Adrenergic Physiology and Pharmacology Tutorial

Overview

• Tutorial focuses on adrenergic physiology and adrenergic drug categories.
• Covers drug mechanism of action, adverse effects, and contraindications.
• Includes practice questions to test understanding.

Key Concepts

• Adrenergic Pathway: Also known as the sympathetic pathway.
• Cholinergic Pathway: Referred to as the parasympathetic pathway.
• Terms:
  • Sympathomimetic/Anticholinergic: Refers to the adrenergic pathway.
  • Parasympathomimetic/Sympatholytic: Refers to the cholinergic pathway.

Adrenergic Response Mechanism

• Triggered by specific stimuli leading to preganglionic neuron impulse.
• Neurotransmitters:
  • Acetylcholine released by preganglionic neuron binds to nicotinic receptors.
  • Norepinephrine released binds to adrenergic receptors.
• Epinephrine Release: Direct stimulation of the adrenal gland leads to epinephrine release.

Receptor Responses

• Adrenergic Receptors:
  • Alpha-1, Beta-1, Beta-2: Lead to adrenergic (fight-or-flight) response.
  • Alpha-2: Leads to cholinergic (rest-and-digest) response.
• Locations:
  • Alpha-1 & Beta-2: Found in smooth muscles including blood vessels, heart, bronchioles, etc.
  • Alpha-2 & Beta-1: More limited locations, found in heart and nervous system.

Systemic Responses

• Adrenergic State:
  • CNS heightened, dilated pupils, halted digestive processes.
  • Increased heart rate, blood pressure, bronchodilation.
  • Bladder relaxation and urinary sphincter contraction.
• Cholinergic State:
  • CNS somnolent, constricted pupils, increased digestion.
  • Decreased heart rate, blood pressure, bronchoconstriction.
  • Bladder contraction and urinary sphincter relaxation.

Drug Categories

Alpha-1 Agonists

• Prototype: Sinephrine.
• Suffix: -PHRINE.
• Use: Treat nasal congestion by vasoconstriction.
• Side Effects: Fast heart rate, high blood pressure, insomnia.
• Contraindications: Avoid in cardiac conditions; risk of rebound congestion.

Alpha-2 Antagonists

• Example: Atipamazole (veterinary use).
• Suffix: -EZOLE.
• Mechanism: Blocks norepinephrine binding, triggering adrenergic response.
• Risk: Rapid administration can cause cardiac collapse.

Beta Agonists

• Beta-1:
  • Prototype: Dobutamine.
  • Suffix: -AMINE.
  • Use: Cardiogenic shock treatment; increases cardiac output.
  • Contraindications: Avoid in chronic tachyarrhythmia.
• Beta-2:
  • Prototype: Albuterol.
  • Suffix: -TEROL.
  • Use: Asthma, COPD treatment by bronchodilation.
  • Side Effects: Increased heart rate, palpitations, tremors.
  • Caution: Use cautiously in cardiac conditions.

Practice Questions Summary

• Sympathomimetic drugs result in pupil dilation, insomnia, tachycardia.
• Adrenergic response occurs when blocking alpha-2 receptors.
• Albuterol used for asthma; first-line for respiratory distress.
• Advise waiting 1 minute between inhaler puffs, 5 minutes for different medications.
• Alpha-1 and Beta-2 receptors are located in the lungs.