It is not recommended to reuse the contents of a bottle of Ciprodex for a second time. It is best to not use medication drops for more than 30 days after opening them, especially if they were used to treat an infection. There is a theoretical risk that the drops could now contain enough bacteria to potentially cause harm when instilled in the ear. It is advisable to purchase a new bottle instead. Additionally, in certain situations, it may be better to switch to a different antibiotic to avoid developing antibiotic resistance in the bacteria causing the infection and increasing the risk of treatment failure.