The minimum concentration of menthol to evoke cold sensation (CS) at the menthol application site was determined as the cold sensation detection threshold (CDT). The conventional clinical grading system was used to assess the severity of neurotoxicity in relation to CDT. Patients also completed self-report ratings of their sensitivity to cold sensation, and the results of these objective and subjective findings were compared. Materials and Methods Subjects and treatment regimen A total of 76 subjects were enrolled Inhibitors,research,lifescience,medical in this study: 40 healthy subjects (24 women, 16 men; median age, 54 years; range, 22–85) and 36 patients (22 women, 14 men;

median age, 57 years; range, 33–80) with advanced-stage colorectal cancer who received standard oxaliplatin in combination

with infusional 5-fluorouracil/leucovorin (FOLFOX) as a first-line treatment. In the FOLFOX regimens, oxaliplatin (modified FOLFOX 6, 85 mg/m2) was given intravenously over 2 h on day 1 in conjunction with leucovorin (200 mg/m2) Inhibitors,research,lifescience,medical and followed by a 5-fluorouracil (5-FU) bolus injection Inhibitors,research,lifescience,medical (400 mg/m2), repeated every 2 weeks. A continuous 24-h infusion of 5-FU (600 mg/m2) was given over days 1 and 2. On day 2, leucovorin (200 mg/m2; over 2 h) and 5-FU bolus (400 mg/m2) were given intravenously. The subjects did not consume any spicy food 1 day prior to testing. They were also asked to refrain from eating, drinking, chewing gum, brushing their teeth, and using mouthwash for 2 h before testing, and we verified

that the participants had observed these restrictions at the beginning Inhibitors,research,lifescience,medical of each session. The present study was conducted in accordance with the Declaration of Helsinki for the care for human studies adopted by the Ethics Committee of Higashi-Asahikawa Hospital. All patients provided written informed consent. Assessment of menthol in experiments 1 and 2 A solution of 5% L-menthol (from dry crystals; MERCK, Tokyo, Japan) was Inhibitors,research,lifescience,medical prepared in warm distilled water (41°C) at the time of application, and this solution was further diluted in warm distilled water to yield menthol solutions of 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, and 1% (0.32 mM, 0.64 mM, 3.2 mM, 6.4 mM, 32 mM, and 64 mM, respectively). These solutions were topically applied with a cotton swab to the dorsal anterior tongue in two experiments (Fig. 1a). In experiment 1, the six different menthol solutions were administered to healthy subjects and patients with colon cancer prior to oxaliplatin exposure, and their subjective ratings of cold sensitivity were recorded. In experiment through 2, patients were selleck inhibitor examined for alterations in the menthol-induced cold sensations before and 5–6 h after the patients receiving individual oxaliplatin infusions. The menthol concentrations used in this study were based on a previous human study (Albin et al. 2008). The vehicle control (warmed distilled water) was applied in the same manner. Figure 1 Effects of menthol on cold sensation and the detection threshold in healthy human subjects.