Hi welcome to Health care magic forum.
Thanks for sending quiry to H.C.M.F.
You are using Minocycline
since 7 years. You are feeling it is not working now, and you want to use doxycycline in place of minocycline. Both are containing the same medicine and have the same spectrum , side effects etc. It is an anti biotic and should not be used for longer periods, if it is used like that it will develop resistance and stop working
You have developed bluish discoloration on right shin , the drug can cause discoloration, but not on the skin.
If you want to use anti biotic use only under the guidance of your doctor.
Wishing that every thing will be fine.