Cholinergic and Anti-Cholinergic Drugs Flashcards
called parasympathomimetic or cholinomimetic
?
Cholinergic Drugs
Similar in action as acetylcholine?
Cholinergic Drugs
We don’t use acetylcholine itself, because ?
it acts on both muscarinic and nicotinic (not selective) and has short duration of action (rapidly metabolized by acetycholinesterase)
Cholinergic Drugs Stimulate cholinergic receptors directly or indirectly by
decreasing acetylcholine metabolism (by inhibiting acetylcholinesterase enzyme)
1- Direct acting Cholinergic Drugs ● Examples?
● Acetylcholine ● Carbachol ● Bethanechol ● Pilocarpine
Pharmacological properties of Direct acting Cholinergic Drugs
● Poorly distributed and can not cross BBB (No CNS effects)
● Not metabolized by cholinesterase (except Acetylcholine)
● Have longer duration of action than Acetylcholine.
Direct acting Cholinergic Drugs
- Pharmacological effects ?
● Increased contractility in gastrointesinal smooth muscle wall, with relaxation of sphincters (diarrhea)
● Increased contractility of smooth muscle wall in urinary bladder, with
relaxation of sphincter (urinary incontinence)
● Increased contractility of bronchial smooth muscle, with increased respiratory secretions (induce asthma)
● Constriction of pupils (miosis) and contraction of ciliary muscle (treatment of
glucoma)
Acetylcholine
Receptor? Metabolism by cholinesterase? Selectivity ? Uses?
- Muscarinic / Nicotinic
- Metabolized
- Not selective
- NOT used
Carbachol
Receptor? Metabolism by cholinesterase? Selectivity ? Uses?
- Muscarinic / Nicotinic
- NOT metabolized by cholinesterase
- Eye / Gastrointestinal / Urinary bladder
- Glaucoma
Bethanechol
Receptor? Metabolism by cholinesterase? Selectivity ? Uses?
- Muscarinic
- NOT metabolized by cholinesterase
- Gastrointestinal / Urinary bladder
- Paralytic ileus / Urinary retention
Pilocarpine
Receptor? Metabolism by cholinesterase? Selectivity ? Uses?
- Muscarinic
- NOT metabolized by cholinesterase
- Eye / Exocrine glands
- Glaucoma / Xerostomia
Direct acting Cholinergic Drugs
Contraindications?
● Bronchial asthma ● Peptic ulcer ● Angina pectoris ● Urinary incontinence ● Intestinal obstruction
Also called anticholinesterases ?
Indirect acting Cholinergic Drugs
Indirect acting Cholinergic Drugs
Mechanism of action ?
● Prevent hydrolysis of acetylcholine by inhibiting acetylcholinesterase enzyme
● Thus increase acetylcholine concentrations and actions at the cholinergic receptors (both nicotinic and muscarinic)
Indirect acting Cholinergic Drugs Classification ?
Reversible anticholinesterases: ● Short acting: - Edrophonium (diagnosis of myasthenia gravis) - Donepezil (treatment of Alzheimer's disease) ● Intermediate acting: -Neostigmine -Physostigmine -Pyridostigmine
Irreversible anticholinesterases
● Long acting as Ecothiophate = Phosphates used as insecticides and gas war
Indirect acting Cholinergic Drugs Pharmacological actions?
Nicotinic actions:
- Neuromuscular junction:
At therapeutic dose cause skeletal muscle contraction At toxic dose cause relaxation and paralysis - Ganglia: stimulation of both sympathetic and parasympathetic ganglia
- Adrenal medulla: induce release of catecholamines (adrenaline &
noradrenaline).
Indirect acting Cholinergic Drugs Pharmacological actions: Muscarinic actions
- Eye: Contraction of circular muscle of iris (miosis) / Contraction of ciliary muscles for near vision /Decrease in intraocular pressure
- Cardio vascular : Bradycardia with vasodilatation
- Lung : Constriction of bronchial smooth muscles/ Increase bronchial secretion
- GIT : Increased motility (peristalsis) & relaxation of sphincter
Increased secretion - Urinary bladder : Contraction of muscles & relaxation of sphincter
- Exocrine glands : Increase of sweat, saliva, lacrimal, bronchial, intestinal secretions
Indirect acting Cholinergic Drugs
Actions on?
Both Nicotinic & muscarinic
Diagnosis of myasthenia
gravis (Tensilon test)
Drug used ?
Edrophonium
Treatment of Alzheimer’s disease
Drug used?
Donepezil
Myasthenia gravis treatment
Paralytic ileus
Urinary retention
Used?
Neostigmine
Myasthenia gravis treatment
Drug used?
Pyridostigmine
Glaucoma
Atropine toxicity
Drug used?
Physostigmine
Glaucoma ?
Ecothiophate
Organophosphates toxicity ?
Toxicity of irreversible anticholinesterases (cholinergic crisis)
Symptoms of Organophosphates toxicity ?
● Muscarinic: salivation, lacrimation, urination, diarrhea, emesis,
bronchospasm, bradycardia, miosis
● Nicotinic: muscle fasciculation and weakness.
Organophosphates toxicity Treatment ?
● Decontamination of clothing
● Flushing poison from skin and eyes
● Activated charcoal and gastric lavage for gastrointestinal ingestion
● Atropine for muscarinic effects
● Pralidoxime (cholinesterase reactivator) causes breaking the bond
between the enzyme and poison, so given as soon as possible because if too much time passes, the poison bond becomes too strong
Also called cholinergic blocking drugs or parasympatholytics ?
Anticholinergics
Muscarinic antagonists ?
● Natural: - Atropine - Hyoscine ● Synthetic: - Benztropine - Homatropine - Ipratropium
Treatment of overdose of anti-muscarinic drugs?
Antidote: Physostigmine
Pre-anesthetic medication
Antispasmodic
Drug?
Atropine
Pre-anesthetic medication Antispasmodic
Antiemetic in motion sickness
Drug?
Hyoscine
Parkinson’s disease
Drug?
Benztropine
Fundus examination of eye
Drug used?
Homatropine
Asthma
Drug used?
Ipratropium
Side effects of anti-muscarinic drugs
?
● Eye: blurred vision due to mydriasis
● Tachycardia
● Urinary retention
● Constipation, paralytic ileus
● Dryness of mouth, sandy eye, hyperthermia
● CNS: hallucination, excitation (Toxic dose).
