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cyclobenzaprine (Flexeril)
Tradename: Flexeril.
Indications:
1) muscle relaxant for short term management of muscle spasms
2) ineffective in spasticity due to chronic neurologic disorders
3) used for treatment of fibromyalgia
Dosage: Start 10 mg PO TID, max 60 mg/day.
Tabs: 10 mg.
Pharmacokinetics:
1) duration of action is 12-24 hours
2) highly protein bound
3) extensively metabolized by liver by cyt P450 1A2
4) eliminated in the urine
5) elimination 1/2life 1-3 days
Adverse effects:
1) anticholinergic effects
a) dizziness
b) drowsiness
c) dry mouth
d) confusion
e) nausea
f) constipation
g) urinary retention
2) consider all adverse effects of amitriptyline
3) other (< 1%)
- swelling of face & lips, clumsiness, tinnitus, dermatitis, hepatitis, syncope, urinary frequency, bloating, difficulty speaking, muscle weakness, hypotension, arrhythmias, asthenia, nervousness, rash, dyspepsia, dysgeusia (taste disturbance)
4) risk of falls: baclofen, cyclobenzaprine > tizanidine
- risk of fracture: baclofen, cyclobenzaprine = tizanidine [6]
Drug interactions:
1) MAO inhibitors
2) consider all interactions listed with amitriptyline
3) any drug which inhibits cyt P450 1A2 can increase cyclobenzaprine levels
4) any drug which induces cyt P450 1A2 can diminish cyclobenzaprine levels
5) prevalence of depression is 61% among patients coprescribed gabapentin + cyclobenzaprine [5]
Mechanism of action:
1) centrally-acting muscle relaxant
2) structurally related to tricyclic antidepressants (TCA)
3) ineffective for muscle spasm due to CNS disease
Related
cytochrome p450 1A2 (cytochrome P3-450, phenacetin deethylase, cytochrome p450-4, CYP1A2)
General
dibenzazepine; iminostilbene
skeletal muscle relaxant (tranquilizer)
Properties
MISC-INFO: elimination route LIVER
KIDNEY
1/2life 1-3 DAYS
pregnancy-category B
safety in lactation ?
Database Correlations
PUBCHEM correlations
References
- The Pharmacological Basis of Therapeutics, 9th ed.
Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- Drug Information & Medication Formulary, Veterans Affairs,
Central California Health Care System, 1st ed., Ravnan et al
eds, 1998
- Kaiser Permanente Northern California Regional Drug
Formulary, 1998
- Deprecated Reference
- Qato DM, Ozenberger K, Olfson M
Prevalence of Prescription Medications With Depression as a
Potential Adverse Effect Among Adults in the United States.
JAMA. 2018;319(22):2289-2298
PMID: 29896627
https://jamanetwork.com/journals/jama/fullarticle/2684607
- Hwang YJ, Chang AR, Brotman DJ, Inker LA, Grams ME, Shin JI.
Baclofen and the risk of fall and fracture in older adults:
A real-world cohort study.
J Am Geriatr Soc. 2023 Nov 7.
PMID: 37933734
https://agsjournals.onlinelibrary.wiley.com/doi/abs/10.1111/jgs.18665
Component-of
cyclobenzaprine/magnesium oxide
cyclobenzaprine/methylsulfonylmethane