Nitroglycerin

Chapter 179 Nitroglycerin






PHARMACOLOGY OF NITRATES


As a group, nitrates are absorbed from the skin, the mucous membranes, and the gastrointestinal tract.2 The common preparations include an oral tablet, a transdermal paste or patch, a sublingual spray or tablet, or a powder that is reconstituted and administered intravenously.2,3


NTG relaxes vascular smooth muscle primarily on the venous side and is therefore a preload reducer, although nitroprusside (the intravenous form) can also dilate arteries and is therefore used for severe hypertension or left-sided CHF.3 NTG is oxidized to nitric oxide (NO), a short-lived free radical that stimulates the production of cyclic guanosine monophosphate (cGMP). cGMP reduces cytosolic calcium by inhibiting flow into the cell while stimulating mitochondrial uptake, causing relaxation of smooth muscle cells.4



Tolerance


An important characteristic of NTG administration is tolerance, the loss of efficacy within a short time. Several hypotheses have been proposed to explain this.




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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Nitroglycerin

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