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Therapeutics 2 - Exam 5 > calcium channel blockers > Flashcards

calcium channel blockers Flashcards

hockerman

1
Q

what are ion channels?

A

proteins that form pores in the plasma membrane?

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2
Q

what are ion channels are categorized by?

A

gating (opening and closing)
mechanism
ion selectivity
pharmacology

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3
Q

what is a passive ion channel?

A

allows ions to flow down their electrochemical gradient

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4
Q

what gradients are used to determine the direction of ion flow?

A

concentration
electrical

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5
Q

what is the cause of negative inward potential for excitable cells?

A

selective permeability of the resting membrane to K+

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6
Q

what is the difference of free calcium between the inside and outside of the cell?

A

inside –> very low (100 nM)
outside –> high (1.5 mM) 15,000x

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7
Q

can negatively charged ion cross the membrane?

A

no

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8
Q

what is membrane potential set by during rest?

A

K+ permeability

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9
Q

what is the ion that reduces mV?

A

K+

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10
Q

what is the ion that increased mV?

A

Na+

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11
Q

what is the effect of calcium contraction?

A

reduced mV

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12
Q

where do the opening on ion-selective channels drive the membrane potential towards?

A

the equilibrium potential of the permeant ion

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13
Q

what is the Kcsa?

A

H-gated K+ channel from bacteria
(v shaped)

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14
Q

what is the MthK?

A

Ca2+ gated K+ channel from bacteria that is crystallized in the presence of Ca2+
(up and down swiggling lines)

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15
Q

what is KvAP

A

bacterial voltage-gated K+ channel
(crazy squiggling lines)

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16
Q

what are the voltage-gated calcium channels?

A

Cav1.1
Cav1.2
Cav1.3
Cav2.1
Cav2.2
Cav2.3

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17
Q

what is Cav1.1?

A

L-type calcium channel in the skeletal muscle that is a voltage sensor in E/C coupling

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18
Q

what is Cav1.2?

A

L-type calcium channel in the cardiac and smooth muscle that contracts with calcium entry

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19
Q

what is Cav1.3?

A

L-type calcium channel in the neurons and endocrine cells that is triggered for hormone secretion

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20
Q

what is Cav2.1?

A

P/Q-type calcium channel in the neurons that triggers neurotransmitter release at synapse

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21
Q

what is Cav2.2?

A

N-type calcium channel in neurons that triggers neurotransmitter release at synapse

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22
Q

what is Cav2.3?

A

R-type calcium channel in the neurons with an unknown function

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23
Q

what is the effects of blocked calcium channels in vascular smooth muscle?

A

vasodilation
reduced BP
relief of angina pectoris

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24
Q

what are the Effects of blocked calcium channels in cardiac muscle and SA/AV node?

A

antiarrhythmic

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25
Q

what is CICR?

A

calcium-induced calcium release
cause of vascular smooth muscle contraction

26
Q

what is the MOA of CICR?

A

calcium influx via Cav1.2 induced release of calcium from intracellular stores via RYR2 in the SR

27
Q

what is MOA of vascular smooth muscle contraction?

A

Calcium channels (L-type) open and release intracellular calcium stores –> increases intracellular calcium concentration –> Calcium binds to calmodulin and activates myosin LC kinase (MLCK) –> MLCK phosphorylates myosin LC, creating myosin LC-PO4 –> Myosin LC-PO4 interacts with actin –> leading to muscle contraction

28
Q

what is required for contraction of cardiac and smooth muscle?

A

extracellular calcium

29
Q

what are the effects of PKA phosphorylation of Cav1.2?

A

increased calcium influx –> increases contractility/force of contraction –> increases AV nodal action potential conduction rate

30
Q

what is the MOA of cardiac muscle contraction?

A

Calcium ions are released from the sarcoplasmic reticulum and bind to troponin C –> displacement of tropomyosin –> myosin to bind actin and induce contraction

31
Q

what is the MOA of skeletal muscle contraction?

A

Mechanical coupling between activated Cav1.1 and RYR –> releases calcium from the SR to the muscle cytoplasm –> released calcium binds to troponin –> allows actin and myosin to interact and induce contraction (does not require extracellular calcium)

32
Q

what are the clinical applications of calcium channel blockers?

A

angina pectoris
arrhythmia
hypertension

33
Q

what are the distinct classes of CCBs?

