Atropin Flashcards
Receptors of parasympathetic System
1) Muscarnic receptors (MR) - > More common
2) Nicotinic receptors (NR
Classification, succording to selectivit
1-Non-selective Muscarinic Antagonists: they block all types of muscarinic receptors.
2-Selective Muscarinic Antagonists
Source and chemistry
natural from plant origin (Atropa belladonna).
Absorption
- Oral
2.i.M
3.i.V - Local eye drops
Distribution
pass B.B.B.
Metabolism
partly metabolized by the liver
Excretion
partly excreted in urine unchanged.
Why rabbits don’t effect by atropine
atropinase
M.o. action:
non-selective competitive muscarinic antagonist.
Local actions:
A- On skin: local anesthetic action
On eye:
1- Passive mydriasis
2- Loss of light reflex.
3- Cycloplegia
4- Increase IOP.
5- Xerophthalmia-> decrease lacrimal secretion
Systemic Actions heart
Tachycardia
Atropine may cause initial transient bradycardia followed by tachycardia if given by IV
Give reason for the intial bradycardia
- Central action: atropine stimulates vagal cardio-inhibitory center (CIC)
- Block of presynaptic M2 receptors (before blocking post-synaptic M2 receptors) leading
to stimulation of acetylcholine release which acts on post-synaptic M2 receptors causing
initial bradycardia.
When tachycardia happens
Tachycardia occurs when atropine blocks post-synaptic M2 receptors
Systematic action on blood vessels
1.Therapeutic doses of atropine have no effect on most blood vessels.
2.Large and toxic doses of atropine cause vasodilatation ( Atropine flush), especially in
children affecting face and neck. This may be due to histamine release.
Bronchi
bronchodilatation.
GIT
Inhibition in stomach secrétions
Urinary bladder
relaxation of the wall and contraction of the sphincter
Effect on gland بينشفها علي الكل 5
A)Lacrimal glands: decreases lacrimation causing dryness of the eye (Xerophthalmia).
B) Salivary glands: decreases salivary secretion leading to dry mouth (Xerostomia)
C)Bronchial glands: atropine decreases watery secretion leading to thick viscid secretion
D) Gastric glands: atropine decreases gastric secretion (both volume of secretion and HCl
F)Sweat glands: atropine decreases sweat secretion causing atropine fever
CNS Actions (Stimulant actions:)
1-Stimulation of Respiratory center (R.C).
2- Stimulation of cardio-inhibitory center (C.I.C.)
3- Large doses stimulate the cerebral cortex leading to restlessness, anxiety,
CNS Actions: Depressant actions
1-Antiemetic action: by blocking M receptors in the vomiting center.
2- Antiparkinsonian action: by blocking M receptors in the basal ganglia
Therapeutic uses:
1- CNS:
Treatment of parkinsonism
II. Anti-emetic.
III. Pre-anaesthetic medication to:
Prevent bradycardia
Decrease in salivary and bronchial secretion to avoid pneumonia.
Avoid vomiting that may cause aspiration pneumonia
Therapeutic uses: CVS
treatment of bradycardia and heart block.
Respiratory system:
prevention bronchial asthma
GIT:
Antispasmodic, antidiarrheal and treatment of peptic ulcer
Urinary System
urinary incontinence
Exocrine Glands:
Hyperhidrosis
Adverse effects
1- Tachycardia,
2-Xerostomia.
3-increased IOP
4-contract the urinary sphincter
5-increases skin temperature due to decrease sweat secretions
6-decrease muco-ciliary effect
Contraindications
1-Angina pectoris.
2-Constipation.
3-Glaucoma.
4- fever
Synthetic Atropine Substitutes
1-Homatropine : Shorter duration of action.
And Less cycloplegia
2-Hyoscine butyl bromide (Buscopan): Treatment of intestinal colic and peptic ulcer
3-Benztropine: improves tremors.
4-Oxybutynin: treatment of urinary incontinence
5-Ipratropium- Tiotropium- Oxytropium: used for bronchial asthma
Advantage of atropine 5
1-They are given by inhalation.
2-They do not cause dryness of bronchial secretion.
3- They do not decrease muco-ciliary activity.
4-don’t effect CNS
