Antihypertensive Drugs Free Pharmacology Notes – 2021

Antihypertensive Drugs are used to treat hypertension which is caused due to high blood pressure. In this note, we will learn about the classification of Antihypertensive drugs, their type, mechanism of action, advantages, and side effects of the drugs. At the end of this note, there will be an MCQ test where you test your knowledge of how much you learn about Antihypertensive Drugs. So read this note carefully and participate in the MCQ Test. Best of Luck đź‘Ť.

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Antihypertensive Drugs Pharmacology Notes
Antihypertensive Drugs Pharmacology Notes

Classification of Antihypertensive Drugs

Antihypertensive Drugs are classified into the following types

  • Diuretics
  • Beta adrenergic blockers
  • Calcium channel blockers
  • Angiotensin converting enzyme inhibitors
  • Angiotensin receptor blockers
  • Sympatholytics and adrenergic blockers
  • Direct arterial vasodilators

We will discuss these classifications in this post. We will cover topics like Types of these classifications, Mechanism of Action. Advantages of the drugs, side effects, practical consideration, and special indications.

Diuretics

Diuretics drugs are a type of Antihypertensive drug that are used to treat Hypertension. Diuretics drugs are used to increase the amount of urine produced by the Kidney and increase the excretion of sodium and other types of electrolytes.

Types of Diuretic Drugs

  • Thiazides and related diuretics
  • Loop diuretics
  • Potassium sparing diuretics

Mechanism of Action

  • Initial effects: through reduction of plasma volume and cardiac output.
  • Long-term effect: through the decrease in total peripheral vascular resistance.

Advantages

Advantages of the Diuretics drugs are given below

  • Documented reduction in cardiovascular morbidity and mortality.
  • Least expensive antihypertensive drugs.
  • Best drug for the treatment of systolic hypertension and for hypertension in the elderly.
  • Can be combined with all other antihypertensive drugs to produce a synergetic effect.

Side Effects

Side effects of Diuretic drugs are listed below

  • Metabolic effects (uncommon with small doses): hypokalemia, hypomagnesemia, hyponatremia, hyperuricemia, dyslipidemia (increased total and LDL cholesterol), impaired glucose tolerance, and hypercalcemia (with thiazides).
  • Postural hypotension.
  • Impotence in up to 22% of patients.

Practical Considerations

  • Moderate salt restriction is the key for the effective antihypertensive effect of diuretics and for protection from diuretic-induced hypokalaemia.
  • Thiazides are not effective in patients with renal failure (serum creatinine >2mg /dl) because of reduced glomerular filtration rate.
  • Frusemide needs frequent doses ( 2-3 /day ). Thiazides can be given once daily or every other day
  • Potassium supplements should not be routinely combined with thiazide or loop diuretics. They are indicated with hypokalemia (serum potassium < 3.5mEq/L) especially with concomitant digitalis therapy or left ventricular hypertrophy.
  • Nonsteroidal anti-inflammatory drugs can antagonize diuretics’ effectiveness.

Special Indications

  • Diuretics should be the primary choice in all hypertensives.
  • They are indicated in:
    • Volume dependent forms of hypertension: blacks, elderly, diabetic, renal, and obese hypertensives.
    • Hypertension is complicated with heart failure.
    • Resistant hypertension: loop diuretics in large doses are recommended.
    • Renal impairment: loop diuretics.

Beta – Adrenergic Blocking Agents

Beta-Adrenergic Blocking agents are widely used to treat Hypertension, Angina pectoris, and cardiac arrhythmia. These antihypertensive agents are also used to treat anxiety and to reduce the side effects of Hyperthyroidism.

Mechanism of Action

  • The initial decrease in cardiac output, followed by a reduction in peripheral vascular resistance.
  • Other actions include decrease plasma renin activity, resetting of baroreceptors, the release of vasodilator prostaglandins, and blockade of prejunctional beta-receptors.

Advantages

The advantages of Beta-Adrenergic blocking agents are given below.

  • Documented reduction in cardiovascular morbidity and mortality.
  • Cardioprotection: primary and secondary prevention against coronary artery events (i.e. ischemia, infarction, arrhythmias, death).
  • Relatively not expensive.

Practical Considerations

  • Beta blockers are used with caution in patients with bronchospasm.
  • Contraindicated in more than grade I AV, heart block.
  • Do not discontinue abruptly.

Side Effects

Side effects of the Beta-Adrenergic Blocking Agents are listed below.

