From the Guidelines
Yes, tizanidine can cause hypotension as a significant side effect. This medication, which is primarily used as a muscle relaxant to treat spasticity, works by stimulating central alpha-2 adrenergic receptors, which not only reduces muscle tone but also affects blood pressure regulation. The hypotensive effect is dose-dependent and typically occurs within 1-2 hours after taking the medication, coinciding with peak plasma concentrations. Some key points to consider about tizanidine and its effects on blood pressure include:
- Blood pressure may drop by 20-30% in some patients, with the most pronounced effects usually seen at higher doses (8 mg or more) 1.
- The risk of hypotension increases when tizanidine is combined with other medications that lower blood pressure, such as antihypertensives, or when taken with CYP1A2 inhibitors.
- Patients should be advised to rise slowly from sitting or lying positions to minimize orthostatic hypotension symptoms like dizziness or lightheadedness.
- Blood pressure monitoring is recommended when starting tizanidine or adjusting the dose, particularly in elderly patients or those with cardiovascular conditions. It's also important to note that tizanidine's side effects profile, as seen in the table provided, includes hypotension, sedation, dry mouth, asthenia, dizziness, somnolence, and hepatotoxicity 1. Given the potential for significant hypotension, careful consideration and monitoring are necessary when prescribing tizanidine, especially in vulnerable populations or when used concomitantly with other medications that may exacerbate this effect.
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.
Yes, tizanidine can decrease blood pressure. The drug label warns of the risk of hypotension, particularly when used at higher doses or in combination with other medications that lower blood pressure. Patients should be monitored for signs and symptoms of hypotension, such as dizziness, lightheadedness, and orthostatic hypotension 2.
From the Research
Tizanidine and Blood Pressure
- Tizanidine, a muscle relaxant, can lower blood pressure, as it is metabolized by the cytochrome P450 1A2 (CYP1A2) 3.
- The use of strong CYP1A2 inhibitors with tizanidine can increase the risk of hypotensive episodes, as seen in a retrospective cohort study of 1,626 patients prescribed tizanidine and 5,012 prescribed cyclobenzaprine concurrently with a strong CYP1A2 inhibitor 3.
- Ciprofloxacin, a fluoroquinolone antibiotic, can greatly increase concentrations and hypotensive effect of tizanidine by inhibiting its CYP1A2-mediated presystemic metabolism, as demonstrated in a double-blind, randomized, 2-phase crossover study of 10 healthy volunteers 4.
Interaction with Other Medications
- The interaction between tizanidine and lisinopril, an antihypertensive agent, can cause significant hypotension, as reported in a case study of a 48-year-old woman 5.
- Tizanidine has been shown to have sedative and sympatholytic effects, comparable to those of clonidine, in a double-blind, placebo-controlled, randomized, cross-over study of six healthy male volunteers 6.
Pharmacodynamics and Pharmacokinetics
- A single oral dose of tizanidine (8 mg) has been shown to reduce spasticity in patients with spinal cord injuries, without affecting blood pressure, in a study of five tetraplegic and five paraplegic patients 7.
- Tizanidine has a plasma half-life of 2.7 +/- 0.06 hours, and its levels peak at one hour after administration, as demonstrated in the same study 7.