L26: Drugs used to modify pressure and flow Flashcards
What 3x areas can we target to reduce vascular resistance ??
arterioles (after load determinant)
Capacitance vessels (determine preload, EDV, SV)
Heart
Why would we use drugs to modify heart failure
reducing preload and after load
What are the 4x determinants of blood pressure?
CO, BV, preload, after load
Name one class of venous vasodilators and their general mode of action
Nitrates –> donate NO to dilate veins
Why are nitrate venodilators never administered orally?
all broken down @ first pass
Instead use as ointment!
What are the 3 classes of arterial vasodilators?
Hydralazine
Ca channel blockers
Indirect vasodilators –> A blockers, B blockers
How do Ca++ channel blockers act as arteriolar dilators ?
Blocks the SMC VOCC in the heart and vasculature.
The more active a channel, the more likely to be bound (vascular beds with higher resting tone will dilate more)
How specifically do the Ca++ channel blockers act on the heart?
Decrease HR by dec AV conduction through nodal tissue
Dec force of myocardium contraction
*there are varying affinities of these drugs for vascular:myocardial affinity
How do A blockers work
Dec binding of NA –> SMC relaxation –> arteriolar/ venous dilation
How do B blockers work (include both renal and cardiac effects)
Dec HR (effect @ SA node) Dec SV (cardiomyocyte) Dec CO (reduces SYMP NS)
Blocks action of JG cells –> Dec renin release –> Dec angiotensin –> less vasoconstriction –> Dec TPR
What is the general use of B blockers?
Anti-hypertensives
What are side effects of B blockers?
cold extremities
fatigue
bronchoconstriction
due to inc action A receptors
What are some indirectly acting vasodilators ?
Drugs affecting RAAS
e.g. Angiotensin converting enzyme (ACE) inhibitors
Angiotensin II receptor antagonists
How to ACE inhibitors work?
Reduce vasoconstriction & inhibit aldosterone to dec TPR, Dec fluid retention. Dependant on kidneys for clearance –> check kidney function first
How do Angiotensin II receptor antagonists work?
Inhibits angiotensin competitively for more selective reduction in vasoconstriction
