Safe Muscle Relaxant Use in Dialysis Patients
Muscle relaxants should generally be avoided in chronic hemodialysis patients due to significant risks of altered mental status, falls, and accumulation of parent compounds or metabolites from impaired renal clearance. 1, 2
Primary Recommendation: Avoid Routine Use
The American Geriatrics Society explicitly recommends avoiding muscle relaxants (including cyclobenzaprine, carisoprodol, chlorzoxazone, metaxalone, methocarbamol, and orphenadrine) in older adults due to high risk of CNS adverse effects including sedation and increased fall risk. 3
Muscle relaxants are only appropriate when required for endotracheal intubation and mechanical ventilation in severe respiratory distress, not for routine musculoskeletal complaints. 1
In a large observational study of 140,899 Medicare hemodialysis patients, 10% received muscle relaxants, and their use was associated with 39% higher risk of altered mental status (HR 1.39,95% CI 1.29-1.51) and 18% higher risk of falls (HR 1.18,95% CI 1.05-1.33). 2
Why Muscle Relaxants Are Problematic in Dialysis
Patients with chronic kidney disease have reduced drug clearance, leading to accumulation of parent compounds and active metabolites, which increases toxicity risk. 1
Even though some muscle relaxants like alcuronium and dimethyl tubocurarine have measurable dialysance during hemodialysis, their removal is small and unpredictable, with prolonged neuromuscular blockade documented beyond 20 hours in anuric patients. 4
The combination of uremic encephalopathy risk and sedating medications creates a particularly dangerous scenario for cognitive impairment in this population. 3, 2
Safer Alternatives for Musculoskeletal Symptoms
First-Line: Non-Pharmacologic Approaches
Prescribe a minimum of 150 minutes per week of moderate-intensity physical activity (adjusted for cardiovascular tolerance) as first-line therapy for musculoskeletal pain and spasm. 1
Neuromuscular electrical stimulation (NMES) during hemodialysis sessions has been shown to stabilize blood pressure, improve dialysis efficacy, and counteract muscle wasting without medication risks. 3
NMES training should use stimulation frequencies of 9-10 Hz with on-times of 15-20 seconds to address muscle wasting in hemodialysis patients. 3
Second-Line: Specific Pharmacologic Options
For neuropathic pain or restless legs syndrome contributing to muscle discomfort, gabapentin 100-300 mg after each dialysis session is the preferred first-line pharmacologic agent with proven efficacy and favorable safety profile in dialysis patients. 5
For acute anxiety-related muscle tension, diazepam (0.1-0.8 mg/kg orally) is recommended as a safe option because it is hepatically metabolized and requires no dose adjustment in renal failure. 6
Midazolam (0.5-1 mg/kg, maximum 15 mg) is another hepatically-metabolized benzodiazepine option for acute situations, though it should be used cautiously given fall risks. 6, 7
Critical Contraindications
Succinylcholine is absolutely contraindicated in dialysis patients due to risk of treatment-resistant hyperkalemia, particularly given that these patients already have compromised potassium regulation. 1
Avoid NSAIDs (including aspirin, ibuprofen, diclofenac) for concurrent pain management, as they worsen renal function and increase cardiovascular risk. 6
If Muscle Relaxants Must Be Used
When muscle relaxants are unavoidable for procedural sedation:
Remimazolam, an ultra-short-acting benzodiazepine metabolized by hepatic carboxylesterases (not renally eliminated), may be the safest option as its anesthetic effect is not significantly influenced by renal dysfunction and causes less cardiac depression than propofol. 8
Regular monitoring of estimated glomerular filtration rate (eGFR), serum electrolytes, and mental status is required to detect accumulation and prevent toxicity. 1
Consultation with a clinical pharmacist is recommended for comprehensive medication review and dose optimization. 1
Common Pitfalls to Avoid
Do not prescribe traditional oral muscle relaxants (cyclobenzaprine, carisoprodol, methocarbamol) for chronic musculoskeletal complaints in dialysis patients—the risks far outweigh any potential benefits. 3, 2
Do not assume that "low doses" are safe—even reduced doses accumulate over time due to impaired clearance. 1, 4
Do not overlook non-pharmacologic interventions, which are both safer and potentially more effective for chronic muscle-related symptoms. 3, 1
Avoid attributing muscle symptoms solely to "uremia" without systematically addressing modifiable factors such as dialysis adequacy, volume status, and concurrent depression. 5