Angina 1: Nitrates Flashcards
Enumerate Organic nitrates
- Glyceryl trinintrate/ GTN/ Nitroglycerin
- Isosorbid Dinitrate
- Isosorbid Mononitrate
Which Nitrate has the slowest onset & longest duration
(isosobid Dinitrate)
All Nitrates undergo extensive first pass effect except ____
Isosorbid Mononitrate
Describe mechanism of Action of organic nitrates
- It will be De-nitrated by Glutathione transferase enzyme by consumption of S-H group
- This causes release of Nitric Oxide (NO)
- Nitric Oxide forms cGMP
Action of cGMP:
* dephosphorylate/ inactivate (Myocin Light chain Kinase) MLCK –> relaxation
* decrease Ca2+ entry —> relaxation
* Decrease platelet aggregation
Describe Pharmacological actions of Nitrates on Blood vessels
on BV:
* VD of Normal big vessels, especially veins
* POWERFUL Venodilator: ⬇️ venous return, EDV & Preload
* VD of some arteries: ⬇️ peripheral resistance, ⬇️ afterload
* VD of big normal coronaries
* VD of Meningeal Arteries –> Headache
* Cutaneous VD –> Flushing (nitroid reaction)
* Pulmonary VD: ⬇️ pulmonary pressure
Describe Pharmacological action of Nitrates on the heart
Decrease Cardiac work by decreasing preload & afterload (mainly preload as it is a powerful Venodilator)
Describe Pharmacological action of Nitrates on blood pressure
Hypotension:
* Decrease mainly Systolic bp (and some diastolic)
* with reflex sympathetic tachycardia & increased contractility maintaining diastolic bp
Reflex sympathetic stimulation (tachycardia & increased contractility) cause by nitrates can be antagonized by____
Beta blockers & Verapamil (CCB)
effect of nitrates on smooth muscles
Spasmolytic:
* same for bronchial asthma patients
* safe for pregnent patients (uterus)
* safe for GIT
* safe for biliary system (bile)
* safe for urinary bladder
effect of Nitrates on the respiratory center
reflex stimulation of chemoreceptors & baroreceptors
Enumerate theraputic uses of Nitrates
- All types of Angina
- MI
- Congestive heart failure
- Biliary colic
- Esophageal spasm
- Cyanide posioning
explain how Nitrates treat all types of Angina Pectoris
- Angina of effort (common): decreasing cardiac work (both preload and afterload but preload more)
- Variant Angina: Coronary VD
- Unstable Angina: both decreases Cardiac work & causes Coronary VD + decreases O2 consumption
In MI, GTN is admistrated by____, and why ?
titrated IV infusion, to avoid severe hypotension or reflex symapthetic tachycardia
Explain why GTN is used in MI
- relives chest pain
- Decrease (controls) pulmonary congestion
- limit the area of necrosis by altering O2 balance in partial ischemic zones
explain how and why Sodium Nitrite is used to treat cyanide poisoning
- Sodium Nitrite is a very weak vasodilator so can be given in high doses
- It works along with sodium thiosulfate adminstration
- it turns hemoglobin into methemoglobin for cyanide to turn it into Cyanomethemoglobin
- Sodium thiosulfate turns cyanomethemoglobin into methemoglobin & Sodium thiocynate
- Sodium thiocynate is excreted in urine
