Catecholamine Adrenaline Pharmacology
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Questions and Answers

Why is adrenaline ineffective when administered orally?

  • Due to slow absorption from the GIT
  • Due to rapid metabolism by COMT in the liver
  • Due to rapid metabolism by COMT in the GIT and liver (correct)
  • Due to rapid excretion by the kidneys
  • What percentage of adrenaline is present in the Suprarenal medulla?

  • 90%
  • 50%
  • 60%
  • 80% (correct)
  • What is the approximate duration of action of adrenaline?

  • 2-3 minutes (correct)
  • 15-30 minutes
  • 5-10 minutes
  • 30-60 minutes
  • What is the primary mechanism of termination of adrenaline's action?

    <p>Uptake into nerve terminals</p> Signup and view all the answers

    What is the effect of adrenaline on blood vessels?

    <p>Vasoconstriction of skin and mucous membrane blood vessels</p> Signup and view all the answers

    What is the effect of adrenaline on heart rate?

    <p>Increases heart rate</p> Signup and view all the answers

    What is the effect of adrenaline on the eye?

    <p>Mydriasis</p> Signup and view all the answers

    What is the effect of epinephrine on peripheral resistance?

    <p>It decreases peripheral resistance</p> Signup and view all the answers

    What is the metabolite of adrenaline excreted in the urine?

    <p>Vanillylmandelic acid</p> Signup and view all the answers

    What is the effect of epinephrine on blood glucose levels?

    <p>It increases blood glucose levels through liver glycogenolysis</p> Signup and view all the answers

    What is the effect of epinephrine on skeletal muscle blood vessels?

    <p>It causes vasodilation</p> Signup and view all the answers

    What is the effect of epinephrine on the urinary system?

    <p>It causes relaxation of the detrusor muscle</p> Signup and view all the answers

    What is the effect of epinephrine on respiratory system?

    <p>It causes bronchodilation</p> Signup and view all the answers

    What is the effect of epinephrine on the eye in open angle glaucoma?

    <p>It decreases intraocular pressure</p> Signup and view all the answers

    What is the effect of epinephrine on sweat secretion?

    <p>It increases sweat secretion in palms and soles</p> Signup and view all the answers

    What is the effect of epinephrine on the uterus in pregnant women?

    <p>It relaxes the uterus</p> Signup and view all the answers

    Study Notes

    Catecholamines

    • Adrenaline (Epinephrine) is a natural sympathomimetic catecholamine present in the suprarenal medulla (80%) and CNS.
    • It darkens due to its oxidation to adrenochrome, which is toxic.

    Source and Chemistry

    • Adrenaline is a sympathomimetic amine derived from the amino acid tyrosine.

    Pharmacokinetics

    • Adrenaline is ineffective when administered orally, as it is metabolized by COMT in the GIT and liver.
    • Inhalation, intramuscular, local, intraosseous, and endotracheal routes are effective.
    • The termination of action also occurs by uptake into nerve terminals.
    • Excretion occurs through the kidneys (5% in urine) and small parts remain unchanged.

    Pharmacodynamics

    • Adrenaline has local actions, mainly alpha-1, including:
      • Vasoconstriction (VC) of cutaneous blood vessels, mucous membrane blood vessels of the nose, and conjunctival blood vessels.
      • VC of mucous membrane of bronchi and bronchodilatation.

    Heart

    • Adrenaline acts on the heart, increasing contraction force (inotropic), heart rate (chronotropic), and conduction (dromotropic).
    • It also increases excitability, leading to arrhythmia.

    Blood Vessels

    • Adrenaline causes vasoconstriction of skin and mucous membrane blood vessels (alpha).
    • It increases cardiac output and systolic blood pressure, with varying diastolic pressure.

    Smooth Muscle Effects

    • Adrenaline acts on:
      • Eye: vasoconstriction (alpha), active mydriasis (alpha), and decreased IOP (in open-angle glaucoma).
      • Respiration: bronchodilatation (beta-2) and vasoconstriction (alpha).
      • GIT: relaxation of wall (alpha + beta-1, beta-2) and contraction of sphincters (alpha).
      • Urinary: relaxation of wall (beta-2) and constriction of trigone and sphincters (alpha).
      • Sex organs: ejaculation (male) and relaxation of uterus (female, pregnant).

    Metabolic Effects

    • Adrenaline increases:
      • Blood glucose levels through liver glycogenolysis (beta-2) and insulin secretion (alpha).
      • Blood lactate through glycogenolysis in muscles.
      • Free fatty acid (FFA) through lipolysis (beta-1, beta-3).
      • Calorigenic action by 20% increase in O2 consumption.
    • Initial increase in K+ release from the liver, followed by sustained decrease in K+ due to uptake by muscles (beta-2).

    Antiallergic Effects

    • Adrenaline suppresses allergy by counteracting histamine (bronchospasm, vasoconstriction).
    • It is the physiological releaser of P cells.

    Local Uses

    • Hemostatic in epistaxis as a nasal pack.
    • Decongestant of mucous membranes of the nose and eye.
    • Used as eye drops in open-angle glaucoma to lower IOP.
    • Induction and maintenance of mydriasis during intra-ocular surgery.
    • Inhalation in acute bronchial asthma.

    Systemic Uses

    • Anti-allergic drug of choice in anaphylactic shock.
    • Used in cardiac resuscitation.

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    Description

    Learn about adrenaline, a natural sympathomimetic catecholamine, its chemistry, pharmacokinetics, and properties. Understand its effects and administration methods.

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