In March 2020 a milestone paper related to the peripheral pathogenesis of sciatic pain has been published by us, in collaboration with a Canadian pain specialist. Increasingly we and colleagues all over the world finder phenytoin cream quite remarbable, sometimes even in indications one would not expect phenytoin cream to reduce pain. Sciatic pain is such an indication. Based on a very convincing case description we postulate a new hypothesis explaining pain in sciatic nerve impingement.
We found fast pain reduction after applying topical phenytoin cream at the painful dermatome in a 55-year-old patient suffering from sciatic pain due to pathology of a disc. This patient was treatment resistant for 13 years. Prescribing topical analgesic cream seemed to us at first sight quite counter-intuitive. The clear response in a treatment-resistant patient however provoked us to look deeper in the pathophysiology of sciatic nerve impingement.
Recently, it has been documented that proximal nerve lesions are followed by small fiber pathology in the skin. This might be a responsible peripheral wind-up generator for the chronification of pain in sciatic nerve compression. Topical application of the broad-acting voltage-gated sodium channel blocker phenytoin could reduce neuropathic pain in our case completely, supporting a peripheral mechanism of action for phenytoin cream in sciatic pain.
Phenytoin cream surprises us and patients more often than not…
Russel, AL, Kopsky DJ, Keppel Hesselink JM. Phenytoin cream for the treatment of sciatic pain: clinical effects and theoretical considerations: case report. J Pain Palliat Care Pharmacother. 2020 March 2: 1-7.