Chemotherapy is essential for the cancer treatment. Usually, in the preparation process of the chemotherapy, part of the medication must be discarded to achieve the dose prescribed by the doctor. The dose of medication discarded results in toxic waste production. The objective is to analyze the chemotherapy waste in the preparation process of the drug.

It has been conducted a cross-sectional observational study. The study data were obtained from chemotherapy's requests by oncologists linked to a health insurance plan. It has been calculated the dose of chemotherapy waste in each application, considering the dose prescribed by the doctor and the drug dosage form.

It were analyzed 1,289 prescriptions for intravenous chemotherapy of 106 users with cancer. There were a total of 63,824mg of chemotherapy residue produced, with an average of 602mg by user and 49mg by application. The average percentage of chemotherapy waste was 11.96%, between 0 to 50%.

The number of applications and the dose used in the treatment protocol, the commercial dosage forms and the no use of dose rounding of medication to the nearest vial size were factors related to increased production of chemotherapy waste.