Can cyclobenzaprine (a muscle relaxant) cause dizziness?

Cyclobenzaprine Side Effects and Dizziness Risk

Yes, cyclobenzaprine commonly causes dizziness, which is reported in 11% of patients taking the 10 mg dose and represents one of the three most frequent adverse reactions alongside drowsiness and dry mouth. 1

Primary Side Effect Profile

The FDA-approved labeling identifies the most common adverse reactions with cyclobenzaprine 1:

Most Frequent (>10% incidence)

• Drowsiness: 29-39% (dose-dependent: 29% at 5 mg, 38% at 10 mg) 1
• Dry mouth: 21-32% (dose-dependent: 21% at 5 mg, 32% at 10 mg) 1
• Dizziness: 11% at 10 mg dose 1

Common (3-10% incidence)

• Fatigue: 6% 1
• Headache: 5% 1

Less Common (1-3% incidence)

• Abdominal pain, constipation, nausea 1
• Mental acuity decreased, nervousness 1
• Irritability 1

Mechanism of Dizziness

The dizziness associated with cyclobenzaprine occurs through multiple mechanisms 2:

• Central nervous system depression: As a centrally acting 5-HT2 receptor antagonist structurally related to amitriptyline, cyclobenzaprine affects higher CNS functions 2
• Anticholinergic effects: Both peripheral and central anticholinergic activity contribute to neurologic adverse events including dizziness 2
• Off-target histamine H1 receptor antagonism: Recent evidence demonstrates cyclobenzaprine exhibits high-affinity noncompetitive antagonism at histamine H1 receptors, which likely contributes to sedation and related neurologic effects 3

Clinical Context and Risk Stratification

High-Risk Populations

Elderly patients require special caution 1:

• Plasma concentrations are approximately 1.7-fold higher in elderly patients compared to younger adults 1
• Elderly males show the highest increase (2.4-fold) 1
• Start with 5 mg dose and titrate slowly upward in elderly patients 1

Hepatic impairment significantly increases risk 1:

• Both AUC and Cmax approximately double in hepatic impairment 1
• Use with caution in mild hepatic impairment, starting with 5 mg 1
• Not recommended in moderate to severe hepatic impairment 1

Dose-Related Effects

Lower doses reduce but do not eliminate dizziness risk 1, 4:

• The 5 mg TID regimen maintains efficacy while reducing overall adverse event rates compared to 10 mg TID 4
• Extended-release formulations (15-30 mg once daily) show similar efficacy with potentially lower rates of some CNS effects 5

Additional Serious Neurologic Adverse Events

Beyond dizziness, cyclobenzaprine can cause 1:

• Confusion and hallucinations (anticholinergic effects) 2
• Seizures (rare but documented) 1
• Psychosis: Case reports document reversible mania, particularly in patients with underlying psychiatric conditions 6
• Serotonin syndrome: Risk increases with concomitant MAO inhibitor use 2

Perioperative Considerations

The Society for Perioperative Assessment and Quality Improvement (SPAQI) recommends holding cyclobenzaprine on the day of operation 2:

• Potential interactions with sedatives and anesthetic agents 2
• Anticholinergic effects can complicate perioperative management 2
• With long-term use, taper over 2-3 weeks to prevent withdrawal symptoms (malaise, nausea, headache lasting 2-4 days) 2

Important Clinical Pitfalls

Duration of therapy should be limited 7:

• All muscle relaxant trials were 2 weeks or less in duration 7
• Insufficient evidence supports chronic use for musculoskeletal pain 7
• The American College of Physicians guidelines emphasize short-term use only 7

Efficacy is independent of sedation 4:

• Subanalysis demonstrates meaningful treatment effect in patients who did not report somnolence 4
• This suggests the therapeutic benefit does not require CNS depression, though dizziness and drowsiness remain common adverse effects 4

Drug interactions warrant attention 2:

• Potentiates effects of other CNS depressants 2
• Contraindicated with MAO inhibitors due to serotonin syndrome risk 2
• Norepinephrine potentiation can affect cardiovascular stability 2