Cyclobenzaprine

Not to be confused with cyclosporine.

Cyclobenzaprine
Clinical data
Trade namesFlexeril, Amrix, others
AHFS/Drugs.comMonograph
MedlinePlusa682514
License data
Routes of
administration		By mouth
ATC code
Legal status
Legal status
  • US: ℞-only
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability33–55%[1][2]
Protein binding93%
Metabolismmajor: CYP3A4, CYP1A2; minor: CYP2D6, N-demethylation[3]
MetabolitesNorcyclobenzaprine
Elimination half-life32 hours (extended-release, range 8–37 hours),[3] 18 hours (immediate release, range 8–37 hours)[4]
ExcretionKidney
Identifiers
  • 3-(5H-dibenzo[a,d]cyclohepten-5-ylidene)-N,N-dimethyl-propan-1-amine
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.005.588 Edit this at Wikidata
Chemical and physical data
FormulaC20H21N
Molar mass275.395 g·mol−1
3D model (JSmol)
  • c3cc\2c(\C=C/c1c(cccc1)C/2=C/CCN(C)C)cc3
  • InChI=1S/C20H21N/c1-21(2)15-7-12-20-18-10-5-3-8-16(18)13-14-17-9-4-6-11-19(17)20/h3-6,8-14H,7,15H2,1-2H3 checkY
  • Key:JURKNVYFZMSNLP-UHFFFAOYSA-N checkY
  (verify)

Cyclobenzaprine, sold under several brand names including, historically, Flexeril, is a muscle relaxer used for muscle spasms from musculoskeletal conditions of sudden onset.[5] It is not useful in cerebral palsy.[5] It is taken by mouth.[5]

Common side effects include headache, feeling tired, dizziness, and dry mouth.[5] Serious side effects may include an irregular heartbeat.[5] There is no evidence of harm in pregnancy, but it has not been well studied in this population.[5] It should not be used together with MAOIs.[5] How it works is unclear.[5] In any case, it is known to inhibit serotonin and norepinephrine reuptake and to block serotonin, adrenergic, histamine, and muscarinic acetylcholine receptors.[6][7] Chemically, it is very similar to tricyclic antidepressants like amitriptyline.[6]

Cyclobenzaprine was approved for medical use in the United States in 1977.[5] It is available by prescription as a generic medication.[5] In 2022, it was the 45th most commonly prescribed medication in the United States, with more than 13 million prescriptions.[8][9] It was not available in the United Kingdom as of 2012.[10]

  1. ^ Micromedex® 2010 – DRUGDEX Evaluations (Cyclobenzaprine Hydrochloride)
  2. ^ "Cyclobenzaprine Hydrochloride Tablets USP Revised: April 2005 Rx only". nih.gov. Retrieved 1 October 2016.
  3. ^ a b Teva Pharmaceuticals USA, Inc (May 2016). "AMR40470 (Amrix) Prescribing Information" (PDF).
  4. ^ U.S. Food and Drug Administration. "NDA 17-821/S-045 Flexeril (Cyclobenzaprine HCl) Tablets" (PDF).
  5. ^ a b c d e f g h i j "Cyclobenzaprine Monograph for Professionals". Drugs.com. AHFS. Retrieved 22 December 2018.
  6. ^ a b Cite error: The named reference MestresSeifertOprea2011 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference DaughertyGershellLederman2012 was invoked but never defined (see the help page).
  8. ^ "The Top 300 of 2022". ClinCalc. Archived from the original on 30 August 2024. Retrieved 30 August 2024.
  9. ^ "Cyclobenzaprine Drug Usage Statistics, United States, 2013 - 2022". ClinCalc. Retrieved 30 August 2024.
  10. ^ "Fibromyalgia, psychiatric comorbidity, and the somatosensory cortex". British Journal of Medical Practitioners. 5 (2): a522. 2012.