Antihypertensive Drugs Quiz

Antihypertensive Drugs

• These drugs are used to treat high blood pressure (hypertension).
• Blood pressure (BP) is calculated as cardiac output (CO) multiplied by total peripheral resistance (TPR).

Antihypertensive Agents

• Drugs interfering with storage vesicles: Reserpine
• Drugs altering sympathetic activity:
  • α₂ agonists: clonidine and methyldopa
  • α₁ antagonists: prazosin, doxazosin, terazosin, tamsulosin
  • β-blockers: metoprolol, acebutolol, atenolol
• Direct-acting vasodilators: Hydralazine, Minoxidil, Nitroprusside
• Calcium Channel Blockers:
  • Dihydropyridines (DPH): Nifedipine, amlodipine
  • Non-DPH: Verapamil, Diltiazem
• Diuretics: Thiazides, loop diuretics, potassium-sparing diuretics
• Angiotensin-converting enzyme inhibitors (ACEIs): captopril, enalapril, lisinopril
• Angiotensin receptor blockers (ARBs): losartan, valsartan, telmisartan

Drug Strategy for Treating Hypertension

• BP = CO x TPR
• ↓ sympathetic tone:
  • ↓ TPR (α-blockers, vasodilators)
  • ↓ CO (β-blockers)
• ↓ body fluid volume (diuretics)
• ↓ Angiotensin effects
• Compensatory responses to some drugs: Reflex tachycardia and Reflexive Edema

α₂-agonists

• Reduce sympathetic outflow from vasopressor centers in the brainstem.
• Clonidine, methyldopa
• α₂ receptor activation in the CNS ↓ CO and TPR by inhibiting sympathetic outflow.

α₁-blockers

• Prazosin, Doxazosin (Cardura), Terazosin, Tamsulosin.
• Relax both arterial and venous smooth muscle.
• ↓ arteriolar and venous resistance.
• Reflex tachycardia.
• Uses: Hypertension, benign prostatic hyperplasia (BPH) (Tamsulosin)
• Side effects: first-dose syncope, orthostatic hypotension
• Advantage: favorable effect on lipid profile (↓ LDL while ↑ HDL levels).

β-blockers

• Block β-adrenoceptors; ↓ CO and ↓ renin.
• Side effects: unfavorable lipid profile.
• Caution in use with non-selective β-blockers for patients with diabetes, peripheral vascular disease (Raynaud's) and asthma/COPD.
• Use ISA (pindolol or acebutolol) or cardioselective agents (acebutolol, atenolol or metoprolol) in these patients - they produce fewer respiratory and vascular effects.

Vasodilators

• Direct-acting vasodilators:
  • Oral: Hydralazine (Apresoline) and Minoxidil (Loniten)
  • Parenteral: Nitroprusside, Diazoxide, and Fenoldopam
• Mechanism of action: Relaxation of vascular smooth muscle and decrease of resistance (and PB).
• Calcium channel blockers (CCBs): Used for both oral and parenteral administration.
  • Oral examples: Verapamil, diltiazem, nifedipine, amlodipine
• Mechanism of action: Block L-type Ca2+ channels, resulting in ↓ CO (verapamil and diltiazem) and ↓ TPR (all CCBs).

Hydralazine

• Releases nitric oxide (NO) from endothelial cells.
• ↓ TPR via arteriolar dilation.
• Use: moderate-to-severe hypertension
• Side effects: Drug-induced lupus erythematosus (DILE), edema, reflex tachycardia.
• Concomitant therapy with β-blockers, and diuretics required to counter reflex tachycardia and edema.

Minoxidil

• Uses: hypertensive emergencies (diazoxide, parenteral), severe hypertension (minoxidil), hair growth (topical).
• Side effects: hypertrichosis (minoxidil), hyperglycemia (↓ insulin release), tachycardia and edema.

Nitroprusside

• Available parenterally.
• Releases NO → dilation of arterioles and venules ↓ TPR.
• Uses: hypertensive emergencies, heart failure (HF).
• Side effects: cyanide toxicity (treat with sodium nitrite/sodium thiosulfate).

Calcium Channel Blockers (CCBs)

• Block L-type Ca2+ channels in heart and blood vessels.
• Result in ↓ intracellular Ca++
• ↓ CO (verapamil and diltiazem),↓ TPR (all CCBs).
• Drugs: Verapamil, Diltiazem, Nifedipine, and Amlodipine.

Diuretics

• Effects on kidneys to decrease sodium and water retention.
• Loop Diuretics: Furosemide, Ethacrynic acid, Bumetanide
• Mechanism: Inhibition of active salt transport
• Site of action: Thick ascending limb of the loop of Henle
• Thiazides: Hydrochlorothiazide, Chlorthalidone, Indapamide
• Mechanism: Inhibition of NaCl reabsorption
• Site of action: Early distal tubule
• Potassium-sparing diuretics: Spironolactone, Amiloride, Triamterene
• Mechanism: Late distal tubule and cortical collecting duct. competitive antagonism of aldosterone or by direct action

Angiotensin-Converting Enzyme Inhibitors (ACEIs)

• Block the formation of angiotensin II → ↓ vasoconstriction and ↓ aldosterone release to prevent fluid retention.
• Bradykinin is a potent vasodilator. ACEIs prevent bradykinin degradation, potentiating the vasodilatory properties.
• Drugs: Captopril, Enalapril, Lisinopril.

Angiotensin Receptor Blockers (ARBs)

• Block AT1 receptors.
• ARBs do not interfere with bradykinin degradation, unlike the ACEIs , and do not induce a dry cough.
• Drugs: Losartan, Valsartan, Telmisartan.

Angiotensin-Converting Enzyme Inhibitors (ACEIs) and Angiotensin Receptor Blockers (ARBS) - Clinical Uses

• Mild-to-moderate hypertension
• CHF
• Protective of diabetic nephropathy

Side effects of ACEIs and ARBS

• ACEIs: Dry cough
• Both: : Hyperkalemia, Contraindicated in bilateral renal artery stenosis, pregnancy

Test your knowledge on antihypertensive medications with this quiz focusing on their mechanisms, classifications, and side effects. Evaluate your understanding of diuretics, calcium channel blockers, and more. Perfect for students studying pharmacology or anyone interested in hypertension management.