Long-term stability study of histamine in sterile bronchoprovocation solutions

The long-term stability of histamine in sterile bronchoprovocation solutions stored under different conditions was studied. Histamine solutions (2 and 8 mg/mL) were stored in specially adapted translucent and black plastic bottles and kept in a cool place (12 degrees C) and exposed to fluorescent light (500 foot-candles intensity). Multiple aliquots of each concentration were also stored at -20 degrees C in 12 X 75 mm sterile polypropylene tubes with snap caps and covered with aluminum foil. The content of histamine in the stored samples was determined by a stability-indicating colorimetric assay. The histamine solutions were stable for up to eight months at 12 degrees C when stored in either of the specially adapted translucent or black plastic bottles, irrespective of normal long-term exposure to fluorescent light. No important changes were observed in the histamine concentration when these solutions were stored at -20 degrees C in polypropylene tubes for up to a year. Histamine solutions used in bronchoprovocation tests can be stored in plastic bottles in a cool place or in the refrigerator. It is not necessary to protect these solutions from normal long-term exposures to fluorescent light to ensure clinically acceptable stability.