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. • 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.
4.
5. • Prototype antimuscarinic drug - derived from
Atropa belladonna (deadly nightshade) and
Datura stramonium (thorn apple)
• History:
• plant extracts were used as cosmetic eye drops
• hence the name belladonna or "beautiful lady"
in Italian
6. 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. 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. 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. 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. 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. 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. 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. 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. Urologic disorders-
• Antispasmodic effects seen in overactive
bladder and in urinary incontinence -
Oxybutynin
• Detrusor hyper-reflexia,
• Enuresis
-Increase bladder capacity
-Decrease bladder pressure
20. • 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.
23. • 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. • 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.
