Anti-HTN Pharmacology Flashcards
Formula for blood pressure
BP = CO xSVR
Targets for decreasing blood pressure with drug therapy
- SVR
- CO = HR X SV = speed x (contractility &venous return)
What alters venous return (2)
- Intravascular (blood volume) - determined by ECF volume filtered by renal output of fluids and electrolytes and net intake of fluid, electrolytes.
- Vascular tone
Drugs that alter blood pressure (6 categories)
- Diuretics
- RAAS inhibitors (ACE inhibitors, ARBs, renin inhibitors)
- Ca2+ Channel Blockers
- Sympatholytics: beta blockers, alpha- antagonists
- Vasodilators
- CNS central agents
Diuretics MOA
- draining off fluids via Na+ & K+
- Na+ = effector; inhibit re-uptake in kidney = natriuresis
- K+ = impt. b/c it gets adjusted by body to compensate for changing Na+ levels and may lead to hypo-/hyper-kalemia
Benefits of diuretics (2)
- cheapest
- safest (generally)
Types of diuretics (3)
1) Thiazide (hydrocholorothiazide)
2) Loop diuretics (furosemide)
3) K+ sparing diuretics (spironolactone)
Actions of thiazide (2)
- Vasodilation (MOA unknown)
2. Diuretic effect
Renin Angiotensin System (RAS)
- Stimulation B1 receptors releases renin
- Renin converts angiotensinogen to angiotensin I
- Angiotensin converting enzyme converts angiotensin I to angiotensin II
- Angiotensin II binds to AT1 receptors and causes release of aldosterone (leading to Na+ retention) and leads to vasoconstriction.
How to inhibit RAAS system (5)
- Block B1 receptors (inhibit release of renin)
- Block ACE to reduce production of Ang II
- Direct renin inhibitors
- AT1 receptor antagonist
- Block aldosterone receptor via spirolactone (K+ spring diuretic)
ACE inhibitors example
Ramipril
ACE inhibitor effects
-inhibit aldosterone secretion
-inhibit NaCl reabsorption
- increased vasodilation (bradykinin breakdown inhibited)
Net effect = decreased SVR + natiuresis/diuresis
Important protective effect of ace inhibitors in kidneys (2)
- Delay onset of diabetic nephropathy because reduce intraglomerular pressure (dilation of efferent arteriole)
- Decrease oxidative stress on blood vessels caused by Ang II over time
Adverse effects of ACE inhibitors (4)
- Hacking, dry cough (attributed to bradykinin)
- Angioedema -rare but serious (fatal) swelling especially around the mouth
- Hyperkalemia (due to reduced aldosterone; exchange of Na+ for K+ to increase natiuresis can lead to hyperkalemia)
- Renal dysfunction - ATII maintains GFR by constricting efferent arteriole if hypovolemic or have compromised renal arterial blood flow (renal artery stenosis) without this ACEi may cause acute renal failure
Example of ARBs
Losartan (-sartan)
Effect of ARBs (4)
- inhibit vasoconstriction (less than ACEi)
- inhibit alosterone secretion
- inhibit NaCl reabsorption
- no effect on bradykinin
Renin inhibitors example
Aliskiren (-ren)