A

dihydropyridines
phenylalkylamines
benzothiazepines

34
Q

what is the structure of dihydropyridines?

A

dihydropyridine ring
aryl group
chiral center
ester linked side chains

35
Q

what drugs are dihydropyridines?

A

nifedipine (procardia)
isradipine (dynacirc)
felodipine (plendil)
amlodipine (norvasc)
nisoldipine (sular)
nimodipine (nimotop)
nicardipine (cardene)
clevidipine (cleviprex)

36
Q

what is clevidipine?

A

cleviprex
short-acting dihydropyridine give IV to treat HTN when oral administration is not possible/desirable

37
Q

what is the half-life of clevidipine?

A

1 to 15 minutes

38
Q

what is the metabolism of clevidipine?

A

esterases

39
Q

what is blockade mechanism of dihydropyridines via pair of enantiomers?

A

positive –> blocks current and interferes with gate opening
negative –> potentiates current and interferes with gate closing

40
Q

what are the tissue selectivity of dihydropyridinees?

A

most potent in relaxing smooth as a result of amino acid differences in channel splice variants and differences in membrane potential properties

41
Q

when is vascular selectivity of dihydropyridines observed?

A

in functional/intact cells
not binding assays

42
Q

what are the characteristics of dihydropyridine block?

A

voltage-dependent (affinity of drug the channel is different at different voltages)
no frequency dependence
marked tonic block

43
Q

what is binding of dihydropyridines?

A

bind allosterically (outside of pore) to closed channels and preventing opening

44
Q

what is the vascular selectivity of dihydropyridines?

A

marked decrease in peripheral resistance –> dilation of arterioles/little affect on venules
decreased afterload
little effect on heart rate or force of contraction

45
Q

what dihydropyridines are vasoselective?

A

nisoldipine
felodipine
nicardipine
isradipine
amlodipine
nifedipine

46
Q

what is nimodipine?

A

dihydropyridine that exhibits selectivity for cerebral arteries
used in sub-arachnoid hemorrhage to prevent neuropathy

47
Q

what are the SE of dihydropyridine?

A

reflex tachycardia secondary to vasodilation (except amlodipine)

48
Q

what is nifedipine?

A

dihydropyridine that depresses cardiac function
risk of subsequent heart attack after administration due to rapid decrease in BP leading to reflex sympathetic response/tachycardia

49
Q

what are the clinical pearls of dihydropyridines?

A

reduce oxygen demand in the heart (efficacy in angina)
may inhibit atherosclerosis

50
Q

what is the pharmacokinetics of dihydropyridines?

A

highly bound to serum proteins
undergo extensive first pass metabolism in the liver

51
Q

what is unique about amlodipine?

A

has a slow onset and long duration so it does not cause reflex tachycardia

52
Q

what are the clinical pearls of verapamil?

A

causes vasodilation that is less potent than DHPs
slows conduction through SA and AV nodes –> reduces HR and force of contraction
blunted reflex tachycardia

53
Q

what is the binding of verapamil?

A

channel has to open for verapamil to bind in the pore to block calcium influx

54
Q

what is the characteristics of phenylalkylamine (verapamil) block?

A

marked frequency dependence
very little tonic block

55
Q

what are the clinical pearls of dilitiazem?

A

less potent vasodilation than DHPs
slows conduction through SA and AV nodes
initial reflex tachycardia
directly inhibits the heart less than verapamil but more than DHPs

56
Q

what are the characteristics of a benzothiazepine block (diltiazem)?

A

some tonic block and some frequency dependence

57
Q

what are CV effects of verapamil?

A

intermediate reduction of HR
intermediate reduction of AV conduction
intermediate reduction of myocardial contraction
intermediate increase in arteriole vasodilation

58
Q

what are the CV effects of DHPs?

A

small increase of HR
large increase arteriole vasodilation

59
Q

what are the CV effect of diltiazem?

A

small reduction of HR
small reduction in AV conduction
small reduction in myocardial contraction
small increase in arteriole vasodilation

60
Q

what is the SE of diltiazem?

A

ankle edema
dizziness

61
Q

what are the SE of DHPs?

A

ankle edema
dizziness
facial flushing
HA
tachycardia

62
Q

what are the SE of verapamil?

A

ankle edema
constipation
dizziness
facial flushing

Therapeutics 2 - Exam 5 (14 decks)

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