Organic Nitrates Flashcards
When is GTN administered by IV infusion?
with aspirin - acute coronary syndrome
What conditions are organic nitrates used in?
stable angina and acute coronary syndrome
What is the effect of high doses of an organic nitrate?
arteriolar dilatation - decreases arterial pressure - reduces afterload
What are is the benefit of organic nitrates in angina?
blood redirected towards ischaemic zone from healthy vessels - relieves pain - doesn’t treat disease
What is the effect of small doses of an organic nitrate?
venorelaxation - decreases central venous pressure - decreased preload - reduced SV - reduces work of heart, CO maintained by increased HR - no change in arterial pressure, no change in oxygen consumption - reduced work load but increased HR
Are organic nitrates a relatively safe drug?
yes
When is GTN administered via a transdermal patch?
sustained effect - lipophilic so absorbed via skin
What are the unwanted effects of organic nitrates?
postural hypotension - can lead to fainting, headaches - dilation of cranial arterioles - usually only initially, methaemoglobin formation - rare - stabilised form of haemoglobin - unable to release oxygen to tissues, reflex tachycardia - prevented by a beta blocker
How is isosorbide mononitrate (ISMN) used?
orally, prophylaxis of angina - more sustained effect, one dose at breakfast and one at lunch - low nitrate periods prevent tolerance development - occur during night when angina unlikely to develop
Why is glyceryltrinitrate (GTN) not administered orally?
undergoes extensive first-pass metabolism
What is the mechanism of action of organic nitrates?
cause release of NO in smooth muscle - increases cGMP -fall in intracellular calcium levels
When is GTN administered sublingually?
tablet or spray - rapid effect before exercise - stable angina
How do nitrates work in angina?
Dilate coronary arteries and reduce venous return - reduces work of heart - reduces oxygen demand
