Methocarbamol Can Cause Hypotension
Yes, methocarbamol can cause hypotension and bradycardia as documented adverse cardiovascular effects, and should be held on the day of surgical procedures due to these risks. 1, 2
Evidence from FDA Drug Labeling
The FDA-approved drug label for methocarbamol explicitly lists hypotension, bradycardia, syncope, and flushing as adverse cardiovascular reactions reported with its administration. 2 In overdose situations, hypotension is specifically mentioned as one of the key symptoms alongside nausea, drowsiness, blurred vision, seizures, and coma. 2
Clinical Context and Mechanism
Methocarbamol is a centrally acting skeletal muscle relaxant that does not act directly on skeletal muscle, though its precise mechanism remains unclear. 1 The cardiovascular effects include:
- Bradycardia and hypotension as documented adverse effects 1, 2
- Drowsiness and dizziness which can compound cardiovascular instability 1, 2
- Syncope in some patients 2
Perioperative Considerations
The Society for Perioperative Assessment and Quality Improvement (SPAQI) specifically recommends holding methocarbamol on the day of surgical procedures due to its cardiovascular effects and potential interactions with anesthetic agents. 1 This recommendation acknowledges the risk of bradycardia and hypotension, particularly problematic in the perioperative setting where hemodynamic stability is critical.
Special Populations at Risk
Patients with cardiovascular disease require particular caution. The American Heart Association notes that methocarbamol is among the less-sedating muscle relaxants that can be used for musculoskeletal pain in patients with end-stage cardiovascular disease, but clinicians must be aware that anxiolytics and sedating medications (including muscle relaxants) can significantly increase the risk of falls when combined with antihypertensive agents and diuretics. 1
Drug Interactions Amplifying Hypotensive Risk
The hypotensive effect can be amplified by concurrent use with:
- CNS depressants including alcohol 2, 3
- Antihypertensive medications 1
- Diuretics 1
- Other sedating agents 1
A fatal case report documented the dangerous interaction between methocarbamol and ethanol, demonstrating combined CNS depression from their interactive sedative-hypnotic properties. 3
Renal and Hepatic Impairment
Methocarbamol elimination is significantly impaired in patients with liver and kidney disease, which can lead to drug accumulation and increased risk of adverse effects including hypotension. 1 Dose adjustments are necessary in these populations.
Clinical Monitoring
When methocarbamol is prescribed, monitor for:
- Blood pressure changes, particularly orthostatic hypotension 2
- Heart rate for bradycardia 1, 2
- Signs of CNS depression (drowsiness, dizziness, sedation) 1, 2
- Syncope or near-syncope episodes 2
Common Pitfalls to Avoid
- Do not combine with multiple CNS depressants without careful monitoring, as this increases hypotension risk 2, 3
- Do not use in patients with myasthenia gravis as it interferes with pyridostigmine bromide effects 1
- Avoid abrupt discontinuation in long-term users, though cardiovascular effects are the primary concern rather than withdrawal 1
- Exercise caution in elderly patients who are more susceptible to orthostatic hypotension and falls, especially when taking concurrent antihypertensives 1