Drugs Flashcards
What are the two groups of drugs used to treat heart failure?
Drugs that increase cardiac output
Drugs that reduce workload of the heart
Why are drugs that increase cardiac output not often used to treat heart failure?
Have negative long-term effects on heart
What are the drugs that increase cardiac output?
Cardiac glycosides
B1 adrenoceptor agonists
How do cardiac glycosides work?
Block Na+ K+ ATPase
Increase vagal activity
What is the effect of the Na+ K+ ATPase being blocked?
Increase in intracellular conc. of Na+
Decreased activity of Na+ Ca2+ exchanger, due to reduced diffusion gradient of Na+ to enter cell
Increased intracellular Ca2+ conc.
More Ca2+ stored in sarcoplasmic reticulum
What are the effects of more Ca2+ in SR?
More Ca2+ released during action potentials
Higher intracellular Ca2+ conc.
Increases contractility
Positive inotropy - increased force of contraction
What are the effects of increasing vagal activity?
Decrease in heart rate
Decrease in AV node conduction velocity
When are cardiac glycosides used to treat heart failure?
When the patient has an arrythmia also e.g. atrial fibrillation
What is an example of a beta adrenoceptor agonist?
Dobutamine
What is dobutamine used to treat?
Cardiogenic shock
Acute heart failure
What are the types of drugs that reduce workload of the heart?
ACE inhibitors
Beta adrenoceptor antagonists
Diuretics
How do ACE inhibitors work?
Prevent action of ACE
Prevent it from converting angiotensin 1 into angiotensin 2
How does less angiotensin 2 reduce the workload of the heart?
Decreased sodium and water retention
reduced blood volume
reduced preload of heart
reduced force of contraction
Decreased vasoconstriction
decreases TPR, blood pressure
reduced afterload of heart
What can be used instead if an ACE inhibitor is not tolerated by the patient?
Angiotensin 2 receptor blocker
How do diuretics work?
Increase excretion of water, less reabsorption
decreased blood volume
reduced preload
reduced force of contraction
What are the two groups of drugs used to treat angina?
Drugs that reduce workload of heart
Drugs that increase blood supply to heart
What are the drugs that reduce workload of the heart?
Beta adrenoceptor antagonists
Ca2+ channel blockers
Organic nitrates
What are the drugs that increase blood supply to heart?
Organic nitrates
Ca2+ channel blockers
What type of cell do organic nitrates act on?
Vascular smooth muscle cells
What do organic nitrates react with in smooth muscle cells? What does this release?
Thiol -SH groups
Releases NO2-, reduced to NO
What are some examples of nitric oxides?
Glyceryl trinitrate (GTN)
Isosorbide dinitrate
What is the effect of NO?
Vasodilation
How does NO cause vasodilation?
Activates guanylate cyclase converts GTP into cGMP cGMP activates PKG PKG decreases intracellular Ca2+ conc. causes relaxation of smooth muscle cell
What type of blood vessels do organic nitrates mostly act on?
Veins - venodilation
Collateral coronary arteries
How does venodilation reduce workload of the heart?
Lowers venous pressure
reduced preload of heart
reduced force of contraction
How does collateral coronary artery dilation increase blood supply to heart?
Collateral coronary arteries bypass blockage in coronary artery
increased blood flow through bypass
to ischaemic area
How significant is collateral coronary artery dilation in increasing blood supply to heart?
Not very significant
because there aren’t many end arteries
When might collateral coronary arteries develop?
With myocardial ischaemia
in order to increase blood supply to the area
by bypassing the blocked coronary artery
Why do organic nitrates mostly act on the veins?
Because there is less endogenous nitric oxide in veins
so it has a greater effect in the veins
Which heart conditions carry an increased risk of thrombus formation?
Atrial fibrillation
Acute MI
Prosthetic heart valves
Why does atrial fibrillation carry an increased risk of thrombus formation?
Atria not contracting properly
Blood becomes stagnant, pools
Where in the atria do thrombi tend to form?
Auricles
What are the types of antithrombotic drugs? How are they different?
Anticoagulant drugs - prevent blood clot formation
Antiplatelet drugs
What are the different anticoagulant drugs?
Heparin
Fractionated heparin
Warfarin
How is heparin given?
IV
How does heparin work?
Inhibits thrombin
How is fractionated heparin given?
Subcutaneous injection
How is warfarin given?
Orally
How does warfarin work?
Antagonises action of Vit. K
What is an example of an antiplatelet drug?
Aspirin
When is aspirin used?
Following acute MI
Or if have high risk of MI
When timeframe is heparin used for?
For short-term action
What timeframe is fractionated heparin used for?
For more long-term action
What are the different groups of drugs used to treat hypertension?
ACE inhibitors
Ca2+ channel blockers
Diuretic
Beta blockers
A1 adrenoceptor antagonists
How do Ca2+ channel blockers treat hypertension?
Cause relaxation of smooth muscle in blood vessels
so vasodilation
decreases TPR, blood pressure
How do diuretics treat hypertension?
Decrease water retention
reduce blood volume
reduced preload, SV, CO
reduce blood pressure
How do beta blockers treat hypertension?
Reduce heart rate
reduce force of contraction, SV
reduce CO, blood pressure
How do A1 adrenoceptor antagonists treat hypertension?
Prevent vasoconstriction of smooth muscle in blood vessels
giving vasodilation
reduce TPR, blood pressure
How do ACE inhibitors treat hypertension?
Prevent formation of angiotensin 2
reduced sodium, water retention
reduced blood volume
reduced preload, SV, CO
reduced blood pressure
reduced vasoconsriction, increased vasodilation
reduced TPR, blood pressure
