Pump and Dump 😕

My supply took a nosedive after starting work, taking allergy medacine, having my BC prescription changed, and getting sick. I finally got it to come back up and the dentist put me on antibiotics. The pediatricians said I can take two of the pills and still nurse, but I will need to pump and dump with the third. After the dump they said I can nurse.

So, my question is, is there a certain amount of time I need to wait to pump after taking that last pill? Can I pump immediately? Wait 15 min to get in the milk and then pump? The doctor is closed now and I need to start the medacine. Any advice is appreciated.