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Muscle Relaxants ✔️ Flashcards

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1
Q

What effect do many CNS diseases have on muscle tone?

A

They increase muscle tone, which can be painful and disabling.

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2
Q

What are some possible causes of muscle spasms?

A

• Birth injury

• Spinal cord lesions (can lead to paralysis)

• Cerebral vascular disease

• Multiple sclerosis

• Arthritis

• Chronic back pain

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3
Q

What is the main effect of centrally acting muscle relaxants on muscle tone?

A

They decrease background muscle tone without seriously affecting the muscle’s ability to voluntarily contract transiently.

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4
Q

Why is the selectivity of centrally acting muscle relaxants incomplete?

A

Because the distinction between voluntary movements and background tone is blurred.

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5
Q

What is a potential side effect of centrally acting muscle relaxants due to their impact on motor control?

A

They can cause drowsiness and confusion

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6
Q

What can centrally acting muscle relaxants affect besides tone?

A

Postural control.

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7
Q

What is the main difference between spasticity and spasms in terms of definition and origin?

A

• Spasticity: Velocity-dependent increase in muscle tone due to central causes (upper motor neuron disorders).

• Spasms: Involuntary muscle contractions due to peripheral causes (e.g., sprain, nerve compression).

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8
Q

Read

A

Done

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9
Q

What is the major inhibitory neurotransmitter in the CNS that provides tonic control of excitatory transmission?

A

Gamma-Amino Butyric Acid (GABA)

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10
Q

What type of receptor is GABA-A and what is its function?

A

GABA-A is an ion channel receptor that mediates fast inhibitory synaptic transmission.

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11
Q

What type of receptor is GABA-C?

A

GABA-C is also an ion channel receptor.

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12
Q

What type of receptor is GABA-B?

A

GABA-B is a G-protein coupled receptor

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13
Q

What type of ion channel is GABA-A?

A

A multimeric ligand-gated chloride ion channel.

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14
Q

What is the primary effect of GABA-A receptor activation?

A

Chloride influx that hyperpolarizes the postsynaptic cell, producing inhibition.

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15
Q

What drugs act on the modulatory site of the GABA-A receptor?

A

Benzodiazepines (BZDs) and barbiturates

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16
Q

What is the target receptor for benzodiazepines (BZDs)?

A

GABA-A receptor

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17
Q

What type of synaptic inhibition does the GABA-A receptor mediate?

A

Fast postsynaptic inhibition.

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18
Q

What type of receptor is GABA-B and how is it structured?

A

GABA-B is a G-protein coupled receptor (GPCR) that functions as a heterodimer composed of GABAB1 and GABAB2 subunits.

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19
Q

What type of receptor is GABA-B and how is it structured?

A

GABA-B is a G-protein coupled receptor (GPCR) that functions as a heterodimer composed of GABAB1 and GABAB2 subunits.

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20
Q

How does GABA-B receptor modulate neuronal activity?

A

By modulating calcium and potassium channels, leading to presynaptic and slow postsynaptic inhibition.

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21
Q

What are the roles of GABA-B receptors in the CNS?

A

• Cerebral cortex: modulate synaptic excitability & plasticity

• Cortical & thalamic circuits: generate rhythmic activity

• Spinal cord & brainstem: relay primary afferent input

• Affect activity of dopamine (DA) & monoamine (MA) neurons

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22
Q

What is Baclofen?

A

A lipophilic GABA-like agent used as a muscle relaxant and antispasmodic.

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23
Q

What is the mechanism of action of Baclofen?

A

It acts as a GABA-B receptor agonist

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24
Q

Can Baclofen cross the blood-brain barrier?

A

Yes, because it is lipophilic, unlike GABA which cannot penetrate the BBB.

