Lecture covers the pharmacology of anticholinergic drugs. Includes classification, therapeutic uses, adverse effects of anticholinergics. Atropine has been described as prototype drug.
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
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 M1 receptors on
vagal nerve endings (Inhibit release of Ach)
– Moderate to high doses cause tachycardia
due to blockade of M2 receptors in heart
– ↑ SA and AV nodal conduction ↓ PR interval
7. • Glands
– All secretions under cholinergic influence
reduced (Due to M3 receptor 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 M3 receptors )
Passive Mydriasis
Paralysis of ciliary
muscle
(Blockade of M3
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
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
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.
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
23. Why
• Atropine used in children for mydriasis
• Tropicamide/ cyclopentolate preferred in
adult patients for mydriasis
Hinweis der Redaktion
Large doses- excitement, restlessness, hallucinations, agitation, medullary paralysis, coma and death
Large doses- excitement, restlessness, hallucinations, agitation, medullary paralysis, coma and death
Atropine has minimal action on ventricles which are innervated by adrenergic fibres
Adequate dose of atropine can suppress many type of reflex vagal cardiac slowing or asystole as occurring due to inhalation of irritant vapors stimulation of carotid sinus , pressure in eye balls, peritoneal stimulation, or injection of contrast medium during cardiac catheterization it can also negate cardiac slowing due to drugs like anticholinesterases, digpxin,
Secretions like sweat, salivary, nasal, throat, bronchial, gastric, lacrimal etc.
Secretions like sweat, salivary, nasal, throat, bronchial, gastric, lacrimal etc.
The action of atropine on urinary bladder is useful in relieving the urinary spasm due to inflammation, surgery, and certain neurogenic conditions,. Overactive bladder is a neurogenic bladder disorder.
Absorption: Atropine, scopolamine other tertiary amines well absorbed from the gut and across conjunctival membranes, if prepared in a suitable vehicle, these can be absorbed by the transdermal route example scopolamine transdermal patch
Distribution:
except quaternary compounds rest drugs are widely distributed, scopolamine rapidly and fully distributed in CNS and has greater effects than most of the other antimuscarinic drugs
Metabolism:
50% atropine & 80 % scopolamine metabolized by liver as conjugates . Some animal species as black rabbits are resistant to atropine actions because they possess specific enzyme, atropine esterase which degrades atropine faster than in human
Half life of atropine is 3 hours the effects of atropine decline rapidly in all organs except eye where the effects last about 72 hours or more