title: Effect of topical neuromodulatory medications on oral and skin keratinocytes.
abstract: BACKGROUND
  Neuromodulatory medications (NMs), such as amitriptyline, carbamazepine and gabapentin, are used as topical preparations for the management of neuropathic orofacial pain (NOP) and have produced promising preliminary results. The aim of this study was to investigate the effects of three aforementioned NMs on cell lines relevant to the orofacial tissues in vitro as no published studies have examined the effect of these topical NMs.
  
  
  METHODS
  Cellular viability was measured using alamarBlue®, testing cumulative and specific time point effects of NMs on human skin keratinocytes and oral keratinocytes. Effects of the NMs on cell counts were investigated by CCK-8 assay. Drug concentrations released from NM orabase pastes after 30-min incubation were measured by high-performance liquid chromatography. Using these clinical concentrations, morphological changes and cytokine expression were investigated using scanning electron microscopy (SEM) and human inflammatory antibody array (AAH), respectively.
  
  
  RESULTS
  Cumulative and specific time point viability and cell count methods revealed that amitriptyline caused a significant decrease in cellular viability and counts in both cell lines. Carbamazepine also had significant effects after long-term exposure and at higher concentrations, whilst gabapentin had little demonstrable effect. SEM confirmed the cytotoxicity of amitriptyline, whilst AAH revealed no significant changes in cytokine expression following amitriptyline, carbamazepine or gabapentin exposure compared with control.
  
  
  CONCLUSIONS
  The results raise concerns about the safety of topical amitriptyline as it was cytotoxic to skin and oral keratinocytes in both exposure times and concentrations, whilst carbamazepine was cytotoxic only at high concentrations and after longer exposure times and gabapentin had no demonstrable effects.
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Al-Musawi
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, UK.|Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Justin
authors.initials: J
authors.lastname: Durham
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: John M
authors.initials: JM
authors.lastname: Whitworth
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Stone
authors.affiliation: Division of TMD and Orofacial Pain, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.|Department of Neurology, Medical School, University of Minnesota, Minneapolis, MN, USA.|HealthPartners Institute for Education and Research, Bloomington, MN, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Nixdorf
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, UK.|Human Nutrition Research Centre, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Valentine
mesh_terms: D000287:Administration, Topical; D000588:Amines / Q000494:pharmacology* / Q000633:toxicity; D000639:Amitriptyline / Q000494:pharmacology* / Q000633:toxicity; D000700:Analgesics / Q000494:pharmacology* / Q000633:toxicity; D002220:Carbamazepine / Q000494:pharmacology* / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology* / Q000633:toxicity; D000077206:Gabapentin; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects*; D009055:Mouth / Q000166:cytology; D012867:Skin / Q000166:cytology; D018675:Toxicity Tests; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D000588:Amines; D000700:Analgesics; D003509:Cyclohexanecarboxylic Acids; D000639:Amitriptyline; D002220:Carbamazepine; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin
keywords: amitriptyline; carbamazepine; gabapentin; neuropathic pain; orofacial pain