Study to support the standardization of the prescribing, dispensing and labeling of etoposide formulations in Australia

Aim:  Etoposide is used in a wide variety of solid and hematological tumors. It is available in Australia in two intravenous formulations; etoposide base and the etoposide phosphate salt with 113.6 mg of etoposide phosphate being equivalent to 100 mg of the etoposide base. Variances between the etoposide dose prescribed and that actually given have been reported recently in Australia with patients receiving either too much or too little of the intended dose of etoposide. We carried out a review of national practices of prescribing, dispensing and labeling of etoposide and etoposide phosphate. Methods:  Cancer care clinicians and pharmacists, identified through their membership of the Clinical Oncological Society of Australia (COSA), were asked to complete an online survey or participate in a telephone interview, about their etoposide prescribing and dispensing practices. Results:  Nineteen pharmacists and 11 prescribers provided responses suitable for analysis. The most common reason for using the etoposide phosphate formulation was its shorter infusion time. The most common reason provided for preferring the base formulation over the phosphate formulation was that the original clinical trial data supported its use. There were a variety of methods identified that a prescriber might use to indicate the formulation of etoposide required and a variety of methods used for the labeling of etoposide formulations. Conclusion:  Prescribing, ordering and dispensing practices for etoposide base and etoposide phosphate are inconsistent across Australia, which could lead to dosing errors. We recommend that a national standard is adopted with etoposide phosphate preparations prescribed and labeled as “Etoposide (as the PHOSPHATE) x mg. Where x is the number of milligrams of etoposide base required.” This would move towards minimizing the risk of dosage errors occurring with these formulations.