In this study, the modified stability-indicating RP-HPLC method was validated for quantitative analysis of amlodipine besylate in the presence of its impurity D (3-ethyl 5-methyl 2-[(2-aminoethoxy)methyl]-4-(2-chlorophenyl)-6-methylpyridine-3,5-dicarboxylate). The method was applied for the determination of an analyte in the tablets and irradiated samples packed in the primary packaging (Alu/PVC/PVDC blister packaging). The efficient chromatographic separation was achieved using a ZORBAX Eclipse XDB-C18 column (4.6×250 mm, 5 mm) with isocratic elution of mobile phase which consisted of acetonitrile:methanol:triethylamine solution (15:35:50, v/v/v) (pH 3.0). The flow rate of the mobile phase was 1 mL min-1, while the detection of amlodipine besylate was carried out at 273 nm. Amlodipine besylate and its impurity D were identified at the retention times of 16.529 min and 2.575 min, respectively. The linearity of the method with the coefficient of determination of 0.999 was confirmed in the concentration range of 10 - 75 µg mL-1 for amlodipine besylate. The limit of detection was 0.2 µg mL-1, while the limit of quantification was 0.66 µg mL-1. After UV and Vis radiation of the tablets packed in the primary packaging, the content of amlodipine besylate was reduced by 22.38% and 19.89%, respectively. The presence of new degradation products was not detected under the given chromatographic conditions. The photodegradation of amlodipine besylate followed pseudo-first-order kinetics. Based on the half-life of amlodipine besylate (38.4 days for UV radiation and 43.3 days for Vis radiation), it was concluded that amlodipine besylate in the tablets has satisfactory photostability after its packing in the Alu/PVC/PVDC blister packaging.