Provided is a method for suppressing the generation of diclofenac lactam from a compound represented by a formula (1) in the description, including allowing the compound of the formula (1) and a component (A) that is at least one type of compound selected from the group consisting of a nonionic surfactant, a hydroxyalkylated cyclodextrin, a C1 to C3 mono-alcohol, a C2 to C3 di-alcohol, a C3 to C6 tri-alcohol, a polyalkylene glycol, a γ-lactone, polyvinylpyrrolidone, a chlorogenic acid, and an alkyl sulfate ester, and salts thereof to coexist. A method for producing a pharmaceutical composition containing a compound represented by the formula (1) and a component (A), and a pharmaceutical composition which is a product produced thereby are also provided.