From the Guidelines
Tizanidine is more likely to cause blurred vision compared to flexeril (cyclobenzaprine) due to its mechanism of action as an alpha-2 adrenergic agonist, which can affect blood vessels in the eyes and visual processing pathways. Both medications can cause blurred vision, but the risk is higher with tizanidine, particularly at higher doses 1. The exact incidence of blurred vision with tizanidine is not specified in the provided evidence, but it is mentioned that tizanidine can cause dose-dependent sedation, drowsiness, dizziness, ataxia, or lethargy 1. In contrast, the evidence for flexeril (cyclobenzaprine) does not provide a clear comparison of the risk of blurred vision 2.
Key Points to Consider
- Tizanidine's mechanism of action as an alpha-2 adrenergic agonist may contribute to its higher risk of causing blurred vision 1.
- The risk of blurred vision with tizanidine may increase with higher doses, typically prescribed at 2-8 mg three times daily 1.
- Flexeril (cyclobenzaprine) can also cause visual disturbances, but the frequency is less clear from the provided evidence 2.
- If significant blurred vision occurs with either medication, patients should contact their healthcare provider for potential dosage adjustment or medication change 1, 2.
Clinical Implications
- When prescribing tizanidine or flexeril (cyclobenzaprine), healthcare providers should be aware of the potential risk of blurred vision and monitor patients accordingly 1.
- Patients experiencing blurred vision should be advised to contact their healthcare provider for further evaluation and potential adjustment of their treatment plan 1, 2.
From the FDA Drug Label
Adverse Events Reported in Controlled Studies ... Amblyopia (blurred vision) <1 3 Adverse reactions which were reported in 1% to 3% of the patients were: ... blurred vision
Comparison of Blurred Vision Incidence
- Tizanidine: 3% [@\1@]
- Cyclobenzaprine (Flexeril): 1% to 3% [@\2@] Based on the available data, tizanidine may cause more blurred vision than cyclobenzaprine (Flexeril), but the exact comparison is limited by the available incidence ranges for cyclobenzaprine.
From the Research
Comparison of Tizanidine and Flexeril
- Tizanidine and Flexeril (cyclobenzaprine) are both skeletal muscle relaxants used to treat spasticity and musculoskeletal conditions.
- According to a systematic review 3, tizanidine is associated with more dry mouth, while baclofen is associated with more weakness, but there is no direct comparison with Flexeril regarding blurred vision.
- A study on the relative efficacy of seven skeletal muscle relaxants 4 found that all patients, including those taking tizanidine and cyclobenzaprine (Flexeril), experienced similar improvements in disability questionnaire scores, but it did not specifically address the incidence of blurred vision.
- Another review 5 mentions that the choice of a skeletal muscle relaxant should be based on its adverse-effect profile, tolerability, and cost, but does not provide a direct comparison of tizanidine and Flexeril regarding blurred vision.
Adverse Effects
- A meta-analysis of controlled, double-blind, comparative studies with baclofen and diazepam 6 found that tizanidine had greater tolerability, but it did not specifically address the incidence of blurred vision.
- The studies provided do not offer a direct comparison of the incidence of blurred vision between tizanidine and Flexeril, making it difficult to determine which medication causes more blurred vision 7, 3, 5, 6, 4.