Chemical stabilities of isoetharine hydrochloride, metaproterenol sulphate and terbutaline sulphate after mixing with normal saline for respiratory therapy.

The chemical stabilities of isoetharine hydrochloride inhalation solution, metaproterenol sulphate inhalation solution and terbutaline sulphate injection, after diluting 1 in 10 with sodium chloride 0.9% injection were studied. On storing the solutions in amber-coloured syringes, they were stable for at least 120 days at 5 degrees C. At 25 degrees C they were also stable for 120 days except that isoetharine solution discoloured and lost 7.8% of its potency after 90 days of storage. There was a new peak in the chromatogram from the decomposition product. All other solutions remained clear for 120 days at both temperatures. The initial and final pH values were similar except that after 120 days at both temperatures. The initial and final pH values were similar except that after 120 days at 25 degrees C, the pH value of terbutaline solution had increased from 4.9 to 5.4.