What's the difference between doxycycline monohydrate and doxycycline hyclate?

Doxycycline monohydrate and doxycycline hyclate are two forms of the same medication, but they have different chemical structures. Doxycycline monohydrate is more stable and can be taken with or without food, while doxycycline hyclate is less stable and should be taken on an empty stomach for better absorption.