Study Notes on Peripheral Nervous System Medications

P E R I P H E R A L N E RVO U S S Y S T E M M E D I C AT I O N S

Introduction:

  • Presented by Katie Knott, MSN, RNC-OB

  • Course: NUR 3305

WEEK 5 / 6 TOPICS

  • Peripheral/Autonomic Nervous System Overview

  • Sympathetic Nervous System (SNS) Medications

  • Parasympathetic Nervous System (PSNS) Medications

P E R I P H E R A L N E RVO U S S Y S T E M O V E R V I E W

  • Visual aids are included to enhance understanding.

DIVISIONS OF PNS

Central Nervous System (CNS)

  • Composed of:

    • Brain:

    • Receives and processes sensory information.

    • Initiates responses and stores memories.

    • Generates thoughts and emotions.

    • Spinal Cord:

    • Conducts signals to and from the brain.

    • Controls reflex activities.

Peripheral Nervous System (PNS)

  • Composed of:

    • Motor Neurons:

    • Transmit signals from CNS to muscles and glands.

    • Sensory Neurons:

    • Transmit sensory information from sensory organs to CNS.

Components of PNS:

  • Somatic Nervous System: Controls voluntary movements.

  • Autonomic Nervous System (ANS): Controls involuntary responses.

Divisions of ANS:

  • Sympathetic Division:

    • Often referred to as the "Fight or Flight" system.

  • Parasympathetic Division:

    • Often referred to as the "Rest or Digest" system.

AUTONOMIC NERVOUS SYSTEM

  • Visual aids provide further clarification and understanding.

SNS VS. PSNS

Parasympathetic Nervous System Responses

  • "Rest and Digest"

    • Constricts pupils.

    • Stimulates saliva production.

    • Slows heart rate.

Sympathetic Nervous System Responses

  • "Fight or Flight"

    • Dilates pupils.

    • Inhibits salivation.

    • Increases heart rate.

    • Relaxes airways.

    • Stimulates glucose release and gallbladder activity.

    • Stimulates activity of the intestines.

    • Contracts bladder and promotes erection of genitals.

    • Inhibits activity of the stomach, intestines; promotes ejaculation and vaginal contraction.

BASIC PRINCIPLES IN ANS OPERATIONS

  • A comprehensive exploration of autonomic nervous system principles may include methodologies and functional mechanisms.

NEUROTRANSMITTERS & RECEPTORS

  • Summary of neurotransmitter functions and the types of receptors involved in SNS and PSNS.

    • Distinction between transmitter release mainly from SNS and PSNS.

SYMPATHETIC NERVOUS SYSTEM MEDICATIONS

  • Focus on medications affecting the SNS and their implications.

STUDENT LEARNING OBJECTIVES

  1. Define key terminology relevant to medications that affect the sympathetic nervous system.

  2. Differentiate between the catecholamines and non-catecholamines and how their properties influence pharmacokinetics of adrenergic medications.

  3. Explain the physiological and adverse effects from stimulating alpha 1, alpha 2, beta 1, and beta 2 receptors.

  4. Describe drug selectivity and impact on therapeutic effects of adrenergic medications.

  5. Identify mechanisms of action, therapeutic effects, indications, side/adverse effects, drug interactions, and key considerations for adrenergic agonists and antagonists.

KEY TERMINOLOGY

  • Term: Definition

    • Selective: Specific effects on targeted tissues.

    • Non-selective: Affects multiple receptors indiscriminately.

    • Cardioselective: Greater effects on cardiovascular tissues compared to others.

    • Vesicant: Substance that can cause tissue necrosis or damage when injected.

    • Vasoconstriction: Narrowing of blood vessels.

    • Bronchodilation: Widening of bronchi for airflow improvement.

    • Glycogen: Stored form of glucose in the liver and muscles.

    • Shock: Acute condition marked by a severe drop in blood pressure and cardiac output.

    • Asthma: Chronic inflammatory disease causing airway swelling and difficulties in breathing.

    • Heart Failure: Chronic condition where the heart inadequately pumps blood.

    • Myocardial Infarction: Blockage of blood flow to part of the heart often due to plaque in arteries.

SNS MEDICATIONS OVERVIEW

  • Key focus on catecholamines vs. non-catecholamines

  • Catecholamines: Typically short half-life, cannot cross the blood-brain barrier (polar).

  • Non-catecholamines: Longer half-life, may cross the blood-brain barrier (less polar).

SNS RECEPTORS & RESPONSES & ADVERSE EFFECTS

Receptor Activation and Affected Organs

  • Alpha 1:

    • Organs: Blood vessels in skin, viscera, mucosa, eyes, penis, bladder

    • Effects: Vasoconstriction; mydriasis; ejaculation; sphincter contraction.

    • Adverse Effects: Hypertension, local necrosis (IV route), bradycardia.

  • Alpha 2:

    • Organs: Presynaptic nerve terminals

    • Effects: Inhibits norepinephrine release.

  • Beta 1:

    • Organs: Heart, kidneys

    • Effects: Increases heart rate, contractility, and AV node conduction; release of renin.

    • Adverse Effects: Tachycardia, dysrhythmias, angina.

  • Beta 2:

    • Organs: Arterioles of heart, lung, skeletal muscle, bronchi, uterus, liver, skeletal muscle

    • Effects: Vasodilation; bronchodilation; relaxation of smooth muscle; glycogen breakdown (hyperglycemia).

