Are there any medications that could reduce melanin in your skin?

Probably not: There are bleaching creams available to reduce the skin pigment but they need to be used regularly and are only partly effective. Chemicals such as phenol can destroy the melanin-producting cells altogether by inducing a chemical burn- however that's probably something you won't want. I don't know if the late Michael Jackson' dermatologist or plastic surgeon has other tricks in his bag or not.