Cardiac

Question 1

nitroglycerine

Answer 1

• venous vasodilator > reduces preload
• nitric oxide system: GTP > cGMP > decreased Ca++
• 1 hour onset, lasts 2-12 h
• topical ointment (2%); applied on the pinna of ears for cats; hepatic metabolism; wear gloves, can cause a rash/hypotension

Question 2

isosorbide dinitrite

Answer 2

• venous vasodilator > reduces preload

- for angina, congestive heart failure

Question 3

hydralazine

Answer 3

• arterial vasodilator > reduces afterload
• block IP3 pathway: PLC > block IP3 > no Ca++ from SER
• 1h onset, peaks at 3h, lasts 8-10h
• extensive hepatic metabolism; can cause tachycardia

Question 4

amlodopine

Answer 4

• arterial vasodilator > reduces afterload
• calcium channel blocker
• t 1/2 long, 35h, peak 6h
• oral; dihydropyridine; cats mainly (dogs too), hepatic metabolism

Question 5

nitroprusside

Answer 5

• balanced vasodilator
• nitric oxide system: GTP > cGMP > decreased Ca++
• t 1/2 short, minutes
• IV, CRI; potent; to lower left atrial pressure; metabolized to cyanogen; eliminated in urine, feces, exhalation; can cause cyanide toxicity

Question 6

prazosin *

Answer 6

• balanced vasodilator
• treats congestive heart failure or hypertension
• alpha 1 antagonist
• peak 2-3 hours
• oral; reduces peripheral vascular resistance; metabolized via liver, excreted in bile/feces; not used frequently
• also, in autonomic: treats urinary retention by relaxing sphincter (faster and better than phenoxybenzamine)

Question 7

enalapril *

Answer 7

• balanced vasodilator
• ACE inhibitor (RAAS)
• onset 4-6h, lasts 12-14h
• excretion 95% renal; pro-drug; compete with angiotensin I for Ace binding site; monitor renal; not well absorbed by horses; hyperkalemia, low GFR

Question 8

sildenafil *

Answer 8

-pulmonary vasodilator
-PDE5 inhibitor
-t 1/2 6 hours
= Viagara

Question 9

benazepril *

Answer 9

• balanced vasodilator
• ACE inhibitor (RAAS)
• onset 1.5h, dogs 4h, cats 16-23h
• renal and biliary excretion; treats systemic hypetension; pro-drug; compete with angiotensin I for Ace binding site; monitor renal; hyperkalemia, low GFR

Question 10

quinidine

Answer 10

• class Ia anti-arrhyth.
• blocks sodium influx > prolongs AP duration
• treats supraventricular and ventricular arrhythmia
• t 1/2 5-6h
• for conversion of fibrillation in horses; extensively protein bound; competes with digoxin’s binding site; lots of hypotension and GI disturbances in dogs

Question 11

procainamide *

Answer 11

• class Ia anti-arrhyth.
• blocks sodium influx > prolongs AP duration
• treats supraventricular and ventricular arrhythmia
• t 1/2 3h
• abolishes SVT; second choice after lidocaine for life threatening V-tach; less cardio-depressant than quinidine; occasional GI upset with oral; limited avail.

Question 12

lidocaine *

Answer 12

• class Ib anti-arrhyth.
• blocks sodium influx > prolongs AP duration
• treats ventricular tachyarrhythmia
• IV bolus lasts 10-20 min
• first choice for life threatening ventricular tachyarrhythmias; IV only; high first pass metabolism; CNS excitement and seizures; cats more sensitive
• also, in anesthesia

Question 13

mexiletine

Answer 13

• class Ib anti-arrhyth.
• blocks sodium influx > prolongs AP duration
• ventricular arrhythmia (VPC)
• t 1/2 3-4h
• oral, 85% bioavailability, less 1st pass metabolism than lidocaine; GI (vomiting) issues, reduced if given with food; CNS signs at high doses; no neg. inotrope like sotalol

Question 14

flecainide

Answer 14

• class Ic anti-arrhyth.
• blocks sodium influx > prolongs AP duration
• not used often, this is one example of a class IC

Question 15

propanolol

Answer 15

• class II anti-arrhyth.
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• treats supraventricular and ventricular arrhythmia
• t 1/2 2h
• also decreases ventricular contraction vs. atropine that doesn’t; dose dependent; bronchoconstriction; do not combine with calcium channel blockers (both negative inotropes); liver exc.

Question 16

sotalol

Answer 16

• class II +III anti-arrh
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• treats supraventricular and ventricular arrhythmia
• t 1/2 5 hours; peak at 2h
• also a K+ channel blocker class III (VPC); renal exc.; first choice for ventricular arrhythmias; esp. for boxers with Arrythmogenic Right Vent. Cardiomyopathy (chronic); neg. inotrope

Question 17

carvedilol

Answer 17

• class II anti-arrhyth.
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• treats supraventricular and ventricular arrhythmia
• tabs; selective alpha 1 blocker too; antioxidant effects; reduces morbidity and mortality in humans with dilated cardiomyopathy; controversial in vet. Med.; liver exc.

Question 18

atenolol

Answer 18

• class II anti-arrhyth.
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• treats hypertrophic cardiomyopathy in cats
• 5-6h, lasts 12 hours
• cardioselective beta 1; for atrial fibrillation; prevent sudden death from ventricular arrhythmias; caution in cats with asthma; renal exc.; bradycardia, AV block

Question 19

esmolol

Answer 19

• class II anti-arrhyth.
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• for acute termination of SVT
• t 1/2

Question 20

metoprolol

Answer 20

• class II anti-arrhyth.
• blocks beta adrenergic stimulation (slow AV nodal cond.)
• treats supraventricular and ventricular arrhythmia
• cardioselective beta 1

Question 21

amiodarone

Answer 21

-class III anti-arryhth.
-blocks potassium efflux > prolongs AP > prolongs repol.
-treats supraventricular and ventricular arrhythmia
slow onset; 3 days half lie
-maximal drug action at slower heart rates; blocks all Ikr; for atrial fibrillation in dogs; properties of all 4 classes; drug accumulates in fat, myocardium, liver, lungs; GI upset

Question 22

verapamil

Answer 22

• class IV anti-arrhyth.
• blocks Ca++ influx (slow AV nodal conduction)
• acute termination of SVT
• t 1/2 2-4 h
• high first pass metabolism; IV; binds equally to cardiac and vasculature sites; negative inotrope, give slowly

Question 23

diltiazem

Answer 23

-class IV anti-arrhyth.
-blocks Ca++ influx (slow AV nodal conduction)
-reduced ventricular response rate to SVT
-t 1/2 cat 2h, dog 3h, horse 1.5h
for atrial fibrillation; cardiac specific Ca++ channel blocker; fast absorption oral, moderate 1st pass metabolism; slow release available; neg. inotrope; GI effects in cats

Question 24

digoxin *

Answer 24

• positive inotrope
• inhibits Na+/K+ ATPase > more Ca++ in
• t 1/2 dogs 30h, cats 48h, horses 23h
• negative chronotrope (commonly for atrial fibrillation in dogs; slows SA node discharge and AV nodal conduction); does on lean body mass; renal excr., Gi issues

Question 25

pimobendan *

Answer 25

- inodilator - PDE3 inhibitor and calcium sensitizer - balanced vasodilator (inodilator) - peak 2h, lasts 8-12 hours - hepatic metabolism; minimal adverse effects, possible proarrhythmic;orals sold in Canada; Kaplan curve (lived longer, took longer to treat)