Anticholinergic Drugs – Pharmacology B. Pharma 5th Semester PDF Notes

Anticholinergic Drugs




     Anticholinergic drugs

     Pharmacology of atropine

     Atropine poisoning and its treatment

At the end of this lecture, student will be able to

       List the anticholinergic drugs

       Explain the pharmacology of atropine

       Explain atropine poisoning and its treatment

Anticholinergic drugs (Parasympatholytics)

Muscarinic Receptor Blockers

       Atropine & related alkaloids from  Atropa belladonna

Belladonna Alkaloids

       Atropine (dl – hyoscyamine)

      Ester of tropic acid + Tropine

       Scopolamine (Hyoscine)

      Ester of tropic acid + Scopine

MOA of Atropine

       Block peripheral and central effects of Ach

       Competitive antagonism

       Dose for M blockade varies from organ to organ

       Salivary, bronchial secretion – extremely sensitive

       Vagal stimulation: Not completely abolished

       Large doses: NN Blockade

Differences between Atropine and Scopolamine

Atropine Scopolamine
CNS stimulation CNS depression
More active on heart, gut, bronchial smooth muscle Prominent effects on iris, ciliary body, salivary, bronchial, sweat secretion
Longer duration Shorter

Pharmacological Actions of Atropine

       Secretion: Decreases (except milk)

       Salivary: Dryness of mouth, difficulty in swallowing

       Gastric: Decrease volume and acidity, mucous and gastric enzymes

       Other secretions:

      Bronchial secretions become viscid

      Inhibits sweat secretion

      Not significant on lacrimal secretion

Pharmacological actions of Atropine on smooth muscle

       GIT: Decreases tone and motility, Antispasmodic

       Biliary tract: Weak antispasmodic

       Urinary tract: Decreases ureteral peristalsis, urinary retention

       Bronchi: Relax bronchi and bronchioles, dries up secretion

       Uterus: No significant effect

Pharmacological actions of Atropine on eye

       Mydriasis (Blocks cholinergic nerves of sphincter if iris)

       Photophobia (Sphincter paralysis)

       Ciliary smooth muscle paralysis – cycloplegia

       No changes in i.o.t in normal individuals

       In narrow angle glaucoma: increases

       Due to relaxation of ciliary muscle and crowding of iris

Pharmacological Actions of Atropine on CVS


       Initially decreases HR – ++ of vagal nuclei

       Tachycardia: X of M2 R in SA node

       Counters the vasodilation and hypotension of cholinergic agents

       Toxic dose: Dilation of cutaneous blood vessels – atropine flush+ hypotension

Pharmacological Actions of Acetylcholine on CNS


       Mild  + of medullary vagal nuclei & higher cerebral centers

       Produces bradycardia and increase rate, depth of respiration


       Depress RAS

       Euphoria, drowsiness, amnesia, dreamless sleep

       Motion sickness (Vestibular function)


       All route: Satisfactory absorption

       From eye, intact skin: Not significant

       Partly detoxified by liver, partly unchanged

       Cross placental barrier, sec in milk and saliva

       Excreted through urine


       Infants, children – CNS toxicity

       Elderly – Glaucoma, urinary retension

       Locally –  Allergic dermatitis, conjunctivitis, swelling of eyelids

       Mild – Xerostomia, flushing, constipation

       Acute atropine poisoning

       Children: 10-20 mg, Adults: 80 – 130 mg

       Wide margin of safety

Acute Atropine Poisoning

Peripheral blockade

       Dry mouth, difficulty in swallowing, intense thirst

       Tachycardia, palpitation, flushing


       Dilation of pupils, blurred vision, photophobia

       Urinary urgency, difficulty in micturition, urinary retention

       Rash – Face, neck, upper part of trunk

Acute Atropine Poisoning – Mydriasis

Central effects

       Initial stimulation subsequent depression

       Excitement, restlessness, motor in co-ordination

       Slurring of speech

       Disturbance of memory, confusion, hallucination

       Severe poisoning: Depress vasomotor centre

Treatment of Atropine poisoning

       Gastric lavage

       Universal antidote

       Slow IV – physostigmine (1 – 4 mg) – cross BBB

       SC – neostigmine (2-5mg)

       Restlessness, delirium – Diazepam

       Darkroom – photophobia

       Catheter – for urinary retention

       Tepid sponging – pyrexia

Therapeutic uses

       Gastrointestinal colic

       Ocular conditions

       Preanesthetic medication

       OPC poisoning


       To abolish AV block

       Urinary incontinence

       Motion sickness


       With caution: above 40 years (Acute angle glaucoma)

       Enlarged prostate – urinary retention

       Chronic lung diseases

       CHF with tachycardia

Frequently Asked Questions

  1. Are all anticholinergic drugs associated with cognitive decline?
    • Understanding the nuances of cognitive effects.
  2. Can anticholinergic medications be stopped abruptly?
    • Exploring the challenges and recommended withdrawal strategies.
  3. What are some natural alternatives to anticholinergic drugs?
    • Exploring lifestyle changes and natural remedies.
  4. How do regulatory guidelines ensure the safety of anticholinergic prescriptions?
    • Understanding the role of regulations in healthcare.
  5. Where can I find more resources on anticholinergic drug research?
    • Exploring reliable sources for up-to-date information.


       Block peripheral and central effects of Ach

       Atropine (dl – hyoscyamine)

      Ester of tropic acid + Tropine

      Mild  stimulation of medullary vagal nuclei & higher cerebral centers

       Scopolamine (Hyoscine)

      Ester of tropic acid + Scopine

      Depress RAS

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