A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed

2. CHOLINERGIC DRUGS
Cholinergic drugs are:
• Drugs that stimulate the parasympathetic system
• Also called parasympathomimetics – they mimic the
effects of the PSNS neurotransmitter
• Cholinergic agents copy the action of acetylcholine
(ACh) – a neurotransmitter released from nerve
endings that bind on the receptors of cell
membranes of organs, tissues, and glands

3. • Acetylcholine (ACh) an ester of choline, is the
neurotransmitter of the parasympathetic
system. The nerves that synthesize, store and
release ACh are called ‘cholinergic.’

4. There are two types of cholinergic drugs:
direct-acting and indirect-acting.
Direct-Acting Cholinergic Drugs
• Bind to cholinergic receptors on specific effector
organs, stimulating the organ in a similar way as ACh
• They are synthetic derivatives of choline
• Have widespread systemic effects including cardiac
muscle, smooth muscle, exocrine glands, and the eye

5. Indirect-Acting Cholinergic Drugs
• Inhibit the enzyme ‘acetylcholinesterase,’ resulting in
more ACh available at the receptors
• These drugs have the added cholinergic effect of
improved skeletal muscle tone and strength
• Indirect-acting cholinergic drugs for Alzheimer’s
disease are widely distributed, including to the
central nervous system, thus improving cholinergic
neurotransmission in the brain

6. Cholinergic drugs may be classified as:
Esters of choline
• Acetylcholine
• Methacholine
• Carbachol
• Bethanechol
Cholinomimetic
alkaloids
• Pilocarpine
• Muscarine
Anticholinesterases
• REVERSIBLE
• Neostigmine
• Physostigmine
• Pyridostigmine
• Ambenonium
• Edrophonium.
• IRREVERSIBLE
Organophosphorus
compounds.

7. ACTIONS OF ACETYLCHOLINE
• Acetylcholine is taken as the prototype of
parasympathomimetic drugs.
Muscarinic Actions
• Muscarinic actions resemble the actions of the
alkaloid muscarine found in some mushrooms
• These actions result from the stimulation of the
muscarinic receptors by acetylcholine.

8. 1. Heart The action of ACh is similar to that of vagal
stimulation. It depresses the SA node and thereby
reduces the heart rate and force of contraction. In
larger doses, AV conduction is depressed.
2. Blood vessels ACh relaxes the vascular smooth
muscles and dilates the blood vessels of the skin
and mucous membrane. The BP falls due to a fall in
total peripheral resistance.

9. 3. Smooth muscle ACh increases the tone of all other (non-
vascular) smooth muscles. Gastrointestinal tract–tone
and peristalsis is enhanced, sphincters are relaxed,
resulting in rapid forward propulsion of intestinal
contents.
• Urinary bladder–detrusor contracts and trigonal
sphincter relaxes–promotes voiding of urine.
• Bronchial smooth muscle–contracts resulting in
bronchospasm.

10. 4. Secretory glands Acetylcholine enhances the
secretions of all glands; salivary, lacrimal,
nasopharyngeal, tracheobronchial, gastric and
intestinal secretions are increased.
• Sweating is also increased.
• Enhanced bronchial secretions and bronchospasm
result in severe dyspnoea.

11. 5. Eye Acetylchetine brings about constriction of pupil
(miosis) by contracting the circular muscles of the iris
• Stimulation of muscarinic receptors present in the
sphincter pupillae results in miosis.
• Drainage of aqueous humor is facilitated and
intraocular pressure falls.
• Ciliary muscle contracts resulting in spasm of
accommodation.

12. Adverse effects
• Too much cholinergic medication can result in overstimulation
of the parasympathetic nervous system, causing unwanted
side effects.
• The acronym SLUDGE-M will help us remember the adverse
effects of cholinergic drugs.
S Salivation
L Lacrimation
U Urination
D Defecation
G Gastroenteritis
E Emesis
M Miosis

13. Other Adverse Effects of Cholinergic
Drugs
• ↓ HR and BP
• Conduction abnormalities – AV block and cardiac
arrest
• Headache, dizziness, convulsions
• ↑ bronchial secretions, bronchospasms
Overdosing can cause life-
threatening problems
Antidote for cholinergics is the
anticholinergic drug atropine

14. Nicotinic Actions
• These effects resemble the actions of the
alkaloid nicotine and are brought about by
stimulation of the nicotinic receptors by
acetylcholine.

