II. Indications
- Acute back or Neck Pain interfering with sleep despite Analgesics
- Limit to short-course (<14 days)
-
Fibromyalgia
- Mixed evidence in studies (NNT 8 for 30% pain reduction)
III. Mechanism
- Antispasmodic Skeletal Muscle Relaxant
- Centrally acting cyclical Antidepressant with Sedative qualities
- Tricyclic amine salt similar to Amitriptyline
- Reduces Muscle hyperactivity and somatic motor activity
- Mechanism may act at 5-H2 receptors, inhibiting descending serotonergic pathways in the cord
IV. Medications
- Cyclobenzaprine Immediate Release Oral Tablets (Flexeril): 5 mg, 7.5 mg, 10 mg
- Cyclobenzaprine Extended Release Oral Capsules (Amrix XR): 15 mg, 30 mg
- Cyclobenzaprine sublingual tablets (Tonmya): 2.8 mg
- Released in 2025 for Fibromyalgia with no better efficacy and at a cost of $31/tablet
V. Dosing: Immediate Release
- Start: 5 mg orally at bedtime (5 mg is as effective as 10 mg and with less sedation)
- Maximum: 10 mg orally three times daily (primarily at bedtime for pain interfering with sleep)
VI. Dosing: Extended Release
- Start 15 mg orally daily
- Maximum: 30 mg orally daily
VII. Dosing: Sublingual Tablet
- Start 2.8 mg orally daily at bedtime
- Maximum: 5.6 mg (2 tablets)
VIII. Contraindications
- Older patients
- Seizure Disorder (if concurrently on Tramadol)
- Glaucoma
- Cardiac Arrhythmia
- Congestive Heart Failure
- Recent Myocardial Infarction
IX. Efficacy
- See Antispasmodic Skeletal Muscle Relaxant
- Poor evidence for benefit
- More effective than Placebo for first 4 days of Low Back Pain
- However, no significant functional or pain benefit at 1 week for Acute Low Back Pain (non-Traumatic, non-radicular)
X. Adverse Effects
- See Antispasmodic Skeletal Muscle Relaxant for precautions
- Common: Anticholinergic
- Rare
- Arrhythmia
- Reflex Tachycardia
- Cyclobenzaprine may block alpha-1 Adrenergic Receptors resulting in vasodilation
- QRS Widening
- Fast-acting Sodium channel blockade (as with Amitriptyline)
- Reflex Tachycardia
- Seizure
- GABA Receptor inhibition may lower Seizure threshold
- Myocardial Infarction
- Serotonin Syndrome
- Risk when Cyclobenzaprine is combined with other serotonergic drugs
- Arrhythmia
XI. Resources
- Cyclobenzaprine IR (DailyMed)
- Cyclobenzaprine XR (DailyMed)
XII. References
- (2/2026) Presc Insights, TRC healthcare
- Borenstein (2003) Clin Ther 25(4): 1056-73 [PubMed]
- Browning (2001) Arch Intern Med 161: 1613-20 [PubMed]
- Tofferi (2004) Arthritis Rheum 51:9-13 [PubMed]
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Related Studies
| cyclobenzaprine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| CYCLOBENZAPRINE 10 MG TABLET | Generic | $0.02 each |
| CYCLOBENZAPRINE 5 MG TABLET | Generic | $0.02 each |
| CYCLOBENZAPRINE 7.5 MG TABLET | Generic | $0.66 each |