This document summarizes sympathomimetic drugs. It begins by defining sympathomimetics as drugs that mimic the effects of sympathetic activation on the heart and circulation. It then classifies sympathomimetics as direct-acting, indirect-acting, or mixed-acting based on their mechanisms of action. The document outlines the various receptor-mediated actions of sympathomimetics in different tissues and organ systems. It discusses some examples of commonly used sympathomimetics like epinephrine, dopamine, salbutamol, and phenylephrine. Finally, it lists some therapeutic uses of sympathomimetics including treatment of shock, heart failure, asthma, nasal congestion, and uterine relaxation.

1. SESSION 2022-23
M.PHARM (PHARMACOLOGY)
TOPIC
SYMPATHOMIMETIC DRUGS
PRESENTED BY: REHAN
UMAR
M PHARM1STYEAR

2. CONTENTS
• INTRODUCTION
• CLASSIFICATION OF ADRENERGIC DRUGS (SYMPATHOMIMETICS)
• ACTIONS
• ADVERSE EFFECT AND CONTRAINDICATION
• THERAPEUTIC USES

3. INTRODUCTION
Sympathomimetic drugs mimic the effects of sympathetic activation
on the heart and circulation.
These are drugs with similar to that of Adrenaline or that of
sympathetic stimulation.
Sympathomimetics drugs stimulate the heart through activation of
beta-adrenoceptors.
Sympathomimetics drugs stimulate the release of norepinephrine
from sympathetic nerves in addition to their receptor agonist
activities.

4. 1. DIRECT acting SYMPATHOMIMETICS:-
These are the drugs which act directly as agonists on α or β or both α
and β adrenoceptors.
e.g. Adr, NA, Isoprenaline, Phenylephrine, methoxamine,
Xylometazoline, Salbutamol etc.
2. INDIRECTacting SYMPATHOMIMETICS:-
These are the drugs which act on adrenergic neuron to release NA, and
then acts on the adrenoceptors.
e.g. Tyramine, Amphetamine.
3. MIXEDACTION SYMPATHOMIMETICS:-
These are the drugs which act directly as well as indirectly.
e.g. Ephidrine, Mephentermine.

5. CLASSIFICATION OF ADRENERGICDRUGS
Ex- clonidine
Ex- phenylephrine, methoxamine
Ex- xylometazoline, oxymetazoline
Ex- salbutamol, terbutaline.
Ex- dobutamine.
Ex-
amphetamine.
Ex- cocaine,
TCAs(amitriptyline)
Ex- isoprenaline
Mixed-acting
Ex- Ephedrine
Dopamine
Mephentermine

6. ACTIONS:-
The peripheral actions of Adr in most tissues have been clearly
differentiated into those mediated by α or β receptors depending on
the predominant receptor type present in a given tissue.
The actions of a particular sympathomimetics amines depends on
its relative activity at different types of adrenergic receptor.

7. The Over All Actions Are :-
 HEART :- Adr increases heart rate by enhancing the pacemaker
activity of SA node.
 Adr also activates latent pacemakers in A-V node and Purkinje fibres.
 As a result arrhythmias can occur with high doses that raise Bp
markedly.
 BLOOD VESSEL :- Both vasoconstriction α and vasodilatation β2 can
occur depending on the drug, its dose and the vascular bed.
 BP :- The effect depends on the amine, its dose and rate of
administration.
 NA causes rise in systolic, diastolic and mean BP; it does not cause
vasodilatation (no β2 action).
 Isoprenaline causes rise in systolic but marked fall in diastolic BP (β1
- cardiac stimulation, β2 - vasodilatation).

8.  RESPIRATION :- Adr and Isoprenaline are potent bronchodilator
(β2).NA are not (no β2 action).
 This action is more marked when the bronchi are constricted.
 EYE :- Mydriasis occurs due to contraction of radial muscles of Iris
(α1).
 GIT :- Activation of both α and β receptor produces relaxation in isolated
preparation of gut.
 BLADDER,PROSTATE,VAS DEFERENS :- Detrusor muscle is relaxed
(β2,β3) and trigone is constricted (α1) both actions tend to oppose
bladder voiding.
 UTERUS :- Adr can both contract and relax uterine muscle,
respectively through α and β receptors.

