Vasodilators Flashcards
What effect does cGMP have in the process of myocyte contraction?
It has a negative inotropic effect.
What protein activates myosin light chain kinase?
What is the function of myosin light chain kinase?
- Calmodulin activates myosin light chain kinase.
- Myosin light chain kinase phosphorylates myosin so that it is able to bind to actin (once troponin has moved from the actin binding site by way of Ca2+).
What are the two types of vasodilators?
1 - Direct vasodilators.
2 - Indirect vasodilators.
How do indirect vasodilators cause vasodilation?
By blocking other substances that cause vasoconstriction.
How do direct vasodilators cause vasodilation?
1 - By interfering with the pathways that raise intracellular Ca2+.
2 - By interfering with cGMP.
What is the cause of angina pectoris?
Which drugs are used to treat it?
- Inadequate coronary blood flow for higher levels of activity, usually due to atheromatous obstruction.
- Both direct and indirect vasodilators are used to treat angina.
List 2 nonvasodilator drugs that can decrease cardiac work.
1 - Beta blockers.
2 - Ivabradine.
Briefly describe the mechanism of action for ivabradine.
It inhibits the mechanisms that underpin the pacemaker potential.
List 3 direct vasodilators.
Organic nitrates:
1 - Glyceryl trinitrate (GTN).
2 - Isosorbide mono/dinitrate.
Calcium channel blockers:
3 - Dihydropyridines (DHPs) such as amlodipine.
Describe the mechanism of organic nitrates.
Organic nitrates spontaneously break down to release nitric oxide, which increases cGMP.
What type of vessel is most strongly affected by glyceryl trinitrate (GTN)?
Why is this advantageous?
- Veins (more effect than on arteries).
- This decreases venous return (primary effect of GTN), so decreases cardiac work.
What is the secondary effect of glyceryl trinitrate (GTN)?
To cause vasodilation at coronary arteries, which increases coronary flow.
List 2 unwanted effects of glyceryl trinitrate (GTN).
1 - Excess vasodilation, causing hypotension and headaches.
2 - Decreases activity of other smooth muscle, such as the GIT and bronchi.
List 2 symptoms of hypotension in a patient that is being treated for heart failure.
1 - Syncope.
2 - Reflex tachycardia.
How is glyceryl trinitrate (GTN) administered?
Why?
- Sublingually or via transdermal patches (for patients that need GTN all the time).
- To avoid 1st pass metabolism that the drug would otherwise be subjected to if it was taken orally.
- To increase speed of action (faster than orally).