Drugs acting on blood vessels Flashcards
3 types of vasoconstrictors
- Nonselective alpha-agonists = Epinephrine and Norepinephrine
- Selective alpha-1 agonists = Phenylephrine
- Direct and Indirect Sympathomimetics = Ephedrine, pseudoephedrine, phenylpropanolamine (PPA)
Types of vasodilators
Sympatholytics ACE inhibitors Angiotensin II antagonists Direct-acting vasodilators Calcium channel blockers
7 types of sympatholytics
- Non-selective alpha-blockers = Phentolamine, Phenoxybenzamine
- Selective alpha-1 blocker = Prazosin, terazosin, doxazosin
- Presynaptic alpha-2 agonist = Clonidine
- Nonselective beta-blockers = Propranolol
- Selective beta-1 blockers = Atenolol
- Beta and alpha-1 blocker = Carvediolol
- Indirect sympatholytics = Bretylium
ACE Inhibitor drugs
Captropril
Enalapril
Benazepril
Lisinopril
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)
Therapeutic uses of ACE Inhibitors
CHF
Hypertension
Chronic renal insufficiency in cats
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%)
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
Angiotensin II Antagonists
- drug
- MOA
- Clinical use
Losarten
Competitive antagonist of Angiotensin II receptors
Antihypertensive
Direct-acting Vasodilator drugs
Hydralazine - arteriolar vasodilator
Nitrates - sodium nitroprusside, nitroglcerin, isosorbide dinitrate
MOA of the Direct-acting Vasodilator Hydralazine
Increasing local concentrations of PGI2
May be by inhibiting Ca2+ influx into smooth muscles of arteries
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
Calcium Channel Blockers classification
Diphenyl alkylamines - Verapamil
Benzodiazepines - Diltiazem
Dihydropyridines - Amlodipine, Nifedipine
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
Calcium Channel Blocker effects on the heart
Negative inotropic effect negative chronotropic effect Increase oxygen delivery to the myocardial tissue Decreased afterload Coronary vasodilation
