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51 Cards in this Set
- Front
- Back
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How can you remember the Ca channel blockers?
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14 days in nigeria anytime beats doing pharm with vera
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What is "14 days in nigeria anytime"?
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1,4-dihydropyridine
-Nifedipine -Amlodipine |
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What is "Beats Doing Pharm w/ Vera"?
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Benzothiazepine - Diltiazem
Phenylalkylamine - Verapamil |
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What type of calcium channels do CCBs block?
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L-type calcium channels
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What important physiological mechanism is blocked by blocking calcium channels?
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-Cardiac muslce contractility
-Cardiac conduction at SA/AV nodes -Arterial smooth muscle contraction |
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What is the normal endogenous agonist of L-type calcium channels?
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Voltage
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What is the result of voltage activation of L-type calcium channels?
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Calcium influx
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What 2 cells ARE targets of CCBs?
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-Cardiovascular
-Arterial smooth muscle |
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What 2 cells ARE NOT targets of CCBs?
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-Skeletal muscle
-Neurons |
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Why aren't skeletal muscle cells affected by calcium channel blockers?
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Because they have a different isoform of the l-type calcium channel, and rely on intracellular calcium store release anyway
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Why aren't neurons affected by CCBs?
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-They have N- and P-type calcium channels that mediate NT release
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What is the good thing about CCBs not targeting neurons?
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They cause few CNS side effects
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What are the 3 distinct, heterogenous chemical classes of CCBs?
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-1,4-dihydropyridines
-Benzothiazepines -Phenylalkylamines |
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Phenylalkylamine
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Verapamil
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Benothiazepine
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Diltiazem
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1,4-Dihydropyridines
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-Nifedipine
-Amlodipine |
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What are the CCBs as a group like in general?
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Extremely heterogeneous
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Why do we say the CCBs are so heterogeneous?
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Because they have marked differences in chemical structure, binding sites, and tissue selectivity
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What are the consequences of the heterogeneity of the CCBs?
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Differences in
-Clinical activity -Therapeutic indications |
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Which two CCB classes are most similar?
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-Benzothiazepines
-Phenylalkylamines |
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Why are the CCBs selective for Cardiac cells?
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-Cardiac cells densely express L-type Ca channels
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For what 2 processes is the calcium influx mediated by L-type calcium channels necessary?
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-SA and AV action potential upstrokes
-Atrial and Ventricular muscle contraction |
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Why do the CCBs specifically target arterial smooth muscle cells?
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Because they rely solely on L-type Ca channels for their excitability and contraction.
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How do VSMCs contract?
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In response to GRADED membrane potential changes - not APs
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What is responsible for changes in the graded membrane potentials of VSMCs?
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Circulating neurotransmitters and factors
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What VSMCs are relaxed by CCBs, and what is the implication?
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Only arterial VSMCs - Not venous
So they decrease AFTERLOAD but not preload |
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How do the CCBs block the L-type calcium channels?
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By each binding to specific domains on the channel.
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What does each binding site of the individual ca channel blockers influence?
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The channel's gating mechanism
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How are the individual binding sites of each of the CCBs related?
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By complex interactions
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What is the implication of the complex interactions of the 3 CCB classes?
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They are only prescribed individually, never together to avoid unpredictable effects.
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What is the effect of the CCBs each having different binding sites?
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They have different pharmacological effects
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What 2 types of binding are generally seen with CCBs?
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-Use dependent binding
-Voltage dependent binding |
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What does Use dependent binding mean?
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The drugs bind deeper in the channel when it is open.
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What 2 drugs are Use-dependent binding CCBs, and what cells do they target?
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-Diltiazem
-Verapamil Target Cardiac cells |
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What drug is Voltage dependent binding and what cells does it target?
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Nifedipine
-Targets vascular smooth muscle cells - arterial |
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What does voltage-dependent binding mean?
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Nifedipine binds to the surface of calcium channels.
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What do all 3 CCBs have in common?
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Blocking the Ca pore so that calcium influx cannot occur.
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So what CCB is best at increasing peripheral vasodilation?
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Nifedipine
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Although Verapamil and Diltiazem are "cardio-selective", do they only do they ONLY block AV node conduction?
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No, they can also cause peripheral vasodilation like Nefedipine, just not as good.
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What 2 drugs are best at causing coronary vasodilation?
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-Diltiazem
-Nifedipine |
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Which CCBs affect preload?
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NONE
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Which CCBs decrease Afterload?
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ALL
-Nifedipine is best |
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Which CCB is best at decreasing contractility of the heart muscle?
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Verapamil
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Which CCB is the best at reducing cardiac contractility?
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Verapamil
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What does Diltiazem do to contractility?
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Nothing or decreases it
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What does Nifedipine do to contractility?
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May increase or decrease it
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How does Verapamil affect heartrate?
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May not change it, or decreases it
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How does Diltiazem affect heartrate?
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Decreases it
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How does Nifedipine affect heartrate?
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No change or increase by reflex tachycardia
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How do each of the CCB's affect AV conduction?
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Verapamil strongly reduces it
Diltiazem slightly reduces it Nifedipine has no effect |
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What CCBs reduce SA firing rate?
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Verapamil and Diltiazem
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