Can topical Elidel (pimecrolimus) cause myositis?

Topical Elidel (Pimecrolimus) and Myositis Risk

Based on available evidence, topical Elidel (pimecrolimus) has not been shown to cause myositis, and there are no documented cases of myositis associated with its use in the medical literature. 1

Mechanism and Systemic Absorption

Pimecrolimus is a topical calcineurin inhibitor with:

• Minimal systemic absorption (maximum blood concentration of only 1.4 ng/mL in adults with atopic dermatitis) 2
• Decreasing absorption as skin condition improves 2
• Low permeation potential, even in patients with acute skin inflammation 3

Known Adverse Effects

The documented adverse effects of topical pimecrolimus include:

• Common effects:

  • Skin irritation at application site (burning/itching sensation) that typically:
    • Is mild to moderate and transient 4
    • Occurs in approximately 10% of patients 4
    • Generally reduces with ongoing usage 1
    • Can be mitigated by not applying immediately after bathing 1

• Theoretical concerns:

  • FDA "black box" warning (2005) regarding potential malignancy risk, particularly lymphoma 1
  • However, clinical evidence to date does not reveal any causal link between increased cancer risk and topical calcineurin inhibitors 1

Evidence Regarding Myositis

1. No documented association with myositis:

   • Comprehensive reviews of adverse effects do not mention myositis 1, 5, 4, 6
   • The American College of Allergy, Asthma and Immunology and American Academy of Allergy, Asthma and Immunology task force report does not list myositis as a concern 1

2. Contrasting evidence:

   • Oral corticosteroids (not pimecrolimus) are associated with myopathy 1
   • Topical pimecrolimus has actually been used successfully to treat cutaneous lesions of dermatomyositis 3

Clinical Implications

• Pimecrolimus has a favorable safety profile compared to topical corticosteroids:

  • Does not cause skin atrophy, striae, or telangiectasia 2, 5
  • No evidence of systemic immunosuppression 1, 2
  • No clinically relevant systemic adverse events in long-term studies 5

• The risk/benefit ratio of topical pimecrolimus is similar to conventional therapies for chronic relapsing eczema 1

Important Considerations

• Pimecrolimus should not be used in:
  • Children younger than 2 years of age 1
  • Patients with compromised immune systems 1
  • Patients receiving concurrent phototherapy 1
  • Pregnant or breast-feeding women (pregnancy category C) 1
  • Patients with severely impaired skin barrier function 1

Conclusion

While monitoring for any unusual adverse effects is always prudent with any medication, the current evidence does not support myositis as a risk associated with topical pimecrolimus use. In fact, pimecrolimus has been used therapeutically in patients with dermatomyositis, suggesting it may be beneficial rather than harmful in muscle inflammatory conditions.