Dr. RAGHU PRASADA M S
DEPT. OF PHARMACOLOGY
SSIMS & RC.
Central Nervous System (CNS) - Brain and spinal
Peripheral Nervous System (PNS) - Located
outside the brain & spinal cord Autonomic
Nervous System (ANS) & the somatic
The PNS receives stimuli from the CNS & initiates
responses to the stimuli after it’s interpreted by the
Exception-post ganglionic sympathetic fibres to
All somatic motar neurons
All preganglionic fibres
Post ganglionic parasympathetic fibres
75% of all parasympathetic nerve fibers are in the
These nerves supply the thoracic and abdominal
organs, which innervate the heart, lungs, esophagus,
stomach, small intestine, proximal half of the colon,
liver , gallbladder, pancreas and upper portions of
These agents block muscarinic receptors and
inhibit muscarinic functions, they are useful in
different clinical situations, they have no actions on
skeletal neuromuscular junctions or autonomic
ganglia because they do not block nicotinic
A B C D1 min
M-EFFECTS OF ACH
2 mcg i.v.
2 mg i.v.
A belladonna alkaloid has a
high affinity for muscarinic
receptors, it is a competitive
inhibitor of muscarinic receptors
preventing ACH from
binding to that site.
CNS. Atropine has an overall stimulant action. Its
stimulant effects are not appreciable at low doses which
produce peripheral effects because of restricted entry
into the brain. Hyoscine produces central depressant
effects even at low doses.
• Medullar centers - vagal, respiratory, and vasоmotor.
• By blocking the relative cholinergic overactivity in
basal ganglia, it suppresses tremor and rigidity
• High doses cause cortical excitation, restlessness,
disorientation, hallucinations, and delirium
followed by respiratory depression and coma.
Low dose-M2 receptor on cholinergic N auto-
inhibitary cholinergic action bradycardia
Moderate dose- M2 receptor on post junctional SAN,
AVN blkescape the heart from
action chronotropic, dronotropic
Toxic dose-M3 receptor-endothelium blockade NO
release is blockedsmooth muscle donot
relaxprevention of cholinergic mediated dialation
Autonomic control of pupil (A) and site of
action of mydriatics (B) and miotics (C)
Topical instillation of atropine (0.1%)
causes mydriasis, abolition of light reflex,
and cycloplegia, lasting 7–10 days.
This results in photophobia and blurring
of near vision.
The intraocular tension rises, specially in
narrow angle glaucoma
All visceral smooth muscles with parasympathetic
innervation are relaxed (M3-blokade).
Tone and amplitude of GIT are reduced.
Spasm may be reduced, constipation may occur.
Peristalsis is only incompletely suppressed because it is
primarily regulated by local reflexes and other
neurotransmitters (serotonin, encephalin, etc.).
Atropine causes bronchodilation and reduced airway
resistance, especially in asthma patients.
Inflammatory mediators (histamine, PGs, and kinins)
increase vagal activity in addition to their direct action
on bronchial muscle and glands. Atropine attenuates
their action by antagonizing the reflex vagal component.
It has a relaxant action on the ureter and urinary
bladder. Urinary retention can occur in older men with
Glands. Atropine decreases sweat, salivary, tracheo-
bronchial, and lacrimal secretion (M3-blockade). Skin
and eyes become dry, talking, and swallowing my be
Atropine decreases less the secretion of acid and pep-
sin and more of the mucus in the stomach.
Body temperature. Rise in body temperature occurs at
higher doses, and is due to both inhibition of sweating
as well as stimulation of the temperature regulating
centre in the hypothalamus. Children are highly
Local anaesthetic action. Atropine has a mild
anaesthetic action on the cornea.
The sensitivity of different organs and tissues
to atropine varies and can be graded as
Saliva, sweat, bronchial secretion > eye >
bronchial muscles > heart > intestinal and
bladder smooth muscles > gastric glands
and gastric smooth muscles
Atropine and hyoscine are rapidly absorbed from
GIT. Applied to the eyes they penetrate the cornea.
Passage across BBB is somewhat restricted.
50% of atropine is metabolized in the liver and
excreted unchanged in urine.
It has t1/2 3–4 h.
Hyoscine is more completely metabolized and has
better BBB penetration.
