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Flashcards in Drugs acting on blood vessels Deck (20):
1

3 types of vasoconstrictors

1. Nonselective alpha-agonists = Epinephrine and Norepinephrine
2. Selective alpha-1 agonists = Phenylephrine
3. Direct and Indirect Sympathomimetics = Ephedrine, pseudoephedrine, phenylpropanolamine (PPA)

2

Types of vasodilators

Sympatholytics
ACE inhibitors
Angiotensin II antagonists
Direct-acting vasodilators
Calcium channel blockers

3

7 types of sympatholytics

1. Non-selective alpha-blockers = Phentolamine, Phenoxybenzamine
2. Selective alpha-1 blocker = Prazosin, terazosin, doxazosin
3. Presynaptic alpha-2 agonist = Clonidine
4. Nonselective beta-blockers = Propranolol
5. Selective beta-1 blockers = Atenolol
6. Beta and alpha-1 blocker = Carvediolol
7. Indirect sympatholytics = Bretylium

4

ACE Inhibitor drugs

Captropril
Enalapril
Benazepril
Lisinopril

5

MOA of ACE Inhibitors

Inhibition of angiotensin-converting enzyme
Inhibition of angiotensin II synthesis
Inhibition of aldosterone
Reflex increase in renin
increased bradykinin level (vasodilator and stimulates PGs biosynthesis which is also a vasodilator)

6

Therapeutic uses of ACE Inhibitors

CHF
Hypertension
Chronic renal insufficiency in cats

7

Pharmacokinetics of ACE Inhibitors

Enalapril is available orally and parenterally, but the others are only oral
Food reduces intestinal absorption of Captopril
Enalapril has a slower onset and longer duration of action than Captopril in dogs
Benazepril and Lisinopril are long-acting
Enalapril and Benazepril are activated in the liver
Benazepril is least likely to require dosage modification in renal failure patients because of significant excretion in bile (50%)

8

Adverse effects of ACE Inhibitors

Hypotension
May lower intraglomerular pressure, decreaseing GFR in in animals with systemic hypertension and azotemia
Captopril may cause idiosyncratic glomerular disease in some dogs
Captropril has more GI side effects than Enalapril
Captopril may cause neutropenia, proteinuria, and skin rash in some humans

9

Angiotensin II Antagonists
-drug
-MOA
-Clinical use

Losarten
Competitive antagonist of Angiotensin II receptors
Antihypertensive

10

Direct-acting Vasodilator drugs

Hydralazine - arteriolar vasodilator
Nitrates - sodium nitroprusside, nitroglcerin, isosorbide dinitrate

11

MOA of the Direct-acting Vasodilator Hydralazine

Increasing local concentrations of PGI2
May be by inhibiting Ca2+ influx into smooth muscles of arteries

12

MOA of the Direct-acting Vasodilator Nitrates

formation of the reactive radical nitric oxide (NO) which activates guanylyl cyclase
Increasing cyclic GMP
Stimulation of GMP-dependent protein kinase
Alteration of phosphorylation of proteins in smooth muscle and dephosphorylation of myosin light chain
Relaxation of smooth muscle of blood vessels

13

Calcium Channel Blockers classification

Diphenyl alkylamines - Verapamil
Benzodiazepines - Diltiazem
Dihydropyridines - Amlodipine, Nifedipine

14

MOA of Calcium Channel Blockers

Inhibit the influx of extracellular Ca2+ across myocardial and smooth muscle cell membranes
Decrease in intracellular Ca2+ inhibits myocardial contraction and results in dilation of the coronary and systemic arteries

15

Calcium Channel Blocker effects on the heart

Negative inotropic effect
negative chronotropic effect
Increase oxygen delivery to the myocardial tissue
Decreased afterload
Coronary vasodilation

16

Calcium Channel Blocker effects on blood vessels

Decrease peripheral resistance
Decrease systemic blood pressure

17

Therapeutic use of Calcium Channel Blockers
-Antiarrhythmic

Class IV
Verapamil and diltiazem are used int he treatment of supraventricular tachyarrhythmias

18

Therapeutic use of Calcium Channel Blockers
-Antihypertensive

Amlopdipine is recommended as the first-line antihypertensive in cats unless the cause is hyperthyroidism, in this case Beta-blocker is used

19

Therapeutic use of Calcium Channel Blockers
-Myocardial hypertrophy

Diltiazem is the drug of choice in cats

20

Adverse effects of Calcium Channel Blockers

Bradycardia and AV block
Hypotension
GI side effects
Elevated liver enzymes (temporary)