Antihypertensive Drugs Flashcards
What is hypertension?
BP > 140/90 mmHg
What are the causes of hypertension?
Primary: essential hypertension (90%)
Secondary: specific causes hypertension (10%)
What are the complications caused by hypertension?
- Congestive heart failure
- Ischaemia, Myocardial Infarction
- Renal damage
- Cerebrovascular accidents (strokes)
What are the major factors influencing blood pressure?
Blood pressure = Cardiac Output + Peripheral Resistance
Cardiac Output:
Heart Contractility Rate
Filling Pressure = Blood volume + Venous tone
Peripheral Resistance = Arteriolar Tone
What are the mechanisms for controlling Blood Pressure?
- Increase Sympathetic Activity
a. activation of B1-AR of heart => Increase cardiac output
b. activation of a1-AR in Smooth Muscle => Increase Peripheral Resistance - Low Renal Blood Flow
a. Increase Renin in Kidney => Increase Angiotensin II => Increase Peripheral Resistance
b. Increase Renin in Kidney => Increase Angiotensin II => Increase Aldosterone => Increase Na+/H2O retention => Increase Blood Volume
b. Decrease Glomerular Filtration => Increase Na+/H2O retention => Increase Blood Volume
=> Increase BP
What are the drugs used to treat hypertension?
- Diuretics
a. Thiazides - DCT (5%)
b. Loop Diuretics - TAL (25) - Angiotensin Converting Enzyme (ACE) Inhibitor
- Angiotensin II receptor Type 1 (AT1-R) Antagonist
- Beta Blockers
a. Propanolol (non selective)
b. Atenolol (B1 selective) - Ca Blockers
What is the 1st line diuretics used?
Thiazides
Which is the more potent diuretic?
Loop Diuretics (affects 25% vs 5%)
What is loop diuretics usually used for?
NOT high BP
Chronic Renal Failure
Kidney Disease
Cardiac Failure
What is an example of a Thiazide?
Hydrochlorothiazide
What is the mechanism of action of Thiazides?
- Inhibit Na+ Cl- reabsorption by blocking the co-transporter in the DCT
- Enhance Ca2+ reabsoprtion in the DCT
- Enhance urea reabsoprtion and inhibit urea excretion in the PCT –> hyperuricemia
How are thiazides affected by NSAIDs?
NSAIDS interfere with the actions of thiazides by reducing prostaglandin and prostacyclin production.
Prostaglandin inhibits Na+ reabsorption in the TAL and Prostacyclin increases Na+ reabsorption and K+ excretion.
Since the action of thiazides is depended on PGs synthesis, NSAIDs will negatively interfere with thiazides.
What are the clinical uses of Thiazides?
- Hypertension
2. Congestive Heart Failure
What are the adverse effects (+ contraindications) of thiazides?
- Hypokalemic (K+)
- Hyponatremia (Na+)
- Hyperglycemia -> diabetes X
- Hyperlipidemia
- Hyperuricemia -> gout X
- Hypercalcemia (Ca2+)
What are examples of Beta Blockers?
Propanolol (non-selective)
Atenolol (B1 selective)