Sodium Nitrite and Sodium Azide both have their Megathreads I guess, so you can refer them.
I would rather Domperidone every 7-8 hours for 36 hours before intaking Sodium Azide which I prefer, you can refer here for antiemetics
https://archive.is/HizRA, I would also take some Cimetidine (not available online) or Ranitidine before CTB.
Advocates actually refer also painkillers and sedatives or anxiety pills to be taken before, but I don't think they're absolutely necessary, alas ye shall suffer the wo4st of material existence before CTB if you are to go to heaven. That will give us impetus not to disobey the heavenly father ever again.
Also I wouldn't eat 24 hours before CTB, take Azide an hour after the last Domperidone.