Background Azacitidine is used for haematological pathologies. The summary of product characteristics (Vidaza) indicates stability of 45 minutes at room temperature and 22 hours if prepared with water for injections (WFI) at 2–8°C at reconstitution and refrigerated.

Purpose To assess the chemical-physical stability of azacitidine suspension 25 mg/ml.

Materials and Methods Analysis fofllowed an approved protocol.

The validity of the reference material (azacitidine–Sigma Aldrich-batch-SLBD1299V) was checked before starting the analysis.

100 mg of drug was reconstituted with 4 ml of refrigerated (2–8°C) WFI. The sample and standard suspension were stored at 5°C in a temperature-controlled refrigerator.

For International Conference Harmonization guideline the solution can be considered stable if the % assay of azacitidine with respect to the initial value is reduced by less than 5%.

Azacitidine concentrations were determined by a stability-indicating HPLC method under the following conditions: X-Terra RP18 column (150 × 4.6 mm, 5 µm); 4°C autosampler temperature; phosphate buffer pH = 6.5 and acetonitrile/water = 40/60 as mobile phase; 0.8 ml/min flow rate; 230 nm UV detection; 20 µl injection volume.

At these conditions the sample and a standard suspension were analysed at 0/22/24/48/72/96/168 hours.

The % assay of azacitidine was calculated at each cheque point and the results were compared with the assessed 100% values for assay at t_0.

Results The azacitidine assay (%) determined by HPLC is reported in the table below.

Average values obtained by triplicate injections at each cheque point are reported.

Conclusions The variation of the % assay of azacitidine with respect to the initial value is less than 5% for at least 48 hours.

A microbiological study on azacitidine suspension is ongoing at our hospital. Positive results will allow us to use unused azacitidine suspension within 48 hours of reconstitution with considerable cost savings.

No conflict of interest.