Robaxin and Blood Pressure Effects
Robaxin (methocarbamol) can cause hypotension, bradycardia, syncope, and flushing as documented adverse cardiovascular effects, but it is not listed among medications that raise blood pressure in any major hypertension guideline. 1
Direct Cardiovascular Effects
The FDA-approved drug label for methocarbamol explicitly lists several blood pressure-related adverse reactions 1:
- Hypotension (low blood pressure) is a recognized adverse effect
- Bradycardia (slow heart rate) can occur
- Syncope (fainting) has been reported
- Flushing may develop
- Thrombophlebitis (vein inflammation) is documented
These effects indicate that Robaxin is more likely to lower blood pressure rather than raise it.
Evidence from Hypertension Guidelines
Multiple comprehensive hypertension guidelines that systematically catalog medications affecting blood pressure do not include methocarbamol or muscle relaxants as blood pressure elevating agents 2:
- The JNC 7 guidelines list NSAIDs, alcohol, sympathomimetics, steroids, oral contraceptives, antidepressants (SNRIs, TCAs), and numerous other agents but make no mention of muscle relaxants 2
- The 2020 International Society of Hypertension guidelines provide extensive tables of drugs that exacerbate hypertension, including NSAIDs, oral contraceptives, antidepressants, acetaminophen, steroids, and herbal substances, but do not list methocarbamol 2
- The 2017 ACC/AHA guidelines detail frequently used medications that elevate blood pressure, including amphetamines, decongestants, NSAIDs, alcohol, caffeine, and immunosuppressants, without mentioning muscle relaxants 2
Clinical Implications
Monitor for hypotension rather than hypertension when prescribing Robaxin, particularly in patients 1:
- Taking other medications that lower blood pressure
- With pre-existing cardiovascular disease
- Who are elderly or volume depleted
- Receiving concurrent CNS depressants (especially alcohol, which can cause dangerous interactions) 3
Common Pitfall to Avoid
Do not confuse methocarbamol with medications that actually raise blood pressure. The evidence clearly shows Robaxin causes hypotensive effects, not hypertensive effects 1. If a patient on Robaxin develops elevated blood pressure, look for other causative medications such as NSAIDs (which can raise BP by 3-5 mmHg), decongestants, or other agents documented in hypertension guidelines 2, 4.