Background In order to avoid separate injections of different drugs, admixtures of opioids with other drugs are frequently used in palliative care. Many factors can affect the compatibility and stability of the mixture: type of drug, concentration, solvent, container, temperature and light. There are some mixtures of opioids with other drugs with proven stability, but there is lack of evidence about the stability and compatibility of the combination of morphine and furosemide.

Purpose To evaluate the compatibility and stability of the admixture morphine 1.0 mg/ml – furosemide 0.6 mg/ml in NaCl 0.9% stored at ambient room temperature under normal light for at least 30 days.

Materials and methods On study day 0, a mixture was prepared and diluted in NaCl 0.9% to obtain 1.0 mg/ml of morphine and 0.6 mg/ml of furosemide and stored at ambient room temperature under normal light.

The concentration of each constituent drug was periodically determined using a HPLC-UV method. The drugs were chromatographed on a C₁₈ reverse phase column; the mobile phase was acetonitrile-water 80:20 (v/v); flow rate 1.5 ml/min. Morphine and furosemide concentrations were determined at 235 nm by interpolation from the calibration curves prepared at (0, 1, 2, 5, 7, 9, 12, 15, 19, 23, 26, 30) days from the standards.

Results The admixture remained physically and chemically stable during study period, with no precipitation or colour change and non-significant loss of morphine or furosemide. The StatGraphics Centurion XVI program was used for data processing.

Conclusions Morphine and furosemide mixture diluted in NaCl 0.9% (concentration 1.0 and 0.6 mg/ml, respectively), is physically and chemically stable for at least 30 days.

No conflict of interest.