Chapter 15 Adrenergic agonists Sympathetic responses Stimulation of sympathetic nervous system or use of adrenergic drugs can cause dilation of pupils and bronchioles; increased heart rate; constriction of blood vessels; relaxation of muscles in GI tract, bladder, and uterus. Effects of adrenergic agonists at receptors Alpha 1 receptor Increases cardiac contractility, vasoconstriction Dilates pupils, decreasessalivary gland secretion Increases bladder and prostate contraction Alpha 2 receptor Inhibits norepinephrine release Promotes vasodilation and decreased bp Decreases GI motility and tone Beta 1 receptors Increases cardiac contractility, heart rate Increasesrenin secretion and increases bp Beta 2 receptors Decreases GI tone and motility Bronchodilation Increases blood flow t=in skeletal muscles Relaxes smooth muscle of uterus Activates liver glycogenolysis Increases blood glucose Dopaminergic Located in the renal, mesenteric, coronary, and cerebral arteries Vasodilation-increases flow Neurotransmitter inactivation Inactivation by Reuptake of transmitter back into neuron Enzymatic transformation or degradation MAO inside neuron COMT outside neuron Diffusion away form the receptor Drugs halt termination of neurotransmitter by inhibiting Norepinephrine reuptake Norepinephrine degradation After the transmitter has performed its function, the action must be stopped to prevent prolonging the effect Two enzymesthat inactivate the metabolism of norepinephrine are monoamine oxidase (MAO) and Catechol-O-methyltransferase (COMT). Classification of adrenergic agonists Direct-acting (epinephrine; norepinephrine) Directly stimulates adrenergic receptor Indirectly acting (amphetamine) Stimulatesrelease of norepinephrine from terminal nerve endings Mixed acting (ephedrine) Stimulates adrenergic receptorsties and stimulatesrelease of norepinephrine form terminal nerve endings Also called sympathomimetics Catecholamines Catecholamines Produce sympathetic response Endogenous Epinephrine, norepinephrine, dopamine Synthetic Isoproterenol, dobutamine Noncatecholamines Stimulate adrenergic receptors Most have longer duration of action than endogenous and synthetic Phenylephrine, metaproterenol, albuterol Catecholamines: chemical structures of a substance that can produce a sympathomimetic response Noncatecholamines:stimulate adrenergic receptors Many adrenergic agonistsstimulate more than one adrenergic receptor site ex. Epinephrine acts on alpha 1, beta 1, and beta 2 Epinephrine Nonselective Action Alpha 1 increases the blood pressure Beta 1 increases heart rate Beta 2 promotes bronchodilation Contraindications Cardiac dysrhythmias, hypertension Hyperthyroidism, DM Pregnancy Epinephrine is a nonselective, asit excitesthree different adrenergic receptors approximately equally. Action Uses Inotropic:strengthens myocardial contraction, increasing cardiac output Vasoconstrictor: increases heart rate and systolic BP Bronchodilator Anaphylaxis, anaphylactic shock Bronchospasms,status asthmaticus Cardiogenic shock, cardiac arrest Side effects/adverse reactions Cardiac dysrhythmias, palpitations, tachycardia, hypertension, dizziness, headache, sweating, insomnia, restlessness, tremors, hyperglycemia Drug interactions Beta blockers Decreases epinephrine action Digoxin Causes cardiac dysrhythmias TCAs and MAOIs intensify and prolong effects Nursing interventions Monitor BP, heart rate, urine output Report tachycardia, palpitations, tremors, dizziness, hypertension Monitor IV site for infiltration Antidote: phentolamine mesylate (regitine) Avoid cold medications, and diet pills if hypertensive, diabetic, CAD, or dysrhythmic Albuterol Avoid adrenergic when breastfeeding Avoid continuous use of adrenergic nasalsprays Pt should be placed on cardiac monitor for early detection of dysrhythmias. Monitor urine output for early detection of decreased renal perfusion Selective Acts on beta 2 adrenergic receptors Promotes bronchodilation Uses Treats bronchospasm, asthma, bronchitis, COPD Caution Severe cardiac disease Hypertension, hyperthyroidism DM, pregnancy Renal dysfunction Side effects/adverse reactions Tremors, nervousness,restlessness, dizziness, tachycardia, palpitations, cardiac dysrhythmias Drug interactions May increase effect with othersympathomimetics, MAO inhibitors, and TCAs Antagonize effect with beta blockers Nursing process: adrenergic agonist Assessment Determine the patients health history Assess the patients drug history