parasympathomimetic

1. INTRODUCTION
TO
AUTONOMIC NERVOUS SYSTEM(ANS)
NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
(Brain, Spinal Cord)
PERIPHERAL NERVOUS SYSTEM
Afferent Pathway Efferent Pathway
AUTONOMIC NERVOUS SYSTEM
(Involuntary)
PARASYMPATHETIC
NERVOUS SYSTEM
SYMPATHETIC NERVOUS
SYSTEM
SOMATIC NERVOUS SYSTEM
(Voluntary)

2. AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system is that division of nervous
system that controls all vital functions & supplies the
viscera. It is largely autonomous & its activities are not
under direct control, hence known as involuntary nervous
system. It maintains the internal environment
(homeostasis).
The two divisions of the autonomic nervous system are
sympathetic & parasympathetic that differs in their
anatomical arrangement, their effects & mechanism of
action.
Sympathetic
Adrenaline/Epinephrine
Fight, Flight, Fright
(Emergency)
Parasympathetic
Neurotransmitter: Acetylcholine
Action For Rest, Sleep, Digest :
(Conservation)

3. • Generally an organ is innervated by both sympathetic &
parasympathetic nervous system. Thus the activity of the
organ is dependent upon the activity of these two. If one
gets depressed another gets raised.
• Some organs are innervated by only one system:
Parasympathetic: Ciliary muscles, Glands of stomach,
Pancreas
Sympathetic: Spleen, blood vessels, hair follicles

5. Thoracolumbar
(Adrenaline)
Craniosacral
(Acetylcholine)

8. 1.Muscarinic Receptors
(Metabotropic)
Responses
M1: Ganglionic cells &
Central Neurons
Depolarization,
Learning, memory, motor
functions
M2: Heart Decrease rate, force
M3: Smooth Muscles Contraction, secretion
M4: CNS Inhibits Ach release
M5: CNS Decreases cAMP levels
Cholinergic drugs acts through cholinergic receptors.
Cholinergic Receptors/Cholinoceptors are of 2 types:
Muscarinic receptors are stimulated by muscarine & blocked by atropine

9. 2.Nicotinic Receptors
(Ionotropic)
Responses
NN: Neurones Depolarization
NM: Skeletal Muscles Contraction
Nicotinic receptors are stimulated by nicotine
& blocked by d-tubocurarine or hexamethonium

10. Synthesis of Acetylcholine

11. Synthesis:
Acetyl CoA + Choline
Choline acetyl transferase
Acetylcholine + CoA
Destruction:
Acetylcholine (Ach) Choline + Acetate
Cholinesterase

12. Cholinergic agonist (Directly acting) Anticholinesterases (Indirectly acting)
1.Choline esters Acetylcholine(Ach)
Methacholine
Carbachol
Bethanechol
1.Carbamates
(Reversible)
Physostigmine
Neostigmine
Pryidostigmine
Rivastigmine
Edrophonium
Donepezil
2.Acridine
(Reversible)
Tacrine
2.Alkaloids Pilocarpine
Muscarine
Arecoline
1.Organophosphates
(Irreversible)
Dyflos,
Echothiophate
Parathion,
Malathion
Diazinon, Tabun
Sarin, Samon
2.Carbamates
(Irreversible)
Carbaryl
Propoxur
(Baygon)
Cholinergic Drugs/Parasympathomimetic

13. Mechanism of action of cholinergic drugs
Cholinergic agonists
• These are the drugs which produces similar action
to the Acetylcholine (Ach). They act through direct
stimulation of muscarinic or nicotinic receptors
present in nerve cells of the body.
Anticholinesterase
• They act by inhibiting cholinesterase & protects
Ach from hydrolysis (Amplification of endogenous
Ach). They have additional direct action on
Nicotinic receptors.

14. Acetylcholine (Not used as drug)
Pharmacological actions
Heart Negative ionotropic effect(decrease in force of contraction)
Negative chronotropic effect (decrease in heart rate)
Negative dromotropic effect (decreasein heart conduction)
Glands Secretion
Blood
vessels
Dilation
Blood
pressure
Falls
Smooth
muscles
Tone & contractility of smooth muscles are increased
Eye Miosis (Constriction of pupils)
Skeletal
muscle
Contraction, Paralysis (high dose)

15. A. MIOSIS
B. MYDRIASIS

16. • Pilocarpine is a cholinergic agonist that has miotic action as
well as stimulates ganglia. It can cause sweating, salivation &
secretion. It is stable to hydrolysis by cholinesterase & can
penetrate cornea.
• Mechanism of action: Pilocarpine produces rapid miosis,
contraction of the ciliary muscle & fall in intraocular pressure. It
acts through direct stimulation of muscarinic receptors and
smooth muscle such as the iris and secretory glands.
• It is used as 0.5-4% eye drop.
• Adverse effects: Pilocarpine can enter the brain and cause CNS
disturbances. Poisoning with this agent is characterized by
exaggeration of various parasympathetic effects, including
profuse sweating (diaphoresis) and salivation. The effects are
similar to those produced by consumption of mushrooms of the
genus Inocybe.
• Nursing Management: Parenteral atropine 2mg (until
atropinization), at doses that can cross the blood-brain barrier,
is administered to counteract the toxicity of pilocarpine.