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25
Where does Baclofen exert its antispastic action?
In the spinal cord, by inhibiting mono- and polysynaptic activation of motor neurons.
26
How is Baclofen administered?
Orally
27
What are the side effects of Baclofen?
• Drowsiness • Motor incoordination • Nausea • Some behavioral effects • Seizures in overdose
28
What conditions is Baclofen used to treat?
Spasticity associated with multiple sclerosis or spinal injury, dystonia, Huntington’s disease, and some types of neuropathic pain.
29
Is Baclofen effective in cerebral spasticity due to birth injury?
No, it is ineffective.
30
What are some possible non-standard uses of Baclofen?
Management of drug addiction, anxiety, and visceral pain.
31
How does Diazepam reduce muscle tone?
• Acts centrally on the nervous system • Works independently of its sedative effect • Reduces muscle tone without causing obvious coordination loss
32
What are the uses of Diazepam in muscle conditions?
• Treating skeletal muscle spasms from muscle strain • Treating spasticity from degenerative disorders like MS and CP
33
What is the mechanism of action (MOA) of Diazepam?
• Binds selectively to the modulatory site on the GABA-A receptor • Enhances the response to GABA • Facilitates opening of GABA-activated chloride channels • Increases GABA’s affinity for its receptor • Enhances GABA-mediated inhibition in the CNS
34
What drug class does Diazepam belong to?
Benzodiazepines (BZDs)
35
What is the mechanism of action of Tizanidine?
It is an α2-adrenoceptor agonist
36
Is Tizanidine long-acting or short-acting?
Short-acting.
37
What can occur if Tizanidine is taken in high doses for a long time?
Withdrawal effects
38
What are the therapeutic uses of Tizanidine?
• Relieves spasticity from multiple sclerosis (MS) • Relieves spasticity from spinal cord injury
39
Which drugs should not be taken with Tizanidine?
• Fluvoxamine (antidepressant) • Ciprofloxacin (antibiotic)
40
What interaction risk exists when Tizanidine is taken with CNS depressants or other muscle relaxants?
It potentiates dizziness
41
When should Tizanidine be avoided?
When muscle tone is needed for safe balance and movement.
42
How many pharmacologically active cannabinoids are found in cannabis?
About 60 out of 400 total compounds.
43
What are the two main pharmacologically active cannabinoids?
THC (tetrahydrocannabinol) and cannabidiol
44
What is the main active substance in cannabis?
Tetrahydrocannabinol (THC).
45
What plant products contain cannabinoids?
Marijuana and hashish
46
True or False Like morphine, THC has pharmacologically active metabolites.
True
47
What types of actions do cannabinoids have on the CNS?
Both depressant and psychotomimetic actions
48
How does gut microbiota imbalance affect endogenous cannabinoids?
It reduces them, leading to depressive-like behaviors in animals.
49
True or false Cannabinoids are highly lipid soluble
True
50
What are the routes of administration for cannabinoids?
Smoking or intravenous (I.V.).
51
What is Anandamide?
An arachidonic acid derivative and endogenous cannabinoid ligand for CB1 receptors.
52
What CNS functions are altered by cannabinoids?
Mood and cognition.
53
What are the main receptors for cannabinoids? And where are they located
CB1 (in the brain) and CB2 (in the periphery)
54
What type of receptors are CB1 and CB2?
G-protein-coupled receptors
55
What happens when CB1 receptors are activated?
It can couple to different G-proteins depending on the ligand and its Activation leads to: • Inhibition of adenylyl cyclase (AC) • Activation of potassium (K⁺) conductance • Inhibition of calcium (Ca²⁺) conductance Result: Inhibition of synaptic transmission
56
Where are CB1 receptors primarily distributed?
• Hippocampus (memory impairment) • Cerebellum • Substantia nigra (motor disturbance) • Mesolimbic dopamine pathway (reward) • Cortex
57
Where are CB2 receptors primarily distributed?
Mainly in the lymphoid system
58
Do CB1 and CB2 receptors contribute to analgesic effects?
Possibly, through the activation of PAFs
59
What type of receptor activity does THC have at CB1 and CB2 receptors?
THC is a weak partial agonist at CB1 and CB2 receptors.
60
What are the effects of THC?
• Increased appetite • Decreased pain • Change in mood
61
What is the mechanism of action of Cannabidiol (CBD) at CB1 receptors?
It is a negative allosteric modulator at CB1, acting on a site distinct from agonist/antagonist sites.
62
What other receptors or systems does CBD affect?
CB2, 5HT1a/2a/3a receptors, and TRPV1 vanilloid receptor.
63
What are common psychological effects of cannabis use?
• Euphoria • Relaxation • Sharpened sensory awareness
64
What cognitive and motor effects can cannabis cause?
• Impaired learning • Impaired memory • Impaired motor performance
65
What effect does cannabis have on intraocular pressure (IOP)?
It reduces IOP and can be used in glaucoma treatment.
66
True or False Cannabis use is associated with increased appetite.
True (The munchies)
67
True or False Cannabis has both analgesic and anti-emetic properties.
True
68
What is Nabilone used for?
It is an anti-emetic drug
69
What is cannabidiol approved for?
As an antiepileptic drug for intractable childhood seizures.
70
What is Sativex composed of?
It is a cannabis extract that contains tetrahydrocannabinol (THC) and cannabidiol (CBD).
71
What is the main use of Sativex?
To relieve muscle spasms associated with multiple sclerosis (MS), especially in patients unresponsive to other medications.
72
How is Sativex administered?
As a spray
73
What is the recommended dosing frequency for Sativex?
4–8 doses daily, with 15 minutes between doses.
74
What are some side effects of Sativex?
• Dizziness • Drowsiness (do not drive/operate machinery) • Gastrointestinal issues • Cognitive and psychiatric effects
75
What receptors does Orphenadrine block?
• H1 histamine receptors • Muscarinic receptors • NMDA receptors (Also acts through other unknown mechanisms)
76
What are common side effects of Orphenadrine?
• Dry mouth • Urinary retention • Blurred vision • Drowsiness • Tachycardia
77
What are the therapeutic uses of Orphenadrine?
• Adjunct to physical therapy for muscle spasms • Relief of discomfort from acute painful musculoskeletal conditions • Parkinson’s disease
78
In which condition is Orphenadrine contraindicated and why?
• Myasthenia gravis • Due to its anticholinergic effects
79
What type of drug is Orphenadrine?
• Centrally acting • Antihistaminic • Antimuscarinic muscle relaxant • Has NMDA receptor antagonist properties (may contribute to its analgesic effects)
80
What is the mechanism of action of Methocarbamol?
Unknown, but it has CNS depressant activity
81
What are the physiological effects of Methocarbamol on the nervous system?
• Blocks spinal polysynaptic reflexes • Decreases neurotransmission in spinal and supraspinal polysynaptic pathways • Prolongs the refractory period of muscle cells
82
What is Methocarbamol used for in physical therapy?
Used as an adjunct to relieve discomfort due to acute, painful musculoskeletal conditions.
83
What are the side effects of Methocarbamol?
• Dizziness • Nausea • Flushing • Confusion • Memory problems • Lack of coordination
84
True or False The mechanism of action of Chlorzoxazone is unknown.
True
85
How does Chlorzoxazone help reduce muscle spasms?
It acts at the spinal cord and subcortical levels of the brain to inhibit multisynaptic reflex arcs involved in maintaining muscle spasms.
86
Does Chlorzoxazone have sedative properties?
Yes
87
What are the clinical uses of Chlorzoxazone?
As an adjunct to physical therapy to relieve discomfort from acute, painful musculoskeletal conditions.
88
What are the side effects of Chlorzoxazone?
• GI bleeding • Dizziness • Feeling unwell

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