Ischemic HD Tx Flashcards
Most important use of organic nitrates in IHD?
termination of stable and variant angina episodes
Which vessels are more responsive to organic nitrates?
veins > arteries (decreased pre-load)
large vessels > small vessels
How does NO relax smooth muscle?
- pro drugs are converted to NO by aldehyde dehydrogenase in the mito
- NO activates guanylate cyclase = inc cGMP
- inhibition of calcium channels
How does the liver metabolize organic nitrates?
hepatic enzyme nitrate reductase pulls nitrate groups off
How do the pharmacokinetics of NG and isosorbide dinitrate differ?
- NG = 2-5 minutes (great substrate for nitrate reductase); TERMINATION of angina; pro-phylaxis requires extended release
- ID = 1 hour; better oral viability – prophylaxis
What is the most common method of using NG for termination of angina?
sublingual tablet (also spray, IV)
What two forms of NG are formed for prophylaxis of angina?
- transdermal match (long duration)
- chest ointments (medium duration)
WHat is the big problem with organic nitrates? How is this avoided?
- tolerance
- vascular smooth muscle loses ability to convert organic nitrates to NO (aldehyde dehydrogenase in mito)
- nitrate free periods every day to avoid tolerance
Three adverse effects of organic nitrates?
- due to excessive vasodilation
- headaches (inc cerebral flow, avoid in migraneurs)
- hypotension (careful in the elderly; sit them down)
- tachycardia (reflex response to dec BP)
When is an acute anginal episode Tx with organic nitrates considered an emergency?
doesn’t terminate within 15 minutes
What is an absolute contraindication of nitrate use?
within 24 hours of sildenafil use (inhibits PDE 5 = inc cGMP)
What calcium channels are usually inhibited by CCB’s?
L-type = cardiovascular contraction type
How do half lives differ among dihydropyridine prototype drugs?
- amiodipine = 40 hours
- nifedipine = 2-4 hours
Which CCB class is more often associated with reflex tachycardia?
- dihydropyridines
- non’s additionally directly inhibit SAN which compensates for reflex tachycardia in response to vasodilation
DOC indication for CCB’s in myocardial ischemia?
variant angina (direct vasodilators, no drug-free periods)