17. Glaucoma is an eye disease that is associated with increased
intraocular pressure, in which damage to the eye (optic) nerve can
lead to loss of vision and even blindness. It can be open angle
glaucoma & angle closure glaucoma.
Treatment for Glaucoma
• Pilocarpine is used to treat glaucoma and is the drug of choice in
the emergency lowering of intraocular pressure of both narrow-
angle (or closed-angle) and wide-angle (also called open-angle)
glaucoma. It is extremely effective in opening the trabecular
meshwork around Schlemm’s canal, causing an immediate drop in
intraocular pressure as a result of the increased drainage of
aqueous humor. (action within few minutes, lasts 4-8 hours)
• Carbonic anhydrase inhibitors, such as acetazolamide, as well as
the β-adrenergic blocker timolol, are effective in treating chronic
glaucoma but are not used for emergency lowering of intraocular
pressure.

18. • Myasthenia gravis is an autoimmune disorder
characterized by easy fatiguability & progressive
weakness of striated muscles. It is differentiated from
cholinergic crisis by edrophonium test.
• Myasthenia gravis occurs due to development of
antibodies developed towards nicotinic receptors.
Diagnostic tests
• Ameliorative test: Edrophonium 2mg i.v.(test dose)
followed by 8 mg i.v.after 30-60 sec. reversal of
weakness and short lasting improvement of strength:
+ve for MG
• Provocative test: d-tubocurarine 0.5mg i.v.
• Electromyography
• Biopsy

20. Treatment of myasthenia gravis:
• Tab Neostigmine 15mg orally q6h.
• Tab Pyridostigmine 60mg orally q8h.
• Immunosupressants
• Plasmapheresis
• Surgery-Thymectomy

21. Neostigmine Physostigmine (Eserine)
Source: synthetic Source: Calabar bean
More stable Less stable
Absorption: orally-incomplete,
i.v.-good
Absorption good from GIT,
conjuctiva
Does not crosses BBB Crosses BBB
Inhibits cholinesterase reversibly Inhibits cholinesterase reversibly
Acts on both muscarinic &
nicotinic receptors
It acts directly on skeletal
muscles
Acts on both muscarinic &
nicotinic receptors
It do not act directly on skeletal
muscles
Less toxic More toxic
Uses: myasthenia gravis, curare
poisoning, paralytic ileus,
retention of urine
Uses: miotic, Atropine poisoning

22. Uses of cholinergic drugs:
• Miotic
• Glaucoma
• Myasthenia gravis
• Alzheimer’s disease (rivastigmine, tacrine)
• Post-operative paralytic ileus/urinary retention
(Inj. Neostigmine 0.5-1 mg s.c)
• Post operative decurarization
(Neostigmine 0.5-2 mg i.v. preceeded by atropine)
• Cobra bite (Neostigmine + Atropine)
• Belladona poisoning (Physostigmine 0.5-2 mg i.v. repeated as
required)

23. Symptoms:
Killer B's: Bradycardia, Bronchorrhea and Bronchospasm
SLUDGE: Salivation, Lacrimation, Urination, Diarrhoea, &
Gastrointestinal (Emesis)
DUMBBELLSS: Diarrhoea, Urination, Miosis, Bradycardia,
Bronchospasm, Emesis, Lacrimation, Lethargy, Salivation and
Seizures
Common Substances:
Carbamates, Mushrooms, Organophosphates
Complications:
Rapid onset of respiratory failure, Seizures, Dehydration
ADVERSE EFFECTS:
CHOLINERGIC TOXIDROMES

24. Resuscitation
• ABCDE
Risk Assessment
• Agent(s), Dose(s), Time since
ingestion
• Clinical features and progress
• Patient factors and co-morbidities
Investigations
• Cholinesterase levels
• Specific: ECG, Chest X-ray,
Electrolytes, renal function,
ABG
Supportive Care
•Well ventilated Room
•Universal Precautions
•Catheterization
•Intravenous fluids
Decontamination
•Activated Charcoal
CHOLINERGIC TOXIDROME MANAGEMENT
Antidotes
•Atropine
•Pralidoxime
(for organophosphates)