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Questions and Answers
What is the reason Acetylcholine is not therapeutically useful?
What is the reason Acetylcholine is not therapeutically useful?
- It only stimulates the muscarinic receptors
- It has only nicotinic activity
- It has a multiplicity of actions and is rapidly inactivated by cholinesterase enzyme (correct)
- It is only found in the sympathetic nervous system
What type of receptors does Pilocarpine bind to?
What type of receptors does Pilocarpine bind to?
- Muscarinic acetylcholine receptors (mAChR) (correct)
- Adrenergic receptors
- Dopaminergic receptors
- Nicotinic acetylcholine receptors (nAChR)
What is the effect of Acetylcholine on the heart rate?
What is the effect of Acetylcholine on the heart rate?
- Increases heart rate
- Can either increase or decrease heart rate
- Has no effect on heart rate
- Decreases heart rate (correct)
Which of the following is an indirectly acting cholinergic agonist?
Which of the following is an indirectly acting cholinergic agonist?
What is the effect of Acetylcholine on the salivary secretion?
What is the effect of Acetylcholine on the salivary secretion?
How do directly acting cholinergic agonists work?
How do directly acting cholinergic agonists work?
What is the effect of Acetylcholine on the tone of urinary bladder muscles?
What is the effect of Acetylcholine on the tone of urinary bladder muscles?
What type of receptors does Nicotine bind to?
What type of receptors does Nicotine bind to?
What is the effect of atropine on the pupil?
What is the effect of atropine on the pupil?
What is the therapeutic application of atropine in ophthalmology?
What is the therapeutic application of atropine in ophthalmology?
What is the effect of atropine on heart rate at low doses?
What is the effect of atropine on heart rate at low doses?
What is the use of atropine as an antidote?
What is the use of atropine as an antidote?
What is the effect of atropine on intraocular pressure (IOP) in patients with glaucoma?
What is the effect of atropine on intraocular pressure (IOP) in patients with glaucoma?
What is the source of atropine?
What is the source of atropine?
What is the historical use of atropine?
What is the historical use of atropine?
What is the meaning of 'belladonna'?
What is the meaning of 'belladonna'?
What is the primary mechanism of action of anticholinesterases?
What is the primary mechanism of action of anticholinesterases?
What is the primary use of pilocarpine in ophthalmology?
What is the primary use of pilocarpine in ophthalmology?
What is the primary cause of myasthenia gravis?
What is the primary cause of myasthenia gravis?
What is the purpose of the edrophonium test in diagnosing myasthenia gravis?
What is the purpose of the edrophonium test in diagnosing myasthenia gravis?
What is a common adverse effect of pilocarpine?
What is a common adverse effect of pilocarpine?
What is the name of the disease characterized by fluctuating weakness and fatigability?
What is the name of the disease characterized by fluctuating weakness and fatigability?
What is a treatment option for myasthenia gravis?
What is a treatment option for myasthenia gravis?
What is the duration of action of pilocarpine when applied topically to the cornea?
What is the duration of action of pilocarpine when applied topically to the cornea?
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Study Notes
Cholinergic Transmission
Parasympathomimetics
- Parasympathomimetics can be classified into directly and indirectly acting cholinergic agonists.
- Directly acting cholinergic agonists mimic the effect of acetylcholine (ACh) by binding directly to cholinoreceptors.
- Examples of directly acting cholinergic agonists include:
- Acetylcholine (ACh)
- Pilocarpine
- ACh has both nicotinic and muscarinic activity, but it is therapeutically of no importance due to its multiplicity of actions and rapid inactivation by cholinesterase enzyme.
- Actions of ACh:
- Heart rate: decreased
- Blood pressure: decreased
- Salivary secretion: increased
- GIT secretion and motility: increased
- Bronchial secretion: increased
- Tone of urinary bladder muscles: increased
- Pupil sphincter muscle: contracted
- Ciliary muscle: contracted
Adverse Effects of Cholinergic Drugs
- Cholinergic drugs can cause adverse effects such as:
- Increased salivation
- Increased sweating
- Nausea and vomiting
- Abdominal cramps
- Diarrhea
Cholinergic Antagonists
Anti-Muscarinic Agents
- Examples of anti-muscarinic agents include:
- Atropine
- Scopolamine
- Ipratropium
- Atropine:
- Isolated from Atropa belladonna
- Has muscarinic activity
- Actions:
- Eye: mydriasis, unresponsiveness to light, cycloplegia, increased IOP in patients with glaucoma
- CVS: bradycardia at low doses, modest tachycardia at high doses
- Therapeutic applications:
- Ophthalmic: mydriatic and cycloplegic effect
- Antisecretory: blocks respiratory secretions prior to surgery
- Antidote: for overdose of cholinergic agonists
Indirectly Acting Cholinergic Agonists (Anticholinesterases)
- Examples of anticholinesterases include:
- Neostigmine (Prostigmine)
- Edrophonium
- Uses:
- To stimulate bladder and GIT contraction
- To treat myasthenia gravis
Myasthenia Gravis
- Myasthenia gravis is a neuromuscular disease characterized by fluctuating weakness and fatigability.
- It is an autoimmune disorder caused by circulating antibodies that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting ACh.
- Diagnosis: Edrophonium test
- Treatment:
- Cholinesterase inhibitors to directly improve muscle function
- Immunosuppressant drugs to reduce the autoimmune process
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