Application of the experimental design method to photostability studies of Karvileks tablet

This study was examined a photostability of Karvileks (Zdravlje-Actavis, Serbia), packed in the different primary packs. For these examination, the experimental design with 3 independent variables: wavelength of radiation (X₁), duration of radiation (X₂) and type of packs (X₃) was applied. After irradiation of Karvileks, the content of carvedilol and its impurities A, B and C was taken as a response (Y₁, Y₂, Y₃, Y₄). The obtained mathematical equations can be used for determination of carvedilol and its impurities content in any case. Tablets were packed in an opaque plastic container, as well as in red blister. The content of carvedilol was determined using a stability-indicating RP-HPLC method. The obtained models were: Y₁ = 93.11 + 1.74 X₁ - 2.19 X₂ + 2.01 X₃ + 0.39 X₁X₂ + 0.39 X₁X₃; Y₂ = 0.22 - 0.02 X₁ + 0.14 X₂ - 0.01X₃ - 0.01 X₁X₂ - 0.007 X₂X₃ ; Y₃ = 0.001 + 0.014 X₁ + 0.014 X₂ - 0.001X₃ + 0.014 X₁X₂ - 0.001X₂X₃ ; Y₄ = 0.102 + 0.008 X₁ + 0.064 X₂ - 0.007 X₃. By using an experimental design, the opaque plastic container was selected as an adequate primary pack for Karvileks. This pack provides an adequate protection of the preparation from the effect of sunlight.