Topical Phenytoin Cream Reduces Burning Pain Due to Small Fiber Neuropathy in Sarcoidosis

Abstract

Jan M. Keppel Hesselink and David J. Kopsky

We present a patient case of burning pain and sleep disturbances due to small fiber neuropathy (SFN) in sarcoidosis, treated successfully by topically applied phenytoin 10% cream. Using a single blind, placebo-controlled response test, the patient identified that within a 10 minute period phenytoin 10% cream provided a pain reduction of 50%, while placebo cream did not reduce pain at all. Subsequently, the patient was prescribed phenytoin 10% cream and used this cream for several weeks. Burning pain was reduced by 50% to 60%, resulting in a much improved sleep. The onset of analgesia starts around five minutes after the application of phenytoin 10% cream and in this case lasts for around 20 hours. Plasma levels of phenytoin, measured in 15 comparable patients were below the level of detection, ruling out systemic analgesia. Our hypothesis is that topical phenytoin influences epidermal targets such as nociceptors, small nerve fibers and keratinocytes, all which play a role in the pathogenesis of pain in SF

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