Description

Simple

A muscle relaxant used to treat muscle spasms.

Clinical

A skeletal muscle relaxant that works on the brainstem to treat muscle spasms of local origin.

Overview

Cyclobenzaprine, a centrally-acting muscle relaxant, was first synthesized in 1961[11] and has been available for human use since 1977.[10] It was initially studied for use as antidepressant given its structural similarity to tricyclic antidepressants - it differs from [Amitriptyline] by only a single double bond.[11,10] Since its approval, it has remained relatively popular as an adjunctive, short-term treatment for acute skeletal muscle spasms secondary to musculoskeletal injury.

Pharmacology

Indication

Cyclobenzaprine is indicated as a short-term (2-3 weeks) adjunct therapy, along with rest and physical therapy, for relief of muscle spasm associated with acute, painful musculoskeletal conditions. It has not been found effective in the treatment of spasticity originating from cerebral or spinal cor... Read more

Pharmacodynamic

Cyclobenzaprine is a skeletal muscle relaxant that works on areas of the brainstem to reduce skeletal muscle spasm, though its exact pharmacodynamic behaviour is currently unclear.[15, Read more

Mechanism of action

The exact mechanism of action of cyclobenzaprine has not been fully elucidated in humans, and much of the information available regarding its mechanism has been ascertained from early animal studies. There is some evidence that cyclobenzaprine exerts its effects at the supraspinal level, specificall... Read more

Absorption

The oral bioavailability of cyclobenzaprine has been estimated to be between 0.33 and 0.55.[ Read more

Protein binding

Cyclobenzaprine is approximately 93% protein bound in plasma.[ Read more

Volume of distribution

The volume of distribution of cyclobenzaprine is approximately 146 L.[ Read more

Clearance

The approximate plasma clearance of cyclobenzaprine is 0.7 L/min.[ Read more

Half life

The effective half-life of cyclobenzaprine in young healthy subjects is approximately 18 hours.[ Read more

Route of elimination

After administration of a radio-labeled dose of cyclobenzaprine, 38-51% of radioactivity was excreted in the urine while 14-15% was excreted in the feces.[16] Cyclobenzaprine is highly metabolized, with... Read more

Toxicity

The oral LD50 of cyclobenzaprine in mice and rats is 338 mg/kg and 425 mg/kg, respectively. Signs of overdose may develop rapidly after ingestion and commonly include significant drowsiness and tachycardia, with less common manifestations including tremor, agitation, ataxia, GI upset, and... Read more

Adverse Effects

Effect Regions Age Groups Incidences Evidence Type
Drowsiness US
  • Kind: experimental
    • Percent: 38
  • Kind: placebo
    • Percent: 10
  • Clinical Trial
    Dry Mouth US
  • Kind: experimental
    • Percent: 32
  • Kind: placebo
    • Percent: 7
  • Clinical Trial
    Drowsiness US
  • Kind: experimental
    • Percent: 29
  • Kind: placebo
    • Percent: 10
  • Clinical Trial
    Dry Mouth US
  • Kind: experimental
    • Percent: 21
  • Kind: placebo
    • Percent: 7
  • Clinical Trial
    Headache US
  • Kind: experimental
    • Percent: 5
  • Kind: placebo
    • Percent: 8
  • Clinical Trial
    Headache US
  • Kind: experimental
    • Percent: 5
  • Kind: placebo
    • Percent: 8
  • Clinical Trial
    Fatigue US
  • Kind: experimental
    • Percent: 6
  • Kind: placebo
    • Percent: 3
  • Clinical Trial
    Fatigue US
  • Kind: experimental
    • Percent: 6
  • Kind: placebo
    • Percent: 3
  • Clinical Trial
    Confusion US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Blurred vision US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Unpleasant taste US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Dyspepsia US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Asthenia US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Pharyngitis US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Upper Respiratory Infection US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Nervousness US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Mental acuity decreased US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Irritability US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Nausea US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Dizziness US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Diarrhea US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Constipation US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Acid Regurgitation US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Abdominal Pain US
  • Kind: experimental
    • Percent: 1-3
  • Clinical Trial
    Galactorrhea US
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    Breast enlargement US
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    Gynecomastia US
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    Testicular swelling US
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    Impotence US
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    Dilation of the urinary tract US
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    Impaired urination US
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    Alopecia US
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    Photosensitivity US
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    Dyspnea US
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    Extra-pyramidal symptoms US
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    EEG changes US
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    Bell's Palsy US
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    Peripheral neuropathy US
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    Paranoia US
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    Aggressive Behavior US
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    Delusions US
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    Gait disturbances US
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    Libido increased US
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    Libido decreased US
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    Muscle Soreness US
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    Weight Loss US
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    Weight Gain US
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    Decreased blood glucose US
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    Increased blood glucose US
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    Thrombocytopenia US
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    Contraindications

    • Route:
      • Oral
    • Hypersensitivity:
      • true
    • Regions: US
    • Route:
      • Oral
    • Time Period: During MAO-I therapy or within 14 days after their discontinuation
    • Regions: US
    • With Categories Coadmin:
        • Name: Monoamine Oxidase Inhibitors
        • Drugbank Id: DBCAT001004
        • Mesh Id: D008996
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Arrhythmias
        • Drugbank Id: DBCOND0031410
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Acute recovery phase of myocardial infarction
        • Drugbank Id: DBCOND0107607
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Conduction Disturbances
        • Drugbank Id: DBCOND0071211
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Heart Block
        • Drugbank Id: DBCOND0032425
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Hyperthyroidism
        • Drugbank Id: DBCOND0009048
    • Route:
      • Oral
    • Regions: US
    • Patient Conditions:
        • Name: Congestive Heart Failure
        • Drugbank Id: DBCOND0029751

    Food Interactions

    Avoid alcohol. Cyclobenzaprine is a central nervous system depressant which may be potentiated by the co-administration of alcohol.