Background and importance Stomatitis is a common adverse drug reaction of the mTOR inhibitor everolimus. Rugo et al (2016) reported that the use of a dexamethasone mouthwash solution prevented everolimus related grade >2 stomatitis in patients with hormone receptor positive and HER2 negative metastatic breast cancer. No commercial presentation is available in our country, and so we carried out galenic validation of a formulation for these patients.

Aim and objectives The aim of this study was to develop a dexamethasone 0.01% stable solution for mouth washing to prevent stomatitis in patients started on everolimus treatment.

Material and methods We designed two formulations based on the components of a commercial oral preparation manufactured in USA by Roxane Laboratories. We added EDTA to explore if this affected stability (table 1).

For assignment of the microbiological validity period, we used the risk matrix from Good Manufacture Practices of Hospital Pharmacy. We preserved both solutions under room temperature and refrigeration conditions, always protected from light. We checked for organoleptic characteristics (cleanness, colour, odour, flavour) and pH every week for 30 days.

Results We obtained transparent, homogenous solutions free of visible and rare particles. Physicochemical stability was guaranteed as we used a pre-existing formulation to develop our preparation. Furthermore, organoleptic characteristics were constant and pH remained stable between 3 and 5. We selected the formula without EDTA because its manufacture was easier. We assigned a beyond use date of 30 days, keeping the formulation refrigerated and protected from light.

Conclusion and relevance This formulation was simple to prepare. It can be used in other hospitals for the same purpose and has filled a therapeutic void. Clinical effectiveness might be investigated to confirm the utility of this magistral formula.

References and/or acknowledgements 1. Rugo HS, et al. Lancet Oncol 2017;18:654–662.

No conflict of interest.