Anticholinergic drugs work by blocking the actions of acetylcholine in the parasympathetic nervous system. They are competitive antagonists that bind to muscarinic receptors, reversibly blocking acetylcholine transmission. Atropine is a prototypical anticholinergic derived from deadly nightshade. It causes dilation of the pupils, increased heart rate, decreased secretions, and relaxed smooth muscles. Anticholinergics are used to treat Parkinson's disease, motion sickness, asthma, peptic ulcers, overactive bladder, and other conditions. Side effects include dry mouth, blurred vision, constipation, urinary retention, and excitement or delirium in overdose.

1. Autonomic nervous system
Lecture 3
Anticholinergic Drugs
Dr. Mohit Kulmi

2. • Drugs that block or inhibit the actions of
acetylcholine (ACh) in the parasympathetic
nervous system (PSNS)
• Also called cholinergic blocking agents or
parasympatholytics
• Often referred to as
anticholinergics or antimuscarinics

3. Mechanism of Action
• Competitive antagonists
• Compete with acetylcholine
• Block acetylcholine at the muscarinic
receptors in the PSNS
• Reversible blockade of acetylcholine at
muscarinic receptors by competitive binding
• (reversal by increasing acetylcholine or
agonist ----> decreased blockade)
• Once these drugs bind to receptors, they inhibit
nerve transmission at these receptors.

5. Atropine
• Prototype antimuscarinic drug - derived from
Atropa belladonna (deadly nightshade) and
Datura stramonium (thorn apple)
• History:
• during the Italian renaissance dilated pupils
were considered desirable
• plant extracts were used as cosmetic eye drops
• hence the name belladonna or "beautiful lady"
in Italian

6. Actions
Cardiovascular effects-
• Decreased cardiovascular response to vagal
stimulation resulting in tachycardia
• Mainly, tachycardia due to antagonism of the
vagal affect.
• Vascular
– no (direct) effect
– except, dilate cutaneous vessels (red as a beet)
– block hypotensive effect of muscarinic agonists

7. Actions
CNS –
• At normal doses atropine stimulates medullary
centers, However, at higher doses produce
excitement, agitation, hallucinations and coma.
• Depresses vestibular excitation and has anti
motion sickness properties
• Supresses tremor and rigidity of parkinsonism
by blocking cholinergic overactivity in basal
ganglia.

8. Actions
Eye:
• Dilated pupils (mydriasis)
• Blocks muscarenic innervations on the circular
muscles (Mydriasis) and relaxes cilairy muscles
(Cycloplegia)
• worsens glaucoma
Gastrointestinal:
• Relax smooth muscles of GI tract
• Decrease intestinal and gastric secretions
• Decrease motility and peristalsis
• antispasmodic effect
•  Sphincter contraction

9. Actions
Respiratory system -
• Decreases bronchial secretion (used as
preanesthetic Medication,COPD)
• Dilated bronchial airways (used for treatment of
Asthma)
Genitourinary -
• Relaxes detrusor muscle
• Increased constriction of internal sphincter
• Result: urinary retention
• Relaxation of smooth muscles of ureters.
• Therefore, they are contraindicated for prostate
hypertrophy patients.

10. Glandular –
•  Salivary secretion (Dry mouth)
•  gastric Acid (used for Peptic Ulcer )
•  Sweating  Dry skin  Fever in infants
and children.
•  Bronchial Secretion (used for COPD)

11. Therapeutic Uses
Central Nervous System Disorders-
• Parkinson’s disease – Benztropine,
Trihexyphenidyl
• Those who cannot take Levodopa
• Helpful in decreasing salivation, spasticity and
tremors
• Motion Sickness (Scopolamine)
• Drug-induced extrapyramidal reactions(due to
antipsychotics)

12. Therapeutic Uses
CVS –
• Atropine is used to increase heart rate in
symptomatic bradycardias.
• Sinus node dysfunction
• Symptomatic second-degree heart block
• Sinus or nodal bradycardia (due to myocardial
infarction)

13. Therapeutic Uses
Respiratory system-
• Decreased secretions from nose, mouth,
pharynx, bronchi
• Relaxed smooth muscles in bronchi
and bronchioles
• Decreased airway resistance
• Bronchodilation
Respiratory agents are used to treat:
• Exercise-induced bronchospasms
• Chronic bronchitis
• Asthma
• Chronic obstructive pulmonary disease
• Ipratropium as inhalation (or Tiotropium)

14. Therapeutic Uses
Gastrointestinal:
• Blockade of PSNS results in:
• Decreased secretions
• Relaxation of smooth muscle
• Decreased GI motility and peristalsis
Gastrointestinal agents are used to treat:
• Peptic Ulcer: Pirenzepine
• As antispasmodic :Butylscopolamine
• Irritable bowel disease: Propantheline
• GI hypersecretory states

15. Therapeutic Uses
Urologic disorders-
• Antispasmodic effects seen in overactive
bladder and in urinary incontinence -
Oxybutynin
• Detrusor hyper-reflexia,
• Enuresis
-Increase bladder capacity
-Decrease bladder pressure

16. Therapeutic Uses
Opthalmological Disorders-
• Homatropine,tropicamide
• Accurate measurement of refractive error in
uncooperative patients (e.g, children)
• Examination of retina (Mydriasis)

17. Side Effects of anticholinergics
Body System Side/Adverse Effects
Cardiovascular Increased heart rate,
dysrhythmias
CNS CNS excitation, restlessness,
irritability, disorientation,
hallucinations,delirium

18. Side Effects of anticholinergics
Body System Side/Adverse Effects
Eye Dilated pupils, decreased
visual accommodation,
increased intraocular pressure
Gastrointestinal Decreased salivation,
decreased gastric secretions,
decreased motility

19. Side Effects of anticholinergics
Body System Side/Adverse Effects
Genitourinary Urinary retention
Glandular Decreased sweating
Respiratory Decreased bronchial secretions

20. Toxicity of Anticholinergics
• Anticholinergic overdose syndrome (Belladona
poisoning- consumption of seeds or berries of
belladona or dhatura plant) is characterized by:
Hyperthermia, delirium, dry mouth, tacycardia,
ileus, urinary retention. Seizures, coma and
respiratory arrest may occur.
• Treatment – Gastric lavage with tannic acid,
cold sponging or ice bags, Physostigmine s.c. or
i.v., diazepam to control convulsions.

22. Contraindications
• Glaucoma
• Prostatic hypertrophy
• Urinary tract obstruction
• Gastrointestinal tract obstruction
• Infectious diarrhea
• Reflux esophagitis
• Tachyarrhythmias
• Angina
• Hyperthyroidism
• Pregnancy

23. Individual Drugs
• Atropine - prototype. Antidote in OP
Poisoning.
• Ipratropium - Useful in rhinorrhea. Also
excellent bronchodilator.
• Scopolamine - depresses CNS and causes
amnesia, drowsiness, euphoria, relaxation and
sleep. Also good for motion sickness. Given
parenterally, orally and transdermally.
• Benztropine - temporary use in Parkinson’s
disease. Useful for dystonic reactions caused
by antipsychotics.

24. Individual Drugs
• Trihexyphenidyl - also used for treating EPS by
some antipsychotics. Contraindicated in
glaucoma.
• Flavoxate - relieves dysuria, urgency,
frequency, and pain with GU infections
• Oxybutynin - has direct antispasmodic effects
on smooth muscle and anticholinergic effects.
Decreases frequency of voiding.

25. Thank you!