Week 8 - Chapter 17 (Adrenergic Agents) Flashcards
Adrenergic
Adrenergic agonists produce their effects by activating adrenergic receptors. Since the sympathetic nervous system acts through these same receptors, responses to Adrenergic agonists and responses to stimulation of the sympathetic nervous system are very similar. Because of this similarity, adrenergic agonists are often referred to as sympathomimetics. Adrenergic agonists have a broad spectrum of indications, ranging from heart failure to asthma to preterm labor.
Anaphylaxis
Anaphylaxis can be triggered by a variety of substances, including bee venom, wasp venom, latex rubber, certain foods (eg, peanuts, shellfish), and certain drugs (eg, penicillins).
- Anaphylaxis can develop within minutes of allergen exposure.
- Antihistamines are not especially useful against [BLANK] because histamine is only one of several contributors to the reaction.
Anaphylactic Shock
[BLANK] reaction is characterized by hypotension (from widespread vasodilation), bronchoconstriction, and edema of the glottis. Although histamine contributes to these responses, symptoms are due largely to release of other mediators (eg, leukotrienes).
-Treatment = Epinephrine
Catecholamines
–Agents in the [BLANK] family cannot be taken orally (because of destruction by MAO and COMT), have a brief duration of action (because of destruction by MAO and COMT), and cannot cross the blood-brain barrier (because they are polar molecules).
Mydriasis
Activation of alpha1 receptors on the radial muscle of the iris causes [BLANK] (dilation of the pupil), which can facilitate eye examinations and ocular surgery. Note that producing [BLANK] is the only clinical use of alpha1 activation that is not based on vasoconstriction.
Sympathomimetic
Adrenergic agonists are also known as [BLANK] because their effects mimic those caused by the sympathetic nervous system.
Catecholamine Structure
-The [BLANK] are so named because they contain a catechol group and an amine group. A catechol group is simply a benzene ring that has hydroxyl groups on two adjacent carbons. The amine component of the catecholamines is ethylamine. Structural formulas for each of the major [BLANK]—epinephrine, NE, isoproterenol, dopamine, and dobutamine. Because of their chemistry, all [BLANK] have three properties in common: (1) they cannot be used orally, (2) they have a brief duration of action, and (3) they cannot cross the blood-brain barrier.
Direct Adrenergic Receptor Activation
[BLANK] Adrenergic Receptor Activation:
Results from binding of the drug to alpha and beta receptors.
Indirect Adrenergic Receptor Activation
[BLANK] Adrenergic Receptor Activation:
- Promotion of NE release from adrenergic neurons
- Blockade of NE uptake
- Inhibition of NE breakdown.
Clinical Consequences of Alpha1 Activation
Therapeutic and Adverse effects?
Drugs capable of activating alpha1 receptors include epinephrine, NE, phenylephrine, ephedrine, and dopamine.
Therapeutic effects:
Elicits two responses that can be of therapeutic use: (1) vasoconstriction (in blood vessels of the skin, viscera, and mucous membranes); and (2) mydriasis. Resulting:
—Hemostatis (bleeding arrest via vasoconstriction)
Nasal Decongestion (dilation and engorgement of blood vessels in the nasal mucosa).
—Adjunct to Local Anesthesia (local site of action prolongs anesthesia)
—Elevation of Blood Pressure.
—Mydriasis (is rare)
Adverse effects: Results directly or indirectly from vasoconstriction. ---Hypertension. ---Necrosis ---Bradycardia
Clinical Consequences of Alpha2 Activation
Therapeutic and Adverse effects?
Alpha2 receptors in the periphery are located PRESYNAPTICALLY, and their activation inhibits NE release. Activation of alpha2 receptors in the periphery has little clinical significance because there are no therapeutic applications related to activation of peripheral alpha2 receptors. Furthermore, activation of these receptors rarely causes significant adverse effects.
In contrast to alpha2 receptors in the periphery, alpha2 receptors in the CNS are of great clinical significance.
(1) reduction of sympathetic outflow to the heart and blood vessels.
(2) relief of severe pain. The central alpha2 agonists used for effects on the heart and blood vessels, and the agents used to relieve pain
Clinical Consequences of Beta1 Activation
Therapeutic and Adverse effects?
All of the clinically relevant responses to activation of beta1 receptors result from activating beta1 receptors in the heart; activation of renal beta1 receptors is not associated with either beneficial or adverse effects. Beta1 receptors can be activated by epinephrine, NE, isoproterenol, dopamine, dobutamine, and ephedrine.
Therapeutic effects:
—Heart Failure (beta1 receptors in the heart has a positive inotropic effect (ie, increases the force of contraction), and improve cardiac performance.
—Shock i.e. hypotension. (beta1 stimulants can increase cardiac output and can thereby improve tissue perfusion.
—Atrioventricular Heart Block i.e. impulse condution from Atria to ventricles are blocked (beta1 receptors can enhance impulse conduction through the AV node, beta1 stimulants can help overcome AV block. this is only temporary, eventually you will need a pacemaker for the long term.)
Cardiac Arrest (cardiac beta1 receptors, drugs can initiate contraction in a heart that has stopped beating)
Adverse effects:
- –Altered Heart Rate or Rhythm (Overstimulation of cardiac beta1 receptors can produce tachycardia (excessive heart rate) and dysrhythmias (irregular heartbeat).)
- –Angina Pectoris (activated beta1 receptors increases the demand for oxygen, angina pectoris results when cardiac supply is insufficient to meet cardiac oxygen demand)
Clinical Consequences of Beta2 Activation
Therapeutic and Adverse effects?
Applications of beta2 activation are limited to the lungs and the uterus. Drugs used for their beta2-activating ability include epinephrine, isoproterenol, and albuterol.
Therapeutic effects:
- –Asthma (activation of beta2 receptors in the lungs promote bronchodilation)
- –Delay of Preterm Labor (Activation of beta2 receptors in the uterus relaxes uterine smooth muscle)
Adverse effects:
- –Hyperglycemia (activation of beta2 receptors in the liver and skeletal muscles, which promotes breakdown of glycogen into glucose; this only a problem for diabetics)
- –Tremor (Most common side effect but fades over time; activation of beta2 receptors in skeletal muscle enhances contraction which is common with hyperglycemia. )
Receptor Specificity of Epinepherine
alpha1, alpha2, beta1, beta2
Receptor Specificity of Norepinepherine
alpha1, alpha2, beta1,
Receptor Specificity of Isoproterenol
beta1 and beta2
