Antianginal drugs Flashcards
How do nitrates and nitrites have their action?
Cause vasodilation via NO which is converted into cGMP.
What kind of vasodilation is caused by nitrates?
Uneven, large veins are dilated more, so preload is reduced more than afterload, but afterload is still reduced, thus decreasing cardiac workload and decreasing oxygen demand
What is the DOC for any acute anginal attack (classic or variant)?
Nitrates
What is the downside of nitrate therapy?
A decrease in BP causes baroreflex and an increased HR and contractility, thus decreasing diastolic perfusion time and increasing O2 demand again
What is the predominant mechanism of anginal relief by nitrates?
to decrease myocardial O2 requirements
What is the secondary mechanism of anginal relief by nitrates?
redistribution of regional coronary BF from normal to ischemic areas even though total flow remains unchanged
What are the pharmacokinetics of nitrates?
Rapid metabolization and very fast acting, hence sublingual is the route of choice because it avoids hepatic destruction, effects only last about 30 minutes
What is the inhaled nitrate?
Amyl nitrite
What is sublingual nitrate?
isosorbide dinitrate
What is the IV nitrate?
sodium nitroprusside
What are some adverse side effects of nitrates?
Orthostatic hypo, tachycardia, throbbing HA, TOLERANCE– evidenced by “Monday disease” exhibited by explosive manufacturers– symptoms disappear by Friday due to tolerance
Where do CCBs have their action?
At all smooth muscles that depend on calcium for normal resting tone and contraction
How does nifedipine lead to reflex tachy if it is vascular specific?
reflex tachycardia causes increase in HR
When is the only time slow release nifedipine is indicated?
For HTN, not for angina (may actually provoke angina)
How are CCBs used to treat angina?
As chronic treatment, not immediate relief
What is the most harmful effect of nondihydropyridines and angina?
The potential for serious cardiac depression that could end in cardiac arrest, A-V block, or CHF (don’t use in CHF patients for this reason)
Where does anginal relief from BBlockers come from?
decreased SNS activation, decreased vasoconstriction, hypotension and bradycardia, and decreased demand. Bradycardia has an added benefit for increasing myocardial perfusion time
Why are BBlockers not used for variant angina?
They do not cause direct vasodilation of coronary arteries, it is good to maintaining heart rate to prevent repeat ischemia (see metoprolol graph)
Who are BBlockers contraindicated in?
Asthmatics and diabetics!
How could BBlockers be harmful in variant angina?
Slow HR and long ejection time leads to an increase in LV EDV, which will increase myocardial O2 requirement
What kind of treatment can BBlockers be used for?
Classic angina, NOT VARIANT
What is the MOA of ranolazine? When is it indicated?
It is a partial fatty-acid oxidation inhibitor, so it decreases O2 consumption in ischemic tissue and decreases contractility by inhibiting late inward sodium current; used when other anti-anginal drugs don’t work- it decreases left ventricular wall stiffness and improves coronary circulation
What methods are used to treat variant or angiospastic angina?
Nitrates and CCBs are preferred because BBlockers will not dilate spastic coronary vessels.
What is the most effective drug combo for angina?
B-blockers and a vasodilator (start with nitrates, move to CCBs)
How do you avoid reflex tachycardia with the use of nitrates?
Use CCBs and BBlockers
Why would you never prescribe nifedipine and a nitrate?
Nifedipine causes reflex tachy and so does a nitrate, double reflex tachy is BAD NEWS!
What is the MOA for Sildenafil?
acts as a selective inhibitor of cGMP PDE5 to maintain relaxation of blood vessels
What are indications for Sildenafil use?
Tx for male ED, pulmonary HTN
Max concentrations are reached in ____ minutes with sildenafil and the half-life is ____ hours
30-120, 4 hours
How is Viagra metabolized?
In the liver by CYP3A4
What are two side effects of sildenafil?
Vasodilation side effects, visual impairment due to inhibition of PDE-6 (blue color, photophobia or blurred vision)
What are contraindications for sildenafil?
Pregnant or lactating women, no use in infants or children.
Current use of nitrates or nitrates (causes very low BP) or alpha blockers (not as extreme, but still low BP)
Why does GRAPEFRUIT, cimetidine, erythromycin, quinidine, etc cause an excess in side effects when taken with Sildenafil?
Because they inhibit CYP3A4 and 2C9 enzymes which are supposed to be around to metabolize sildenafil
What are the more selective PDE-5 inhibitors? Why is that a good thing?
Vardenafil (Levitra) and Tadalafil (Cialis); less visual disturbances
What sets vardenafil apart from other PDE5 inhibitors?
It achieves plasma concentration sooner than sildenafil and tadalafil, which may result in faster onset of action
What sets tadalafil from other PDE5 inhibitors?
Duration of action is longer than sildenafil and vardenafil leads to increased spontaneity