15. 1. NMJ Acetylcholine brings about contraction of
skeletal muscles by stimulating NM receptors
present in the neuromuscular junction.
• Large doses cause persistent depolarisation of
skeletal muscles resulting in paralysis.
2. Autonomic ganglia Acetylcholine stimulates the
sympathetic and parasympathetic ganglia and the
adrenal medulla.

16. 3. CNS Acetylcholine is a neurotransmitter at several
sites in the CNS.
• The important actions of acetylcholine are
summarised in Table
Actions of acetylcholine
CVS ↓HR ↓BP
Non-vascular contraction, ↑gut peristalsis, promotes urine
voiding
Smooth muscle bronchospasm
Glands ↑secretion
Eye miosis, spasm of accommodation, ↓IOP
NMJ muscle contraction
Ganglia stimulation

17. Uses
• Acetylcholine is destroyed in the gut when given orally.
• On intravenous administration, it is rapidly metabolised
by pseudocholinesterases in the plasma and by true
cholinesterase at the site of action.
• Therefore it is not used therapeutically except
occasionally as 1% eyedrops to produce miosis during
some eye surgeries.

18. • Esters of choline are effective orally; carbachol and
bethanechol are resistant to both cholinesterases
and have a longer duration of action.
• Their muscarinic actions are prominent with a
sustained effect on g.i. smooth muscles and urinary
bladder.
• Methacholine is rarely used.
• Carbachol is used in glaucoma.

19. • Bethanechol may be used in hypotonia of bladder
and g.i. smooth muscles and in some cases of
postoperative paralytic ileus and urinary retention; It
may also be used in xerostomia as an alternative to
pilocarpine.

20. • Adverse effects include diarrhoea, flushing,
salivation, sweating, bradycardia,
hypotension, syncope and bronchospasm.

21. CHOLINOMIMETIC ALKALOIDS
• Pilocarpine is an alkaloid obtained from the leaves of
Pilocarpus microphyllus.
• Like ACh it stimulates cholinergic receptors, but its
muscarinic actions are prominent.

22. • Its actions on the eye are important–when applied to
the eye it causes miosis, spasm of accommodation
and a fall in intraocular tension.
• It also increases sweat (diaphoretic) and salivary
secretions (sialogogue).

23. Adverse effects
• When used as eyedrops, burning sensation
and painful spasm of accommodation,
browache and corneal edema can occur.
• Long term use can cause retinal detachment.

24. Uses
1. Pilocarpine is used in glaucoma (see below).
Pilocarpine ocusert is available and can deliver
pilocarpine constantly for 7 days.
2. Pilocarpine is also used alternately with mydriatics
like homatropine to break the adhesions between
the iris and the lens.
3. It is used to counter dryness of mouth that is seen
following radiation of head and neck.

25. Glaucoma
• Glaucoma is an eye disease
characterised by increased
intraocular pressure.
• Aqueous humor is secreted by
the ciliary body and it drains
through the canal of Schlemn.
• Rise in intraocular pressure
(above 30 mm of Hg) can
damage the optic nerve.

26. • If untreated, irreversible damage can occur - optic
nerve degenerates leading to permanent blindness.
• Glaucoma is one of the common causes of blindness.
• Hypertension, myopia and family history of glaucoma
are risk factors.

27. Glaucoma is of two types :
1. Acute congestive/narrow angle/closed angle glaucoma—in
this, iris blocks the drainage of aqueous humor at the canal of
Schlemn leading to increased intraocular pressure. It needs
immediate treatment.
2. Chronic simple/wide angle/open angle glucoma–onset is
slow; needs long term treatment. Surgery is the preferred
option.

28. Two categories of drugs may be used in
the treatment of glaucoma. They are -
1. Drugs that decrease the formation of aqueous
humor–Timolol, betaxolol, levobunolol, carteolol,
apraclonidine, brimonidine, dipivefrine, adrenaline,
acetazolamide, dorzolamide.
2. Drugs that increase the drainage of aqueous humor-
Carbachol, pilocarpine, physostigmine,
echothiophate, latanoprost.

