From what I've generally heard, most mums on Dostinex start to feel real relief within about 2 to 3 days, and milk supply tends to fully stop within a week or so, though it can depend a little on how long you've been breastfeeding. One thing that seems to help in the meantime is wearing a firm, supportive bra and doing a little hand expressing, just enough to ease the pressure without stimulating more supply. A mum I know mentioned her gynae actually prescribed Dostinex and asked her to stop nursing before starting the tablets, so the timing of when you stop feeding matters too