This document provides an overview of sympathomimetic drugs, also known as adrenergic drugs. It defines them as drugs that have actions similar to adrenaline or sympathetic stimulation. It classifies them as direct, indirect, or mixed sympathomimetics and discusses examples of each. It then describes their pharmacological actions in detail, focusing on their effects on the cardiovascular system, respiration, eyes, gastrointestinal tract, bladder, uterus, skeletal muscle, central nervous system, and metabolism. Specific drugs discussed include adrenaline, noradrenaline, isoprenaline, dopamine, dobutamine, and phenylephrine. Therapeutic uses and adverse effects are also summarized.

1. SYMPATHOMIMETICS
(ADRENERGIC DRUGS)
PRESENTED BY:
NAVEEN K L
1ST M Pharma
Dept. of Pharmacology
Srinivas College Of Pharmacy
Valachil, Mangalore.
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2. CONTENTS:
 Introduction
 Definition
 Classification of Sympathomimetic agents
 Pharmacological Actions
 Reference
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4. Definition :
 These are drugs with actions similar to that of adrenaline or
that of sympathetic stimulation . They can be classified as
Direct sympathomimetic--- Adr, NA, Isoprenaline,
Phenylephrine, Salbutamol, etc
Indirect sympathomimetic--- Tyramine, Amphetamine,
Mixed sympathomimetic---- Ephedrine, Mephentermine
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5. Therapeutic classification
 Vasopressor agents:
α1 receptor agonist : Noradrenaline, Phenylephrine, Methoxamine,
Mephantermine.
 Cardiac stimulants:
Non selective : Adrenaline, Isoprenaline.
β1 receptor agonist : Prenalterol, Dopamine, Dobutamine.
 Bronchodilators:
Non selective: Adrenaline, Isoprenaline.
Selective β2 agonist: Salbutamol, Terbutaline, Salmetrol, Formoterol.
 CNS Stimulant:
Amphetamine, Methamphetamine, Dexamphetamine, Ephedrine
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6.  Nasal decongestant:
α1-receptor agonist: Phenylephrine, Pseudoephedrine,
Phenylpropanolamine.
α2-receptor agonist: Oxymetazoline, Xylometazoline, Naphazoline.
 Uterine relaxant:
Selective β2 agonist: Isoxsuprine, Ritodrine, Salbutamol, Terbutaline,
Orciprenaline.
 Anorectic agents:
Amphetamine, Methamphetamine, Dexamphetamine,
Phenylpropalamine.
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7. Adrenaline as prototype
 Potent stimulant of alpha and beta receptors
 Complex actions on target organs
Adr→ α1+α2+β1+β2 and weak β3 action
NA→ α1+α2+β1+β3 and no β2 action
Iso→ β1+β2+β3 action but no α action
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8. Pharmacological effects:
 On Cardiovascular System:
 The effects are prominent bcz of wide spread distribution of alpha & beta
receptors in heart, BV, neural & hormonal system involved in control of
blood pressure.
Effects on Cardiovascular System: Heart
Blood vessel
Blood pressure
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9. Heart:
Mainly acts on β1 → ↑ Ca+ influx in cardiac cells.
o HR---- ↑ +ve chronotropic effect. Pace maker activity of both SA node &
purkinje fibers is ↑
o Contractility --- ↑↑ +ve inotropic effects, relaxation is accelerated.
o Excitability and automaticity is ---- ↑
o Conduction velocity ---- ↑ in AV node & refractory period is ↓
o Stroke volume---- ↑ & cardiac output also ↑
o Work load ---- ↑ and also ↑ oxygen demand.
o Mechanical efficiency of heart is decreased.
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10.  Blood Vessels:
 Both vasoconstriction (Alpha) and vasodilatation (Beta) can
occurs depends on drug, its dose and vascular bed.
 Contraction --- Cutaneous, Mucous membrane & Renal
beds (Alpha -1)
 Vasoconstriction occurs through both alpha 1 & 2 receptors
, however, location of alpha 2 ------ activated by circulating
CAs, whereas
alpha 1 ---- responded to neuronally released NA.
 Dilatation ---- Predominate in skeletal muscles, liver and
coronaries.
 Larger arteries and veins are affected at higher doses.
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11. Blood Pressure:
Effects depends on amine, its dose, rate of administration.
 Adr:
Slow i.v. infusion or s.c. injection ------ Rise in systolic, fall in diastolic BP
PR ↓ bcz of vascular Beta 2 receptors
are more sensitive than Alpha receptor and mean BP, Pulse pressure is increased.
Rapid i.v. injection ------- marked increased in both systolic and diastolic BP
At high concentration alpha response predominates
BP returns to normal within few min and secondary fall
in mean BP --- rapid uptake and dissipation of Adr → concentration around the
receptor is reduced → low concentration are not able to act on Alpha receptor but
continue to act on Beta 2 receptor.
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12. When alpha blocker is given only fall in BP seen --- vasomotor reversal of dale
 Noradrenaline : Rise in systolic BP ↑↑
Rise in diastolic BP ↑↑
Rice in mean BP ↑↑
No Beta 2 action -- no vasodilatation
 Isoprenaline: Rise in systolic BP ↑
Fall in diastolic ↓↓
Fall in mean BP ↓
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14.  Respiration:
 Adr and isoprenaline having powerful bronchodilator effects but not NA.
 Rapid i.v. injection causes transient apnoea due to reflex inhibition of RC.
 Adr cause pulmonary oedema by shifting blood from systemic to pulmonary
circuit----- Toxic doses.
 Eye:
Mydriasis ----- due to pupil dilation; contraction of radial muscles of iris (α-1)
↓ IOP Especially in wide angle Glaucoma
 GIT :
Relaxation effects seen by both activation of alpha and beta receptors.
reduction in peristalsis and contraction of sphincters.
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 Bladder:
relaxation of detrusor muscles (β2 & β3) constriction of trigone sphincter (α)
 Uterus :
action is depends on species, hormonal and gestational status, so Adr can both
contraction and relaxation of uterine muscles (α & β).
Contraction ----- non pregnant ----- alpha
Relaxation ----- pregnant.
Skeletal muscle :
alpha receptor activation----motor nerve endings ----- Ach release.
Enhanced firing of muscle spindles is responsible for tremor produced by β2.

