How many doses of mirolax is safe at once for quick cleansing?

Use as directed: Read the packaging instructions to use the correct dose. Individual packets are labeled and the bottle has a measuring cap for you to fill the proper amount/dose and mix with 4-8 ounces of water. Use Miralax (polyethylene glycol) for constipation, not for a "cleanse". Inducing bowel movements when not necessary could be unhealthy and if constipation is persistent you need to contact a physician.