well I'm glad you brought this up, cause I'm dealing with something similar,
I know that teens were stopped being given tetracycline for acne because of teeth staining. And I'm pretty sure that doxycycline is in the same family. My husband was given tetracycline at 16 and his teeth look like they were dipped in dark tea and the stain stayed. And the dentist said bleaching would not help.
The drug book says for doxy: serious reactions: tooth discoloration (<8y.o), Common Reactions: skin/ tissue discoloration. It says the same for tetracycline.
I would have to say it's going to be a personal decision to stop taking it or not. At least there are other choices.
I have been dealing with a greenish black plaque build up for the last couple of months. My LLMD told me to rinse with a half hydrogen peroxide half water mixture twice a day. I think it's helping, but I don't do it twice daily every day either.
good luck with your decision
11/07 symptoms start
7/4/08 IGenX LD positive,gluten sensitivity,low magn, low WBC's,+yeast/bacteria/tapeworm/roundworm, EBV,HHV,CMV,Parvo,
7/25/08 started on Biaxin
9/08 IGenX co-infections neg, but probable Bart, Bab, Erhl
11/08 Biaxin,Plaquenil,Cipro, Artemisinin,3 probiotics,Transfer Immune, Bcomplex,MultiVit,omega3,magnesium,