Muscle Relaxants Flashcards
Muscle Spasm Drugs
DTMCC
Diazepam Tizanidine Metaxalone Cyclobenzaprine Carisoprodol
Diazepam (Valium)
-Facilitates action of GABA, a CNS inhibitory neurotransmitter
Therapeutic Use:
- used as adjunct for skeletal muscle spasms due to joint or muscle inflammation or trauma
- can also be used for spasticity from upper motor neuron disorders (cerebral palsy)
CNS side effects are common
Beers Criteria: AVOID
Generally avoid as muscle relaxant due to risk of dependency and tolerance
Schedule IV medication
Tizanidine (Zanaflex)
- Central alpha-2 agonist
- Indications:
> mgmt of spasticity
> some efficacy for acute musculoskeletal conditions
> acute back pain for antispasmodic effects plus sedation action for sleep
Tizanidine (Zanaflex) Side Effects
Very Sedative
- Hypotension, hallucinations, delusions, hepatotoxicity
Tizanidine (Zanaflex) Contraindications
- Foods affect absorption
- HEPATOTOXIC: monitor baseline liver function, 1 month after max dose is reached and then when clinically indicated
- Use with caution with other drugs that cause QT prolongation
- Contraindicated with potent CYP1A2 inhibitors LIKE CIPROFLOXACIN
- Use with caution with other CYP1A2 inhibitors LIKE ACYCLOVIR, FAMOTIDINE, ORAL CONTRACEPTIVES
- Not on Beers list which is weird
Metaxalone
- Unknown mechanism of action
- Used as adjunct treatment of acute, painful musculoskeletal conditions
- Relatively low risk of drowsiness or cognitive effects
- Serotonin Syndrome Reported when used at higher than the recommended dose or in combo with SSRI, SNRI’s tricyclic antidepressants
- Contraindicated with liver or renal impairment
» NEEDS MONITORING - Beers List: AVOID
Cyclobenzaprine (Flexiril)
- Acts primarily in the brain stem
- Relieves acute muscle spasm and associated pain, tenderness, movement restriction
> not effective for CNS muscle spasms - Serotonin Syndrome reported when used at higher than recommended dose or in combo with SSRI, SNRI, tricyclic antidepressants
- Considered first-line for acute musculoskeletal conditions
- Beers list: AVOID
Cyclobenzaprine (Flexiril) Side Effects
Anticholinergic Effects:
- constipation, urinary retention, dry mouth, blurred vision, increased HR, increased BP, dilated pupils, increased sweating, diarrhea, loss of muscle coordination, muscle twitching
- COMPARED to carisoprodol: dry mouth is more frequent but dizziness is less frequent
DOES NOT NEED MONITORING BUT CANNOT USE IN LIVER DISEASE
Carisoprodrol
- Euphoria, sedation
- significant withdrawal, tolerance, and dependency
- Schedule IV medication
- Generally avoided due to abuse potential
Drugs for Muscle Spasticity
Baclofen
Dantrolene
Baclofen (5 bullets)
- Indicated for spasticity associated with MS, SCI, or other spinal cord diseases
> Decreases flexor and extensor spasms - Inhibits monosynaptic and polysynaptic reflexes at the spinal cord
> precise mechanism is unknown - Withdrawal Syndrome is possible: Hallucinations, Seizures (taper over 1-2 weeks)
- Use cautiously with renal impairment and seizure disorder pts
- Usually first choice for spasticity
Dantrolene Therapeutic Uses
- Spasticity associated with MS, Cerebral Palsy, Stroke, SCI
- Malignant Hyperthermia
> potentially fatal condition cause by succinylcholine and general anesthetics
Dantrolene Symptomatic Hepatotoxicity (5 bullets)
- Most common between 3-12 months of use
- More common in women, > 35yo, concurrent medications, high dosages (800mg/day)
- Can be severe and sometimes fatal
- Contraindicated in patients with active liver disease
- Baseline and periodic liver function tests are recommended
Dantrolene Adverse Effects
Diarrhea can be severe prompting temporary or permanent discontinuation of drug
If no benefit after 45 days of use, discontinue due to risk of hepatotoxicity
