3. Pharmacokinetics
Atropine and hyoscine are rapidly absorbed from g.i.t. (In contrast,
only 10ā30% of a dose of a quaternary antimuscarinic drug is absorbed after oral administration)
penetrate cornea on topical application
Atropine ā t1/2 = 3 to 4 hours
50% metabolized in liver, rest excreted unchanged in urine.
Ipratropium has positive charge so does not enter systematic circulation or
CNS (effect limited to pulmonary system)
Hyoscine can cross BBB more efficiently.
4. Pharmacological Action - antimuscarinic agents (atropine as
prototype)
all anticholinergics are competitive antagonists
CNS CVS Eye Smooth muscles Glands Body Temp.
minimal
stimulant
action(vagal,
respiratory,
vasomotor
center)
Depresses
vestibular
excitation-
antimotion
sickness
Block cholinergic
overactivity in
basal ganglia-
suppresses
tremors and
rigidity in
parkinsonism
Tachycardia (M2
block)
Initial
bradycardia due
to M2 auto
receptors block on
vagal nerve
ending
no marked effect
on bp
Topical appl.-
Mydriasis,
Cycloplegia
(M3 block),
Abolition of light
reflex
Decreased
lacrimal secretions
(dry or sandy
eyes)
visceral smooth
muscle Relaxation
(M3 block)
Bronchodilatation
Relaxant action on
ureter and urinary
bladder
Decreases sweat,
salivary,
tracheobronchial
and lacrimal
secretions
(M3 block)
Decreased secretion
of acid, pepsin and
mucus in stomach.
Bicarbonate
secretion is also
reduced
Rise in body
temperature
(high doses) ā
Inhibition of
sweating,
Stimulation of
hypothalamus
5. Antisecretory Antispasmodic Respiratory
disorders
Ophthalmologic
al
CVS Central action Poisoning
Preanesthetic
medication
(Atropine,
hyoscine,
glycopyrrolate)
Pulmonary
embolism
Peptic ulcer
selective M1
blockers
(Pirenzepine,
Telenzepine)
Intestinal and
renal colic ,
abdominal
cramps
Nervous,
functional and
drug induced
diarrhea
Relieve urinary
frequency and
urgency,
Enuresis in
children.
M3 selective
blockers ā
Oxybutynin,
Tolterodine
Ipratropium
bromide ā in
asthmatic
bronchitis and
COPD
Tiotropium
bromide ā
longer acting
(Atropine
depresses
mucociliary
clearance by
bronchial
epithelium,
Ipratropium does
not)
Diagnostic -
Testing errors
of refraction-
Tropicamide
and
phenylephrine
are used in
adults
Atropine in
children
Therapeutic ā
Atropine in
iritis,
iridocyclitis,
corneal ulcer
counteract
bradycardia
and partial
heart
block in
patients with
increased vagal
tone .
Digitalis
toxicity
Parkinsonism
As adjuvant to
L-dopa
Motion
sickness ā
Hyoscine,
Dicyclomine
(prophylactics)
Hyoscine as lie
detector
(amnesic and
depressant)
Atropine is
specific
antidote for
antiChE and
early
mushroom
poisoning.
Atropine and
Glycopyrrolate
blocks the
effects of
excess Ach
resulting
from
cholinesterase
inhibitors
(neostigmine,
physostigmine
)
Therapeutic uses
6. Adverse effects
ādry as a bone, blind as a bat, red as a beet, mad as a hatterā
Dry mouth , difficulty in swallowing and talking.
Dry sandy eyes, blurring of near vision.
Dry, flushed and hot skin (especially over face and neck)
Excitement , ataxia, delirium, dreadful visual hallucinations.
children, especially infants, are very sensitive to the hyperthermic effects of
atropine (atropine fever)
Belladonna poisoning.
C/I
In individuals with narrow iridocorneal angle (may precipitate acute
congestive glaucoma)
In elderly males with BPH (urinary retention can occur)
7. Neuromuscular blockers
(blocks NM receptors)
ā¢ Tubocurarine
ā¢ Atracurium
ā¢ Mivacurium
ā¢ Pancuronium
ā¢ Vecuronium
ā¢ Rocuronium
Non-
depolarizing
ā¢ Succinylcholine
ā¢ Decamethonium
Depolarising
ā¢ used therapeutically as adjuvant drugs in
anesthesia during surgery to relax skeletal
muscle.
ā¢ also used to facilitate intubation as well as
during orthopedic surgery.
Succinylcholine initially produces short-lasting
muscle fasciculations, followed within a few
minutes by paralysis.
Use- succinylcholine is useful when rapid
endotracheal intubation is required during the
induction of anesthesia.
Adverse effects- apnea, hyperthermia,
hyperkalemia
8. Ganglion blockers (NN blockers)
ā¢Quaternary ammonium compounds
ā¢Hexamethonium
ā¢Pentolinium
ā¢Amines
ā¢Mecamylamine
ā¢Monosulfonium compounds
ā¢Trimethaphan
Competitive
blockers
ā¢Nicotine
ā¢Anticholinesterases
Persistent
depolarizing
blockers
Large doses
Wide range of
relative
sympathetic and
parasympathetic
effects (no clinical
relevance)
Editor's Notes
Commonly known as antimuscarinics, these agents (for example, atropine and scopolamine) block muscarinic
receptors causing inhibition of all muscarinic functions. In addition, these drugs block the few
exceptional sympathetic neurons that are cholinergic, such as those innervating salivary and sweat glands.
Hyoscyamys niger
Atropa belladonna and Datura stramonium (hyoscyamine)
Dicyclomine ā antispasmodic
Pirenzepine , telenzepine ā peptic disease
Propantheline- gastritis, peptic ulcers
Hyoscine butyl bromide ā antispasmodic
Tolterodine ā selective m3 , cyp3a4 (dose reduced with inhibitors like ketoconazole and erythromycin)
Overactive bladder , urinary incontinence and urgency and frequency
Lage doses atropine cns effects ā hallucinations delirium restlessness
