Anti cholinergic drugs
Are those which antagonise the effect of neurotransmitter
Acetylcholine (ACh) on autonomic effectors & in the CNS
exerted through “Muscarinic receptors”. Though nicotinic
antagonists also block certain actions of Ach, they are
referred to as “Ganglion blockers” & “Neuromuscular
• Muscarinic receptor site-
• Salivary glands
• Smooth muscles of GIT
• Genitourinary tract
• Urinary bladder
• Nicotinic acetyl choline receptor site-
– Nerve endings of neuromuscular junction.
• Acetylcholine is also the neurotransmitter at
postganglionic nicotinic receptors located at
the NMJ (Neuromuscular junction) &
• Effects of anticholinergic drugs at nicotinic
cholinergic receptors is little / nil as compared
at muscarinic receptors.
• Anticholinergic drugs are considered –
Naturally Occurring (Tertiary Amine)
(Alkaloids of belladonna plants
• More potent than parent
• Lack CNS activity because of
poor penetration in brain
Mechanism of action
• Anticholinergic are the class of drugs that
block the neurotransmitter acetylcholine in
CNS and PNS.
• Anticholinergic drugs combine reversibly with
muscarinic cholinergic receptors thus
preventing access of neurotransmitter
acetylcholine in these sites.
Muscarinic Receptor Subtypes
M1 M2 M3 M4 M5
Location • CNS
Clinical Effects • Hydrogen
• Bradycardia • Salivation
Yes No No No No
• Atropine sulphate is a tertiary amine & the
naturally occuring levorotatory form is active.
• Administered IV/IM in a range of 0.01-0.02
mg/kg upto adult dose of 0.4-0.6 mg.
• Larger IV doses upto 2 mg may be required to
completely block the cardiac vagal nerves in
treating severe bradycardia.
• CNS :
-Atropine has CNS stimulant action. However
these effects are not appriciable at low doses.
-Atropine stimulates many medullary centres –
vagal, respiratory, vasomotor.
- It depresses vestibular exitation and has anti-
motion sickness property.
- It supresses tremor & rigidity of parkinsonism.
- High doses cause cortical exitation, restlessness,
disorientation, hallucination & delirium followed
by respiratory depression & coma.
• CVS :
- Most prominent effect is to cause tachycardia
due to blockade of M2 receptors at SA node.
• Eye :
- Topical instillation of atropine causes
mydriasis, abolition of light reflex and
cycloplegia resulting in photophobia &
blurring of near vision.
• Smooth muscles :
- All visceral smooth muscles that receive
parasympathetic motor innervation are relaxed
by atropine due to M3 blockade.
- Tone & amplitude of contractions of stomach &
intestine are reduced, the passage of chyme is
slowed – constipation may occur & spasm may be
- Atropine causes bronchodilatation & reduces
airway resistance especially in COPD & Asthma
- Atropine has relaxant action on ureter & urinary
• Glands :
- Atropine markedly decreases sweat, salivary,
tracheobronchial & lacrimal secretions by M3
- Skin & eyes become dry, talking & swallowing
may be difficult.
• Body temperature :
- Rise in body temperature occur at high doses due
to both inhibition of sweating as well as
stimulation of temperature regulating centre in
- Children are highly succeptible to Atropine fever.
• Local anaesthetic : Atropine has mild anesthetic
action on the cornea.
• Sensitivity of different organs & tissues to
atropine varies & can be graded as –
• Saliva, sweat, bronchial secretion > eye,
bronchial muscle, heart > smooth muscle of
intestine, bladder > gastric glands & smooth
• As anti-secretory :
- Pre-anesthetic medication : reduces excessive
salivation & respiratory secretions.
- Peptic ulcer : decreses gastric secretions &
provide symptomatic relief in peptic ulcer now
been superseded by H2 blockers.
• As anti-spasmodic :
- If there is no mechanical obstruction intestinal &
renal colic, abdominal cramps symptomatic relief
- Gastritis, gastric hypermortility.
- To relive urinary frequency & urgency.
• Can be given in patients of Bronchial Asthma
• As mydiatric & cycloplegic.
• As cardiac vagolytic
• For central actions in Parkinsonism as an
adjuvant to levodopa.
• To antagonise muscarinic effects of anti-
Cholinesterase i.e OP Poisoning with dose 2mg
IV with repeated doses and early mushroom
• Belladona poisoning due to drug overdose.
• Dry mouth, difficutly in swallowing and talking.
• Dry ,flushed and hot skin.
• Fever difficulty in micturition , decreased bowel
• Dilated pupil, photophobia, blurring of near
• Excitement, ataxia, delirium, hallucination.
• Convulsion and coma may occur in severe
• Treatment :
Physostigmine 15- 60 micro gram / kg IV every
1- 2 hourly.
• Contraindications :
- Narrow angle glaucoma
• Glycopyrolate is a synthetic product that differs from
atropine in being a quaternary amine.
• The pre-medication dose is 0.005 – 0.01 mg/kg upto 0.2-0.3
mg in adults.
• Clinical consideration :
• Because of its quaternary structure, glycopyrolate can’t
cross BBB & is almost devoid of CNS & Opthalmic activity.
• Potent inhibition of salivary gland & respiratory tract
secretions is the primary rationale for using glycopyrolate
• Heart rate increases after IV administration.
• It has longer duration of action than atropine sulphate i.e 2-
• Scopolamine is a naturally occuring tertiary amine.
• It’s dose is 0.3-0.5 micro gram I/M.
• Clinical Consideration :
• Lipid soluble.
• Easy penetrate BBB.
• More potent antisialagogue than Atropine & causes
greater CNS effects
• Clinical doses results in restlessness, drowsiness,
amnesia, dizziness & delirium.
• It has the added virtue of preventing motion sickness.
• The lipid solubility allows trans-dermal absorption &
has been used to prevent post-operative nausea &
• Best avoided in patients with closed angle glaucoma.
1. Lipid solubility - Lipid soluble - Poorly soluble (Quaternary
2. Blood brain
- Good - Minimum ability of crossing
3. Metabolization - 50% from liver -
4. Excretion - 18% unchanged - 80% unchanged
5. Treatment - bradycardia at low dose
- 0.2 – 0.4 mg IV
-Dose for intra operative
-Max dose for bradycardia
Hiccups (Occurring after
laryngeal mask placement)
Intra operative bradycardia
7. Effect on smooth
Decreases tone of smooth
muscles of biliary tract & ureter
- Less then scopolamine More
9. T½ - 2.3 hrs Prolonged in uremic patients
Central Anticholinergic Syndrome
• Anticholinergic drugs like scopolamine, atropine can
enter central nervous system (CNS) and produce some
unusual symptoms which are characterized in a
syndrome which is known as central anticholinergic
Symptoms are -
– Hallucination to somnolence
Glycopyrrolate does not easily cross BBB & not likely
• References :-
Stoelting’s Pharmacology & Physiology.
Morgan & Mikhail’s Clinical Anesthesiology.
KD Tripathi Essentials of Medical Pharmacology.