Topical JAK inhibitors for Alopecia areata: Are Lab Abnormalities still possible?

Are lab abnormalities still possible with topical JAK inhibitors?

Topical medications are generally viewed as 'safer' than oral medications. However, one must always study in this is, in fact, true. One must always carefully consider whether topical medications are similarly effective as the oral formulation or whether it is less effective.

Lab Abnormalities with Oral JAK Inhibitors

The oral JAK inhibitors tofacitinib and ruxolitinib have the potential to produce several lab abnormalities. These include changes in blood counts, increased creatinine kinase (CK), increased cholesterol, and changes in liver enzymes.  Prior to starting these medications I typically order a range of blood tests, along with an ECG, a TB skin test, and Hepatitis B/C and HIV testing.

The Topical JAK Inhibitors

Extensive studies of topical JAK inhibitors have not been done. A recent study of 4 patients who had blood tests while using topical JAK inhibitors showed that 50 % had lab abnormalities while using the drug.  Fortunately, none were serious. One had a slight decrease in her white blood cell count but it eventually normalized.  One other patient had a slight increase in her liver enzymes but they too returned to baseline levels. It was not clear in either patient whether the lab changes were really attributable to the JAK inhibitor or not.

CONCLUSION

Lab abnormalities can occur while using tofacitinb but tend not to be severe in studies to date. Close monitoring is needed to ensure the safety of these medications.

Reference

Bayarat et al. Topical Janus kinase inhbitors for the treatment of pediatric alopecia areata. J Am Acad Dermatol 2017; 77(1):167-169