56 Questions
Which side effect is specifically mentioned as being diminished with regular use of cholinergic antagonists?
Blurred vision
What is the neurochemical effect of nicotine at low doses?
Decreases blood pressure
Which drug is a non-depolarizing skeletal neuromuscular junction blocker?
Vecuronium
What is the therapeutic use of curare (d-Tubocurarine)?
Muscle paralysis as an adjuvant in anesthesia
Which drug interaction inhibits acetylcholine release from the neuromuscular junction, potentiating the effect of blockers?
Aminoglycosides
What does succinylcholine attach to when exerting its action?
Nicotinic receptor
Which adverse effect is NOT commonly associated with cholinergic antagonist atropine?
Drowsiness
What is the primary therapeutic use of ipratropium and tiotropium?
Management of asthma and COPD
Which medication is NOT a synthetic atropine-like drug used in the treatment of an overreactive bladder?
Benztropine
What is the primary action of scopolamine in addition to being a belladonna alkaloid like atropine?
Central nervous system sedation
Which of the following is a common pharmacokinetic characteristic of cholinergic antagonist medications like atropine?
Rapid hepatic metabolism
What is the primary therapeutic use of tropicamide and cyclopentolate?
Cycloplegic refraction and uveitis
What is the primary mechanism of action of succinylcholine?
Causes prolonged depolarization at the neuromuscular junction
What is the therapeutic use of succinylcholine?
Rapid endotracheal intubation during anesthesia induction
Which adverse effect can result from using succinylcholine in conjunction with halothane?
Malignant hyperthermia
What is the primary mechanism of action of baclofen?
Enhances GABA neurotransmission
How does dantrolene exert its effect on skeletal muscles?
Directly inhibits Ca++ release from sarcoplasmic reticulum
What is the primary mechanism of action of orphenadrine for causing analgesia and muscle relaxation?
Blocks the action of acetylcholinesterase
How does nicotine affect the autonomic nervous system and striated muscle at a low dose?
Increases blood pressure, heart rate, peristalsis, and secretions
Which cholinergic antagonist is specifically effective in treating organophosphate intoxication?
Atropine
What is the primary therapeutic use of curare (d-Tubocurarine)?
Adjuvant in anesthesia
What is the primary effect of scopolamine, a belladonna alkaloid similar to atropine but with a longer action in the CNS?
Reduces motion sickness and induces sedation
At high doses, what is the action of Curare (d-Tubocurarine) at the skeletal neuromuscular junction?
Blocks Na+ ion channels of the end plate
What is the synthetic atropine-like medication used in the treatment of overactive bladder?
Oxybutynin
Which drug interaction potentiates the effect of blockers like tebocurarine and other competitive blockers in neuromuscular blockade?
Calcium channel blockers
Which centrally acting antimuscarinic agent is primarily employed as an adjuvant therapy in Parkinson's Disease?
Benztropine
What is the last muscle affected by muscle paralysis caused by Curare (d-Tubocurarine)?
Diaphragm
What is the primary pharmacokinetic characteristic of cholinergic antagonist medications like atropine?
Readily absorbed, partially metabolized in liver, and eliminated in urine
Which type of neuromuscular blocker attaches to nicotinic receptors acting like acetylcholine?
Depolarizing blocker
Which cholinergic antagonist is NOT commonly associated with blurred vision as an adverse effect?
Benztropine
Which drug binds to GABAB receptors and causes hyperpolarization of the neuronal membrane?
Baclofen
What is the primary mechanism of action of dantrolene in inhibiting muscle contractions?
Inhibiting Ca++ release from sarcoplasmic reticulum
Which adverse effect can occur when succinylcholine is used in genetically deficient patients of plasma cholinesterase?
Apnea
What is the primary therapeutic use of diazepam (Valium)?
Muscle spasms
How does baclofen exert its muscle relaxant effect?
Causing an influx of potassium into the neuron
Which drug, when used with halothane, may lead to malignant hyperthermia in genetically susceptible individuals?
Succinylcholine
Which drug, when used with halothane, may lead to malignant hyperthermia in genetically susceptible individuals?
Succinylcholine
Which of the following drugs binds to GABAB receptors leading to hyperpolarization of the neuronal membrane?
Baclofen
What is the primary adverse effect associated with Succinylcholine in genetically deficient patients of plasma cholinesterase?
Apnea
What is the mechanism of action of Orphenadrine in causing analgesia and skeletal muscle relaxation?
Direct inhibition of Ca++ release from sarcoplasmic reticulum
What effect does Diazepam (Valium) have on muscle spasms?
Enhancing GABA neurotransmission
Which drug causes hyperpolarization of the neuronal membrane by binding to GABAB receptors?
Baclofen
What is the primary therapeutic use of Baclofen?
Treating muscle spasms
What is a common adverse effect associated with Succinylcholine?
Apnea
How does Dantrolene exert its effect on skeletal muscles?
By inhibiting Ca++ release from the sarcoplasmic reticulum
What can occur when using Succinylcholine in conjunction with halothane in susceptible individuals?
Malignant hyperthermia
Dantrolene causes an influx of calcium into the neuron, leading to hyperpolarization of the neuronal membrane.
False
Succinylcholine can be administered via intravenous continuous infusion.