Some rabbits have a specific atropine
esterase which degrades atropine very rapidly.
Scopalamine (hyoscine): A belladdona alkaloid
produce peripheral effects similar to atropine, it has
greater actions on CNS and longer duration of
Most effective in motion sickness, it is effective also
in blocking short term memory, it produce sedation
but at higher doses cause excitement.
Depresses CNS and causes amnesia, drowsiness,
euphoria, relaxation and sleep.
Given parenterally, orally and transdermally.
It is inhalational derivative of atropine useful in
treating asthma and COPD in patients unable to take
adrenergic agonist. Useful in rhinorrhea. Also
Agents like homatropine, cyclopentolate, and
tropicamide used mainly in ophthalmology.
Benztropine-used in drug induced Parkinson’s
disease. Useful for dystonic reactions caused by
Trihexyphenidyl -also used for treating Extra
Pyramidal Symptoms caused by some antipsychotics.
Flavoxate-relieves dysuria, urgency, frequency and
pain with genito-urinary infections
Oxybutynin -has direct antispasmodic effects on
smooth muscle and anticholinergic effects.
Decreases frequency of voiding.
Tolterodine -is competitive, antimuscuranic
anticholinergic that inhibits contraction. More
selective for this area than elsewhere in the body.
- They act on nicotinic receptors of the autonomic
- They have no selectivity toward the parasympathetic
or sympathetic ganglia .
- The effect of these drugs is complex and
unpredictable so rarely used therapeutically,
- Used mainly in experimental pharmacology.
- Increase peristalsis and secretions.
- On large dose of nicotine
- A)Blood pressure falls because of ganglionic blockade
- B)Activity both in GIT and UB musculature decrease.
Short acting competitive nicotinic ganglionic blocker
that must be given by i.v infusion
It is used for the emergency lowering of the blood
pressure in hypertension caused by pulmonary
edema or dissecting aortic aneurysm, when other
agents cannot be used.
- Drugs that block cholinergic transmission between
motor nerve ending and the nicotinic receptors on
the neuromuscular end plate of the skeletal muscle.
- They are structural analogs of ACH.
Mydriatic and cycloplegic agent in the eye to permit
measurement of refractive errors. Mydriasis and
cycloplegia for surgery
RS-In bronchospasm whether related to asthma or
COPD bronchodilating effects
CVS-Atropine is used to increase heart rate in
symptomatic bradycardias and higher blocks
GIT-Antispasmodic agent: Relax GIT and bladder.
Helpful in treating irritable colon or colitis
Useful in gastritis, pylorospasm and ulcerative colitis
as they slow motility
Antispasmotic effects seen in overactive bladder and
in urinary incontinence
Antidote for cholinergic agonists: To treat
organophsphorus poisoning (present in insecticides),
and mushroom poisoning.
Antisecretory agent: To block the secretion of upper
and lower respiratory tracts prior to surgery.
Helps to prevent vagal stimulation and potential
CNS- Parkinson’s Disease-
Useful in those with minimal side effects
Those who cannot take Levodopa
Helpful in decreasing salivation, spasticity and tremors
Absorption of other drugs is slowed because atropine
delays gastric emptying. So dose of levodopa, in
parkinsonism may have to be increased. But the extent of
digoxin and tetracyclines absorption may be increased.
Antacids interfere with the absorption of anticholinergics.
Antihistaminics, tricyclic antidepressants, phenothiazines,
pethidine have anticholinergic property additive side
MAO inhibitors interfere with the metabolism of central
antiparkinsonian drugs (biperiden and others) delirium
Dry mouth, difficulty in swallowing and talking;
Difficulty in micturition
Dilated pupils, photophobia, blurring of near vision;
palpitation; excitement, psychotic behavior,
Ataxia, delirium, hallucinations; hypotension, weak
and rapid pulse, cardiovascular collapse with
Convulsion and coma (in very high doses).
It is very risky in individuals with glaucoma and BPH
Diagnosis: 1 mg neostigmine s.c. fails to induce
Treatment: Gastric lavage with tannic acid (KMnO4 is
ineffective in oxidation of atropine). The patient must
be kept in a dark quiet room. Galantamine or physo-
stigmine (1-3 mg s.c./i.v.), diazepam against
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