Can muscle relaxants, such as cyclobenzaprine (Flexeril) or baclofen, be used to treat pelvic pain?

Muscle Relaxants for Pelvic Pain

Yes, muscle relaxants can be used for pelvic pain, particularly for pain associated with muscle spasm, but they should be considered as part of a multimodal approach rather than first-line monotherapy. 1

Types of Muscle Relaxants for Pelvic Pain

Centrally Acting Muscle Relaxants

1. Cyclobenzaprine (Flexeril)

   • FDA-approved for acute, painful musculoskeletal conditions with muscle spasm 2
   • Effective for short-term use (2-3 weeks) 2
   • Dosage: 5-10 mg three times daily 3
   • Not indicated for spasticity associated with cerebral or spinal cord disease 2

2. Baclofen

   • FDA-approved for spasticity from multiple sclerosis and spinal cord diseases 4
   • Not specifically indicated for musculoskeletal spasm from rheumatic disorders 4
   • Requires careful monitoring due to significant withdrawal symptoms if discontinued abruptly 1
   • Should be taken preoperatively including the day of operation if used long-term 1

3. Tizanidine

   • α2-adrenergic receptor agonist with fewer cardiovascular effects than other muscle relaxants 1
   • Can be taken preoperatively including the day of surgical procedure 1
   • May have perioperative benefits including improved pain control and decreased opioid consumption 1

Evidence for Use in Pelvic Pain

• The National Comprehensive Cancer Network (NCCN) guidelines include muscle relaxants in their pharmacologic recommendations for pain management, including for chronic pelvic pain 1

• Skeletal muscle relaxants, particularly cyclobenzaprine, have been identified as potentially beneficial for myofascial pelvic pain and high-tone pelvic floor disorders 5

• Diazepam is the most studied medication for myofascial pelvic pain in both oral and vaginal formulations, though it carries dependency risks 5

Treatment Approach

1. First-line treatments (before considering muscle relaxants):

   • Physical therapy with pelvic floor strengthening exercises 1
   • Proper hydration 1
   • Anti-inflammatory drugs (NSAIDs) 1
   • Bowel regimen for gastrointestinal/urinary/pelvic pain 1

2. Second-line treatments:

   • Muscle relaxants for muscle spasm component 1, 6
   • Antiepileptic drugs (gabapentin, pregabalin) for neuropathic component 1
   • Tricyclic antidepressants or SNRIs for central sensitization 1

3. Refractory cases:

   • Consider referral to pain management services 1
   • Dorsal column stimulation for chronic cystitis and chronic pelvic pain 1, 7
   • Interventional procedures (nerve blocks) 7

Important Considerations and Precautions

• Limited duration: Muscle relaxants should be used only for short periods (2-3 weeks) due to limited evidence for long-term efficacy 2

• Sedation risk: Most muscle relaxants cause sedation, which can impact daily activities 3

• Withdrawal concerns: Abrupt discontinuation of baclofen can cause severe withdrawal symptoms including hallucinations, anxiety, tremors, and seizures 1

• Drug interactions: Avoid combining muscle relaxants with benzodiazepines or opioids due to increased risk of respiratory depression 3

• Monitoring: Regular assessment of efficacy and side effects is essential 3

Special Populations

• Liver concerns: Tizanidine and chlorzoxazone should be avoided due to hepatotoxicity risk 3

• Elderly patients: Start with lower doses due to increased risk of sedation and falls 3

• Pregnancy: Limited safety data; risks and benefits must be carefully weighed

While muscle relaxants can be helpful for the muscle spasm component of pelvic pain, they are most effective when used as part of a comprehensive approach that addresses all contributing factors to pelvic pain, including physical therapy, proper hydration, and appropriate analgesics.