From the Guidelines
Methocarbamol use is associated with significant side effects, including drowsiness, dizziness, and cardiovascular effects such as bradycardia and hypotension, as reported in a recent study published in the Mayo Clinic Proceedings in 2021 1. When considering the use of methocarbamol, it is essential to weigh the potential benefits against the risks of these adverse effects. The precise mechanism of action of methocarbamol is unclear, but it is known to act as a centrally acting skeletal muscle relaxant and sedative, which does not directly act on skeletal muscle. Some of the key side effects to be aware of include:
- Drowsiness
- Dizziness
- Cardiovascular effects, including bradycardia and hypotension These side effects can be significant and may impact the patient's quality of life and ability to perform daily activities. It is crucial to monitor patients taking methocarbamol for these side effects and adjust the dosage or discontinue use if necessary. Additionally, methocarbamol elimination is significantly impaired in certain patients, which may increase the risk of adverse effects 1. Overall, the use of methocarbamol should be carefully considered, and patients should be closely monitored for potential side effects, particularly in the context of its potential benefits in reducing postoperative opiate consumption and improving physical therapy progress, as reported in recent studies 1.
From the FDA Drug Label
ADVERSE REACTIONS Adverse reactions reported coincident with the administration of methocarbamol include: Body as a whole:Anaphylactic reaction, angioneurotic edema, fever, headache Cardiovascular system:Bradycardia, flushing, hypotension, syncope, thrombophlebitis Digestive system:Dyspepsia, jaundice (including cholestatic jaundice), nausea and vomiting Hemic and lymphatic system:Leukopenia Immune system:Hypersensitivity reactions Nervous system:Amnesia, confusion, diplopia, dizziness or lightheadedness, drowsiness, insomnia, mild muscular incoordination, nystagmus, sedation, seizures (including grand mal), vertigo Skin and special senses:Blurred vision, conjunctivitis, nasal congestion, metallic taste, pruritus, rash, urticaria
Methocarbamol side effects include:
- Anaphylactic reaction
- Angioneurotic edema
- Bradycardia
- Confusion
- Dizziness or lightheadedness
- Drowsiness
- Dyspepsia
- Fever
- Headache
- Hypersensitivity reactions
- Hypotension
- Insomnia
- Jaundice (including cholestatic jaundice)
- Leukopenia
- Mild muscular incoordination
- Nausea and vomiting
- Nystagmus
- Sedation
- Seizures (including grand mal)
- Syncope
- Thrombophlebitis
- Vertigo 2
From the Research
Methocarbamol Side Effects
- Methocarbamol is a skeletal muscle relaxant used to treat musculoskeletal conditions, but there is limited data on its effectiveness and safety compared to other muscle relaxants 3, 4.
- A systematic review found that methocarbamol had very limited or inconsistent data regarding its effectiveness compared to placebo in patients with musculoskeletal conditions 3.
- Another study found that methocarbamol did not improve outcomes more than placebo in patients with acute low back pain, and adverse medication effects were more common with cyclobenzaprine than with placebo 4.
- A meta-analysis found that non-benzodiazepine antispasmodics, which include methocarbamol, might increase the risk of an adverse event and have little to no effect on acceptability compared to control for acute low back pain 5.
- Common side effects of muscle relaxants, including methocarbamol, may include drowsiness, dizziness, and nausea, but the specific side effects of methocarbamol are not well-documented in the available studies 3, 4, 5.
Comparison to Other Muscle Relaxants
- Methocarbamol has been compared to other muscle relaxants, such as cyclobenzaprine, carisoprodol, and tizanidine, but the results are inconsistent and limited by the quality of the studies 3, 4.
- One study found that cyclobenzaprine was associated with more adverse effects than methocarbamol, but the difference was not statistically significant 4.
- Another study found that non-benzodiazepine antispasmodics, including methocarbamol, might have a higher risk of adverse events compared to other muscle relaxants, but the evidence was limited by the quality of the studies 5.
Cross-Reactivity and Allergic Reactions
- There is limited data on the cross-reactivity of methocarbamol with other medications, but one study found that patients with anaphylaxis to muscle-relaxant drugs may have cross-reactivity between different drugs 6.
- Another study found that patients with anticonvulsant hypersensitivity syndrome may have cross-reactivity with tricyclic antidepressant agents, but the relevance to methocarbamol is unclear 7.