My doctor prescribed metronidazole for possible vaginal infection. i'm breastfeeding fulltime, will this affect my baby?

Nope!: Metronidazole can come in oral or vaginal suppository forms. The suppository form is not absorbed through your blood stream in the same way as the oral form, and is even safe enough to use during pregnancy. Additionally, the american academy of pediatrics have found no studies that have demonstrated negative effects on your baby if you use the oral form during breastfeeding.

No it should not: If you are every worried about medications being passed on through breastmilk check out lactmed: http://toxnet.Nlm.Nih.Gov/cgi-bin/sis/htmlgen?Lact it is an excellent resource from the national institutes of health and provides trusted information on any compound. They also have apps for smart phones.