Anticholinergic drugs

Lecture covers the pharmacology of anticholinergic drugs. Includes classification, therapeutic uses, adverse effects of anticholinergics. Atropine has been described as prototype drug.

1. Anti-cholinergic drugs
Dr Naser Ashraf Tadvi

2. Objectives
•Classify anticholinergic drugs
•Describe the mechanism of action,
pharmacological actions, therapeutic uses
and adverse effects of anticholinergic
drugs
•Describe the treatment of atropine toxicity

3. Classification of antimuscarinic drugs
Natural alkaloids
•Atropine
•Hyoscine
(Scopolamine )
Semisynthetic derivatives
•Atropine Methonitrate
•Homatropine
•Hyoscine butylbromide
•Ipratropium bromide
•Tiotropium bromide
Synthetic Compounds
Antisecretory-antispasmodics
Quaternary Comps.
•Propantheline
•Oxyphenonium
•Clidinium
•Glycopyrrolate
Tertiary amines
•Dicyclomine
•Valethamate
•Pirenzepine
Mydriatics
Cyclopentolate
Tropicamide
Vasicoselective
•Oxybutinin
•Tolterodine
•Flavoxate
•Darifenacin
•Solifenacin
•Trospium
Antiparkinsonian
•Trihexyphenidyl
(Benzhexol)
•Procyclidine
•Biperiden
•Benztropin

4. Mechanism of action of
anticholinergic drugs

5. Pharmacological actions of atropine
•CNS:
–Mild CNS stimulant action in therapeutic
doses
–Large doses-excitement, restlessness,
hallucinations
–Antiparkinsonian effect by reducing
cholinergic overactivity in basal ganglia
–Antimotion sickness effect by suppressing
vestibular disturbances

6. Pharmacological actions of atropine
•CVS :
–Low doses of atropine cause bradycardia due
to blockade of presynaptic M
1receptors on
vagal nerve endings (Inhibit release of Ach)
–Moderate to high doses cause tachycardia
due to blockade of M
2receptors in heart
–↑ SA and AV nodal conduction ↓ PR interval

7. •Glands
–All secretions under cholinergic influence
reduced (Due to M
3receptor block)
–Except Milk and Bile secretion
–Skin and mucus membrane become dry
Pharmacological actions of atropine

8. •Smooth muscles
–GIT:
•↓Tone and motility
•↑ Sphincter tone may cause constipation
•Relaxes smooth muscle of gall bladder
–Genitourinary tract
•Relaxes detrusor muscle of bladder & ↑ tone of trigone
and sphincter (Retention of urine)
–Bronchi
•Relaxes bronchial smooth muscle
•↓ secretion & muco-ciliary clearance (mucus plug may
form)
Pharmacological actions of atropine

9. Pharmacological actions of atropine
Paralysis of constrictor pupillae
(Blockade of M
3receptors )
Passive Mydriasis
Paralysis of ciliary
muscle
(Blockade of M
3
receptors )
Cycloplegia
(loss of accommodation)
Atropine action on eye on topical administration

10. Pharmacokinetics of anticholinergic
drugs
•Absorption :
–Atropine, scopolamine other tertiary amines well absorbed
•Distribution:
–except quaternary compounds rest drugs are widely
distributed.
•Metabolism:
–50% atropine & 80 % scopolamine metabolized by liver as
conjugates
•Excretion
–50% atropine excreted unchanged in urine
–t ½ = 3 hours

11. Therapeutic uses of anticholinergic
drugs
1.Parkinsonism
2.Motion sickness
3.Bronchial Asthma & COPD
4.Vagolytic to treat sinus bradycardia, partial
heart block
5.Antispasmodic in dysmennorhoea
6.Intestinal, renal, biliary colic
7.Relieve bladder spasm after uro-surgery,
Urinary incontinence

12. 8. Ophthalmic uses
–Mydriatic and cycloplegic for refraction testing
–Mydriatic for fundoscopy
–Iridocyclitis used alternatingly with miotics to
break the adhesions between iris and lens
9. Preanaesthetic medication
–Atropine or glycopyrrolate used to prevent vagal
bradycardia and laryngospasm
Therapeutic uses of anticholinergic
drugs

13. 10. Sialorrhoea
11. Organo-phosporus Poisoning
12. some type of mushroom poisoning
13. Along with neostigmine to counter its muscarinic
effects
Therapeutic uses of anticholinergic
drugs

14. Adverse effects
•Dry mouth, difficulty swallowing
•Photophobia, blurred vision
•May precipitate acute congestive
glaucoma
•Retention of urine
•Constipation
•Restlessness, excitement
•Tachycardia, palpitations

15. Atropine toxicity
•Hot as a hare: hyperpyrexia
•Red as beetroot: cutaneous vasodilation
•Dry as a bone: dry skin
•Blind as a bat: mydriasis and cycloplegia
•Mad as hatter: restlessness, excitement

16. Treatment of atropine poisoning
•Hospitalization
•Gastric lavage
•Tepid sponging
•Diazepam to control convulsions
•Antidote for atropine poisoning is
physostigmine 1-4 mg injected slowly.

17. Contraindications of atropine
•Acute congestive glaucoma
•Elderly patients (More prone for urinary
retention)

18. Classification of anticholinergics according
to clinical use
S.NUse Drug
1Ophthalmic use Cyclopentolate, tropicamide,
homatropine
2Antispasmodic Dicyclomine, Hyoscine methyl
bromide, propantheline
3Urinary
antispasmodic
Oxybutinin, flavoxate, darifenacin,
trospium
4BronchodilationIpratropium, tiotropium
5Parkinsonismbenztropine, biperidine, benzhexol

19. Summary
•Classification
•Pharmacological actions
•Therapeutic uses
•Adverse effects
•Contraindications

20. What is the rationale of
•Use of atropine in preanesthetic
medication
•Preference of physostigmine over
neostigmine in treatment of OPP
•Scopolamine in motion sickness

21. What are differences between
•Atropine and scopolamine
•Ocular actions of atropine and ephedrine

22. Name
•Specific M1 receptor blocker
•Specific M3 blockers

23. Why
•Atropine used in children for mydriasis
•Tropicamide/ cyclopentolate preferred in
adult patients for mydriasis