5.adrenergics and antiadrenergics

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