Adrenergic drugs act on the sympathetic nervous system by mimicking neurotransmitters like epinephrine and norepinephrine. They can be classified as direct-acting, indirect-acting, or mixed-acting. Direct-acting drugs like dopamine directly stimulate adrenergic receptors. Indirect-acting drugs like pseudoephedrine stimulate the release of neurotransmitters. Mixed-acting drugs like ephedrine have both direct and indirect effects. These drugs are used to treat conditions like asthma, hypertension, shock, and congestion by increasing heart rate, relaxing bronchial muscles, and constricting blood vessels.

1. ADRENERGIC DRUGS

2. Adrenergic Drug :
 Adrenergic drugs are the agents which acts directly on the
Symphathetic nervous system and these drugs are also known as
symphatomimetic drugs as these agents mimics (copy) the action of
symphathetic nervous system.
 On stimulation of symphathetic nervous system following response
are produced :
 1. Cardiac stimulation results in increase in heart rate and force of
contraction
 2. Stimulation of CNS
 3. Relaxation of bronchial muscle
 4. Increase in rate of glycogenolysis
 5. Liberation of free fatty acids

3.  Neurotransmitters-
 Epinephrine(Adrenaline), Norepinephrine ( Noradrenaline) and
Dopamine are the naturally occurring Catecholamines and controla
various response of “ Fight, Fiight, Fear” System
 Biosynthesis of neurotransmitter ( Catecholamines)
 The biosynthesis take place in adrenergic and Dopaminergic neurons in
the CNS, in symphathetic neurons in the ANS and in the adrenal medulla.
Various enzymes which are responsible for biosynthesis are:
 1. Tyrosine Hydroxylase ( tyrosine-3-monooxygenase)
 2. DOPA Decarboxylase
 3. Dopamine- Beta-hydroxylase
 4. Phenylethanolamine-N-methyl transfer

5. Adrenergic Receptors

6. SAR of adrenergic drug
1. Symathomimatic drug are considered as derivative of beta
– Phenylethylamine. Structurally, Substitution is possible on
 -Substitution on Aromatic ring of Phenylethylamine
 - substitution on beta –Carbon
 - substitution on alpha- carbon
 - substitution on the amino group

7.  A. Substitution on the aromatic Ring of Beta-phenylethylamine
 1. The presence of –OH group in the benzene ring at 3 and 4 positions
givves maximum alpha and beta activity. If –OH group is absent overall
potency get decreased. For example, Phenylephrine is less potent than
Adrenaline

8.  2. The presence of – OH group at 3 and 5 position with bulky Substituents on
the amino nitrogen gives beta2 selective drug.
For example, Orciprenaline and Terbutaline relaxes bronchial muscle without
effecting cardiac muscle.
3. The Unsubstituted or alkyl substituted Adrenergic amines easily cross the
BBB and have more CNS activity. For ex. Amphetamine & Ephedrine

9.  B. Substitution on the beta- carbon
 A – OH group on the beat carbon decrease the central stimulant action
due to lower lipid solubility of the drug ( OH give polar effect) This increase
agonist activity of the drug at alpha and beta receptor. For ex. Ephedrine
has less central stimulant effe than amphetamine but more bronchial Dilating
effect

10.  C. Substitution on the alpha- carbon
 Drug having Substituents on the alpha- carbon block the metabolism
and these have longer duration of action. For ex. Amphetamine resists
degradation by MOA.
 D. Substitution on the amino group
 1. Lesser the substitution on the amino group, higher wiill be selectivity for
alpha- receptor.
 2. More the size of alkyl Substituent, higher will be beta 2 -selective action.
For ex . Isoprenaline, Turbutaline and Salbutamol have selective Beta 2
activity

11. Classification of adrenergic drugs
( symphatomimetic drugs)
Direct acting drug
1. Norepinephrine
2. Epineprine
3. Phenylephrine
4. Dopamine
5. Methyldopa
6. Salbutamol
7. Clonidine
8. Dobutamine
9. Terbutaline
Indirect acting
1.
Hydroxyamphetamine
2. Propylhexeridine
3. Pseudoephedrine
Mixed acting
1. Ephidrine
2. Metaraminol

12. Direct acting Drugs 💊💉
 These agents produce a Symphathetic response by
interacting directly with Adrenergic receptors The action
produced are of rapid onset and of short duration. This
drugs effect both alpha & beta receptor.

13.  1. Norepinephrine
 IUPAC name: R -2-Amino-1-(3, 4-dihydroxyphenyl) -2-methylaminoethanol
 MOA : It is potent agonist at alpha receptor and no effect on beta
receptor.
 Uses: 1. it is used to reduced the absorption and effects of local
Anaesthetics
 2. It decrease chance of hemorrhage during operation
 3. It has strong Vasoconstriction property

14.  2. Epinephrine
 IUPAC name : R - 1-(3, 4Dihydroxyphenyl) -2-methylaminoethanol
 MOA:
 Uses : 1. Vasoconstrictor
 2. It is mainly used in treatment of anaphylaxis and anaphylactic
shock in the cardiopulmonary disease.
 3. It is used in the management of glaucoma as it decreases
Intraocular pressure.
 4. It relaxes bronchial muscle and is used in treatment of asthma.

