What is the effect of Tizanidine (Zanaflex) on blood pressure?

From the Guidelines

Tizanidine can lower blood pressure as a side effect, and patients taking this medication should be monitored for hypotension, especially when starting or increasing the dose 1. When taking tizanidine, patients may experience hypotension (low blood pressure), particularly due to its effects on alpha-2 adrenergic receptors, which can cause blood vessels to dilate and blood pressure to drop.

Key Considerations

• Tizanidine is a centrally acting spasmolytic agent, and its use can lead to significant sedative and hypotensive effects, especially in patients with hepatic or renal dysfunction and in elderly patients 1.
• The medication should be avoided in patients with certain conditions, and its clearance is significantly reduced when given concomitantly with ciprofloxacin and fluvoxamine, making it contraindicated in such cases.
• Patients taking tizanidine should be informed about the potential risks of low blood pressure and the importance of monitoring their blood pressure while on the medication.

Management of Hypertension

While the provided evidence on hypertension management 1 is relevant for understanding blood pressure control, the key consideration for patients taking tizanidine is the potential for hypotension.

• The American College of Physicians and American Academy of Family Physicians recommend initiating treatment in adults aged 60 years or older with systolic blood pressure persistently at or above 150 mm Hg to achieve a target systolic blood pressure of less than 150 mm Hg 1.
• However, for patients taking tizanidine, the focus should be on monitoring and managing potential hypotension rather than solely on hypertension treatment goals.

Recommendations

Patients taking tizanidine should be closely monitored for signs of hypotension, and their healthcare provider should adjust their treatment plan accordingly 1.

• This may involve regular blood pressure checks, especially when starting or increasing the dose of tizanidine.
• Patients should be informed about the potential risks of low blood pressure and the importance of seeking medical attention if they experience symptoms such as dizziness, lightheadedness, or fainting.

From the FDA Drug Label

Tizanidine is an α2-adrenergic agonist (like clonidine) and can produce hypotension In a single dose study where blood pressure was monitored closely after dosing, two-thirds of patients treated with 8 mg of tizanidine had a 20% reduction in either the diastolic or systolic BP. The reduction was seen within 1 hour after dosing, peaked 2 to 3 hours after dosing and was associated, at times, with bradycardia, orthostatic hypotension, lightheadedness/dizziness and rarely syncope The hypotensive effect is dose related and has been measured following single doses of ≥ 2 mg.

Tizanidine can cause a significant reduction in blood pressure, with two-thirds of patients experiencing a 20% reduction in either diastolic or systolic blood pressure after a single 8mg dose. The hypotensive effect is dose-related and can be associated with bradycardia, orthostatic hypotension, lightheadedness/dizziness, and syncope. Therefore, caution is advised when using tizanidine, especially in patients with pre-existing hypotension or those taking concurrent antihypertensive therapy 2.

From the Research

Tizanidine and Blood Pressure

• Tizanidine, a muscle relaxant, can lower blood pressure and is metabolized by the cytochrome P450 1A2 (CYP1A2) 3
• The use of tizanidine with strong CYP1A2 inhibitors can increase the risk of hypotensive episodes, with severe hypotension occurring more often in patients prescribed tizanidine compared to those prescribed cyclobenzaprine 3
• Concomitant administration of tizanidine and lisinopril, an angiotensin-converting enzyme inhibitor, can cause significant hypotension due to the interaction between the two medications 4, 5, 6, 7
• This interaction can lead to profound hypotension, which can be life-threatening, and is classified as a possible drug interaction according to the Naranjo probability scale 4, 5
• The combination of tizanidine and lisinopril can also cause bradycardia, and the hypotensive episodes can be more pronounced with concomitant administration of these medications 5, 6
• Providers should be aware of this potential adverse reaction when prescribing tizanidine and lisinopril together, especially in patients with a history of hypertension or those taking other antihypertensive medications 5, 6, 7