Skeletal Muscle Relaxants Flashcards
Diazepam
Central spasmolytic
MECHANISM
GABA a agonist
Increases interneuron inhibition
INDICATION
Acute / chronic spasm - caused by cerebral palsy or stroke
KINETICS
Oral / Parenteral
12-24h
Hepatic excretion
SIDE EFFECTS
Sedation
Weakness
Baclofen
Central spasmolytic
MECHANISM
GABA b agonist
INDICATION
Acute SEVERE muscle spasm - caused by cerebral palsy or stroke
KINETICS
Oral / intrathecal
SIDE EFFECTS
Sedation
Weakness
Respiratory depression
Tizanidine
Central spasmolytic
MECHANISM
a2 agonist in spinal cord
Pre and postsynaptic inhibition
Related to clonidine
INDICATION
Acute / chronic spasm - caused by cerebral palsy or stroke
KINETICS
Oral
SIDE EFFECTS Sedation Weakness Hypotension Less cardiovascular side effects compared to clonidine
Tolperisone
Central spasmolytic
MECHANISM
VDNa inhibitor
VDCa inhibitor
In reticular formation in brain stem
INDICATION Acute / chronic spasm Multiple sclerosis Encephalomyelitis Myelopathy
KINETICS
SIDE EFFECTS
Cyclobenzaprine
1/4
Central spasmolytic
MECHANISM
Unknown
Antimuscarinic
INDICATION
Acute muscle spasm - caused by local trauma
KINETICS
Oral
SIDE EFFECTS
Sedation
Hallucinations
Respiratory depression
Mephenesine
2/4
Central spasmolytic
MECHANISM
Unknown
Antimuscarinic
INDICATION
Acute muscle spasm - caused by local trauma
KINETICS
Oral
SIDE EFFECTS
Sedation
Hallucinations
Respiratory depression
Guaiphenesine
3/4
Central spasmolytic
MECHANISM
Unknown
Antimuscarinic
INDICATION
Acute muscle spasm - caused by local trauma
KINETICS
Oral
SIDE EFFECTS
Sedation
Hallucinations
Respiratory depression
Chlorzoxazone
4/4
Central spasmolytic
MECHANISM
Unknown
Antimuscarinic
INDICATION
Acute muscle spasm - caused by local trauma
KINETICS
Oral
SIDE EFFECTS
Sedation
Hallucinations
Respiratory depression
Omega-conotoxin
(Ziconotide)
Peripheral spasmolytic - presynaptic
MECHANISM
Ca channel inhibitor
NT vesicle release inhibitor
INDICATION Surgical narcosis (main indication) Chronic pain (CSF injection) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
CSF injection for chronic pain, FDA approved
SIDE EFFECTS
Botulinum toxin
Peripheral spasmolytic - presynaptic
MECHANISM
NT vesicles release (Snare) inhibitor
INDICATION
Plastic surgery, muscle relaxant
KINETICS
SIDE EFFECTS
Aminoglycosides
Tetracyclines
Peripheral spasmolytic - presynaptic
MECHANISM
INDICATION
KINETICS
SIDE EFFECTS
Muscle weakness
d-tubocurarine (not used)
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Isoquinoline competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
IV only
Full paralysis in 2-6min
No CNS effect
SIDE EFFECTS
Muscle weakness
After the drug is gone, unknown reason
Acetylcholinesterase inhibitors used to antagonise effect
Neostigmine
Distigmine
Atropin must be coadministered to antagonize parasympathetic effects on heart
Doxacurium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Isoquinoline competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS Long acting (60-180min)
SIDE EFFECTS
Muscle weakness
After the drug is gone, unknown reason
Acetylcholinesterase inhibitors used to antagonise effect
Neostigmine
Distigmine
Atropin must be coadministered to antagonize parasympathetic effects on heart
Atracurium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Isoquinoline competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS Medium acting (30-60min)
SIDE EFFECTS
Histamine release - Itching, hypotension
Muscle spasm - metabolite Laudanosin is causing it
Cisatracurium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Isoquinoline competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS Medium acting (30-60min)
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Mivacurium (not used)
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Steroid competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
Short acting (10-15min)
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Pancuronium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Steroid competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
Long acting (60-180min)
Kidney excretion
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Pipecuronium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Steroid competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
Long acting (60-180min)
Kidney excretion
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Vecuronium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Steroid competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
Medium acting (30-60min)
Liver excretion
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Rocuronium
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Steroid competitive antagonist
INDICATION Surgical narcosis (main indication) Severe COPD (on artificial respiration) Intubation Electroshock therapy (in catatonic schizophrenia) Seizure / epilepsy Amphetamin overdose
KINETICS
Medium acting (30-60min)
Liver excretion
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle weakness - antagonise with neostigmine
Succinylcholine
Peripheral spasmolytic - postsynaptic
MECHANISM
nAchR muscular type (NMJ)
Depolarization blockade
Succinylcholine is not degraded by Acholinesterase and causes continuous stimulation of nAchR, Na+ influx, and inactivation of the channel, causing a blockade for 5-10min.
Phase 1 - muscle fibrillation, inactivation
Phase 2 - muscle desensitization after drug removal
INDICATION
Short surgical interventions
Intubation
Laprascopy
KINETICS
Medium acting (30-60min)
Liver excretion
Sugammadex - neutralizes steroids in the plasma
SIDE EFFECTS
Muscle pain - due to fibrillation
Malignant hyperthermia
in case of mutated Ryanodine receptor. Succinylcholine activates it permanently –> muscle shivering, hyperthermia, lactic acidosis, myoglobinemia. Treatment is:
1) Dantrolene (ryanodin receptor antagonist - Hepatotoxic effect in 1-2%
2) Bicarbonate to counteract acidosis
3) Physical cooling
Hyperkalemia - due to nAchR outward K+ current
Bradycardia - SA node M2 receptor stimulation -Antagonise this effect using atropine.
Increased intraoccular pressure - don’t use in glaucoma
