Chapter 30

Adrenergic Agonists

  • Also known as sympathomimetic drugs; mimic effects of the sympathetic nervous system (SNS).

  • Stimulation can be direct or indirect; affects both alpha- and beta-receptors.

Physiological Effects of Adrenergic Stimulation

  • Eyes: Pupils dilate, loss of accommodation

  • Mouth: Decreased salivation

  • Respiratory tract: Bronchodilation, increased rate and depth of respiration

  • Cardiovascular: Increased heart rate and contractility, vasoconstriction, increased blood pressure, increased blood flow to muscles

  • GI tract: Decreased motility and perfusion; sphincter contraction

  • Renal: Decreased blood flow, bladder relaxation, sphincter contraction

  • Skin: Vasoconstriction, increased sweating

Use of Adrenergic Agents Across the Lifespan

  • Children: At risk for tachycardia, hypertension, GI complications. Dosage based on body weight.

  • Adults: Require monitoring in critical situations; cautious with OTC drugs.

  • Older Adults: Increased risk of adverse effects due to mixed metabolism and excretion issues; lower doses recommended.

Alpha- and Beta-Adrenergic Agonists

  • Key Drugs: Dobutamine, Dopamine, Ephedrine, Epinephrine, Norepinephrine.

  • Indications: Hypotensive shock, bronchospasm, asthma.

Pharmacokinetics & Contraindications

  • Rapid absorption via injection; metabolized in the liver.

  • Contraindications: Hypersensitivity, certain arrhythmias, hypovolemia.

Alpha-Selective Adrenergic Agonists

  • Key Drugs: Clonidine, Dexmedetomidine, Guanfacine, Phenylephrine.

  • Indications: Hypertension, ADHD, sedation, orthostatic hypotension.

Adverse Effects

  • CNS, cardiovascular, gastrointestinal, and genitourinary effects; possible hypokalemia.

Beta-Specific Adrenergic Agonists

  • Key Drugs: Albuterol, Isoproterenol, Levalbuterol.

  • Indications: Bronchospasm, acute hyperkalemia, shock.

Adverse Effects

  • Related to sympathetic stimulation; includes CNS, cardiovascular, pulmonary effects.

Teaching Points

  • Sympathomimetics are "fake adrenaline."

  • Beta 1 = heart, Beta 2 = lungs.

  • Check for drug interactions, especially with antidepressants and beta-blockers.

  • Important to assess for contraindications like pheochromocytoma.