  • Bronchospasm and obstructive airway disease.
  • Bradycardia
  • Metabolic effects (raise triglyceride levels and decrease HDL cholesterol; may worsen insulin sensitivity and cause glucose intolerance). Increased incidence of diabetes mellitus.
  • Coldness of extremities.
  • Fatigue.
  • Mask symptoms of hypoglycemia.
  • Impotence.

Special Indications

special indications of Beta-Adrenergic are discussed below.

  • First-line treatment for hypertension as an alternative to diuretics.
  • Hypertension associated with coronary artery disease.
  • Hyperkinetic circulation and high cardiac output hypertension (e.g., young hypertensives).
  • Hypertension associated with supraventricular tachycardia, migraine, essential tremors, or hypertrophic cardiomyopathy

Calcium Channel blockers

Calcium channel blockers are one type of Antihypertensive drug that is used to control high blood pressure. These calcium channel blockers work by slowing the movement of calcium into the cells of the human heart and blood vessel walls, which makes it easier for the heart to pump and widens blood vessels.

Types

  • Dihydropyridine: nifedipine, amlodipine, felodipine, nicardipine, lacidipine.
  • Nondihydropyridine: Phenylalkylamine, verapamil, Benzothiazepine, diltiazem

Mechanism of Action

  • It decreases the concentration of free intracellular calcium ions results in decreased contraction and vasodilation.
  • It shows diuretic effect through an increase in renal blood flow and glomerular filtration rate
  • Inhibition of aldosterone secretion.

Advantages

Some advantages of the calcium channel blockers are discussed below.

  • No metabolic distrubances: no change in blood glucose, potassium, uric acid and lipids.
  • May improve renal function.
  • Maintain optimal physical, mental, and sexual activities.

Practical Considerations

Short-acting dihydropyridine should be combined with beta-blockers in coronary artery disease and should be avoided in stroke, and hypertensive crisis.

Special Indications

Some special indication of calcium channel blockers are discussed below.

  • Ischemic heart disease: when beta-blockers are ineffective or contraindicated and in vasospastic angina.
  • Elderly hypertensives: second agent of choice after diuretics.
  • Peripheral vascular disease (e.g., Raynaud’s phenomenon).

Side Effects

Some side effects of calcium channel blockers are

  • Dihydropyridine: flushing, headache, and lower limb oedema.
  • Nondihydropyridine: aggravation of heart failure and heart block. Verapamil may cause constipation.

Angiotensin Converting Enzyme Inhibitors

Angiotensin-converting enzyme (ACE) inhibitors are a type of antihypertensive drug that is used to treat high blood pressure and to prevent heart attacks. Calcium channel blockers are work by relaxing the blood vessels and by decreasing the blood volume.

Types

  • Class I: captopril
  • Class II (prodrug) : e.g., ramipril, enalapril, perindopril
  • Class III ( water soluble) : lisinopril.

Mechanism of Action

  • Inhibition of circulating and tissue angiotensin- converting enzyme.
  • Increased formation of bradykinin and vasodilatory prostaglandins
  • Decreased secretion of aldosterone; help sodium excretion.

Advantages

  • Reduction of cardiovascular morbidity and mortality in patients with atherosclerotic vascular disease, diabetes, and heart failure.
  • Favorable metabolic profile.
  • Improvement in glucose tolerance and insulin resistance.
  • Renal glomerular protection effect especially in diabetes mellitus.
  • Do not adversely affect the quality of life.

Special Indications

  • Diabetes mellitus, particularly with nephropathy
  • Congestive heart failure
  • Following myocardial infraction.

Side Effects

  • Cough (10 – 30%): a dry irritant cough with tickling sensation in the throat.
  • Skin rash (6%).
  • Postural hypotension in salt depleted or blood volume depleted patients
  • Angioedema (0.2%) : life threatening.
  • Renal failure: rare, high risk with bilateral renal artery stenosis
  • Hyperkalaemia.
  • Teratogenicity.

Practical considerations

  • Contraindications include bilateral renal artery stenosis, pregnancy, known allergy, and hyperkalemia.
  • High serum creatinine (> 3 mg/dl) is an indication for careful monitoring of renal function and potassium. Benefits can still be obtained in spite of renal insufficiency.
  • A slight stable increase in serum creatinine after the introduction of ACE inhibitors does not limit use.
  • ACE-I is more effective when combined with diuretics and moderate salt restriction.

