Medications and breastefeeding

I am the mother of a one month old very healthy, weight gaining, baby boy. During pregnancy and during one month post partum breastfeeding I have taken Labetalol, Digoxin and Hydrocodone for various medical problems and there have been no ill effects during pregnancy or after birth to my son from these medications (i.e., no withdrawal after birth, no birth defects, healthy weight gain, etc.)
Now my doctors are now recommending that I start taking Zoloft and Ritalin. I am still breastfeeding and am very concerned as to what affect the additions of these medications might have. And if they are unsafe to take while nursing and I stop nursing to take them, will my son have affects from not nursing, considering what medications have probably already been in my breastmilk up until this point?
Thank you.
Heather Harris

[Kevin Kennedy, Ph.D.]

Re: Zoloft, you can expect, on average, that 1%-2% of the active ingredient will be secreted in breast milk. There is no evidence thus far that infants incur damage from such exposure, but due to lack of certainty there is a risk. I am not aware of studies which reveal if methylphenidate (Ritalin) is secreted in breast milk. To be entirely safe, it is best not to nurse while taking the medications you are prescribed. If you must take the medicines, it is best to stop breast feeding. If you must take the Ritalin, take your dose immediately after you have fed your child, or just at the point your child is beginning his long nap.