15.  3. Phenylephrine
 IUPAC name : ®-2-methylamino-1-(3-hydroxyphenyl) ethanol
 Synthesis : it is prepared by reaction of m-chloroacetylphenol and Methylamine
followed by the reduction of the intermediate formed
 MOA: activation of alpha-1 receptors causes Vasoconstriction of the Arterioles, iris,
and contraction of uterus.
 Uses : 1. it is mainly used in decongestant in rhinitis and sinusitis.
 2. Used in the eye for production Mydriasis when Cycloplegia is not required

16.  4. Dopamine
 IUPAC name: 4-(2-aminoethyl)-1, 2-diol
 MOA: it interacts directly on beta- adrenergic receptors ( agonist at beta
receptor) and indirectly on alpha –adrenergic receptors.
 uses : 1. Dopamine is used in patient of shock
 2. Used in server CHF where increase BP and urine output.
 3. It is used in myocardial infraction, trauma, septic shock and cardiac
surgery.

17.  5. Methyldopa
 IUPAC name : 3-(3, 4-dihydroxyphenyl-2-methyl-L-alanine
 MOA : it’s competitive inhibitor of enzyme DOPA Decarboxylase which
results lower BP and CNS effect
 Uses: 1. used in treatment of hypertension in combination with a diuretics
 2. It’s prefered in Gestational hypertension by given orally.

18.  6. Salbutamol
 IUPAC name : (2-butylamino-1[hydroxymethyl-4-hydroxy) phenyl]
 MOA: It is strong beta-2 adrenergic agonist. It’s directly acting on
symathomimatic drug having strong action on beta- 2 receptors.
 Synthesis :salbutamol is prepared from 4,3-dihydroxy methyl Benzaldehyde
which is acetylated and kept for 10 days in ether with cyanide and acetic
acid.
 Uses: used in treatment of bronchitis and obstructive pulmonary disease

19.  7. Clonidine
 IUPAC name : 2-[(2, 6-Dichlorophenyl)amino]-2-imidazoline
 MOA : it’s centrally acting alpha alpha-2 receptor agonist leading to
reduction in sympathetic outflow from CNS
 Uses: 1. Clonidine has mild sedative action
 2. used in treatment of Tourette syndrome ( Neuropsychiatric
disorder With onset of childhood ) And ADHD
 3. Clonidine may be used to ease withdrawal symptoms associated
with long term use of alcohol, narcotics, nicotine ( smoking)

20.  8. Dobutamine:
 IUPAC name: 4-(2-[4-(4-hydroxyphenyl) butane-2-yl] amino)ethyl)
benzene 1,2- diol
 MOA: it directly stimulate beta- 1 receptor Sympathetic nervous system and
alpha-1 receptor.
 Uses : 1. used in treatment of of CHF because of positive inotropic effect

21. 9. Terbutaline
IUPAC name : ( 2- t-butylamino-1-[3, 5-dihydroxyphenyl] ethanol-1-ol)
MOA : it’s a selective beta-2 agonist
Uses : 1. It is very effective as Bronchodilator and is used in treatment of
asthma.
2. Used to arrest premature labour.

22. Indirect acting Drugs 💊💉

23.  1. Hydroxyamphetamine
 IUPAC name : 4-hydroxy-alpha-Methylphenethylamine
 MOA : derivative of amphetamine lacks CNS stimulant action. It release of
noradrenaline from nerve synapses and cause dilation of pupil.
 Uses : 1. it is used as an eye drops to dilate the pupill.
 2. It’s used as a diagnostic agent for testing Hornets syndrome ( damage of
nerves of eyes)

24.  2. Propylhexeridine
 IUPAC name : 1- Cyclohexyl-N-methylpropan-2-amine
 Uses : 1. It has symathomimatic, adrenergic, Vasoconstrictive
and Psychostimulant effect.
2. Used medicinally for relief of congestion due to colds,
allergies and rhinitis.

25.  3. Pseudoephedrine
 It is an optically active isomer of Ephedrine. Ephedrine occurs naturally in
Ephedra
 IUPAC name : ( 1S , 2S) -2-methylamino-1-phenylpropane-1-ol
 MOA : it has both alpha and beta adrenergic activity. It stimulates CNS. It
increases the BP by Increasing cardiac output.
 Uses : 1. mainly used as a nasal and bronchial decongestant.
 2. It causes Vasoconstriction si results in hypertension

26. Mixed acting drugs💊💉
 These drug indicates they act directly on the adrenergic
receptors and also effect the release of noradrenaline.
This drug at both directly and indirectly acting drugs.

27.  1. Ephedrine
 IUPAC name : (1R, 2S) -2-methylamino-1-phenylpropan-1-ol
 MOA : it has alpha and beta Adrenergic activity.It has high stimulating effect on the
CNS. It has both direct and indirect effect on adrenergic receptor.
 Uses : 1. used to control bronchial spasm in asthma
 2. Used as a CNS stimulant in narcolepsy
 3. Used ias a nasal decongestant in the form of nasal drops and nasal sprays

28.  2. Metaraminol
 IUPAC name : ( 1R, 2S)-2-amino-1(3-hydroxyphenyl) -propan-1-ol
 MOA : Same like to ephidrine
 Uses : 1. It is used as a pressor agent in various hypotensive states
 2. It is used in the treatment of Hypotension which is due to
complication of anesthesia.