Drugs

1. 1
Bangbandhu Sheikh Mujibur Rahman Science and
Technology University
Antimuscarinic Agents
A Presentation On
MD. GOLAM RABBANI
(RABBI)
Department of Pharmacy, BSMRSTU

2. Contents
 Antimuscarinic Agents
 Classification of Antimuscarinic Agents
 Antimuscarinic Drugs
 Types of Muscarinic Receptors
 Source of Antimuscarinic Drugs
 Atropine
 Scopolamine
 Pharmacological Actions of Antimuscarinic Agents
 Therapeutic Uses of Antimuscarinic Agents
 Side Effects of Antimuscarinic Agents

3.  Antimuscarinic drugs are agents
which block the effects of
acetylcholine on cholinergic
receptors.
 Also called as Anticholinergic
and Parasympatholytic drugs .
Activity of antimuscarinic agents
Antimuscarinic Agents
These are the drugs which blocks the actions of Acetylcholine especially
mediated through muscarinic receptor.

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Classification of Antimuscarinic Agents
Natural
Alkaloids
Semi
Synthetic
Derivatives
Synthetic
Compounds
Quaternary
Ammonium
Compounds
Tertiary
Amines
Antiparkinsonism
Drugs Miscellaneous
Antimuscarinic Agents
Atropine Homatropine Tropicamide Oxyphenium Oxybutynin Procyclidine Disopyramide

5. Selective Muscarinic Receptor
Antagonists
Nonselective Muscarinic Receptor
Antagonists
Antimuscarinic Drugs
M1
Antagonists
M2
Antagonists
M3
Antagonists
M4
Antagonists
Pirenzepine,
Trihexyphenidyl,
Telenzepine
Methoctramine
Hexahydrosiladifenidol,
4-DAMP
Himbacine
Atropine,
Scopolamine

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Five subtypes of muscarinic receptors have been identified-
• The M1 receptor subtype is located on CNS,neurons,
autonomic postganglionic cell bodies, and many presynaptic
sites.
• M2 receptors are located in the myocardium, smooth
muscle organs, and some neuronal sites.
• M3 receptors are foundon effector cell membranes, glandular
and smooth muscle cells.
• M4 and M5 receptors are less prominent and appear to play
a greater role in the CNS than in the periphery.
Types of Muscarinic Receptors

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 Atropine is found in the following plants-
1. Atropa belladonna, or deadly nightshade.
2. Datura stramonium or jimsonweed.
 Scopolamine (hyoscine) is found in-
1. Hyoscyamus niger or henbane.
Source of Antimuscarinic Drugs

8. Atropine is a medication to treat
certain types of nerve
agent and pesticide poisonings as well
as some types of slow heart rate and to
decrease saliva production during
surgery. Eye drops are also available
which are used to treat uveitis and
early amblyopia.
Common side effects include a dry
mouth, large pupils, urinary retention,
constipation, and a fast heart rate.
Atropine

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Datura stramoniumAtropa belladonna
Plant Source of Atropine

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Mechanism of Action of Atropine

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Scopolamine
Scopolamine is a medication used to treat motion
sickness and postoperative nausea and vomiting. It is also
sometimes used before surgery to decrease saliva.
Common side effects include sleepiness, blurred vision, dilated
pupils, and dry mouth.
Scopolamine

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Plant source of Scopolamine
Hyoscyamus niger

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Mechanism of Action of Antimuscarinic Agents

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1. CNS
 At low doses atropine do not cross BBB.
 At higher doses it produce CNS stimulant action.
 Hyoscine produce CNS depressant effect even at low doses.
 Atropine stimulates many medullary centers – vagal, respiratory,
vasomotor.
 It depresses vestibular excitation and has antimotion sickness property.
 It suppresses the tremor and rigidity of parkinsonism by blocking the
cholinergic over activity in basal ganglia
 In high doses cause cortical excitation, restlessness, disorientation,
hallucinations and delirium followed by respiratory depression and coma.
Pharmacological Actions of Antimuscarinic Agents

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2. CVS
 In heart, M2 receptor is blocked by atropine in S.A node
 and A.V node leads to tachycardia.
 It also blocks muscarinic auto receptors on vagal nerve
 endings augmenting ach release, this leads to
 Predominant bradycardia and finally tachycardia
3. Blood vessels
 Atropine at high doses has direct vasodilatory effect and
 also enhances the release of histamine.
 This leads to hypotension.
 Ach vasodilatation
Pharmacological Actions of Antimuscarinic Agents

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4. Eye
 Topical instillation of atropine causes mydriasis, lack of
 light reflex and cycloplegia lasting 7-10days.
 This results in photophobia and blurring of near vision.
 Intraoccular tension tends to rise, specially in narrow
 angle glaucoma.
Pharmacological Actions of Antimuscarinic Agents

