Drugs for Angina and IHD Flashcards
What approaches are used to increase coronary blood flow?
- coronary artery bypass grafting
- percutaneous transluminal coroanry anioplasty (PTCA)
- atherectomy (tip of catheter shears off plaque)
- stent (expandable tube keeps vessel open)
When are vasodilators useful to increase coronary blood flow?
vasospastic (Prinzmetal) angina
- to relieve coronary spasm
- to restore blood flow into ischemic area
When would vasodilators NOT be useful in increasing coronary blood flow?
atherosclerotic (classic) angina
What is the “coronary seal” phenomenon?
redistribution of blood to non-ischemic areas
- associated with dilation of small arterioles
What drug example is given of the “coronary seal” phenomenon?
Dipyridamole
- increases blood flow to normal area
- decreases blood flow to ischemic area
What determines myocardial oxygen demand?
- heart rate
- contractility
- preload
- afterload
What causes the release of endolethium-derived relaxing factor (EDRF)?
ACh
What produces endogenous NO?
endothelial nitric oxide synthase (NOS)
Why are admission routes other than oral used with nitrates?
high nitrate reductase activity in the liver = significant first pass metabolism
What compounds are required to release NO from nitrates?
thiol compounds
What effect do nitrates have on vascular smooth muscle?
NO dilates veins and large arteries (at much higher concentrations)
NOTE: no “coronary seal” phenomenon
- nitrates inhibit platelet aggregation
What does venous dilations cause?
- increased venous capacitance
- reduced ventricular preload
NOTE: these are the major effects)
What does arterial dilation cause?
- may reduce afterload
- may dilate large epicardial coronary arteries
NOTE: no substantial increase in coronary blood flow
also note that much higher concentrations of nitrates are needed to produce this effect
What effects do nitrate tolerance cause
- depletion of thiol compounds
- increased generation of superoxide radicals
- reflex activation of sympathetic nervous system (tachycardia, decreased coronary blood supply)
- retention of salt and water
What does increased generation of superoxide radicals lead to?
depletion of NO in tissues
What are the adverse effects of nitrates?
- headache
- orthostatic hypotension
- increased sympathetic discharge (tachycardia, increased cardiac contractility)
- increased renal sodium and H2O reabsorption
What is the most important nitrate-drug interaction discussed?
ED meds!
- sildenafil
- vardenafil
- tadalafil
Why are nitrates contraindicated for someone on ED medication?
it causes a severe increase in the amount of cGMP -> dramatic drop in BP
-AMI have been reported
What are the nitrates discussed?
- nitroglycerin
- isosorbide dinitrate
- isosorbide mononitrate
What are the non-cardioactive calcium channel blockers mentioned?
- Amlodipine (t1/2=30-50hrs)
- Nifedipine (t1/2=4hrs)
- Nicardipine (t1/2=2-4hrs)
What are the cardioactive calcium channel blockers mentioned?
- Diltiazem
- Verapamil
What are the anti-anginal mechanisms of CCBs?
- decrease myocardial O2 demand (by dilating peripheral arteries, and decreasing cardiac contractility)
- increase blood supply (by dilating coronary arteries to relieve local spasm)
What are the major adverse effects of CCBs?
- cardiac depression, cardiac arrest, acute heart failure
- bradyarrhythmias, AV block
- vasodilation triggers reflex sympathetic activation
What are the minor adverse effects of CCBs?
- flushing, headache, anorexia, dizziness
- peripheral edema
- constipation
