Does Flexeril (Cyclobenzaprine) Affect Blood Pressure?
Yes, cyclobenzaprine can affect blood pressure, causing both hypertension and hypotension, though these effects are generally uncommon and less severe than those seen with tricyclic antidepressants.
Blood Pressure Effects in Overdose
The FDA label clearly documents blood pressure changes as manifestations of cyclobenzaprine toxicity 1:
- Hypertension is listed among the less frequent manifestations of overdose 1
- Severe hypotension is noted as a rare but potentially critical manifestation 1
- Both effects occurred in a retrospective review of 402 pure cyclobenzaprine ingestions, where both hypertension and hypotension were observed 2
Blood Pressure Effects at Therapeutic Doses
At standard therapeutic doses, blood pressure effects are minimal but documented:
- Cyclobenzaprine is structurally related to tricyclic antidepressants like amitriptyline, which are known to affect cardiovascular parameters 1
- The drug has peripheral and central anticholinergic activity and can cause norepinephrine potentiation, which theoretically could influence blood pressure 3
- However, in clinical trials using doses of 2.5-10 mg three times daily, cardiovascular adverse events beyond sinus tachycardia were infrequent and not life-threatening 4, 2
Clinical Significance and Monitoring
For most patients taking therapeutic doses, clinically significant blood pressure changes are unlikely:
- The Mayo Clinic guidelines identify cyclobenzaprine as a high-risk anticholinergic medication in older adults primarily due to CNS impairment, sedation, and fall risk—not specifically for blood pressure effects 5
- When deprescribing antihypertensives in older adults, the guidelines focus on orthostasis and fall risk rather than drug interactions with muscle relaxants 5
Important Caveats
Older adults require special consideration 5:
- Cyclobenzaprine's anticholinergic burden can cause sedation and impaired mobility, indirectly increasing fall risk which may be compounded by orthostatic hypotension from other medications 5
- The drug should be avoided or used cautiously in elderly patients due to broad muscarinic receptor blockade effects 5
Drug interactions matter 5:
- While the JNC 7 guidelines on hypertension do not specifically list cyclobenzaprine as a blood pressure-elevating agent, they emphasize reviewing all medications including muscle relaxants when evaluating resistant hypertension 5
Serotonin syndrome can cause autonomic instability 1:
- When cyclobenzaprine is combined with serotonergic drugs (SSRIs, SNRIs, tramadol), serotonin syndrome may develop, which includes labile blood pressure and tachycardia as autonomic manifestations 1
Practical Recommendation
Routine blood pressure monitoring is not necessary for patients on therapeutic doses of cyclobenzaprine unless they have pre-existing cardiovascular disease, are elderly, or are taking multiple medications that affect blood pressure 5, 1. If blood pressure changes occur, they are more likely related to the drug's anticholinergic effects, sedation causing orthostasis, or drug interactions rather than direct hypertensive or hypotensive effects 5, 3.