What muscle relaxer is best to prescribe in patients with Impaired renal (kidney) function?

From the Guidelines

For patients with reduced kidney function, baclofen is generally considered the best muscle relaxer to prescribe. Baclofen is primarily eliminated via the kidneys, so dosage adjustments are necessary based on the degree of renal impairment. Start with a low dose of 5 mg once daily and titrate slowly based on response and tolerability. The dose can be gradually increased to 5 mg three times daily in moderate renal impairment, but should not exceed this without careful monitoring. Tizanidine is another option that may be used with caution, starting at 2 mg once daily and titrating slowly.

• Avoid metaxalone, as it is contraindicated in patients with significant hepatic or renal dysfunction, and has been associated with drug-induced, hemolytic, or other anemias 1.
• Other muscle relaxants like cyclobenzaprine, and carisoprodol should also be avoided as they have active metabolites that can accumulate in renal impairment, potentially causing excessive sedation and other adverse effects.
• Methocarbamol may be used with caution in mild to moderate renal impairment. Regular monitoring of renal function is essential when using any muscle relaxant in these patients. The recommendation for baclofen is based on its predictable pharmacokinetics and the ability to adjust dosing based on creatinine clearance, making it safer for patients with compromised kidney function.

From the FDA Drug Label

Tizanidine clearance is reduced by more than 50% in elderly patients with renal insufficiency (creatinine clearance < 25 mL/min) compared to healthy elderly subjects; this would be expected to lead to a longer duration of clinical effect. Tizanidine should be used with caution in renally impaired patients In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased These patients should be monitored closely for the onset or increase in severity of the common adverse events (dry mouth, somnolence, asthenia and dizziness) as indicators of potential overdose.

Tizanidine is a muscle relaxer that can be prescribed with reduced kidney function, but it should be used with caution. The dose should be reduced during titration, and patients should be monitored closely for adverse events 2.

From the Research

Muscle Relaxers for Patients with Reduced Kidney Function

• The choice of muscle relaxer for patients with reduced kidney function should be based on the pharmacodynamics and pharmacokinetics of the specific drug 3.
• A study comparing vecuronium, atracurium, mivacurium, and rocuronium in patients with end-stage renal failure found that all four muscle relaxants could be safely used in this population 3.
• However, the study also found that the no-response period and duration of action of vecuronium and rocuronium were prolonged after repeated incremental doses in patients with end-stage renal failure 3.
• Atracurium, on the other hand, did not show any significant difference in duration of action or recovery between patients with end-stage renal failure and those with normal renal function 3.
• Another study found that cumulative muscle relaxant exposure was associated with a higher risk of incident frailty in patients with diabetic kidney disease 4.
• The study suggested that moderation of muscle relaxant use in this population may be of potential importance 4.
• A study on hemodialysis patients found that muscle relaxant use was common and associated with altered mental status and falls 5.
• The study also found that muscle relaxant use was not statistically significantly associated with a higher risk of fracture, but was associated with a lower hazard of death 5.

Considerations for Muscle Relaxer Use

• When prescribing muscle relaxers to patients with reduced kidney function, it is essential to consider the potential risks and benefits of each drug 3, 4, 5.
• The choice of muscle relaxer should be based on the individual patient's needs and medical history 3.
• Close monitoring of the patient's renal function and overall health is crucial when using muscle relaxers in this population 3, 4, 5.
• Alternative treatments, such as physical therapy or other medications, may be considered for patients with reduced kidney function who require muscle relaxation 4, 5.