Opie calcium channel blockers

Question 1

The long-lasting opening calcium channel is termed ___, which is blocked by ___ and increased in activity by ____

Answer 1

L-type; calcium channel blockers; catecholamines

Question 2

The function of the L-type channel is to ____

Answer 2

The function of the L-type is to permit the influx of the requisite amount of calcium ions needed for initiation of contraction via the release of stored calcium ions from the SR

Question 3

T-type channels open and more negative or more positive potentials compared to the L-type

Answer 3

opens at more negative potentials

Question 4

Which channel plays an important role in the initial depolarization of the SA and AV nodes

Answer 4

T-type (transient)

Question 5

CCB’s block the entry of calcium through the calcium channel on both ___ and ___, so that less calcium is available to the contractile apparatus. The result is ___ and ___

Answer 5

smooth muscle, myocardium; vasodilation and negative inotropic effect

Question 6

How are CCBs classified?

Answer 6

Dihydropyridines (DHPs) vs non-dihydropyridines

Question 7

DHP’s bind to the same site on the __-subunit

Answer 7

alpha-1 (N sites); greater inhibitory effect on vascular smooth muscle compared to myocardium (conferring property of vascular selectivity)

Question 8

non-DHP’s are also known as ___

Answer 8

heart rate lowering CCBs

Question 9

Name a DHP

Answer 9

Amlodipine

Question 10

Name a non-DHP

Answer 10

diltiazem and verapamil

Question 11

What is the most important distinguishing factor between non-DHP and DHPs

Answer 11

non-DHPs act on nodal tissue and furthermore they are effective with SVTs (decrease impulse formation from sinus node and slow HR)

Question 12

List the 5 clinical effects of non-DHPs

Answer 12

(Verapamil / Diltiazem)

1. antiarrhythmic
2. arterial dilator
3. negative inotropic
4. LVH decrease
5. Postinfarct

Question 13

Serum 1/2 life of verapamil in dogs

Answer 13

Serum half lives of 0.8 and 2.5 hours reported in dogs (2-8 hours after single IV dose in people)

Question 14

Verapamil is high or low protein bound

Answer 14

90% is bound to plasma proteins

Question 15

Verapamil MOA

Answer 15

Inhibits action potential of upper and middle regions of AV node where depolarization is calcium mediated. Inhibits one limb of reentry circuit, believed to underlie most paroxysmal SVTs

Question 16

Bioavailability of diltiazem in cats and dogs

Answer 16

Bioavailability in cats ranges from 50-80% with peak levels occurring after oral dosing

Bioavailability approximately 25% in dogs

Question 17

Serum 1/2 life of diltiazem

Answer 17

Cats - 2 hours

Dogs - 3 hours

Question 18

Diltiazem is approximately __ bound to proteins

Answer 18

70-75%

Question 19

Diltiazem is metabolized by the ___

Answer 19

Liver into several metabolites; 2 of which are active

Question 20

2 major forms of diltiazem we use

Answer 20

Cardiazem CD - In cats, bioavailability 22-59%, half life 411 minutes (+/- 59 minutes), peak levels achieved in 340 minutes (+/- 140 minutes)

Dilacor XR - In cats, bioavailability of 94%, doses of 1 mg/kg maintained therapeutic serum levels for 8 hours

Question 21

Dose of diltiazem IV for tx of SVT in dog

Answer 21

0.05 to 0.25mg/kg IV over 5 to 15 min

Question 22

Dose of verapamil for tx of SVT in dogs

Answer 22

Verapamil is administered as 0.05-mg/kg boluses administered over 3 to 5 minutes up to 3 times (0.15 mg/kg total dose) over a total of 15 to 30 minutes while monitoring the ECG

Question 23

Dose of diltiazem PO for atrial fibrillation / flutter

Answer 23

1.5mg/kg PO

Question 24

Calcium channel blockers are effective for ___

Answer 24

Suppressing accelerated idioventricular rhythms in dogs following shock-induced myocardial injury and myocardial infarction

Question 25

Amlodipine - high or low protein bound?

Answer 25

High (93%)

Question 26

Terminal plasma half-life of amlodipine in dogs

Answer 26

30 hours in dogs (prolonged in dogs with hepatic dysfunction or hypertension)

Question 27

In cats, amlodipine has effects on blood pressure within __ hours

Answer 27

4 hours; can last up to 30 hours

Question 28

Amlodipine is metabolized by

Answer 28

Liver

Question 29

Diltiazem can be administered at a dose of ___ to __ mg/kg IV over __ minutes 3

Answer 29

Diltiazem can be administered at a dose of 0.05 to 0.25 mg/kg IV over 5 to 15 minutes and appears to be as effective as verapamil in dogs

Question 30

The main electrophysiologic effect is a negative or positive chronotropic and dromotropic effect on the ___ node

Answer 30

The main electrophysiologic effect is a negative chronotropic and dromotropic effect on the AV node

Question 31

Amlodipine should be used cautiously in patients with __ due to __ effects

Answer 31

Because amlodipine may have slight negative inotropic effects, it should be used cautiously in patients with heart failure or cardiogenic shock

Question 32

In dogs, ___ hyperplasia has been reported when used long term

Answer 32

gingival hyperplasia