Post on 27-Dec-2015
1.Adrenaline (Epinephrine)
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It is the major constituent of the
adrenal medulla secretion (80%).
Hydrochloride aqueous solutions
are hydrolyzed rapidly in alkaline or
neutral media but are stable at low
pH and in the presence of reducing
agents (ascorbic acid).
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• Absorption and Fate:
It is not effective orally because:
A.Poor absorption from the GIT
B.Rapid destruction by digestives
juices
C.Rapid metabolism by the liver
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• Absorption and Fate:
It is absorbed slowly from s.c. tissues
due to local vasoconstriction (α-effect).
It is more rapidly absorbed from i.m.
sites (β2-mediated vasodilatation).
Inhaled solutions have a restricted
action to the respiratory tract.
Intracardiac: emergency.
Infusion: adrenaline and noradrenaline.
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• Pharmacological actions:
I. Local actions:
1. On mucous membranes or abraded
surfaces vasoconstriction A. Added to local anesthetics to prolong
their duration of action.
B. A haemostatic action when applied to
bleeding surface.
C. A delay in the absorption of associated
drugs when injected subcutaneously
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2.Local application of adrenaline to the eye:
It has a limited effect on the size of the
pupil because:
A.It is partly destroyed by the alkalinity
of tears.
B.It causes v.c. of the conjunctival blood
vessels hinders its own absorption.
In patients with open angle glaucoma, it
helps to the formation of the A.H. & its
drainage the IOP.
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Adrenaline causes mydriasis in the
following conditions:
1. Acute hemorrhagic pancreatitis.
2. Postganglionic sympathetic
denervation of the dilator pupillae
muscle.
3. Some cases of glaucoma.
4. Hyperthyroidism.
5. Diabetic coma.
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II.Systemic actions:
1.Cardiovascular system:
A.Heart (β1 receptors)
.i Heart rate (+ve chronotropic action,
tachycardia).
.ii Force of contraction (+ve inotropic
action).
.iii Cardiac output.
.iv Heart work and O2 consumption.
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B.Blood vessels (α and β2)
i. α-Stimulation v.c. of the blood
vessels of the skin, mucous
membrane and kidney.
ii.β2-Stimulation v.d. of the skeletal
muscle and coronary blood
vessels.
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C.Blood pressure (B.P.):
SBP (due to COP) while DBP changes up
or down depending on the final effect on
the PVR.
Therapeutic doses PVR due to the
dominant action on β2 receptors DBP.
Experimentally, epinephrine (low dose)
B.P. because of its β effects. Gradual
epinephrine doses B.P. (marked α effects)
and ergotamine (α-adrenergic blocker)
administration B.P. (epinephrine reversal)
as epinephrine would act only on β-
receptors. 10
The pressor effect of phenylephrine (a
selective α1-stimulant) is abolished by
ergotamine.
The pressor effect of NE is partially
blocked by ergotamine [the pressor
effect of NE is partly due to its v.c. (α1-
receptors) and partly due to a cardiac
stimulant action (β1-receptor) that
remains in effect after α-receptors
blockade].11
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2.Effect on Eye:
Active mydriasis (α1-receptors )!!!
No loss of light reflex &
accommodation.
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3.Effect on bronchi:
It stimulates β2-receptors in the
bronchioles bronchodilatation.
Adrenaline acts also on α-receptors
of blood vessels v.c. bronchial
mucosal congestion.
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4.Gastrointestinal tract:
The GIT contains both α and β
receptors.
Stimulation of either types of
receptors leads to inhibition of tone
and motility.
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5.Urinary bladder
Adrenaline relaxes the detrusor
muscle (β2-receptors) and contracts
the sphincter (α1-receptors) urine
retention.
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6.Uterus:
Adrenaline relaxes the pregnant
human uterus (β2).
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7.Metabolic Actions:
.A Blood glucose through:
i. Enhancement of hepatic
glycogenolysis (β2).
.ii Glucose uptake by peripheral
tissues.
.B Blood lactate ( breakdown of
glycogen to lactate in skeletal
muscles).
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7.Metabolic Actions:
.C Blood concentration free fatty
acids (due to lipolysis β1 & β3).
( Breakdown of TGs in adipose
tissues)
.D O2 consumption (20-30%) due to
metabolism.
E. A transient in plasma K+ level
followed by a prolonged fall. 19
8.Action on the CNS:
Adrenaline has a weak stimulant
effect restlessness, headache &
tremors.
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9.Skeletal muscle action:
It facilitates neuromuscular
transmission by sensitization of the
motor endplate and hastens
recovery from fatigue by increasing
blood flow to the muscles.
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10.Antihistamine and antiallergic
action.
Adrenaline is the physiological
antagonist of histamine.
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• Therapeutic Uses:
1) Acute bronchial asthma
bronchodilatation & bronchial
mucosal congestion and edema.
2) Allergy, urticaria, edema and
anaphylactic shock.
3) Insulin hypoglycemia.
4) Cardiac resuscitation (intracardiac
injection of adrenaline in cardiac
arrest).23
3)Adrenaline is given with local
anesthetics (s.c.) v.c.
A.Prolong their durations of action.
.B Bleeding from the operation
sites.
6)Local hemostatic (stop hemorrhage
from the nasal mucosa, epistaxis).
7)As eye drops in some cases of
glaucoma.
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• Contraindications:
1.Coronary heart diseases ( anginal attacks)
2.Hypertension ( cerebral hemorrhage).
3.Cardiac arrhythmias.
4.During anesthesia with halogenated
inhalational anesthesia.
5.In patients receiving digitalis
6.Hyperthyroidism.
7.With local anesthetics in fingers and toes.
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