March 28, 2023

Centrally acting muscle relaxants are used to control muscle spasticity and muscle pain associated with multiple sclerosis or spinal cord injuries. Drugs like baclofen, tizanidine and diazepam are mainly used in these conditions.

Hi everyone today in this video we are going to discuss about centrally acting major relaxants muscle spasticity is one of the condition where there is an increased repetitive muscle movements along with increased muscle pain and involuntary movements and sometimes it may also be associated with the immobility all these symptoms are associated with the muscle

Spasticity and this condition can be observed with few other disorders like the multiple sclerosis multiple sclerosis is one of a neurodegenerative disorder which mainly affects the skeletal muscle resulting in the muscle spasticity and sometimes muscle spasticity can also be observed with the spinal cord injuries and these plastic conditions are associated with

The increased muscle pain as well as muscle spasm in such conditions we can use the centrally acting muscle relaxants we can also use the peripherally acting material accents like the dendrolene neuromuscular blockers directly blocking the nicotinic receptors like the saxa methodium pancronium all this can produce some skeletal muscle relaxation but today in this

Video we are going to discuss the centrally acting material accents which are mainly indicated for the conditions as well as spinal cord injuries what are the centrally acting muscle accents we have three important central active muscular accents the first one is that gaba b agonis one of the drug is the baclofen and second one is the alpha to agonise one of

The drug is a tizanidine and this drug is angular suffix like needing which resembles the and the drug clonidine clonidine is an alpha to agonist as well as thaizanidine is also an alpha to organist but here this thaizanidine is used as skeletal muscle accent third one is a benzodiazepines benzodiazepines produces anxiolytic sedative and hypnotic effect and

Apart from these they can also produce some anti-convulsant and muscle relaxant activities so one of the benzodiazepine is a daiji palm that can be used as skeletal muscular accent other drugs include chlorozox zone and other related racks which are mainly used as adjuvants to produce the muscle relaxation so now let us see how these skeletal muscle relaxants are

Working all these drugs are centrally acting that’s why they produce some central depression resulting in the drowsiness and dizziness in the patients so now let us see how these centrally acting muscle accidents are going to act within the central nervous system the motor neuron is going to control the skeletal muscle activity and this motor neuron is equipped

With the ampa receptors amp receptors are the receptors for glutamate which are the inotropic receptors and they are fast acting and whenever the glutamate acts on these amp receptors motor neurons are rapidly activated to send the signals to the skeletal muscle now these motor neurons are going to be supplied with the presynaptic neurons where the glutamate is

Going to be stored and released which acts on the amp receptors on the motor neuron to produce the skeletal muscle contraction so when the impulse are going to reach to the corticotropic neurons they are going to release one of the important mediator glutamate which binds to the amp receptors and when these amp receptors are activated they are inotropic receptors

So they are going to allow for the ions like the sodium now this sodium produce the depolation of the motor neuron and this depolation is transmitted through the motor neuron to the skeletal muscle such that skeletal muscle is undergoing the contraction in this way glutamate plays an important role in skeletal muscle contraction but this signaling is going to be

Controlled by other inhibitory neurotransmitters within the cns so within the presynaptic neuron we can observe one of the receptor alpha two receptors and similarly another one is the gaba b receptors both are g protein coupled receptors which are controlling the glutamate release and similarly on the motor neuron we can observe again the gaba b receptors and

We cannot observe inotropic gaba a receptors so here glutamate acts as a excitatory amino acid which produce the motor activation but at the same time the inhibitory neurons can release one of the important mediator that is the gaba gaba is a inhibitory amino acid neurotransmitter this gaba can bind to the gaba b receptors which are expressed presynaptically

Such that these receptors are going to inhibit the release of glutamate so that glutamate is not released norepinephrine can act on the alpha-2 receptors again they inhibit the release of glutamate thereby they inhibit the glutaminergic transmission in this way the glutamate release is controlled pre-synaptically by alpha-2 receptors as well as gaba-b receptors

And here the inhibitory neurotransmitter gaba can also act on the motor neurons so it can bind to the gaba b receptors which produce a slow modulatory response otherwise it can bind to the gaba a receptors where it is going to produce the inhibited response by opening of chloride channels because of these two actions gaba can produce the inhibited response on

The motor neuron so that it can prevent the skeletal muscle contraction in this way the motor activity can be controlled by mainly alpha to receptors gaba b receptors and gaba a receptors now let us see what are the drug targets for the centrally acting muscle relaxants one of the drug target is the tizonidine which is going to act as an agonist on the alpha 2

Receptors which are located presynaptically and they inhibit the release of the glutamate similarly and the drug target is a baclofen which is going to activate the gaba b receptors located on presynaptic as well as post synaptically such that it is going to inhibit the motor response similarly the benzodiazepines are going to bind to the benzodiazepine binding

