From the Guidelines
Cyclobenzaprine (Flexeril) is generally considered the least sedating muscle relaxer among commonly prescribed options. It works by blocking certain nerve impulses that are sent to the brain and is typically prescribed at 5-10 mg doses taken up to three times daily for acute muscle spasms. While all muscle relaxers can cause some degree of drowsiness, cyclobenzaprine tends to produce less sedation than alternatives like carisoprodol (Soma) or metaxalone (Skelaxin) 1. Tizanidine (Zanaflex) and baclofen are other options that some patients tolerate well regarding sedation, though individual responses vary significantly. The reduced sedative effect of cyclobenzaprine is related to its more selective action on certain receptors in the central nervous system compared to other muscle relaxers that have broader effects.
Some key points to consider when prescribing cyclobenzaprine include:
- Starting with the lowest effective dose and taking it at bedtime can help minimize daytime drowsiness while still providing muscle relaxation benefits.
- It's advisable to take the first dose when you don't need to drive or operate machinery until you understand how it affects you personally.
- Cyclobenzaprine has been found to be moderately superior to placebo for short-term pain relief in acute low back pain, with a higher-quality Cochrane review showing RRs for not achieving pain relief of 0.80 (CI, 0.71 to 0.89) at 2 to 4 days and 0.67 (CI, 0.13 to 3.44) at 5 to 7 days 1.
- However, there is insufficient evidence to conclude that any specific muscle relaxant is superior to others for benefits or harms, and individual responses may vary significantly 1.
Overall, cyclobenzaprine is a reasonable option for patients who require a muscle relaxer and are concerned about sedation, but it's essential to weigh the potential benefits and risks and consider individual patient factors when making a prescribing decision.
From the FDA Drug Label
Although the frequency and severity of adverse reactions observed in patients treated with cyclobenzaprine were comparable to those observed in patients treated with diazepam, dry mouth was observed more frequently in patients treated with cyclobenzaprine and dizziness more frequently in those treated with diazepam The incidence of drowsiness, the most frequent adverse reaction, was similar with both drugs. Analysis of the data from controlled studies shows that cyclobenzaprine produces clinical improvement whether or not sedation occurs.
The answer to which muscle relaxer is the least sedating cannot be determined from the provided information, as the comparison is only made between cyclobenzaprine and diazepam, and they have a similar incidence of drowsiness. 2
From the Research
Muscle Relaxers and Sedation
- The sedating effects of muscle relaxers can vary depending on the specific medication and individual response 3, 4.
- Tizanidine, a central alpha 2 adrenergic agonist, has been shown to cause sedation, but this effect can be minimized by dose titration 3.
- A study comparing the sedative and sympatholytic effects of tizanidine to clonidine found that tizanidine had similar effects, but of shorter duration 4.
Comparison of Muscle Relaxers
- A systematic review of skeletal muscle relaxants found that tizanidine, baclofen, and dantrolene were effective in treating spasticity, while cyclobenzaprine, carisoprodol, and orphenadrine were effective in treating musculoskeletal conditions 5.
- Another study found that tizanidine, diazepam, and cyclobenzaprine had similar efficacy in improving outcomes in patients with acute low back pain, and that adverse effects were more common with cyclobenzaprine 6.
Least Sedating Muscle Relaxer
- Based on the available evidence, tizanidine may be considered a relatively less sedating option compared to other muscle relaxers, particularly when taken at night and with dose titration 3, 4.
- However, it is essential to note that individual responses to medication can vary, and the sedating effects of tizanidine can still occur, especially at higher doses 4, 7.