Nitrates Flashcards
What is the mechanism of action of nitrates? (2)
Principal benefit comes from a reduction in venous return which reduces LV work
Also act as potent coronary vasodilators
What are the indications of nitrates? (3)
- Angina (prophylaxis and treatment)
- Acute coronary syndromes
- HF
- Control of BP during surgery
- Anal fissure
What are the different nitrates available? (3)
- GTN (glyceryl trinitrate)
- Isosorbide dinitrate
- Isosorbide mononitrate
What are the main side effects of nitrates? (6)
- Flushing
- Headache
- Postural hypotension
- Dizziness
- Cerebral ischemia
- Arrhythmias
What form of nitrate is available in sublingual preparations?
GTN; provides rapid symptomatic relief of angina but only lasts 20-30 min
What is the main drawback to nitrate therapy in angina management and how is it managed?
Tolerance; Reduction of blood-nitrate concentrations to low levels for 4 to 12 hours each day usually maintains effectiveness in such patients. If tolerance is suspected during the use of transdermal patches they should be left off for 8–12 hours (usually overnight) in each 24 hours; in the case of modified-release tablets of isosorbide dinitrate (and conventional formulations of isosorbide mononitrate), the second of the two daily doses should be given after about 8 hours rather than after 12 hours. Conventional formulations of isosorbide mononitrate should not usually be given more than twice daily unless small doses are used; modified-release formulations of isosorbide mononitrate should only be given once daily, and used in this way do not produce tolerance.
What are the indications of GTN? (7)
- Angina prophylaxis (sublingual or aerosol)
- Treatment of angina (sublingual or aerosol)
- Control of HTN and myocardial ischemia during cardiac surgery (IV)
- Induction of controlled hypotension during surgery (IV)
- Congestive HF (IV)
- Unstable angina (IV)
- Anal fissure (topical)
What are the indications of isosorbide dinitrate? (3)
- Prophylaxis and treatment of angina (oral, immediate-release or IV infusion, sublingual, or aerosol)
- LV failure (oral using immediate-release or IV)
- Angina prophylaxis (modified release)
What are the main contraindications to nitrates? (7)
- Severe aortic stenosis
- Hemodynamic instability and hypotension
- Must not be coadministered with phosphodiesterase inhibitors (eg sildenafil) due to risk of hypotension
- Other cardiac conditions that limit cardiac output eg cardiac tamponade, constrictive pericarditis, HOCM, mitral stenosis
- Raised ICP due to cerebral hemorrhage
- Toxic pulmonary edema
- Marked anemia
How is tolerance avoided when prescribing transdermal nitrate patches?
Leave off for 8-12 hours (usually overnight) every 24 hours
How is tolerance avoided in patients taking modified-release tablets of isosorbide dinitrate?
Second of two daily doses should be given after 8 hours rather than after 12 hours
How is tolerance avoided in patients taking conventional (rapid acting) formulations of isosorbide mononitrate?
Should not be given more than twice daily unless small doses are used
How is tolerance avoided in patients taking modified-release preparations of isosorbide MONOnitrate?
Should only be given once daily
What are the monitoring requirements for nitrate administration?
Monitor BP and HR during IV infusion
Can nitrates be stopped abruptly?
Avoid abrupt withdrawal
