Formulation of an oral solution of urea

Introduction

Urea is recommended in 2nd line treatment in moderate or severe hyponatraemia due to a syndrome of inappropriate antidiuretic hormone secretion (SIADH) if water restriction is insufficient. A posology of 0,25-0,5 g/kg daily is recommended. Up to now, the pharmacy prepares urea 10g powder sachets to be dissolved in 100mL water prior to the administration.

Purpose

The aim of this study was to develop an oral solution with better organoleptic characteristics to improve treatment adherence and reduce the preparation time.

Material and method

• Formulation of a 0,5g/mL urea oral solution in Inorpha®
• pH control by potentiometry and clearness control by UV-visible spectroscopy at 620 nm
• Palatability testing of oral solution versus powder formulation dissolved in water

Results

To obtain 100mL of a 0,5g/mL urea oral solution, 50g of urea are added to 64g of Inorpha®.

A complete dissolution of urea is obtained in twenty minutes with warming against sixty minutes without warming.

After 32 days, pH remains stable for samples preserved in fridge at 2-8°C (pH 5,3 at J0 vs pH 5,5 at J32) whereas a linear increase (r² = 0,99) of pH is observed for the samples preserved in ambient temperature (pH 5,3 at J0 vs pH 7,2 at J32). After 32 days, the solution remains clear. The acceptability of the oral solution is greater than powder formulation dissolved in water.

Conclusion

Jointly to the preparation time decrease, the urea oral solution allows a decrease in water intake recommended in treatment of hyponatreamia due to SIADH. Oral solution induces an increase in treatment adherence thanks to a better palatability. Physicochemical stability for a 0,5g/mL urea oral solution is 1 month in fridge at 2-8°C. A complementary physicochemical stability study is in progress for the urea oral solution in Inorpha®.