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5. Smooth muscle
 All visceral smooth muscles are relaxed by atropine (M3
 blocked).
 The tone & contraction of stomach and intestine are
 reduced; the passage of chyme is slowed – constipation
 may occur, spasm may be relieved.
 Atropine causes bronchodilatation and reduces air way
 resistance, specially in COPD and asthma patients.
 It has a relaxant action on ureter and urinary bladder;
 Urinary retention may occur in older males with BPH.
 Relaxation of biliary tract and uterus is minimal.
Pharmacological Actions of Antimuscarinic Agents

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6. Glands
Atropine decreases sweat, salivary, tracheobronchial and
lachrymal secretion (M3 blockade).Skin & eye become dry, talking
and swallowing may be difficult.It also decreases G.I secretions like
pepsin, mucous, HCl etc.
7. Body temperature
Rise in body temperature occurs at higher doses. It is due to both
inhibition of sweating as well as stimulation of temperature
regulating centre in the hypothalamus.
8. Local anesthetic effect
Atropine has a mild anesthetic action on the cornea
Pharmacological Actions of Antimuscarinic Agents

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A- rapid by G.I.T and cornea on topical application.
D- crosses BBB and produces CNS effects
M- in liver (50%)
E- urine, as metabolite or unchanged form
t ½ - 3 – 4hrs.
Atropine sulfate : 0.6 – 2mg I.M; I.V
10μg/kg for children
1 – 2% topically in eye.
Hyoscine hydrobromide : 0.3 – 0.5mg oral, I.M, also
transdermal patch.
Pharmacokinetics
Preparations & Dose

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I. As antisecretory
Pre anesthetic medication when irritant general anesthetics (ether) are used,
prior administration of anticholinergics ( atropine, hyoscine, glycopyrrolate)
are imperative to check increased salivary and tracheobronchial secretions.
II. Peptic ulcer
atropine drugs decrease gastric secretion and afford symptomatic relief in
peptic ulcer (but it is not using nowadays due to their side effects as well as
the entry of H2 – blockers).
• In pulmonary embolism
• To check excessive sweating or salivation. E.g.:- parkinsonism.
Therapeutic Uses of Antimuscarinic Agents

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III. As antispasmodic
1. Intestinal and renal colic, abdominal cramps.
2. Nervous and drug (reserpine, guanethidine) induced
diarrhea, functional diarrhea.
3. Spastic constipation, irritable colon.
4. Pylorospasm, gastric hyper motility, gastritis, nervous
dyspepsia.
5. To relieve urinary frequency and urgency, enuresis in
children
Therapeutic Uses of Antimuscarinic Agents

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IV. Bronchial asthma, asthmatic bronchitis, COPD
These drugs are less effective than adrenergic
drugs.Ipratropium bromide is used in COPD. It has additive
bronchodilator action with adrenergic drugs and theophylline.
V. As mydriatic & cycloplegic
 Diagnostic :- for testing error of refraction, both mydriasis and
cycloplegia are needed. Tropicamide is used widely.
To facilitate fundoscopy only mydriasis is needed.
 Therapeutic :- atropine is used in the treatment of iritis,
iridocyclitis, choroiditis, keratitis and corneal ulcer.
Therapeutic Uses of Antimuscarinic Agents

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VI. As cardiac vagolytic
Atropine is useful in counteracting bradycardia and partial heart block
in selected patients where increased vagal tone is responsible, e.g.:-
in some cases of M.I, digitalis toxicity.
VII• For CNS action
1. Parkinsonism
These drugs are used only in mild cases because they
are less effective than L-dopa.
2. Motion sickness
Hyoscine is most effective.
3. Hyoscine has been used to produce sedation and
amnesia during labour and to control maniacal states.
Therapeutic Uses of Antimuscarinic Agents

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VIII. To antagonize muscarinic effects of drugs &
poisons
Atropine is an antidote for anti chE and early
mushroom poisoning.
It also block muscarinic actions of neostigmine used
for myasthenia gravis, decurarization or cobra
envenomation.
Therapeutic Uses of Antimuscarinic Agents

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1. Absorption of most drugs is slowed.
L-dopa dose should be increased in presence of these drugs,
because the absorption slower and greater peripheral
degradation occurs, thereby less of it reaches the brain.
But in case of tetracycline and digoxin absorption may be
increased due to longer transit time in the G.I.T.
2. Antacids interfere with absorption of anticholinergics.
3. Antihistaminics, tricyclic antidepressants, phenothiazines,
pethidine have anticholinergic property – additive side
effects with atropinic drugs.
4. MAO inhibitors interfere with metabolism of
anticholinergic antiparkinsonian drugs - delirium may
occur.
Drug Interactions

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A) Narrow iridocorneal angle – may
precipitate acute congestive glaucoma.
B) In patients with BPH – urinary retention
may occur.
Contraindications

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 Constipation
 Transient bradycardia followed by tachycardia and increased BP
 Palpitations and arrythmias
 Decreased bronchial secretions
 Dry mouth and thirst
 Blurred vision, pupilary dilation, loss of accommodation
 Urinary urgency and retention
 Photophobia
 Confusion (elderly)
 Nausea and vomiting
 Giddiness
Side Effects of Antimuscarinic Agents

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