title: Potency and Stability of Intradermal Capsaicin: Implications for Use as a Human Model of Pain in Multicenter Clinical Trials.
abstract: Intradermally injected capsaicin has been used extensively both as a human pain model and to assess analgesic efficacy. Factors such as dose, formulation, route, and site are known to affect its sensitivity. We determined whether potency and stability of capsaicin solutions were further sources of variability when following strict manufacturing guidelines. Capsaicin solution (1.0 mg/mL) was prepared according to Current Good Manufacturing Practice (cGMP) guidelines and aseptically filled into sterile amber borosilicate vials and stored at 5°C, 25°C, and 30°C. All samples were analyzed at one, three, six, and twelve months. Chemical stability was determined using HPLC and physical stability was evaluated by visual inspection of color changes, clarity, particulate matter, and product/ container closure abnormalities during each sampling time. Capsaicin intradermal injection was found to be sterile and retained 95% of the initial concentration for at least one year, regardless of studied storage temperatures (P<0.0001). Visual inspection indicated no changes in color, clarity, particulate matter, and product/ container closure abnormalities in all samples. These data show that capsaicin solutions (1.0 mg/mL) maintain their potency and stability over one year when manufactured according to cGMP guidelines. These results suggest that in clinical trials manufacturing of capsaicin solutions is recommended over extemporaneous compounding.
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Pavan
authors.initials: P
authors.lastname: Balabathula
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Bhattacharjee
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Thoma
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nolly
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Horton
authors.affiliation: Plough Center for Sterile Drug Delivery Systems, College of Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Gwendolyn D
authors.initials: GD
authors.lastname: Stornes
authors.affiliation: Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Jim Y
authors.initials: JY
authors.lastname: Wan
authors.affiliation: Biomedical Informatics, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Brooks
authors.affiliation: University Medical Dental School of New Jersey-Robert Wood Johnson, New Brunswick NJ, USA.
authors.forename: Gloria A
authors.initials: GA
authors.lastname: Bachmann
authors.affiliation: Department of Obstetrics and Gynecology, University of Rochester School of Medicine and Dentistry, Rochester NY, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Foster
authors.affiliation: Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis TN, USA.
authors.forename: Candace S
authors.initials: CS
authors.lastname: Brown
keywords: Capsaicin; Human pain model; Intradermal; Manufacture; Variability
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