Background The chemical stability of coadministered ondansetron (OND) and haloperidol (HAL) in parenteral admixtures has not been described yet.

Objective The aim of the present work is to study the chemical stability and the compatibility of OND and HAL admixtures.

Methods Normal saline solution and dextrose were used to prepare the admixture solutions of the drugs; the materials of the containers were the original plastic bags of the diluents and the stability was studied at 20°C. Compatibility was studied by visual inspection of no colour change and turbidity or precipitation appearance. The concentration of the drugs was studied by ultraviolet detection high-performance liquid chromatography. The method was validated following the Food and Drug Administration and European Medicines Agency guidelines, and the assay enables the measurement of both drugs with a linear calibration curve (r=0.999) over the concentration range 10–100 µg/mL, with acceptable values of linearity, precision and accuracy. Darunavir was used as internal standard.

Results Most of the admixtures have an adequate concentration until 24 hours(less than 10% of loss). 25% of the samples show a higher loss at 24 hours, and the chemical stability of these samples is 12 hours.

Conclusions The stability and compatibility of OND and HAL in the coadministered admixtures in Viaflo plastic bags with normal saline or dextrose are suggested at 12 hours.