When Should I Stop Taking Spironolactone and Doxycycline Before Mommy Makeover?

I don't see any reason for stopping the doxycycline. The spironolactone needn't be stopped either, but is can effect electrolyte balance (sodium, potassium, chloride, etc) so those should be checked before you undergo surgery to assure that the procedure is carried out with maximum safety. Discuss both meds with your own surgeon. 

All the best. 

I do not believe that either of the medications that you are currently on will have a negative impact on your planed surgery.  If in doubt contact your surgeon and check with anesthesia about the Spironolactone.