diuretics
  • Used in combination
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13
Q

Beta-blockers

A
  • Propranolol, Metoprolol, Atenolol, Pindolol
  • Used only as add-on therapy to first line agents in primary prevention patients
  • First-line therapy only for patients with coronary artery disease, heart failure or post-MI
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14
Q

alpha1-blockers

A
  • Prazosin, Doxazosin
  • Na+ & H20 retention does occur
  • Effective in lowering BP but more side effects than other antihypertensives
  • Hypertension (due to side-effect profile, development of tolerance & advent of safer antihypertensives, alpha- blockers are seldom used in treatment of hypertension)

Adverse

  • Orthostatic hypotension (which may lead to syncope) upon first-dose or large increases in dose
  • Concomitant use of a Beta-blocker may be necessary to blunt short-term effect of reflex tachycardia
  • Dizziness, drowsiness, headache, lack of energy, nausea, and palpitations,
  • Doxazosin shown to incr rate of CHF
  • reflex tachycardia
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15
Q

Labetalol

A
  • Oral & parenteral admin.
  • Used in hypertension management (safe in pregnancy)
  • IV labetalol = rapid reduction in BP -> useful in hypertensive emergencies
  • Advantages: decr in BP associated with alpha1-blockade is not associated with reflex increase in HR or cardiac output
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16
Q

Clonidine

A
  • DOES NOT decr renal blood flow or GFR
  • Used in hypertension management, including hypertensive crises (other drugs with fewer side effects are now generally preferred)
  • Drowsiness, dry mouth, dizziness, headache & sexual dysfunction occur commonly
  • Rebound hypertension may occur following abrupt withdrawal (avoid concomitant use with Beta-blockers)
17
Q

Methyldopa

A
  • DOES NOT decr renal blood flow or GFR
  • Usually treatment of choice for pregnancy-induced hypertension
  • Used in hypertension management (other drugs with fewer side effects are now generally preferred)

Adverse

  • Nightmares, mental depression, vertigo (infrequent)
  • Development of positive Coombs test (10-20% patients on long-term treatment (>1 year)). Can result in hemolytic anemia, hepatitis & drug fever
18
Q

Direct vasodilators

A
  • Hydralazine, Minoxidil
  • Not used as first-line antihypertensives
  • Direct acting smooth muscle relaxants
  • Produce reflex tachycardia, increase plasma renin -> Na+& H20 retention
  • Major side effects can be blocked if combine with diuretic & beta-blocker
19
Q

Hydralazine

A
  • Can be given oral or IV
  • Acts mainly on arterioles
  • Used to treat pregnancy induced hypertension / pre- eclampsia, ie emergency situations
  • Used in management of hypertension as last-line therapy

Adverse

  • Fluid retention & reflex tachycardia are common
  • Reversible lupus-like syndrome
  • Headache, nausea, sweating, flushing
  • peripheral neuritis
  • Usually administered with beta-blocker & thiazide
20
Q

Minoxidil

A
  • Causes direct peripheral vasodilatation of arterioles
  • Oral treatment for severe-malignant hypertension (refractory to other treatments)
  • Reflex tachycardia & fluid retention may be severe (combine with loop diuretic & beta-blocker)
  • Causes hypertrichosis (also used topically to treat male pattern baldness)
21
Q

Epoprostenol

A
  • Synthetic PGI2
  • Lowers peripheral, pulmonary, and coronary resistance
  • Given via continuous infusion
  • Adverse effects include flushing, headache, jaw pain, diarrhea and arthralgias
22
Q

Bosentan

A
  • Nonselective endothelin receptor blocker
  • Blocks both the initial transient depressor (ETA) and the
  • prolonged pressor (ETB) responses to IV endothelin • Pregnancy category X
23
Q

Causes of Hypertensive Emergency (partial list)

A
  • Drug withdrawal eg, clonidine, nifedipine etc.
  • CNS disorders eg, injury, stroke, tumor
24
Q

Hypertensive Emergency: Management

A

(a) Lower BP by no more than 25 % (within min – 1 h). Appropriate goal is 100-110 mmHg (DBP)
(b) If stable, followed by further reduction towards goal of 160/100 mmHg (SBP/DBP) within 2-6 h and gradual reduction to normal over next 8-24 h

  • Sodium nitroprusside
  • Labetalol
  • Fenoldopam
  • Nicardipine
  • Nitroglycerin
  • Diazoxide
  • Phentolamine
  • Esmolol
  • Hydralazine
25
Q

Sodium Nitroprusside

A
  • Drug of choice for hypertensive emergencies
  • Always given IV (poisonous if given orally)
  • t1/2 = 1-2 min ->requires continuous infusion
  • NO releaser
  • Prompt vasodilation &
  • Equal effect on arterial & venous smooth muscle

Adverse

  • Hypotension (overdose), goose bumps, abdominal cramping, nausea, vomiting, headache
  • Cyanide toxicity (rare)
  • Nitroprusside metabolism -> cyanide ion
  • Can be treated with sodium thiosulfate infusion -> nontoxic thiocyanate
  • reflex tachycardia
26
Q

Labetalol

A
  • Combined alpha and beta blocker
  • IV bolus or infusion for hypertensive emergency
  • t1/2 =3-6h
  • DOES NOT cause reflex tachycardia

Contraindications

Asthma, COPD, patients with 2nd or 3rd-degree AV block or bradycardia

27
Q

Fenoldopam

A
  • Peripheral dopamine-1 (D1) receptor agonist
  • Evokes arteriolar dilation
  • IV infusion for hypertensive emergency
  • t1/2 = 30 min
  • Maintains or increases renal perfusion as lowers BP
  • Promotes naturesis
  • Safe to use in all hypertensive emergencies (particularly beneficial in patients with renal insufficiency)
  • Contraindications: Glaucoma
28
Q

Nicardipine

A
  • Calcium-channel blocker
  • IV infusion for hypertensive emergency
  • t1/2 = 30 min
  • Evokes reflex tachycardia
29
Q

Nitroglycerin

A
  • Venous and arterial and vasodilator
  • Drug of choice for hypertensive emergencies in patients with cardiac ischemia or angina, or after cardiac bypass surgery
  • t1/2 = 2-5 min
  • Hypotension = most serious side effect
30
Q

Diazoxide

A
  • Arteriolar dilator
  • Prevents vascular smooth muscle contraction by opening K+ channels and stabilizing membrane potential
  • t1/2 =~24h

Adverse Effects:

  • Hypotension, reflex tachycardia, Na+ & H20 retention
  • Inhibits insulin release and can be used to treat hypoglycemia secondary to insulinoma

Pharm S2015 (47 decks)

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