Cardiac pharmacology Flashcards
What are acute coronary syndromes?
Cardiovascular conditions characterised by sudden occlusion of coronary arteries by thrombus blocking blood supply to cardiac muscle.
[STEMI, NSTEMI, unstable angina]
What are the principles of treating acute coronary syndromes?
- Increase oxygen supply to myocardium (by improving coronary blood flow and administering oxygen)
- Reduce oxygen demand of myocardium (by reducing heart rate/ force of contraction, reducing cardiac preload and cardiac afterload)
What is heart failure?
Inability of the heart to deliver oxygen at a sufficient rate to metabolising tissues throughout the body - caused by abnormality of cardiac structure or cardiac function
What is the treatment strategy for chronic heart failure?
- Improve contractibility using positive ionotropes - Sympathomimetics (e.g. Dobutamine) and sometimes a Beta Blocker
- Reduce oedema - loop diuretics commonly used (e.g. Furosemide)
- Reduce preload and afterload - ACE inhibitors (e.g. Ramipril) and Angiotensin II receptor blocker (e.g. Losartan)
Describe how a contraction is initiated in a vascular smooth muscle cell
- Calcium enters cell via L-type calcium channels and is also released from the sarcoplasmic reticulum (triggered by binding of Inositol Triphosphate to calcium channels on SR membrane) - IP3 release is triggered by binding of angiotensin II to angiotensin II-receptors on the cell membrane
- Calcium binds to Calmodulin (a calcium-binding protein)
- Calcium activates the enzyme Myosin Light Chain Kinase which phosporylates MLC initiating a contraction
What is the mechanism of action for calcium channel blockers?
Prevent opening of voltage-gated calcium channels (L-type) which reduces the influx of Ca2+ into muscle cells.
Has a vasodilator effect on resistance in vessels and reduced afterload
Generally act on arteries to improve blood flow (not veins)
What are the common calcium channel blockers?
Nifedipine
Amlodipine
What is the MoA of nitrate vasodilators?
- Metabolised to release Nitric Oxide
- NO stimulates Guanylate Cyclase
- Increased cGMP in vascular smooth muscle cells (via dephosphorylation of GTP)
- Drives dephosphorylation of myosin light chains via activation of MLC Phosphatase
- Increased intracellular cGMP inhibits influx of calcium ions into smooth muscle cells
= Vascular smooth muscle relaxation
What are the common nitrate vasodilators?
Glyceryl Trinitrate (GTN) Isosorbide Mononitrate (ISMN)
What are the key side effects of calcium channel blockers?
Ankle swelling
Palpitations
What is the key side effect of nitrate vasodilators?
Headache
How do nitrate vasodilators effect the heart?
Dilate arteries and veins
Reduce cardiac preload (by promoting venodilation)
Increased blood and oxygen supply to the myocardium (by promoting coronary artery vasodilation)
Reduce cardiac afterload (by promoting moderate arteriolar dilation)
What is the MoA of Beta Blockers?
Competitive inhibitors of adrenaline and noradrenaline at Beta-adrenoreceptor sites (thus inhibiting sympathetic stimulation of heart muscle) Negative inotropes (decrease HR) and negative chronotropes (decrease contractility), reducing workload of heart which relieves oxygen demand
What is a key example of a Beta1-antagonist selective for the heart?
Atenolol
Bisoprolol
What are the key side effects of Beta Blockers?
Dizziness
Constipation