9.  CNS :- Activation of α2 receptor in the brainstem (by selective α2
agonist like clonidine) results in decreased sympathetic outflow -
fall in BP and Bradycardia.
 SKELETAL MUSCLE :- Neuromuscular transmission is facilitated.
 In contrast to action on autonomic nerve endings, α receptor
activation on motor nerve endings augments ACh release, probably
because it is of the α1, subtype. The direct effect on muscle fibres is
exerted through β2, receptors and differs according to the type of
fibre.
 METABOLIC :- Adr causes glycogenolysis – hyperglycemia,
hyperlactacidaemia(β2).
 These are due to direct action on liver, muscle and adipose tissue
cells.

10. ADVERSE EFFECT AND CONTRAINDICATIONS :-
• Transient restlessness, headache, palpitation, anxiety, tremor and
pallor may occur after s.c./i.m. injection of Adr.
• Marked rise in BP leading to cerebral haemorrhage, ventricular
tachycardia, angina, myocardial infarction are the hazards of large
doses or inadvertent i.v. injection of Adr.
• Adr is contraindicated in hypertensive, hyperthyroid and angina
patients.
• Adr should not be given during anaesthesia with halothane (risk of
arrhythmias) and to patients receiving β blockers (marked rise in BP
can occur due to unopposed α action).

11. Sympathomimetics Drugs

12. • Dopamine (DA) :- It is a dopaminergic (D1 and D2) as well as weaker
adrenergic β1 (but not β2) + very weak α receptor agonist.
• Dopamine is used in patients of cardio-genic or septic shock and acute
heart failure wherein it increases BP and urine outflow.
• It is administered by i.v. infusion (0.2-1 mg/min) which is regulated
by monitoring BP and rate of urine formation.
• DOPAMINE, INTROPIN, DOPACARD 200 mg in 5 ml amp; to be diluted and infused I.V.
• D0BUTAMINE :- A derivative of DA, but not a D1 or D2 receptor
agonist.
• Dobutamine acts mainly on β adrenergic receptors, and is a weak α
agonist.
• It is used as an inotropic agent in pump failure accompanying
myocardial infraction, cardiac surgery, and for short term
management of severe congestive heart failure.
• CRDIJECT 50 mg/4 ml and 250 mg per 20 ml amp, DOBUTREX, DOBUSTAT 250 mg vial.

13. • AMPHETAMINE :-
• These are synthetic compounds having a pharmacological profile
similar to ephedrine. (CNS stimulant)
• Orally active with relatively long duration (4-6 hours).
• It stimulate respiratory centre.
• It suppresses the appetite.
• It is used to treat ADHD(Attention defict hyperactivity disorder).
• It is a drug of abuse, high doses produce euphoria, restlessness,
insomnia, aggression, panic.
• Amphetamine: 5-15 mg oral; Dexamphetamine: 5- 10 mg ( children
2.5-5 mg) oral.

14.  PHENYLEPHRINE :-
 It is selective α1 agonist with negligible β action.
 It raises BP by vasoconstriction.
 It is used for nasal decongestant.
 Frenin 10 mg in 1 ml inj;
 Sinarest 10 mg with chlorpheniramine 2 mg, paracetamol 500 mg,
caffeine 30 mg Tablet.
 METHOXAMINE :-
 Another selective α1 agonist.
 It is used as a pressor agent.
 Vasoxine 20 mg / ml.

15. Selective β2 stimulants :-
 Salbutamol , Terbutaline , Salmetrol , Formoterol these are the drugs
which causes bronchodilation , vasodilation They are primarily used in
bronchial asthma.
 Ritodrine is used as uterine relaxant.
ISOXSUPRINE :-
 Orally active β2 receptor stimulant.
 Used as smooth muscle relaxant and uterine relaxant.
 Side effect – nausea , tachycardia , hypotension , dizziness , tremor.
 Duvadilan 10mg tablet.

16. THERAPEUTIC USES :-
1.VASCULAR USES :-
 SHOCK/ACUTE HYPOTENSION
 PERSISTANT/POSTURAL HYPOTENSION
 ALONG WITH LOCAL ANAESTHETICS
 CONTROL OF LOCAL BLEEDING
 NASAL DECONGESTANT

17. 2.CARDIAC USES :-
• CARDIAC ARREST
• PARTIAL OR COMPLETE A-V BLOCK
• CONGESTIVE HEART FAILURE
• DOBUTAMINE STRESS TEST

18. 3.BRONCHIAL ASTHAMA AND COPD
4.ALLERGIC DISORDER
5.OCULAR USE
6.UTERINE RELAXANT
7.INSULIN HYPOGLYCAEMIA