Urine drops will nullify your Wudhu. However, if the drops is continuous for one Salah duration then you will be classified as a Ma'zur (excused person). So you will pray that Salah and other Salah like Nawafil, until the next Salah time which then you will have to renew your Wudhu.
Also, when urine drops comes on your pants whilst praying Salah in that state, you complete your Salah and after Salah you wash that pants and wear it again for the next Salah and re-do your Wudhu and your Salah will be valid.
صاحب عذر من به سلسل بول أواستطلاق بطن أوانفلات ريح أواستحاضة.........ان استوعب عذره تمام وقت صلاة مفروضة ولوحكما.......وحكمه الوضوء لكل فرض ثم يصلي به فيه فرضاونفلافاذاخرج الوقت بطل
