CV Stimulants Flashcards
Alpha receptors in blood vessels affect
contraction on the vessels
Affects of epinephrine
locally increase BP through alpha receptors; increase HR and CO through Beta
Affects of norepinephrine
increased BP through alpha receptors
Affects of dopamine
at high doses increase BP (alpha) and increase HR and CO (beta)
Affects of isoproterenol
increase HR and CO (beta)
Affects of Phenylephrine
increase BP (alpha)
Affects of ephedrine
at high doses increase BP (alpha) and increase HR and CO (beta)
Activation of Alpha 1
formation of IP3 and DAG, increased intracellular calcium
Activation of Alpha 2:
inhibition of adenylyl cyclase, decreased cAMP
Activation of Beta 1:
stimulation of adenylyl cyclase, increased cAMP
Activation of Beta 2:
stimulation of adenylyl cyclase and increased cAMP
Activates cardiac Gi under some conditions
Activation of Beta 3:
stimulation of adenylyl cyclase and increased cAMP
Activation of D1 and D5
stimulation of adenylyl cyclase and increased cAMP
Activation of D2
decreased adenylyl cyclase; increase K+ conductance
Direct acting drugs MOA
stimulate postsynaptic receptors
Indirect acting drugs MOA:
increase availability of NE or E by releasing or displacing NE from sympathetic nerves, blocking transport of NE into sympathetic neurons, block metabolizing enzymes
Mixed-acting drugs
direct activation of postsynaptic receptors and indirect release of NE
Reserpine’s effect on effectiveness of direct, indirected, and mixed-acting drugs
Direct: response are not reduced
Indirect: responses are abolished
Mixed: responses are blunted, but not abolished
Differences in CV effects by E and NE
E: increases HR, CO, unpredictable effect on diastolic arterial pressure with large increase in systolic, decreased peripheral resistance
NE decreases HR and has no effect or decreases CO, increases Diastolic arterial pressure and large increase in systolic, increased peripheral resistance
Epinephrine effect on the heart
increased HR, shortened systole, increased CO, increased Oxygen consumption
Can cause premature ventricular contractions, leading to extrasystoles, tachycardia, or fibrillation
Epinephrine vascular effects
decreased cutaneous BF, increased B2 mediated skeletal BF, increased renal resistance with decreased BF, increased pulmonary pressures, and increased coronary BF
Epinephrine absorption
IV, Inhaled, IM, SC (slow due to vasoconstriction)
Cannot give orally due to high metabolic rate
Epinephrine toxicity
Cerebral hemorrhage especially with non-specific beta blockers, ventricular arrhythmias, and angina
Uses of epinephrine
emergency relief of hypersensitivity reactions, vasoconstrictor with local anesthetics, topical hemostatic agent, restoring cardiac rhythm in patients with cardiac arrest
Toxicity of norepinephrine
cerebral hemorrhage, ventricular arrhythmias, angina, extreme increases in BP, necrosis at sites of IV infusion
Dopamine
Concentration dependent receptor specificity from low to high dose (D1 -> B1 -> A)
Used acutely in CHD or RF
Given IV infusion; has short duration of action
Must monitor urine output as secondary marker of drug effect - may have bad effects on kidneys, where it is metabolized
Dobutamine
Racemic mixture of a beta agonsit and alpha1 agonist and antagonist
Increases CO and SV without effect on HR through increased myocardial contractility with decreased LV filling pressure; increased urinary output secondary to increased CO
Very short half life (2min), IV
For short term treatment of cardiac decompensation post surgery, CHF, or acute MI
Isoproterenol
Acts on beta receptors; increases CO, decreases diastolic BP
Given parenteral or by aerosol
SE: palpitations, tachy, headache, flushing
Uses: Emergency to stimulate HR in pts with brady or heart block - especially patients with torsades or about to receive implanted pacemaker
Phenylephrine
Direct acting alpha adrenergic agonsit; causses systemic vasoconstriction, thus increased SBP&DBP
Can cause reflex decreased HR and CO
SC, IM, IV
use of control of hypotension (also associated with regional/spinal anesthesia
SE: angine, anxiety, hallucinations, HTN, excitability, dizziness, insomnia, pallor, restlessness - all more likely with parenteral administration
Ephedrine
Mixed acting sympathomimetic agonist at both alpha and beta receptors and enhances release of NE from sympathetic neurons
Orally active, eliminated unchanged in urine
Uses: hyptonesion and hypotension of analgesia
increased HR and CO, variable increased in peripheral resistance and BP
SE: angina, ventricular dysfunction including arrhythmias and palpitations, fatal arrhythmias including V tach
