title: Chemical analysis of freshly prepared and stored capsaicin solutions: implications for tussigenic challenges.
abstract: The purpose of this study was to assess the stability of stored capsaicin solutions and the actual concentrations of prepared solutions. Capsaicin solutions ranging in concentration from 0.5 to 128 microM were mixed and analyzed using high performance liquid chromatography. Samples of varying concentrations were then stored under 4 environmental conditions: 4 degrees C and protected from light, room temperature (RT) exposed to light, RT protected from light, and -20 degrees C and protected from light. The concentrations were measured every other month for 1 year. Actual concentrations of freshly prepared solutions were on average 88.3% of predicted. For solutions stored at 4 degrees C, there was a decrease only in the lower concentrations (0.5, 1, and 2 microM) after 2 months (P=0.003). Solutions stored at RT exposed to light decreased in concentration after 6 months (P=0.020), and solutions stored at RT protected from light decreased in concentration after 4 months (P=0.026). The group stored at -20 degrees C decreased in concentration after 1 year (P=0.033). We conclude that the actual concentration of capsaicin solution is less than predicted, and solutions of 4 microM or higher concentration are stable for 1 year if stored at 4 degrees C protected from light.
authors.affiliation: The Division of Pulmonary, Allergy, and Critical Care Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA. kopecs@ummhc.org
authors.forename: Scott E
authors.initials: SE
authors.lastname: Kopec
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: DeBellis
authors.forename: Richard S
authors.initials: RS
authors.lastname: Irwin
mesh_terms: D000280:Administration, Inhalation; D002211:Capsaicin / Q000008:administration & dosage / Q000032:analysis* / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004339:Drug Compounding; D004355:Drug Stability; D004356:Drug Storage; D008027:Light; D019999:Pharmaceutical Solutions / Q000008:administration & dosage / Q000032:analysis* / Q000737:chemistry*; D012129:Respiratory Function Tests; D013696:Temperature; D013997:Time Factors
chemical_list: D019999:Pharmaceutical Solutions; D002211:Capsaicin