    • Adverse Effects: Hyperglycemia, tremors.

ADRENERGIC MEDICATIONS

ADRENERGIC AGONISTS / SYMPATHOMIMETICS

Epinephrine (Adrenaline, EpiPen)

  • Mechanism of Action: Stimulates alpha 1 & 2, beta 1 & 2 receptors.

  • Therapeutic Effects:

    • Alpha 1 & 2: Vasoconstriction; blood supply control; elevation of BP in shock.

    • Beta 1: Increased contractility and heart rate during cardiac arrest.

    • Beta 2: Bronchodilation in asthma/anaphylaxis.

  • Pharmacokinetics: Catecholamine with a short half-life (< 5 minutes).

  • Side/Adverse Effects:

    • Vasoconstriction leading to hypertension crisis and possible stroke.

    • Dysrhythmias; angina.

  • Interactions: MAOIs & TAs may increase/prolong effects.

  • Route(s): IV, IM, topical, SUBQ.

  • Other Considerations: Monitor cardiac function and IV sites closely; recognize potential overuse of therapeutic effects.

Norepinephrine (Levophed)

  • Mechanism of Action: Stimulates alpha 1 & beta 1 receptors.

  • Therapeutic Effects: Elevates BP in shock/hypotension; improves contractility and heart rate in cardiac arrest.

  • Pharmacokinetics: Catecholamine with a short half-life (2 minutes).

  • Side/Adverse Effects:

    • Similar to epinephrine: vasoconstriction leading to hypertension crisis/stroke, dysrhythmias, angina.

  • Interactions: MAOIs & TAs may increase/prolong effects.

  • Route(s): IV.

  • Other Considerations: Close monitoring of cardiac function and IV sites necessary.

Alpha 1 Agonists
Examples:

  • Phenylephrine (Neosynephrine, Afrin):

    • Mechanism of Action: Activates alpha 1 receptors.

    • Therapeutic Effects: IV route increases BP (hypotension/shock); local administration for nasal decongestion and dilating pupils.

    • Pharmacokinetics: Non-catecholamine; half-life varies by route.

    • Side/Adverse Effects: Anxiety, restlessness, tremors, palpitations, tachycardia or bradycardia, angina.

    • Interactions: MAOIs & TAs may increase/prolong effects.

    • Route(s): IV, nasal, ophthalmic, topical.

    • Other Considerations: Monitor cardiac function and IV sites closely.

Beta 1 & 2 Agonists

  • Isoproterenol (Isuprel):

    • Mechanism of Action: Activates beta 1 & 2 receptors.

    • Therapeutic Effects:

    • Beta 1: Increases HR in shock; improves conduction rate in heart block/cardiac arrest; increases cardiac output in shock.

    • Beta 2: Bronchodilation in asthma.

    • Pharmacokinetics: Catecholamine with a short half-life (2-5 minutes).

    • Side/Adverse Effects: Tachycardia, dysrhythmias, angina, tremors, insomnia, hyperglycemia.

    • Interactions: MAOIs & TAs may increase/prolong effects.

    • Route(s): IV, inhaled.

  • Dobutamine:

    • Mechanism of Action: Activates beta 1 receptors.

    • Therapeutic Effects: Increases contractility during CHF and cardiac surgery.

    • Pharmacokinetics: Catecholamine with a short half-life (2 minutes).

    • Side/Adverse Effects: Anxiety, palpitations, tachycardia, hypertension.

    • Interactions: MAOIs & TAs—use with caution, lower dosages.

    • Route(s): IV.

Beta 2 Agonists

  • Albuterol (Ventolin), Terbutaline:

    • Mechanism of Action: Activates beta 2 receptors.

    • Therapeutic Effects: Relaxes smooth muscle of bronchi (asthma/COPD); relaxes uterine muscle (preterm labor).

    • Pharmacokinetics: Non-catecholamine with a longer half-life (3-5 hours).

    • Side/Adverse Effects: Tremors, restlessness, insomnia; palpitations, tachycardia; high doses may stimulate beta 1.

    • Interactions: MAOIs & TAs—use with caution, lower dosages.

    • Route(s): Inhaled, nebulizer, SUBQ, IV, PO.

Dopamine

  • Mechanism of Action:

    • Low doses activate dopamine receptors.

    • Moderate doses activate beta 1 & dopamine receptors.

    • High doses activate alpha 1, beta 1 & dopamine receptors.

  • Therapeutic Effects:

    • Dopamine: Dilates renal vessels, increasing perfusion.

    • Beta 1: Increases cardiac output (shock, HF).

    • Alpha 1: Causes vasoconstriction (hypotension).

  • Pharmacokinetics: Catecholamine.

  • Side/Adverse Effects: Tachycardia, dysrhythmias, angina.

  • Interactions: MAOIs & TAs—use with caution, lower dosages.

  • Route(s): IV.

  • Other Considerations: Monitor urine output closely; noted as a vesicant at high doses; demonstrated 'dose-dependent' selectivity.

Conclusion

  • The information encapsulates a comprehensive view of the Peripheral Nervous System medications, encompassing both theoretical knowledge and applicable clinical considerations as outlined in various sections of the notes.