Drug interactions between : Synthroid 5g and another 5 mg cut in half), N.A.C .(1,800 mg.s sustained released per day)( I have a problem with mucous build up),and doxycycline , 20 mg. twice daily(submicrobial ) for rosacea .. I take synthroid and the r0 mg doxy at night and the n.a.c. and the other 20 mg doxy in the morning with two glasses of water,.(not protien food whcih apparantly decreases NAC s effectiveness. Thankyou