Treatment of Angina Flashcards
(53 cards)
Nitroglycerine
• MOA
- Nitroglycerine (glycerine with three nitrates) is ingested then denitrated to release NO that goes to activate Guanylate Cyclase
- Guanylate Cyclase generates cGMP that goes on to activate PKG that mediates smooth muscle relaxation
What are the 2 main effects of nitroglycerine?
VENOdilation = reduction in PRELOAD
• Decreased Pressure during diastole increasing subendocardial bloodflow
ARTERIAL dilation = Reductino in AFTERLOAD
CORONARY vasodilation
• SELECTIVE vasodilation of epicardial and collateral coronary vessels
• REVERSES/PREVENTS coronary VASOSPASM
**ONLY DRUG that produces venodilation and reduction in preload*
What other effects does nitroglycerine have on hemodynamics (besides reduced preload and venodilation)? • BP • HR • Vascular Resistance • Cardiac Output
BP: unchanged or SLIGHT reflexive increase
HR: unchanges or SLIGHT reflexive increase
Vascular Resistance - DECREASE PULMONARY vascular resistance
Cardiac Output: slight reduction
What are some different methods of administration for nitroglycerine?
- Oral
- Transdermal (patch)
- Mucosal
- Intravenous
What are the main adverse side effects associated with nitrates?
HYPOTENSION: Results from higher doses of nitrates that cause ARTERIAL vasodilation
• Reflex tachycardia or WORSENING Angina
• Dizziness, Orthostatic HypoTN, SYNCOPE
HEADACHE: Vasodilation of meningeal vasomotor arteries
RASH: caused by LONG acting nitrates (cutaneous patches)
What drugs are contraindicated with nitrates?
BONER PILLS - both cause act on the cGMP pathway, may result in MYOCARDIAL ISCHEMIA
Sildenifil = Viagra
What is the problem with dosing the nitrates?
TOLERANCE - Dosing has to be sporadic to keep your body from adjusting to the continuous exposure
What are the mechanisms of Nitrate Tolerance?
CYSTEINE STORES DEPLETED
• cysteine is vital for the conversion of nitrates to nitric oxide
VOLUME EXPANSION
• just increase the amount of fluid in the vasculature
NEUROHUMORAL ACTIVATION
• would lead to volume expansion via RAAS
Should you terminate Nitrate treatment immediately if a patient gets hypotensive on IV nitrates?
NO - this can cause abrupt vasospasm
What are the 2 groups of CCBs (calcium channel blockers)?
- Dihydropyridine
* Non-dihyropyridine
What drugs are classified as Dihydropyridine CCBs?
"dipines" • Amlodipine • Nefidipine • Nicardipine • Felodipine • Isradipine
What two drugs are the Non-dihyropyridines?
- Verapamil (group: phenylalkyamines)
* Diltiazem (group: benzothiazapines)
What 3 conditions are often treated by use of CCB’s?
- ANGINA
- HYPERTENSION
- SUPRAVENTRICULAR arrhythmias (atrial flutter, Atrial Fibrillation, Paroxysmal SVT)
Why does increased Ca2+ cause contraction in:
• Cardiac Myocytes
• Smooth Muscle
Cardiac:
• Ca2+ binds to TROPONIN C and reduces inhibition of ACTIN-MYOSIN cross-bridges
Smooth:
• CALMODULIN activates MLCK which PHOSPHORYLATES MYOSIN and triggers contraction
How does calcium inside the cell increase 10x in a period of only a few msec?
- Release from the ER/SR
* Capacitive Ca2+ entry
Why don’t CCB’s cause effects on all systems in the body that highly dependent on Ca2+ like neurons?
- They only act on Voltage Dependent Large Conductance (L-TYPE CALCIUM CHANNELS)
- Cardiovascular system = really the only place these are found
other calcium channel types remain unaffected)
Differentiate the dependence the different parts of the heart on L-type Calcium Channels.
Atria and Ventricles
• Ca2+ used to activate contractile machinery
SA and AV nodes:
• L-type channels are activated after the initial voltage increase induced by T-type channels
How do the CCBs modulate the actions of calcium channels?
ALL:
• Reduce the magnitude of the Ca2+ current
Verapamil and Diltiazem (non-dihydropyridines)
• Slow the recovery of the channel
What is the effects of CCBs on Cardiac and Venous/Arterial Smooth Muscle?
Cardiac Muscle:
• Reduces FREQUENCY and FORCE of contraction - Reduced CO
Arterial:
• Relaxation of arterial smooth muscle
Veins = NO EFFECT
Lack of effect on veins means that AFTERLOAD is reduces but preload is not
Differentiate the effects of Dihyropyridines and Non-dihydropyridines on Smooth muscle and Cardiac tissue.
Dihyropyridines:
• ONLY VASODILATE but they work on BOTH CORONARY AND Peripheral Arteries
Non-dihydropyridines:
• EQUIPOTENT on Cardiac Tissue and Vasculature
How does the mechanism of action explain the differences in effect of the Dihydropyridines and Non-dihydropyridines?
Dihydropyridines:
• ONLY Bind at a PARTICULAR VOLTAGE so Target SMOOTH muscle - which stays at a pretty CONSTANT VOLTAGE
Non-Dihyropyridines:
• BIND INSIDE the Ca2+ channels so they need channels that are constantly OPENING AND CLOSING TO GET INSIDE AND PERFORM ACTION
Cardiac Muscle is best at doing the opening and closing thing
Calcium Channel Blockers:
• Bioavailability
• Elimination
• Halflife
Bioavailability:
• Rapid GI absorption and EXTENSIVE 1st PASS metabolism reduces bioavailability
Elimination:
• Drug Terminated via Hepatic Metabolism
Halflife:
• SHORT for most of these EXCEPT for - Isradipide and Felodipine
What is the Bolus effect of CCBs?
• how has it been prevented?
Bolus Effect:
• Rapid absorption leads to REFLEX TACHYCARDIA, Headache, CORONARY STEAL
What precautions should you take with CCBs in a patient who has liver cirrhosis?
• which drugs would grapefruit juice be bad for?
LIVER metabolism is significant
non-dihydropyridines are acted on by CYP3A4
• Verapamil > Diltiazem