Introduction:
> most common CVS disease |
> elevated arterial BP damages vessels in renal, heart and brain |
Complications: |
Renal failure, Coronary disease, Heart failure, Stroke, Diamentia |
Classification:
Classification: |
Systolic BP |
Diastolic BP: |
Normal: |
<120 |
<80 |
Pre-hypertension: |
120-139 |
80-89 |
Stage 1 HTN: |
140-159 |
90-99 |
Stage 2 HTN: |
>= 160 |
>=100 |
Types of Hypertension:
Essential Hypertension (85-90%): |
Primary hypertension, no identifiable cause (genetic), can't be cured, can be controlled |
Secondary Hypertension (10-15%): |
Specific identified cause (comorbid disease or drug), can be cured when cause is eliminated |
Secondary Causes of HTN:
> Genetic factors |
> Psychological stress |
> Environmental and Dietary Factors: |
high salt diet, decreased calcium and phosphate intake, sedentary lifestyle |
> Diseases: |
renal, endocrine, vascular, renal diseases |
> Drugs: |
sympathomimetic amines, amphetamines, oral decongestants (eg. pseudoehedrine), corticosteroids, osteogens (C0Cs), NSAIDs, COX-2 inhibitors |
Clinical presentation:
- Often incidental finding |
- Adults should get BP checks once a year |
- Severe cases: |
Headaches, visual disturbances, target organ damage (stroke, ischemic heart disease, renal failure) |
Potential Mechanisms of Parthogenesis:
BP= CO x PVR |
Increased Cardiac output: |
Increased fluid volume from excessive sodium intake or renal sodium retention Venous constriction: due to excess stimulation of RAAS |
Increased Peripheral resistance: |
Excess stimulation of RAAS Sympathetic nervous system over-activity |
Antihypertensive Drugs:
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Classes of Antihypertensive Agents:
> Diuretics: |
Reduce blood volume=Depletes the body of sodium, Venodilation |
> Sympathoplegic agents: |
Reduce peripheral vascular resistance, Inhibit cardiac function, Increase venous pooling capacitance vessels |
> Direct vasodilators: |
Reduce peripheral vascular resistance, Increase venous pooling capacitance vessels |
> Angiotensin antagonists: |
Reduce peripheral vascular resistance, Reduce blood volume |
Diuretics:
- Reduce blood volume and cardiac output |
- Cardiac output returns to normal |
But peripheral vascular resistance declines |
- Sodium |
Contributes to vascular resistance = Increase vessel stiffness |
- Venodilation |
Altered sodium-sodium calcium exchange |
Vasodilation mechanism by Diuretics:
Use of Diuretics:
> Lower BP by 10-15 mmHg in most patients |
> Thiazide diuretics –mild to moderate HTN |
> Loop diuretics – severe HTN and hypertensive emergencies |
Adverse Effects (Thiazide Diuretics):
Potassium depletion – hypokalemia
Magnesium depletion
Hyperuricemia- gouty attacks
Glucose intolerance
Increase serum lipid concentrations
Sympathoplegic Drugs:
Centrally-acting Drugs: |
Methyldopa, clonidine |
Adrenoceptor antagonists |
Beta-blockers, alpha-1 blockers |
Ganglionic-blocking Agents: |
No longer used clinically ; hexamethonium |
Adrenergic neuron blocking agents: |
Block the release of noradrenaline, Reserpine, guanethidine, debrisoquin, Not/rarely used clinically |
Centrally-Acting Drugs:
- Methyldopa, clonidine |
rarely used except clondine |
- Reduces sympathetic outflow |
- Compensatory response mechanism: |
salt retention |
- Clonidine, guanabenz, guanfacine |
Stimulate central alpha-2 adrenoceptors |
- Methyldopa – anologue of L-dopa |
Results in the synthesis of a false neurotransmitter |
|
Alpha-methylnoradrenaline = Stimulates central alpha-2 adrenoceptors |
Clonidine:
Reduces cardiac output, PVR, relaxation of capacitance vessels
Rarely causes postural hypotension
Adverse effects:
- Dry mouth
- Sedation
Contraindication: Patients with depression
Caution: Abrupt discontinuation can lead to hypertensive crisis
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Adrenoceptor antagonists: Beta-blockers
Non-selective: Propranolol |
Beta-1 selective: “BBEAM” |
Betaxolol, bisoprolol, esoprolol, atenolol, metoprolol, Cardioselective |
Vasodilator beta-blockers |
Also block alpha-1 receptors,Labetolol, carvidelol, nebivolol |
Decrease cardiac output
Decrease peripheral vascular resistance
Inhibit stimulation of renin production by catecholamines
Adverse effects= Heart block, bronchoconstriction, diabetes, vivid dreams
Alpha-1 blockers:
Prazosin, terazosin, doxazosin |
Block alpha-1 receptors in arterioles and veins |
Vasodilation |
Reduce peripheral resistance |
Compensatory mechanism: |
salt and water retention |
More effective when used with other drugs
Calcium Channel Blockers:
> Dihydropyridines |
amlodipine, isradipine, nicardipine, nimodipine, felodipine, nisoldipine, lacidipine |
> Non-dihydropyridines |
Verapamil, diltiazem, hydralazine |
|
Benzothiazepine (diltiazem) |
Mechanism of action:
- Inhibit calcium influx through voltage-dependent L-type calcium channels
- Relax arteriolar smooth muscle, reduce peripheral vascular resistance
- Cause coronary and peripheral vasodilation
CCB: Mechanisms of Action:
Dihydropyridine CCBs |
Primary vasodilators (reduce PVR), All decrease cardiac contractility except amlodipine and felodipine |
Non-dihydropyridines (diltiazem, verapamil) |
directly block the AV node, decrease heart rate,decrease cardiac contraction |
Adverse effects: |
1. Flushing, peripheral oedema, tachycardia, bradycardia, heartblock |
2. Headache, flushing, dizziness, palpitations, hypotension
occur within a few hours of dosing, Associated w high initial doses or rapid increase in dose, Common with short-acting preparations
3. Ankle oedema: Due to a rise in intracapillary pressure as a result of selective dilatation of precapillary arterioles, NOT due to sodium retention, Relieved by bed rest
4. Gum Hypertrophy: dihydropyridines
5. GIT: constipation (verapamil), nausea, and vomiting
Inhibitors of Angiotensin:
Angiotensin converting enzyme inhibitors (ACEIs) |
Captopril, enalapril, Ramipril, fosinopril, trandopril |
Angiotensin receptor blockers (ARBs) |
Losartan, valsartan, telmisartan, irbesartan, candesartan |
Renin-inhibitors |
Aliskiren |
Inhibitors of Angiotensin:
Adverse Effects
ACEIs =
Dry cough
Can cause hyperkalemia – potassium monitoring essential
Angioedema (substance P?)
ARBs =
No dry cough
Hyperkalemia
Angiodema is less common than ACEIs
Contraindicated in pregnancy
Combination Treatment: Vasodilators:
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Management Approach:
First-line agents: “ACD” drugs:
- A: ACEIs and ARBs
- C: Calcium channel antagonists
- D: Diuretics (Thiazides)
Second-line agents:
- Beta-adrenoceptor blockers
- Aldosterone antagonists (spironolactone, eplerenone)
- Alpha-blockers (doxazosin, prazosin, terazosin)
- Loop diuretics (frusemide, torsemide)
- Direct vasodilators (hydralazine, minoxidil) [last-line of therapy]
- Central α-2 agonists (clonidine)
- Adrenergic antagonists (reserpine)
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