A lot, but since I don't pump I don't know exactly how much. But ds stopped gaining weight between 4 and 6 months, and 2 weeks after I started the domperidone he gained almost a pound which apparently was astounding (according to the ped). I felt like it started to work within 24 hours.
Similar experience. My LO was very slow to regain birthweight. I started Domperidone (3 a day) when he was 3 weeks old and he gained 19 oz in the first 14 days I was on Domperidone. I've kept taking it, and we've had very good weight gain since. I'm down to 2 pills a day, with fenugreek and lactation cookies (just for an excuse to eat 4 cookies a day!).
Re: How much did Domperidone increase your supply?