ANTICHOLINERGIC DRUGS

Prof. Alhaider Pharmacology Department

Prof. Hanan HagarPharmacology Department

What students should know:Student should be able to :

• Describe Kinetics of muscarinic antagonists • The effects of atropine on the major organ systems.• To list the clinical uses of muscarinic antagonists.• To know adverse effects & contraindications of anticholinergic drugs.• To identify at least one antimuscarinic agent for each of the following special uses:mydriasis, cyclopedia, peptic ulcer & parkinsonism.

Anticholinergic drugs

are drugs that block cholinergic receptors.

Anticholinergic drugs

Antimuscarinics(Parasympatholytics)

Antinicotinics

synthetic atropine substitutes

Ganglionic blockers

Neuromuscular blockers

Anticholinergic drugs

Naturally occurring alkaloids

synthetic atropine substitutes

Antimuscarinics

Naturally occurring alkaloids

Antimuscarinics

Natural alkaloidsDrugs as : Atropine - Hyoscine • Esters of tropic acid and tertiary amines• Lipid soluble• Good oral absorption• Good distribution• Cross blood brain barrier (have CNS actions)

AntimuscarinicsMuscarinic antagonists

Synthetic atropine substitutes

AntimuscarinicsMuscarinic antagonists

BenztropineHomatropineTropicamaidePirenzepineIpratropiumGlycopyrrolateOxybutynin

Mechanism of action • Reversible competitive blockade of muscarinic

receptors.• Atropine can block all muscarinic receptors.

Antimuscarinic drugs

CNS– Sedation – Antiemetic effect (block vomiting center)– antiparkinsonian effect (block basal

ganglia).

– Toxic dose: Hyperthermia - excitement-hallucination.

Pharmacological effects ofatropine

Cardiovascular system (CVS) Tachycardia (increase in heart rate) AV conduction ( + ve dromotropic effect) Therapeutic dose: Vasodilatation induced

by cholinomimetics. Toxic dose: Cutaneous vasodilatation

(atropine flush).

Respiratory system Relaxation of bronchial muscles

(bronchodilator) Bronchial secretion viscosity

EyePassive mydriasis

due to paralysis of circular muscleCycloplegia (loss of near accommodation) due to paralysis of ciliary muscle.Loss of light reflex. increase I.O.P # glaucoma. Lacrimal secretion sandy eye

Secretions

¯ Salivary secretion ( Dry mouth ). Sweating Dry skin Fever in infants and

children. Bronchial secretion Viscosity¯ Lacrimal secretion Sandy eye

GIT– Relaxation of smooth muscles.– GIT motility Antispasmodic effect.– Sphincter contractions– Constipation

Urinary Tract– Relaxation of smooth muscles of urinary

bladder.– Sphincter contraction. – Urinary retention.

Hyoscine (SCOPOLAMINE)

What is difference between atropine and hyoscine?

Hyoscine has• Shorter duration of action• More CNS depressant action• Antiemetics action in motion sickness• Can produce amnesia. • Less CVS effect

Anticholinergic actions Cholinergic actions

relaxation (mydriasis)

relaxation (cycloplegia) loss of accommodation

EyeCircular muscle of iris

Contraction (miosis)Ciliary muscles Contraction

(accommodation for near vision)

Tachycardia H.RHeartbradycardia ( H.R.)

Relaxation of musclescontraction of sphincter Urinary retention

Urinary bladderContraction of musclesRelaxation of sphincter

Anticholinergic drugs Cholinergic drugs

Decrease all secretionsExocrine glandsIncrease of sweat, saliva, lacrimal, bronchial, intestinal secretions

peristalsis secretionContraction of sphincter

constipation

GIT peristalsis secretion relaxation of sphincter

1. Bronchodilatation2. Decrease secretion

Lung1. Bronchoconstriction2. bronchial secretion

Uses organ DrugsPre-anesthetic medication

Antispasmodic CNS Atropine

Pre-anesthetic medication, Motion sickness, antispasmodic

CNS Hyoscine

Parkinson's disease CNS BenztropineFundus examination of eye Eye Homatropine

asthma, COPD, inhalation Respiratory system

Ipratropium

Peptic ulcer Stomach PirenzepineAntispasmodics in

hypermotilityGIT Glycopyyrolate

Urinary urgency, Urinary incontinence

GUT Oxybutynin

Uses of antimuscarinic drugs

Adverse effectsEye: Blurred vision – Mydriasis CVS: Tachycardia - Atropine flushGUT: Urinary retention GIT: Constipation, paralytic ileusSecretions: Dryness of mouth , Sandy eyeIncreased body temperature.CNS: sedation, hallucination, excitation (Toxic dose).

Treatment– Gastric lavage.– Anticonvulsant.– Cooling blanket.

Antidote: Physostigmine ( IV slowly).

Contraindications– Glaucoma (angle closure glaucoma)– Tachycardia– Prostate hypertrophy in old patients.– Constipation, paralytic ileus, intestinal

obstruction.– Children in case of atropine

Can antimuscarinic drugs reverse the actionof neostigmine on skeletal muscles?

SUMMARY

– Antimuscarinics reverse action of cholinomimetics on muscarinic receptors.

– Are useful in many applications including intestinal spasm, constipation, urinary retention, vomiting, parkinsonism, asthma and peptic ulcer.

– Are contraindicated in constipation, Prostate hypertrophy, tachycardia and glaucoma.

Thank you

Questions ?