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Therapeutics 2 Exam 5 > Calcium Channel Blockers > Flashcards

Calcium Channel Blockers Flashcards

1
Q

What is the main determinant of the direction of ion flow through an ion channel?
(Concentration Gradient or Electrical Gradient)

A

Electrical gradient

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2
Q

Which ion is higher INSIDE the cell: K or Na?

A

K is higher inside the cell

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3
Q

Why is it important to keep Ca low inside the cell?

A

Ca functions in muscle contraction

-So it is important to keep Ca tightly regulated to prevent continuous muscle contraction

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4
Q

True or False: Negatively charged ions are able to cross the membrane

A

FALSE
-negatively charged ions cannot cross the membrane
-basis for potassium and chloride

(potassium and chloride typically balance out charges across the membrane, however, when K moves, Chloride cannot follow and the charge is not balanced)

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5
Q

What is the function of sodium channels?

A

Run opposite potassium channels

-Sodium increase and movement through channels is used to cause depolarization and action potentials

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6
Q

What is Kcsa?

A

A H+ gated K+ channel from bacteria

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7
Q

What is MthK?

A

A calcium gated K channel from bactria

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8
Q

What is the function of a voltage sensor in a K channel?

A

The voltage sensor has positively charged amino acids that allow for responses to voltage changes across the membrane

-The voltage sensor moving pulls the helix away to open the channel

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9
Q

Which calcium channel blocker is important for cardiac smooth muscle contraction?

A

Cav 1.2

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10
Q

What calcium channel blocker is important in the skeletal muscle?

A

Cav 1.1

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11
Q

When calcium channel blockers such as Cav 1.1 block channels in the vascular smooth muscle, what does this cause?

A

Vasodilation

-decrease in blood pressure
-relief of angina pectoris

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12
Q

When calcium blockers such as Cav 1.2 block channels in the cardiac muscle, what is the result?

A

Antiarrhythmic

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13
Q

What is the function of the ryanodine receptor 2 (RYR2)?

A

Membrane depolarization opens calcium channels which allows calcium into the cell where it binds RYR2

-RYR2 opens after binding and functions as a calcium channel which allows calcium to be released out of its intracellular stores in the SR

-The release of calcium from the SR triggers contraction

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14
Q

What is the result of PKA phosphorylation of Cav 1.2?

A

Increases calcium influx

(increasing contraction force and AV node action potential conduction rate)

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15
Q

Extracellular Ca is responsible for contraction of what muscle?

A

Vascular Smooth Muscle

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16
Q

What is the mechanism by which calcium released from the SE is able to produce contraction?

A

Ca bind to troponin C

This causes a displacement of tropomyosin

This allows myosin to bind to actin

Resulting in contraction

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17
Q

Is extracellular Ca required for skeletal muscle contraction?

A

NO

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18
Q

What are the indications for calcium channel blockers?

A

Angina Pectoris

Arrhythmia

Hypertension

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19
Q

What are the 3 classes of calcium channel blockers?

A

Dihydropyridines

Phenylalkylamines

Benzothiazepines

20
Q

Which dihydropyridine blocker does not have a chiral center?

A

Nifedipine

21
Q

Which calcium diydropyridine has the highest affinity for the calcium channel?

A

Isradipine

22
Q

Which dihydropyridine has a slow onset of action?

A

Amlodipine

*is a good thing, blocking channels too quickly can throw off the heart

23
Q

Which calcium dihydropyridine is hydrophobic and used in hemorrhage?

A

Nimodipine

24
Q

Which calcium dihydropyridine is given IV to treat hypertension when PO drugs cannot be used?

A

Clevidipine

25
Q

How do the positive and negative enantiomers of dihydropyridines effect gating?

A

+ enantiomer interferes with gate opening, blocks current

  • enantiomer interferes with gate closing, potentiates
26
Q

What tissue are dihydropyridines more selective for?

A

Smooth muscle

27
Q

Due to the selectivity of dihydropyridines, how does this contribute to their effects?

A

-Do not compromise cardiac function

-Not antiarrhythmics

28
Q

At what membrane potential are dihydropyridines more potent?

A

Positive values

29
Q

Where do dihydropyridines bind on the calcium channel?

A

On the outside, between helices that are needed for the channel to open

*Bind closed channels and prevent opening (tonic block)

30
Q

What are some special considerations with Nimodipine use?

A

-Selective for cerebral arteries
-Used in sub-arachnoid hemorrhage to prevent neuropathy

31
Q

Which dihydropyridine depresses cardiac function?

A

Nifedipine

32
Q

What are some important pharmacological factors of dihydropyridines?

A

-Highly bound to serum proteins
-Undergo first pass metabolism in the liver

33
Q

What warnings are associated with Nifedipine rapid release?

A

DO NOT USE
-increased risk of myocardial infarction
-Rapid BP decrease can cause tachycardia

34
Q

What is the only drug in the phenylalkylamine class?

A

Verapamil

35
Q

Is Verapamil more or less potent than dihydropyridines?

A

Less potent

36
Q

What are some important effects of Verapamil?

A

-Slows conduction through the SA and AV nodes

(sometimes good, sometimes bad)

Blunts reflex tachycardia

Exhibits frequency dependent block

37
Q

Where does verapamil bind on the calcium channel?

A

In the pore

*blocks Ca influx
*Channel must be open for drug to bind (frequency dependent block)

38
Q

What drug is the only benzothiazepine?

A

Diltiazem

39
Q

Is diltiazem more or less potent than dihydropyridines?

A

Less potent

40
Q

How does diltiazem work?

A

It directly inhibits the heart
(less than verapamil, but more than DHPs)

41
Q

What kind of block does diltiazem use?

A

Frequency dependent block with some tonic block

42
Q

Where does diltiazem bind on the calcium channel?

A

Binds on the side but some of it projects into the pore

(shows both tonic and frequency dependent block)

43
Q

What are the significant side effects of dihydropyridines?

A

Ankle edema

Facial flushing (vasodilator)

Tachycardia

44
Q

What are the significant side effects of diltiazem?

A

Ankle edema

45
Q

What are the significant side effects of verapamil?

A

Ankle edema
Constipation

Therapeutics 2 Exam 5 (9 decks)

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