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Questions and Answers
Why is adrenaline ineffective when administered orally?
Why is adrenaline ineffective when administered orally?
What percentage of adrenaline is present in the Suprarenal medulla?
What percentage of adrenaline is present in the Suprarenal medulla?
What is the approximate duration of action of adrenaline?
What is the approximate duration of action of adrenaline?
What is the primary mechanism of termination of adrenaline's action?
What is the primary mechanism of termination of adrenaline's action?
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What is the effect of adrenaline on blood vessels?
What is the effect of adrenaline on blood vessels?
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What is the effect of adrenaline on heart rate?
What is the effect of adrenaline on heart rate?
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What is the effect of adrenaline on the eye?
What is the effect of adrenaline on the eye?
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What is the effect of epinephrine on peripheral resistance?
What is the effect of epinephrine on peripheral resistance?
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What is the metabolite of adrenaline excreted in the urine?
What is the metabolite of adrenaline excreted in the urine?
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What is the effect of epinephrine on blood glucose levels?
What is the effect of epinephrine on blood glucose levels?
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What is the effect of epinephrine on skeletal muscle blood vessels?
What is the effect of epinephrine on skeletal muscle blood vessels?
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What is the effect of epinephrine on the urinary system?
What is the effect of epinephrine on the urinary system?
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What is the effect of epinephrine on respiratory system?
What is the effect of epinephrine on respiratory system?
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What is the effect of epinephrine on the eye in open angle glaucoma?
What is the effect of epinephrine on the eye in open angle glaucoma?
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What is the effect of epinephrine on sweat secretion?
What is the effect of epinephrine on sweat secretion?
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What is the effect of epinephrine on the uterus in pregnant women?
What is the effect of epinephrine on the uterus in pregnant women?
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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.
