Vasodilators 1 Flashcards
Dopamine
Class: Vasoconstrictor
Uses/Indications: increase BP (in hypotensive conditions)
-restore CO (by constricting the systemic vessels)
-improve blood flow to pressure-dependent vasodilated organs under special conditions (e.g. hemorrhagic or hypotensive shock)
-reduction of local/regional blood flow (e.g. achieving hemostasis in surgery, for reducing diffusion of local anesthetic, and for reducing mucous membrane congestion)
IV Only
- useful in patient with hypotensive shock (after hypovolemia is corrected)
- acute heart failure
Dose-dependent Differential Receptor MOA
- low dose: acts on peripheral D1 receptors to produce selective dilation of renal and splanchnic nerves
- mid dose: acts on B1 receptors in the heart to produce tachycardia and increased contractility (in acute decompensated HF)
- high dose: acts on alpha1 receptors to increase peripheral vascular resistance (used for shock)
adverse effects similar to other catecholamines
Why Use Vasodilator Drugs
Blood flow improvement (ischemic tissues/organs)
Blood Pressure Reduction
Heart Pump Function Improvement
Clonidine
Class: Presynaptic Alpha 2 receptor agonist
- causes reduction in the adrenergic outflow from the CNS and thereby reduces catecholamine release from peripheral adrenergic nerves
- also reduces renin release and its consequent actions
- lowers HR and CO more than methyldopa
Indications/Uses: HTN (reduces BP in supine position, rarely causing postural hypotension)
Cautions:
- severe coronary insufficiency
- recent MI
- cerebrovascular disease
- chronic renal failure
Adverse Reactions:
- dry mouth (activation of salivary gland alpha 2 adrenergic receptors)
- drowsiness and dizziness
- constipation
- rebound HTN on abrupt withdrawal (downregulation of alpha 2 receptors and upregulation of alpha 1 receptors)
Alpha-MethylDopa
Class: presynaptic alpha 2 agonist
- reduction of adrenergic outflow from the CNS and thereby reduces catecholamine release
- *acts at different pre-synaptic alpha 2 receptor sites than those for clonidine
Indications/Uses:
-HTN during pregnancy (reduces BP in the supine position, rarely causing postural hypotension)
Contraindications:
-liver disease
Adverse Reactions:
- positive Coombs test
- sedation
- lactation in men and women (inhibition of dopaminergic system in hypothalamus)
- fever
- jaundice
Phentolamine
Class: competitive non-selective alpha1/2 receptor blocker
- leads to arterial and venous dilation resulting in reduced peripheral vascular resistance and venous return
- BP is reduced more in upright than supine position
- Reflex tachycardia
- Retention of salt and water (need to administer with a diuretic)
- more effective when used in combo with diuretic and beta-blocker
Indications/uses: pheochromocytoma and prevention of dermal necrosis after IV NE and Dopamine
Contraindications:
-CAD (hypotension can evoke angina and AMI)
Adverse Reactions:
- acute and prolonged hypotension (due to B2 receptor activation and high NE levels)
- accompanying tachycardia and arrhythmias (high levels of NorEpi at Beta receptors)
Prazosin
Class: competitive selective alpha 1 antagonist
- causes arterial and venous dilation
- BP more reduced in the upright position
- NO reflex tachycardia
- retention of salt and water: use in combo with diuretic and other anti-hypertensive
Indications/uses:
- HTN (second line Tx)
- benign prostate hyperplasia (bladder and prostate smooth muscle relaxation improves urine flow)
Contraindications:
-Hypersensitivity to congener drugs (i.e. terazosin, doxazosin)
Adverse Reactions:
- “first dose” hypotension, dizziness and syncope
- nasal congestion (vasodilation by unopposed B-receptor action of NorEpi)
Benefits of B-Receptor Blockers
Lowers BP in mild to moderate HTN
In severe HTN: prevents reflex tachycardia of direct vasodilators
Reduces mortality after MI (propranolol, timolol, metoprolol)
Reduces mortality in patients with HF (carvedilol, metoprolol succinate)
**Advantageous for treating HTN in patients with these conditions
Side Effects of B-Blockers
- Smooth muscle Spasm (bronchospasm)
- exaggeration of cardiac actions (bradycardia, heart block, and negative inotropic effect)
- CNS effects (insomnia, depression)
Contraindications of Beta-Blockers
Cardiac Contraindications:
- severe bradycardia
- preexisting high-degree heart block
- untreated overt LV heart failure
Pulmonary Contraindications:
- asthma
- severe bronchospasm
CNS
-severe depression (especially for propranolol)
Active peripheral vascular disease with rest ischemia
Propranolol
Class: nonselective B1/2 receptor blocker
- reduces adrenergic outflow from the CNS and thus decreases peripheral catecholamine release from adrenergic nerves
- decreases renin release and subsequent angiotensin and aldosterone
Indications/Uses:
- HTN
- Angina Pectoris
- Hypertrophic subaortic stenosis
- supraventricular Arrhythmias
- tachycardia of digitalis intoxication
- MI
- Pheochromocytoma (in presence of alpha1 blocker)
- migraine
- essential tremor
Contraindications:
- sinus bradycardia
- > 1st degree heart block
- overt HF
- bronchial asthma or bronchiospasm or COPD
- pheochromocytoma in absence of alpha 1 receptor antagonist
Adverse Reactions
- bradycardia
- vertigo and fatigue
- sexual dysfunction
- dry mouth and assorted GI
- after prolonged regular use, some patients experience withdrawal symptoms
Precautions:
- blunting/masking of signs (i.e. tachycardia) of diabetes (hypoglycemia) and thyrotoxicosis
- increased lipids (but not HDL)
Metoprolol
Class: Selective B1 receptor blocker -decreases renin release, reduces HR and contractility Indications/Uses: -HTN -HF -Angina Contraindications: -2nd or 3rd degree heart block
Adverse Reactions:
- cardiac depression
- AV conduction block
- sexual dysfunction
Carvedilol and Labetalol Sites
Class: non-selective B1/2 and alpha 1 receptors antagonists
- decreased catecholamine release from adrenergic nerves, vasodilation, decreased HR and also renin release and subsequent angiotensin and aldosterone
- Carvedilol has an anti-oxidant properties
- Labetalol has a 5:1 Beta:alpha antagonism
Carvedilol
indications/uses:
- HTN
- HF
Contraindications:
- bronchial asthma
- 2nd or 3rd degree heart block
Adverse Reactions:
- cardiac depression
- sexual dysfunction (rare)
- blunting/masking of signs (i.e. tachycardia) of diabetes (hypoglycemia) and thyrotoxicosis
- combination of those with propranolol and prazosin
Labetalol
Indications/Uses:
- HTN (oral form)
- Pregnancy-induced HTN
- HTN emergencies (IV form)
Contraindications:
- HF
- Bronchial Asthma
- 2nd or 3rd degree Heart block
Adverse Reactions
- cardiac depression
- sexual dysfunction (rare)
- hepatic injury
- blunting/masking of signs
- combo of those with propranolol and prazosin