16.  CNS:
Adr, at clinical doses ---- doesn’t produce any marked CNS effects-----
bcz of poor penetration in brain -----restlessness, apprehension, tremor may
occurs .
α2 receptor activation in brainstem (selective alpha 2 agonist like clonidine) -----
sympathetic outflow → fall in BP and bradycardia occurs.
 Metabolic :
Adr causes Glycogenolysis → hyperglycaemia, hyperlactacidaemia (β2).
lipolysis ---- rise in plasma free fatty acid and calorigenesis (β2 + β3)
on alpha 2 ----- reduction in insulin Secretion
on beta 2 ----- augmentation of glucagon
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17. Pharmacokinetic:
 Destroyed in the gut wall by MAO And COMT So not given orally.
 Given by s.c, i.m, by inhalation, topically on mucous membrane, eye.
 i.v injection is avoided ----- risk of fatal ventricular fibrillation.
 Onset 1-2 min.
 Crosses placenta but not BBB.
 Excreted mainly in urine (84-95%)
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18. Adverse effect and contraindication
 Transient restlessness, headache, palpitation, anxiety, tremor.
 Marked rise in BP leads to cerebral haemorrhage, ventricular
tachycardia or fibrillation, angina.
 Adr contraindicated in hypertensive, hyperthyroidism and
angina patient.
 Adr shouldn't be given during anaesthesia with halothane (risk
of arrhythmias )
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19. Therapeutic uses:
 Vascular uses : Hypotensive state
Along with LA
Nasal decongestant
 Cardiac uses : Cardiac arrest
CHF
 Central uses : ADHD
Epilepsy
Parkinson's
Obesity
 Uterine relaxant .
 Allergic disorders.
 Mydriatic .
 Bronchial asthma & COPD
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20. DOPAMINE :
 Immediate metabolic precursor of NA.
 High concentration in basal ganglia, limbic system and hypothalamus.
 Central neurotransmitter.
 Metabolized by MAO and COMT.
 In effective orally and used in IV only.
 Short t 1/2 ---- 3-5min
 Agonist at dopaminergic D1. D2 Receptors.
 Agonist at Adrenergic alpha 1 & beta 2.
 Used in hypovolemic shock and cardiac failure
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21.  Small doses (2-5 µg/kg/min) :
 Stimulate D1 receptors in renal, mesenteric, and coronary vessels -----
vasodilation.
 Increases renal blood flow, GFR.
 Moderate doses (5-10µg/kg/min):
 Stimulate β1 receptor --- heart--- +ve inotropic & little chronotropic actions.
 Releases NA from nerves by β1 stimulation.
 No changes in PR & HR.
 High doses (10-20µg/kg/min):
 Stimulation alpha 1 receptors----- vasoconstriction and renal blood flow
decreased.
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22. Dobutamine:
 Derivative of dopamine.
 Doesn’t act on D1 & D2 receptors.
 Its act on both alpha and beta adrenergic receptors, mainly on beta 1
receptor ----- prominent action of clinically employed doses 2-8 µg/kg/min-
--- i.v infusion.
 ↑ force of contraction of cardiac cells & output, no changes in HR, PR, BP.
 Used as inotropic agent.
 Half life 2 min.
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23. Phenylephrine: 23
 Selective alpha 1 agonist. No beta action.
 Topically used as nasal decongestant and mydriasis agent.
 It raise BP by causing vasoconstriction.
 Reduces the IOT by constricting ciliary body blood vessels.

24. Reference:
 KD Tripathi. Essential of MEDICAL PHARMACOLOGY, 8th edition. New
dehli;Jaypee brothers medical publisher;2019 p 136 -152.
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25. Thank
You………
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