Occupational allergic contact dermatitis to Piperamido Nitrotoluene in pharmaceutical workers: A case series

Imatinib mesylate is a first-generation tyrosine kinase inhibitor. Piperamido Nitrotoluene, also known as F5, is an intermediate used in the manufacturing of imatinib. We present a case series of allergic contact dermatitis to F5 in pharmaceutical workers.

Four male pharmaceutical workers were referred between 2007 and 2021 with new dermatitis predominantly affecting the periorbital region. All were involved in the production of imatinib and particularly exposed to F5. Following medical history and examination, they underwent patch testing to standard series and F5 diluted in white soft paraffin (WSP).

All patients tested positive confirming a diagnosis of contact allergy to F5. The first case tested positive to F5 diluted to 1% in WSP, the second to F5 diluted to 10% in WSP and the third and fourth to F5 diluted to 1% and 10% in WSP. In all four cases, dermatitis resolved when they were removed from exposure to F5.

To the best of our knowledge, these are the first cases of allergic contact dermatitis to F5 confirmed by patch testing in the literature. In February 2016, a generic formulation of imatinib entered the market. Globalized production of imatinib may result in further cases presenting to dermatology departments worldwide.