Amlodipine is a dihydropyridine drug that is used to lower high blood pressure. In this study, the photostabilities of orally disintegrating (OD) amlodipine tablets, both original and generic versions, and their powdered and suspended forms were evaluated. The concentration of the active pharmaceutical ingredient (API) was monitored by high-performance liquid chromatography (HPLC), revealing that residual amounts of API in powders and suspensions significantly decreased after ultraviolet light (UV) irradiation for 24 hr. Amlodipine OD tablets and their powders were packaged and stored at a house and a pharmacy for up to 90 days for the evaluation of their photostabilities in clinical use, and that amounts of API in the powdered form significantly decreased when they were stored in the house. ESI-LC/MS/MS analysis was performed to determine the chemical structure of photoproducts generated by photo-irradiated amlodipine OD tablets. It revealed that mainly a dehydrogenated form of amlodipine was generated concomitant with the photodegradation by UV and sunlight irradiation. This is the first study that evaluated the photostabilities of original amlodipine OD medicines, their generic OD versions and their altered forms.