Antiemetics are ordered to control nausea and vomiting in the child undergoing chemotherapy. How can the nurse most effectively use these medications?

Administer the antiemetic before starting chemotherapy.

Use the antiemetic after it is clear that nonpharmacologic methods are not effective.

Start the antiemetic on a scheduled basis when the chemotherapy begins to cause nausea.

Provide the antiemetic as needed (PRN) when nausea and vomiting are reported.