29. Drugs used in glaucoma are
summarised
Drugs Adverse effects Comments
β blockers
Timolol, betaxolol,
carteolol, levobunolol
Conjunctival irritation,
redness and
discomfort
• first line drugs
• No miosis-hence no
headache
or browache
Cholinergics
• Pilocarpine,
carbachol
Corneal edema, spasm
of accommodation,
browache, myopia
Used with β blockers
Physostigmine,
echothiophate
Browache, cataract,
retinal detachment

30. Drugs Adverse effects Comments
Adrenergic agonists
Dipivefrine, adrenaline
Conjunctival redness,
photosensitivity,
allergic reactions
2nd line drugs—may
be combined with β
blockers
α2 adrenergic agonists
Apraclonidine,
brimonidine
Conjunctival redness,
photosensitivity
Higher topical activity
than clonidine
Carbonic anhydrase
inhibitors
Acetazolamide,
methazolamide,
dorzolamide
Hypokalaemia,
anorexia, drowsiness
2nd line drugs—given
orally; slow release
acetazolamide is
better tolerated;
topical dorzolamide is
now available - has
fewer side effects

31. ANTICHOLINESTERASES
• Anticholinesterases (antiChEs) or cholinesterase
inhibitors are drugs which inhibit the enzyme
cholinesterase.
• As their structure resembles that of ACh, they bind
to acetylcholinesterases and inactivate them.
Acetylcholine
Cholinesterase
Choline + Acetic acid

32. • Thus ACh is not hydrolysed and it accumulates.
• The actions of all these drugs are due to this
accumulated ACh.
• Hence the actions are similar to cholinergic agonists.
• The structure of AChE contains an anionic site and an
esteratic site

33. Acetylcholine and reversible anticholinesterases bind to both anionic and esteratic sites of the
acetylcholinesterase (AChE) enzyme. Edrophonium binds only the anionic site and is short acting as the
binding is rapidly reversible. OP compounds bind only esteratic site but exception is echothiophate which
binds both anionic and esteratic sites

34. • Reversible anticholinesterases except edrophonium bind to
both anionic and esteratic sites.
• Edrophonium binds only to anionic site and the binding is
quickly reversible—hence it is very short acting.
• Organophosphates (OP) bind only to the esteratic site but the
enzyme is phosphorylated (by covalent bonds) and the
binding is stable.
• With some OPs the binding takes many days to be reversed
while with others it is not fully reversible at all.

35. Specific Cholinergic Drugs
1. Direct-acting
• Bethanechol (Urecholine) – ↑ the tone and motility
of the bladder and GI tract (should cause urination
within 60 min in a pt with urinary retention).
• Pilocarpine (Pilocar) – used to constrict pupils, which
↓ intraocular pressure (glaucoma).

36. 2. Indirect-acting
• Neostigmine (Prostigmin) – given for the diagnosis
and treatment of myasthenia gravis—it causes
skeletal muscle contractions.
• Donepezil (Aricept) – used to treat mild-moderate
Alzheimer’s disease—it ↑ ACh in the brain and helps
↑ or maintain memory or learning capabilities (it
manages the symptoms, but is not a cure).

37. Contraindications to using cholinergic
drugs
• Asthma
• Hyperthyroidism
• Peptic ulcer
• Coronary artery disease Cholinerg
ic drugs
can
exacerbat
e these
condition
s and
should be
avoided.

38. Nursing Considerations for
Cholinergic Agonists
Here are important nursing considerations when administering
cholinergic agonists:
Nursing Assessment
These are the important things the nurse should include in
conducting assessment, history taking, and examination:
• Assess for contraindications or cautions (e.g. history of allergy
to drug, GI obstruction, pregnancy or lactation status, etc.) to
avoid adverse effects.

39. • Establish baseline physical assessment to monitor for any
potential adverse effects.
• Assess orientation, affect, reflexes to monitor CNS drug
effects.
• Assess vital signs, especially pulse and blood pressure to
monitor for possible excess stimulation of the cardiac system.
• Assess abdomen, auscultating for bowel sounds and palpating
for distention.
• Monitor intake and output, noting any complaints of urinary
urgency to monitor for drug effects on the urinary system.

40. • Administer oral drug on empty stomach to decrease
nausea and vomiting.
• If drug is given intravenously, administer slowly to avoid
severe cholinergic effects.
• Monitor patient response closely (e.g., blood pressure,
ECG, urine output) to arrange to adjust dose accordingly
to ensure the most benefit.
• Maintain a cholinergic-blocking drug on standby such
as atropine to use as an antidote for excessive doses of
cholinergic drugs

41. • Discontinue drug if excessive salivation, diarrhea, emesis, or
frequent urination becomes a problem to decrease the risk of
severe adverse reactions.
• Provide safety precautions if the patient reports poor visual
acuity in dim light to prevent injury.
• Provide comfort measures (e.g., quiet room, support and
relaxation measures) to help patient cope with drug effects.
• Provide patient education about drug effects and warning
signs to report to enhance knowledge about drug therapy and
promote compliance.