Drugs used in the treatment of the cardiovascular system Flashcards
What is meant by an antiplatelet agent?
a drug that reduces the activity of platelets and reduces their ability to cross link and form thrombus
What are the antiplatelet agents and why?
Aspirin (main one)- cyclooxygenase inhibitor and reduces production of Thromboxane A2 (active chemical that signals to platelets to reveal receptors that are involved in cross linking)
Clopidogrel/ Ticagrelor (other main ones) - irreversibly affect receptor on surface of platelets that is involved in platelet activation
Dipyridimole- Phosphodiesterase inhibitors )
(GPIIB/IIIA fibrinogen receptor antagonists)
What are the antiplatelet agent’s life span?
life span within circulation is about 7-10 days
What does the enzyme , cyclooxygenase, do?
converts fatty acid (Arachidonic acid) into various vasoactive mediators and inflammatory mediators called prostaglandins and thrombooxane A2
What are prostaglandins involved in?
involved in maintaining vascular tone in various vascular beds - in particular kidneys.
Where prostacyclin is important in maintaining perfusion within the kidneys involved in secretion of mucus within GI tract
What clinical problem does blocking cyclooxygenase within GI tract cause?
reduce the amount of mucus that’s produced in the GI tract and can lead to problems with indigestion.
Aspirin also makes you bleed and can irritate GI tract.
Bleeding from GI tract
What are the two isoforms of cyclooxygenase?
COX 1 - runs in background and produces prostaglandins to help with vascular tone and mucus production.
COX 2 - induced by pro-inflammatory signals and can produce a whole host of inflammatory mediators. These mediators are involved in pain reception.
When are antiplatelets used?
in secondary prevention
When is aspirin used?
used in patient who have got stable angina or have had a heart attack.
They will be left on aspirin and a small dose of aspirin for the rest of their lives.
High doses during first couple week after stroke and then switched to clopidogrel.
When is Clopidogrel used?
mainstay secondary prevention antiplatelet in patients with stroke disease
In combination with Aspirin- following Percutaneous Intervention in Stable patient and some Stroke patients
When is Ticagrelor used?
used In combination with Aspirin in all patient with ACS for upto 1 year in NHSG
Side effects of antiplatelet agents?
Bleeding
Roughly 0.25 to 1% annual risk of a significant bleed with a single agent,
synergistic effect (risk of bleeding goes up) when multiple agents used
Effect will last for up to 1 week as they irreversible
Interactions antiplatelet agents?
when used with anticoagulating can increase bleeding
NSAID and SSRIs - increased tendency to bleed
Clopidogrel and omeprazole - as omeprazole has risk of reducing patient to clopidogrel and therefore increasing risk of thrombosis.
What are the main receptors in the sympathetic nervous system?
alpha and beta adrenergic receptors
What does activation of alpha 1 receptors on smooth muscle mean?
smooth muscle contraction
What does activation of beta 1 receptors on heart mean?
activation of these receptors leads to tachycardia (increasing heart rate) and a more forceful contraction
What does activation of beta two receptors on vascular tree mean?
dilation of the arteries due to smooth muscle relaxation
What is the main neurotransmitter in sympathetic NS?
Noradrenaline
What is the stress hormone produced by the adrenal medulla?
adrenaline
What do alpha and beta receptors have a greater interaction with?
alpha receptors- noradrenaline
beta receptors-adrenaline
positive effects of beta blockers?
reduce mortality in ischaemic heart disease and heart failure
also reduce symptoms in angina (beta blockers slow heart down) , Atrial fibrillation and super ventricular tachycardia
Antihypertensive (2nd line now)- (multiple mechanisms of action both central and peripheral)