False
Baclofen binds to GABA receptors to cause muscle spasms.
False
Orphenadrine is a derivative of diphenhydramine and primarily acts as a stimulant.
False
Halothane combined with Succinylcholine may lead to hypothermia in genetically susceptible individuals.
False
Benzodiazepines enhance the action of glutamate, an excitatory neurotransmitter.
False
In genetically deficient patients of plasma cholinesterase, Succinylcholine may cause prolonged paralysis due to slow hydrolysis.
True
Diazepam (Valium) is primarily used for treating hypertension.
False
Baclofen inhibits potassium influx into neurons, leading to muscle contraction.
False
Succinylcholine is a non-depolarizing neuromuscular blocking agent.
False
Study Notes
Cholinergic Antagonists
- Derived from Belladona alkaloid
- Central and peripheral activity
- Actions:
- Ophthalmic: mydriasis and cycloplegia
- GI system: antispasmodic
- Urinary system: enuresis
- CV: tachycardia
- Endocrine (secretory): xerostomia, xerophthalmia (dry mouth and eye)
- Therapeutic use:
- Ophthalmic: cycloplegic refraction, uveitis
- Antispasmodic
- Antidote: organophosphate intoxication (insecticides)
- Pharmacokinetics:
- Readily absorbed
- Partially metabolized in liver
- Eliminated in urine
- t 1/2 life of 4 hrs
- Adverse effects:
- Dry mouth
- Blurred vision
- Tachycardia
- Constipation
- Confusion
- Hallucinations
- Delirium
Scopolamine
- Belladona alkaloid with similar action to atropine
- Longer action in CNS
- Effective anti motion sickness/sedation
- Cycloplegic refraction, uveitis
Ipratropium / Tiotropium
- Quaternary derivative of atropine
- Used by inhalation for asthma and COPD
- Decreases smooth muscle contraction of bronchi
Tropicamide / Cyclopentolate
- Ophthalmic solutions
- Producing similar effects to atropine
Benztropine
- Centrally acting antimuscarinic agent
- Employed as adjuvant Tx in Parkinson Disease
- Minimizes dystonia in Tx with anti-psychotic medications
Darifenacin / Fesoterodine / Oxybutyin / Solifenacin / Tolterodine
- Synthetic atropine-like meds
- Used for overreactive bladder
- Increase capacity by lowering intravesical pressure
- Side effects:
- Dry mouth
- Constipation
- Blurred Vision (Diminished with regular use)
Nicotine
- Depolarize Ganglia ANS and striated muscle
- Low dose increases BP, HR, peristalsis, and secretions
- High dose decreases BP and diminishes muscular activity
- Neurochemical effects:
- Non-depolarizing (competitive) blockers
- Depolarizing blockers
Non-Depolarizing (Competitive) Blockers
- Curare (d-Tobocurarine,1st drug)
- Skeletal neuromuscular junction blocker
- Actions:
- Muscle paralysis
- Small muscles of face, eyes, fingers, limbs, neck, and trunk muscles
- The last one affected is the diaphragm
- Therapeutic use: adjuvant in anesthesia
- Pharmacokinetics: used IV, does not cross readily blood brain barrier
- Benefits: decrease concentration of general anesthetic drugs by achieving adequate muscle relaxation
Vecuronium / Rocuronium - Others
- Drug interactions:
- Cholinesterase inhibitors (neostigmine, etc.) overcome depolarizing action at low dose
- Aminoglycosides (gentamycin or tobramycin) inhibit acetylcholine release from neuromuscular junction – potentiate the effect of blockers
- Calcium channel blockers increase neuromuscular block of tebocurarine and other competitive blockers
Depolarizing Blockers
- Succinylcholine
- Attaches to nicotinic receptor acting like acetylcholine
- Depolarizing the neuromuscular junction persisting in cleft at [higher] for longer time followed by an altered repolarization
- 2 phases: twitch/flaccid paralysis during depolarization, desensitization during repolarization flaccid paralysis
- Actions: paralyzing process similar to non-depolarizing agents ending in respiratory muscles
- Therapeutic use: rapid endotracheal intubation during induction of anesthesia to avoid gastric aspiration
- Pharmacokinetics: rapid onset of short duration (minutes) due to hydrolysis by plasma cholinesterase
- Administered by IV continuous infusion
- Adverse effects:
- Hyperthermia
- Apnea in genetically deficient patients of plasma cholinesterase
Miscellaneous Muscle Relaxants
- Neural acting
- Benzodiazepines enhance or facilitate the action of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter
- Diazepam (Valium)*: use for muscle spasms
- Baclofen binds to GABAB receptors, causing influx of potassium into the neuron, leading to hyperpolarization of the neuronal membrane and decreased calcium influx at presynaptic nerve terminals
- Others:
- Dantrolene directly inhibits Ca++ release from sarcoplasmic reticulum
- Orphenadrine (methyl derivative of diphenhydramine) causes analgesia and skeletal muscle relaxation
Test your knowledge on the cholinergic antagonist Atropine, derived from the Belladona alkaloid. Explore its actions on the ophthalmic, GI, urinary, cardiovascular, and endocrine systems, as well as its therapeutic uses and antidote applications.
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