Drugs for Regional Ischemia- CAD/ Angina Flashcards
What is Coronary Ischemia?
- Inadequate supply of oxygen to to the heart which occurs due to narrowing of the coronary blood vessels.
- CAD
What is angina pectoris?
- The result of decreased blood supply to meet the increased metabolic demands on the heart.
- ->Results in left side chest pain!
What are the 2 main goals to treating Angina?
1) Decrease oxygen demand to the heart (decrease workload on the heart)
2) Increase blood supply to the heart (promoting dilation)
What are Organic Nitrates, and what pathway do nitrates activate?
- Prodrugs which act to release NO
- ->NO activates soluble guanylyl cyclase (sGC) which leads to the increase in cGMP, causing dephosphorylation of the myosin light chain, resulting in a decrease in cytosolic Ca2+ and relaxation of both arteriolar and venous blood vessels.
- Decreases myocardial wall tension/ O2 demand
What is Nitroglycerin most prevalent in treating?
Acute Angina
–>Increasing venous capacity, decreasing preload on the heart, venous return and heart rate.
What are the common Nitrate drugs?
- Nitroglycerin
- Isosorbide dinitrate
- Sodium nitropruisside (SNP)
- Minoxidil
- Hydralazine (Mechanism not known- Ca2+ blocker)
What are some of the symptoms of using Nitrates?
- TOLERANCE*
- Flushing (due to subcutaneous dilatation)
- Headaches
Why is SNP inappropriate for long term use of nitrates in controlling Angina?
-SNP can be used to temporarily bring down heart rate and blood pressure, but long term use can lead to cyanide poisoning.
True or False:
Nitrates dilate both arteriolar and venule blood vessels.
True.
*Mainly venodilation, but in high doses arteries/ arterioles also dilate!
Organic Nitrates :
(Mimics NO)
Acts directly on vascular smooth muscle cells (endothelial independent pathway) to increase NO which leads to activation of sGC, increased cGMP and decreased calcium (Vasorelaxation)
- MAINLY act on venous capacitance vessels.
- Rapidly deactivated by first pass metabolism.
What is problematic about administration of nitroglycerin?
-Can’t be administered orally.
Must be administered sublingually (transdermal patch)
-Fast onset and short half life!
Isosorbide dinitrate:
-After sublingual or oral administration, peak plasma concentration occur after 6 minutes!
(about twice the half life of nitroglycerin)
-Used for angina pectoris relief and as a prophylactic in situations likely to provoke angina. Short or Long term use
Isosorbide-2-mononitrate/ isosorbide-5-mononitrate:
-Active metabolites with a much longer half life than isosorbide dinitrate.
Approx. 3-6 hours.
–>isosorbide-5-dinitrate can be administered orally (excellent bioavailability)
What is the difference between true vascular tolerance and pseudotolerance using organic nitrates?
True vascular tolerance is due to reduced venous capacity, and a decreased ability to convert nitroglycerin into NO.
Psuedotolerance may be due to inactivation of mechanisms extraneous to the vessel wall.
Sodium Nitroprusside (SNP):
- Nitrovasodilator used to increase levels of NO in vascular tissue.
- NO activates sGC, cGMP, decrease in Ca2+ and vasodilation.
- Mechanism not completely understood.
- Dilates both arterioles and venules.
- ->Can only be used during hypertensive emergency.
- Especially used in patients with hypertension experiencing pulmonary edema.