title: Non-irritant concentrations and amounts of active ingredient in drug patch tests.
abstract: BACKGROUND
  Drug patch tests (DPTs) with medicaments suspected of causing an allergic reaction represent a method of diagnostic testing that is low risk; DPTs can reproduce delayed hypersensitivity to drugs, and entail only a moderate re-exposure of patients to potential offending drugs. We assessed the non-irritating concentrations of DPTs and determined the amounts of active ingredient (AI) contained in the drugs used in the tests.
  
  
  OBJECTIVE
  The objectives were to assess the non-irritating concentration of DPTs and determine the amounts of active ingredient (AI) contained in the drugs used in the tests.
  
  
  METHODS
  From a retrospective, single-centre study of all patients investigated during a 6-year period with a drug eruption, each potentially responsible drug was tested with the commercially available preparation diluted to 30% in water, petrolatum, or alcohol. Data collection was performed with a customized computer database. For each type of DPT studied, the numbers of positive and negative test results were recorded. The amount of AI contained in the DPT (as a percentage) was then calculated after weighing of each tablet.
  
  
  RESULTS
  Of the 5558 DPTs studied, all were non-irritant. The average concentration of AI was 9.8%; 25% of DPTs had an AI concentration of < 2%, and 25% had an AI concentration of > 16%. The AI concentration ranged from 0.05% (digoxin) to 30% (paracetamol lyophilisate).
  
  
  CONCLUSIONS
  These data provide thresholds for the non-irritating concentration of AI of 68 different drugs, and thresholds for the non-irritating dilution for 82 drugs, and will help to standardize DPT methods.
authors: Dermatology and Allergy Department, Brabois Hospital, Batiment des Specialites Medicales, University Hospital of Nancy, Rue du Morvan, 54500, Vandoeuvre les Nancy, France.
authors: Delphine
authors: D
authors: Brajon
authors: Sophie
authors: S
authors: Menetre
authors: Julie
authors: J
authors: Waton
authors: Claire
authors: C
authors: Poreaux
authors: Annick
authors: A
authors: Barbaud
mesh_terms: D004342:Drug Hypersensitivity / Q000175:diagnosis; D006801:Humans; D007509:Irritants / Q000032:analysis*; D010328:Patch Tests / Q000379:methods / Q000592:standards*; D012189:Retrospective Studies
chemical_list: D007509:Irritants
keywords: active ingredient; drug allergy; drug patch tests; non-irritant concentration; threshold for specificity