Background In epicutaneous patch testing, the substance suspected of being responsible for the skin reaction (contact dermatitis and/or delayed drug reaction) is applied (in excipient) on the skin under occlusion to confirm/rule out a delayed hypersensitivity response. Various epicutaneous patch test batteries are commercially available.
Purpose To develop a work procedure for the Pharmacy Department to meet the demand for epicutaneous patches not commercially available.
Materials and methods The preparation procedure depends on the physical form of the active principle (AP) and the selection of excipient (according to the solubility of the AP). The solubility characteristics of the APs were recorded and The authors searched for commercially-available dosage forms and concentrations of the APs requested and for the pure APs. 1st option: use of pure AP; 2nd option: solid oral dosage form: pulverisation; 3rd option: syrup/drops; 4th option: parenteral form. When the AP was water-insoluble, a lipophilic excipient (vaseline) was used, when it was water-soluble, a hydrophilic excipient (lanolin-vaseline ointment) was used. Finally, the mixture was placed in a labelled 5-mL syringe.
Results The authors evaluated 13 patients during the 10-month study period. The authors prepared 29 types of patch (21% corticosteroids, 14% antiepileptics, 31% antibiotics and 34% other). The authors used the pure product in 6 patches and the commercial dosage form in 23 patches. 8 APs were water soluble and 21 were insoluble or poorly soluble in water. The authors diagnosed two delayed fixed drug exanthema-type reactions (to amoxicillin/clavulanic acid and metronidazole) and one contact dermatitis (from povidone-iodine); these tests were positive at 48 and 96 h.
Conclusions Preparation of epicutaneous patches in the Hospital Pharmacy Department is an effective option to diagnose contact dermatitis and/or delayed drug reaction in cases for which no commercial patch test is available.
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