What muscle relaxer does not significantly affect blood pressure?

Metaxalone is the Muscle Relaxant Least Likely to Affect Blood Pressure

Metaxalone is the preferred muscle relaxant when blood pressure stability is a priority, as it lacks the cardiovascular adverse effects (bradycardia and hypotension) associated with methocarbamol and the postural hypotension and tachycardia risks of carisoprodol. 1

Cardiovascular Profile of Common Muscle Relaxants

Muscle Relaxants That DO Affect Blood Pressure

Methocarbamol has documented cardiovascular effects:

• Causes bradycardia and hypotension as adverse effects 1
• Should be held on the day of surgical procedures due to these cardiovascular risks 1

Carisoprodol presents multiple cardiovascular concerns:

• Associated with tachycardia and postural hypotension 1
• Has significant abuse potential and is classified as a controlled substance 1
• Requires slow tapering (4-9 days) to avoid severe withdrawal symptoms 1

Orphenadrine has cardiovascular instability risks:

• Should be used with extreme caution in patients with tachycardia, cardiac decompensation, coronary insufficiency, and cardiac arrhythmias 1
• Has anticholinergic properties that can cause cardiovascular instability 1

The Safest Option: Metaxalone

Metaxalone stands out as having no documented cardiovascular effects:

• The adverse effect profile includes drowsiness, dizziness, and irritability—but notably excludes any cardiovascular effects 1
• It is a centrally acting skeletal muscle relaxant that does not act directly on skeletal muscle 1
• Should be held on the day of operation, but this is a general precaution rather than due to cardiovascular concerns 1

Important contraindications for metaxalone:

• Contraindicated in patients with significant hepatic or renal dysfunction 1
• Has been associated with drug-induced, hemolytic, or other anemias 1

Cyclobenzaprine: A Reasonable Alternative

Cyclobenzaprine does not have documented blood pressure effects:

• The adverse effect profile includes anticholinergic effects (hallucinations, confusion, drowsiness, constipation, urinary retention, dry mouth) but no cardiovascular effects are mentioned 1
• It is structurally related to amitriptyline and has peripheral and central anticholinergic activity 1
• Effective for acute musculoskeletal spasm with 5 mg three times daily showing similar efficacy to 10 mg with lower sedation rates 2

Clinical Algorithm for Selection

When blood pressure stability is the primary concern:

1. First choice: Metaxalone - No cardiovascular effects documented, but check hepatic and renal function first 1

2. Second choice: Cyclobenzaprine - No blood pressure effects, but monitor for anticholinergic side effects, particularly in elderly patients 1

3. Avoid: Methocarbamol - Direct cardiovascular effects including hypotension and bradycardia 1

4. Avoid: Carisoprodol - Causes postural hypotension and tachycardia 1

5. Avoid: Orphenadrine - Cardiovascular instability, especially problematic in patients with existing cardiac conditions 1

Common Pitfalls to Avoid

• Do not use metaxalone in patients with liver or kidney disease - it is absolutely contraindicated in significant hepatic or renal dysfunction 1
• All muscle relaxants should be held on the day of surgery - this is a consensus recommendation regardless of cardiovascular profile 1
• Duration of therapy should be limited - skeletal muscle relaxants have only been studied for 2 weeks or less (except one 3-week trial), and efficacy in chronic conditions is less established 1
• Monitor for sedation with all agents - drowsiness and dizziness are common across all muscle relaxants and increase fall risk 1