This document discusses the adrenergic system including adrenergic receptors, location and functions of different receptor types, adrenergic drugs, and pharmacological actions. It also covers adrenergic receptor antagonists including classifications of alpha-blockers and beta-blockers, their uses and adverse effects. The key points are: there are alpha and beta adrenergic receptors which are located in various organs and tissues and have different functions; common adrenergic drugs act as pressor agents, bronchodilators or cardiac stimulants; and adrenergic receptor antagonists like alpha-blockers and beta-blockers are used to treat conditions like hypertension, angina, heart failure and gl

1. ADRENERGIC
SYSTEM

2. ADRENERGIC RECEPTORS
Alpha receptors (α) – α1 & α2
Beta receptors (β) – β1 , β2 & β3
Dopamine receptors (D) – D1 to D5
Receptor type Location & Function
Postsynaptic α1
 Smooth muscles – Contraction
 Blood vessels – Vasoconstriction
 Radial muscle of iris – Mydriasis
Salivary glands – Secretion
Gut – Relaxation
 Liver - Glycogenolysis

3. Receptor type Location & Function
Presynaptic α2 Adrenergic & Cholinergic nerve endings –
decreases the release of neurotransmitters
Postsynaptic α2
 Blood vessels – Constriction
 Ciliary epithelium – decreases aqueous
secretion by the ciliary body

4. Receptor type Location & Function
Postsynaptic β1
 Heart – increases heart rate and force of
contraction
Postsynaptic β2
 Smooth muscles ( bronchi, bladder wall,
blood vessels, pregnant uterus ) –
Relaxation
 Liver – glycogenolysis
 Vasodilatation
Increases the secretions of ciliary
epithelium
Postsynaptic β3
 Adipocytes – stimulates lipolysis
 Thermogenesis

5. Adrenergic drugs:
 Pressor agents – Noradrenaline, dopamine,
phenylephrine, ephedrine
 Cardiac stimulants – Adrenaline, isoprenaline
 Bronchodilators – salbutamol, terbutaline
 Nasal decongestants – Phenylephrine,
xylometazoline, oxymetazoline, naphazoline
 CNS stimulants – Amphetamine
 Anorectics – Fenfluramine, sibutramine
 Uterine relaxants – Ritodrine, isoxsuprine

6. PHARMACOLOGICAL ACTIONS
 Heart :
Increase in heart rate, force of contraction,
conduction velocity , cardiac output
Rise in BP
 Vascular effects :
α action – vasoconstriction (cutaneous, renal,
viscera, mucous membrane)
β2 action – vasodilatation (skeletal muscle, liver,
coronaries)

7.  Effects on smooth muscles :
a. Bronchi – bronchodilatation and decreases
secretion and relieves mucosal congestion
b. Gut – relaxation
c. Urinary tract – detrusor muscle relaxation
contraction of trigone and sphincter
Hinders micturition.
d. Uterus – Non-pregnant –contraction
Pregnant – Relaxation

8.  Metabolic effects :
a. Glycogenolysis in liver& skeletal muscle
– hyperglycemia
b. Increase in FFA due to lipolysis in adipose tissue
c. Inhibition of insulin release
 Eye:
Active mydriasis
Decreases intraocular pressure

9. Therapeutic uses-
 Acute anaphylactic shock- adrenaline -
life saving drug
 Bronchial asthma
 To prolong the duration of local
anaesthetic action – adrenaline +LA
 As a local haemostatic- epistaxis &
capillary oozing
 Cardiac resuscitation- cardiac arrest
due to drowning, electrocution- i.v.
adrenaline
 Glaucoma- dipivefrine(prodrug)

10. ADRENERGIC RECEPTOR
ANTAGONISTS

11. Adrenergic receptor antagonists
Alpha-blockers Beta-blockers

12. ALPHA BLOCKERS

13. ALPHA-BLOCKERS
1) Non-selective(α1 and α2) blockers
Reversible: Phentolamine
Irreversible: Phenoxybenzamine
2) Selective α1-blockers;
Prazosin, terazosin, doxazosin, tamsulosin
3) Selective α2-blockers;
Yohimbine

14. USES OF ΑLPHA-BLOCKERS
1) Pheochromocytoma
Phenoxybenzamine ( preoperatively)
2) Hypertensive emergencies
3) Tissue necrosis Phentolamine
4) Male sexual dysfunction
5) Essential hypertension - α1-blockers- less
tachycardia & favorable effects on lipid profile
6) Benign prostatic hyperplasia

15. ΒETA BLOCKERS

16. Classification:
o Non-selective (β1 & β2) blockers :
• Propranolol
• Timolol
• Sotalol
• Nadolol
• Pindolol

17. Selective β1 Blockers :
• Atenolol
• Acebutolol
• Bisoprolol
• Esmolol
• Metoprolol
Selective β2 blocker :
. Butoxamine

18. β blockers with additional α blocking/
vasodilator property
• Labetalol
• Carvedilol
• Celiprolol
• Nebivolol

19. Pharmacological actions:
CVS : cardiac β1 receptor blockade –
 HR, FOC, conduction velocity – decreases CO
 cardiac work load & myocardial O2 demand
 S-A node & A-V nodal activity – depressed
 Automaticity of heart – suppressed
 Chronic use – BP in hypertensive patients.

20. Respiratory tract :
• In asthmatics - Blockade of β2 receptors in
bronchial smooth muscle.
Severe bronchoconstriction
Eye:
o Decreases aqueous humor secretion - IOP
in glaucoma.

21.  Therapeutic uses of β-blockers :
Hypertension- preferred in patients
with angina, MI
Advantages: Less sodium water
retention
Longer duration of action
Cheaper, well tolerated
Angina pectoris
Cardiac arrhythmias- mainly in atrial
arrhythmias

22. Congestive heart failure- carvedilol,
metoprolol, bisoprolol
decreases mortalilty rate
Pheochromocytoma- to control cardiac
manifestations but should be given alone
Glaucoma – reduce production of
aqueous humor
Timolol, carteolol, levobunolol, betaxolol
Timolol- does not affect pupil size,
longer duration of action, well tolerated

23. Prophylaxis of migraine
Hyperthyroidism
Essential tremors
Acute anxiety states
Alcohol withdrawal

24. Adverse effects
 Bradycardia
 Bronchoconstriction – Bronchial asthma &
COPD
 Sleep disturbances, hallucinations, fatigue &
mental depression
 Hypoglycemia – patients receiving insulin &
oral hypoglycemic drugs.

25.  Muscular weakness
Abrupt withdrawal symptoms

26. THANK YOU