Site on the gaba a thereby increase the binding of gaba to the gaba-a receptors resulting in the opening of chloride channels and hyperpolation of the motor neurons so benutizipins can also inhibit the motor response by binding to the gaba a receptors in this way these three drugs can produce the muscle relaxation by increasing the inhibited response on the

Presynaptic as well as postsynaptic motor neurons so first drug is the baclofen baclofen is having the structure like this and you can observe it is having the structure just similar to the gaba here it is having a carboxylic acid and we can start the numbering one two three four so fourth portion is having an amino group so this is a four amino butanoic acid so

Four amino butanoic acid is nothing but the gamma amino butyric acid so it’s a gaba derivative but it’s having a substitution at the third portion so which is nothing but the para chlorophenide so third portion we can observe four chlorophenyl ring is present so baclofen is a modified structure of the gaba with para chlorophenyl substitution at the third portion

Now this baclofen mainly acts as an agonist at the gaba b receptors which are the g protein carbon receptors which produce the inhibitory response on the motor activity that’s why this backlog fan can be used to treat the conditions as well as to control the muscle pain in the spinal cord injuries and since this drug is going to act centrally produce we have the

Central side effects like the drowsiness dizziness and weakness so whenever this drug is given the drowsiness is one of the important side effect that can be observed in most of the patients and whenever this drug is withdrawn suddenly so it shows few of the withdrawal effects particularly it can produce you have the psychotic symptoms like hallucinations and it

Can also stimulate the reflux mechanisms and the sympathy system such that it produces a tachycardia hesitation in the patients so the drug should not be stopped suddenly in order to prevent these withdrawal effects second drug is the thai zanidine tyson it is having a structure like this and here you can observe one of the heterocyclic system with two nitrogens

And one sulfur so we can start the numbering here one two three four five and so on so now this heterocycline system is having the sulfur at second portion and nitrogen’s at first and third portion so we can write this as 2 1 3 bingo third diagonal so 2 1 3 benzodiazole is attached with an amine group at the fourth portion so 4 mi so that is the ring system

Present in this tizen editing and fifth portion we can observe a chloro group and it’s having another hydrocyclone system on the mn group at the fourth position let us give the numbering to this heterocyclic ring so this is one two three four five so this is simply imidazole which is saturated fourth and fifth position so we can write this as n dash four five

Dihydroimidazole two i so that is a complete name of the tizen eating just we have seen the mechanism of this track this drug is going to bind to the alpha receptors which are located pre-synaptically thereby it inhibits the release of the exaggerated neurotransmitters like the glutamate thereby inhibits the motor actuation so again this drug is central acting so

It produces we have the central representative effects like sedation hypotension dizziness and it can also produce few of the other side effects like dry mouth and constipation so this like is a alpha to igneous and related with the another drug like clonidine clonidine is a centrally acting antihypertensive but tizen identity is a centrally acting material accent

Again this type produces hypotension under normal conditions but when this drug is suddenly stopped it can produce a a rebound hypertension and tachycardia so again this drug should not be stopped suddenly third one is a daisy pump daisy palm is a benzodiazepine having the structure like this and daisy pump binds the benzodiazepine binding site thereby facilitates

The action of the gaba on the gaba-a receptors so this drug is a positive endostatic modulator for the gaba-a receptors this is particularly used as anxiolytic and anti-convergent and apart from these two indications daisy palm can also be used to produce the muscle relaxation and since it’s a benzodiazepine again it produces sedation dizziness drowsiness and

It can also produce some loss of memory resulting in the amnesia so these are the common side effects of daisy palm drugs to treat the muscle spasm so till now we have seen the three drags which are mainly used for the conditions but we have the other drugs which are centrally acting to control the muscle spasm and they are mainly used as muscle relaxants we

Have few other drugs like the chloroxyzone carcinol methyl carbamal cyclobenzaprine orphenadrine and metaexolone all these are the central acting measural accents which are mainly used to control the pain during the conditions so even these drugs are not completely relieving the conditions they can reduce the pain and the spasm that’s why these ducts can be

Used as adjuvants in the treatment of conditions and these drugs are intended for a short-term use in order to reduce the pain and spasm among this chlorized oxygen is one of the drug which is widely used so this is a clergy oxygen structure so simply it’s a bench oxazole with a ketone so binge oxazolone is the ring system present in the closed oxone and this

Drag and this duck mainly acts on the spinal cords thereby inhibits the multi synaptic reflexes resulting in the relieving of the muscle spasm again this red produce we have the central side effects like dizziness and drowsiness in the patients but these drugs are not the main line of drugs they are mainly used as adjuvants to control the pain as well as spasm

In the musculoskeletal disorders so that’s about the central acting skeletal muscle relaxants hope you have enjoyed this video if you like this video please subscribe to our channel share this video with your friends post your comments in the comment box thank you for watching this video

Transcribed from video
Centrally acting muscle relaxants By egpat