Standardized method for solubility and storage of capsaicin-based solutions for cough induction

Abstract

BackgroundPreparation of inhaled capsaicin solutions for cough induction varies greatly from one lab to another, which creates inconsistencies between tussigenic challenge results. The addition of Tween to these capsaicin solutions provides increased solubility and stability; however, the foul taste of Tween makes inhaling the solution for any prolonged period of time unpleasant. We sought to create a standard method for preparing soluble and stable capsaicin-based solutions (in 10% ethanol/water), without the addition of Tween.MethodsCapsaicin solutions were created at concentrations ranging from 0 to 500 μM in a variety of solvent systems, with and without Tween. Samples were stored in four different environments (-20°C, 3°C, and room temperature, protected from light; and room temperature, exposed to light) to test stability. Detection of capsaicin was carried out by UV absorption. A Grubb’s test was performed on all data to remove statistical outliers.ResultsSimilar capsaicin concentrations were seen for solutions prepared with or without Tween (Tween provided a slight increase in solubility), with neither solvent system providing complete solubility. Of the four environments tested, storing capsaicin solutions at 3°C while protected from light afforded the greatest stability, for a minimum of 30 weeks.ConclusionWe recommend the use of a 10% ethanol/water solvent system without Tween in the preparation of capsaicin solutions for tussigenic challenges. While this solvent system does not provide complete solubility, we have detailed a method for capsaicin solution preparation that will account for this loss of solubility, while maintaining a solution that is Tween-free and safe for human inhalation.

Functional Measurement of Respiratory Muscle Motor Behaviors Using Transdiaphragmatic Pressure

“…In general the amplitude for a sneeze will be at about 2 times that of eupnea. Alternative concentrations of capsaicin may be considered (28). Note that you must clean the syringe thoroughly with water and 70% alcohol after use.…”

Laboratory Safety of Capsaicin Inhalation in Healthy Younger and Older Populations Potential Template for Inhalation Research

“…The investigation employs a more than 99% pure pharmaceutical grade capsaicin via an Investigational New Drug (IND 69,642) submission [21]. A Registered Pharmacist mixes individual pharmaceutical grade capsaicin doses because purity and solubility are essential qualities for the capsaicin stock solution and are prerequisites for accurate dilute capsaicin doses [5,[22][23][24]. Analyses of prepared capsaicin solutions are by high performance liquid chromatography (HPLC); other investigators employ ultraviolet absorption spectrophotometry to determine capsaicin concentrations [22].…”

Preliminary Evidence of Reduced Urge to Cough and Cough Response in Four Individuals following Remote Traumatic Brain Injury with Tracheostomy

“…The aerosols were delivered through a DeVilbiss T piece connected to a dosimeter programmed to deliver an aerosolized solution (delivery duration of two seconds) upon inhalation. Participants completed a capsaicin challenge with three randomized blocks of 0 (nonstimulus control solution), 50, 100, 200, and 500 μ M capsaicin dissolved in a base solution of 80% physiological saline and 20% ethanol [ 31 ]. Note that only participants with TBI (no HCs) were presented with an additional three presentations of concentration of 500 μ M capsaicin in solution (randomly presented among all other concentrations) in order to explore response to stimulation above 200 μ M, should responses be dampened in those with TBI.…”