Epinephrine

Posted on by Dr.Ajita A
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Produced by adrenal medulla

ACTIONS:

DIRECT AGONIST OF ALPHA 1 ,2, BETA 1 AND 2 RECEPTOR.

DOSE (mcg/kg/min)

RECEPTOR ACTION

SVR

10-30

 beta May decrease

30-150

 beta and alpha Variable

>150

 alpha and beta Increase

 

PROTOTYPE  DRUG.

NATURAL FUNCTIONS-

  1. Increase myocardial contractility
  2. Increase heart rate
  3. Increase vascular and bronchial smooth muscle tone
  4. Increase glandular secretions
  5. Increase metabolic processes- glycogenolysis and lipolysis
  6. 2-10 times more potent than nor-epinephrine
  7. More than 100 times potent than isoproterenol
  8. It is not administered orally as it is metabolized by GIT  and liver
  9. Poorly lipid soluble preventing its entry in CNS

 

CLINICAL USES

  1. Increases myocardial contractility
  2. Severe life threatening allergic conditions
  3. Addition to local anaesthetic solutions to decrease absorption and enhance action

CARDIOVASCULAR EFFECT

☛ Small dose1-2 mcg/min IV beta 2 receptor stimulation in peripheral vasculature
☛ Beta1- 4 mcg/min IV both alpha and beta -10-20 mcg/minIV
☛ Alpha effect predominantly most vascular bed, cutaneous and renal circulations

Beta2 action-

  • Increase systolic blood pressure , heart rate and cardiac output.
  • Decrease blood pressure because of vaso dilatation in skeletal muscle.

So net effect is increase in pulse pressure and minimal change in mean arterial pressure

Heart rate increases by accelerating rate of spontaneous phase 4 depolarisation

Increase cardiac output , increase myocardial contractility, increase venous return , increase heart rate

Alpha 1 action – vaso constriction in skin , mucosa and hepato renal vasculature ,increase renal vascular resistance

Coronary blood flow is increased, no cerebral arteriole effect

Airway, smooth muscle – beta 2 action – relaxation

Increase  CAMP –decreases release of vaso active mediators associated with smptoms of  bronchial asthama

METABOLIC EFFECTS

☛ Beta 1- liver glycogenolysis, adipose tissue lipolysis by triglyceride lipase
☛ Alpha 1 -inhibit insulin release

 

ELECTROLYTES:

Activation of Na – K+ pump in skeletal muscle and transfer of K+ in cell and causes hypokalemia

Ocular Effects – MYDRIASIS

GASTRO INTESTINAL AND GENITO URINARY

☛ Relaxation of GIT
☛ Beta relaxes detrussor muscle of bladed
☛ Alpha contracts trigone and sphincter muscle
☛ Coagulation- accelerated , increase activity of factor V

dr.ajita

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