From the Guidelines
Muscle relaxers, including baclofen (10-25 mg three times daily), cyclobenzaprine (5-10 mg three times daily), carisoprodol (250-350 mg three to four times daily), methocarbamol (500-1000 mg four times daily), tizanidine (2-8 mg up to three times daily), metaxalone (800 mg three to four times daily), chlorzoxazone (250-500 mg three to four times daily), and orphenadrine (100 mg twice daily), are available for treating muscle spasms, spasticity, and pain, with tizanidine being efficacious for acute low back pain in 8 trials 1. The following muscle relaxers are commonly used:
- Centrally-acting muscle relaxants:
- Baclofen (10-25 mg three times daily)
- Cyclobenzaprine (5-10 mg three times daily)
- Carisoprodol (250-350 mg three to four times daily)
- Methocarbamol (500-1000 mg four times daily)
- Tizanidine (2-8 mg up to three times daily)
- Metaxalone (800 mg three to four times daily)
- Chlorzoxazone (250-500 mg three to four times daily)
- Orphenadrine (100 mg twice daily)
- For spasticity specifically:
- Dantrolene (25-100 mg up to four times daily)
- Diazepam (2-10 mg three to four times daily) These medications work by affecting the central nervous system to reduce muscle tone and involuntary contractions, with skeletal muscle relaxants being moderately superior to placebo for short-term pain relief in acute low back pain 1. Side effects commonly include drowsiness, dizziness, and dry mouth, so patients should avoid driving or operating machinery until they know how the medication affects them, and skeletal muscle relaxants were associated with a higher total number of adverse events and central nervous system adverse events compared with placebo 1. Most muscle relaxants are intended for short-term use (2-3 weeks) due to potential for dependence and diminishing effectiveness over time, and patients with liver or kidney disease may require dose adjustments, with these medications being used cautiously in elderly patients due to increased risk of falls and confusion.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION Dosage should be individualized for maximum beneficial effect. While the usual daily dosages given below will meet the needs of most patients, there will be some who may require higher doses. In such cases dosage should be increased cautiously to avoid adverse effects. ADULTS: USUAL DAILY DOSE: ... Adjunctively for Relief of Skeletal Muscle Spasm. 2 mg to 10 mg, 3 or 4 times daily Based on the findings, cyclobenzaprine hydrochloride tablets should be used with caution in subjects with mild hepatic impairment starting with the 5 mg dose and titrating slowly upward.
The available muscle relaxers and their doses are:
- Diazepam: 2 mg to 10 mg, 3 or 4 times daily 2
- Cyclobenzaprine: 5 mg, titrating slowly upward, 3 times a day 3
From the Research
Available Muscle Relaxers
- Baclofen: used to treat spasticity, with a fair evidence of efficacy compared to placebo 4
- Tizanidine: used to treat spasticity and musculoskeletal conditions, with a fair evidence of efficacy compared to placebo 4
- Dantrolene: used to treat spasticity, with a fair evidence of efficacy compared to placebo, but associated with rare serious hepatotoxicity 4
- Cyclobenzaprine: used to treat musculoskeletal conditions, with a fair evidence of efficacy compared to placebo 4
- Carisoprodol: used to treat musculoskeletal conditions, with a fair evidence of efficacy compared to placebo 4
- Orphenadrine: used to treat musculoskeletal conditions, with a fair evidence of efficacy compared to placebo 4
- Metaxalone: used to treat musculoskeletal conditions, with very limited or inconsistent data regarding its effectiveness compared to placebo 4
- Methocarbamol: used to treat musculoskeletal conditions, with very limited or inconsistent data regarding its effectiveness compared to placebo 4
- Chlorzoxazone: used to treat musculoskeletal conditions, with very limited or inconsistent data regarding its effectiveness compared to placebo, and associated with rare serious hepatotoxicity 4
- Diazepam: a benzodiazepine used for muscle relaxation, with a mean improvement in RMDQ of 11.1 (95% CI 9-13.2) 5
Dosage Information
The dosage information for these muscle relaxers is not provided in the given studies. However, the studies provide information on the efficacy and safety of these medications, which can be used to inform dosage decisions.
Efficacy and Safety
The efficacy and safety of these muscle relaxers vary, with some having a fair evidence of efficacy compared to placebo, while others have very limited or inconsistent data. Additionally, some muscle relaxers are associated with rare serious hepatotoxicity or other adverse events 4, 5, 6.
Combination Therapy
The use of combination therapy, such as concurrent opioid, benzodiazepine, and muscle relaxant use, is associated with an increased probability of emergency department visits 7.