Angiotensin Receptor Blockers

Angiotensin receptor blockers (ARBs), also known as angiotensin II receptor antagonists, These are a type of antihypertensive drugs that are used to treat high blood pressure and heart failure

Mechanism of Action

They act by blocking type I angiotensin II receptors generally, producing more blockade of the renin-angiotensin-aldosterone axis.

Advantages

  • Similar metabolic profile to that of ACE-I
  • Renal protection.
  • They do not produce cough

Practical Indications

Patients with a compelling indication for ACE-I and who can not tolerate them because of cough or allergic reactions.

Sympatholytics And Alpha Adrenergic Blockers

Types

  • Alpha 1-receptor blockers: prazocin,doxazocin.
  • Centrally acting alpha 2- agonists: methyldopa, clonidine.
  • Peripherally acting adrenergic antagonists: reserpine
  • Imidazoline receptor agonists: rilmenidine, moxonidine.

Advantages

  • Alpha1- receptor blockers and imidazoline receptor agonists improve lipid profile and insulin sensitivity
  • Methyldopa: increases renal blood flow. Drug of choice during pregnancy.
  • Reserpine: neutral metabolic effects and cheap.

Special indications

  • Diabetes mellitus: alpha1- receptor blockers, imidazoline receptor agonists.
  • Dyslipidemia: alpha 1- receptor blockers, imidazoline receptor agonists.
  • Prostatic hypertrophy: alpha 1- receptor blockers.
  • When there is a need for rapid reduction in blood pressure: clonidine.

Side Effects

  • Prazosin: postural hypotension, diarrhea, occasional tachycardia, and tolerance (due to fluid retention).
  • Methyldopa: sedation, hepatotoxicity, hemolytic anemia, and tolerance
  • Reserpine: depression, lethargy, weight loss, peptic ulcer, diarrhea, and impotence.
  • Clonidine: dry mouth, sedation, bradycardia, impotence, and rebound hypertension if stopped suddenly

Practical Considerations

  • Prazosin, methyldopa, and reserpine should be combined with a diuretic because of fluid retention.
  • In Egypt, reserpine is only available as a combination pill with thiazide (Bernardine) which contains 0.1 mg of reserpine per tablet.

Direct Arterial Vasodilators

Types

  • hydralazine
  • diazoxide
  • nitroprusside
  • minoxidil

Patients’ compliance to antihypertensive medications

Poor adherence to antihypertensive therapy remains a major therapeutic challenge contributing to the lack of adequate control of blood pressure in more than two-thirds of patients with hypertension. One-half of all patients discontinue antihypertensive medications within one year

Causes of Poor Compliance.

  • Hypertension has no symptoms and treatment has to continue indefinitely.
  • Poor communication with the patient. Very long intervals between follow-up visits, and frequent change of doctors impair the doctor-patient relationship.
  • Logistic barriers e.g. expense of medications, inability to read instructions, complicated multidose regimens, etc….
  • Adverse drug effects

Strategies to Improve Compliance

  • Educate patients about the disease and involve their families in the treatment
  • Stress that treatment is life-long.
  • Consider cost while prescribing.
  • Consider adverse effects at initial prescription and follow up visits.
  • Prescribe simple once-daily regimens.
  • Allow extra visits for blood pressure measurement at no extra charge to the patient.
  • Arrange follow-up visits at intervals no more than three months apart, during the first year.
  • Encourage life style modifications.

Preparations and Dosages of Antihypertensive Drugs

ClassGeneric NameDaily Dose (mg)
DiureticsHydrochlorothiazide12.5-50
Indapamide1.25-5
Chlorthalidone25-50
Frusemide200-4000
Bumetanide1-4
Beta adrenergic blockersAtenolol25-100
Metoprolol50-200
Bisoprolol2.5-10
Calcium antagonistsVerapamil120-480
Diltiazem90-240
Nifedipine20-80
Amlodipine2.5-10
Lacidipine2-4
ACE inhibitorsCaptopril50-100
Enalapril2.5-4
Lisinopril10-40
Ramipril2.5-20
Perindopril2-8
Angiotensin Receptor
blockers
Losartan25-100
Valsartan80-230
Candesartan4-32
Telmisartan20-80
Alpha-adrenergic blockersPrazocin1-16
Doxazocin1-16
Centrally acting drugsMethyldopa500-2000
Clonidine0.1-1.2
Rilmenidine1-2
Reserpine0.1
Commonly Used Oral Antihypertensive drugs

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