title: A sensitive LC-MS/MS method for quantifying capsaicin and dihydrocapsaicin in rabbit plasma and tissue: application to a pharmacokinetic study.
abstract: Prescription and nonprescription products for topical management of pain, including cream, lotion and patch forms, contain capsaicin (CAP) and dihydrocapsaicin (DHC). There are few in vivo studies on absorption, bioavailability and disposition of CAP and DHC. We established a sensitive and rapid LC-MS/MS assay to determine CAP and DHC levels in rabbit plasma and tissue. Bio-samples prepared by liquid-liquid extraction using n-hexane-dichloromethane-isopropanol (100: 50: 5, v/v/v) mixture were separated by isocratic chromatography with an Extend C18 column. The mobile phase was acetonitrile-water-formic acid (70: 30: 0.1, v/v/v). The method was linear from 0.125 to 50 ng/mL for a 100 μL bio-sample, and the lower quantification limit was 0.125 ng/mL. Total run time to analyze each sample was 3.5 min. We used this validated method to study pharmacokinetics and tissue distribution of CAP gel administered topically to rabbits. A very small amount of CAP and DHC was absorbed into the systemic circulation. The highest plasma concentration was 2.39 ng/mL, and the mean peak plasma concentration value after 12 h of CAP gel application was 1.68 ng/mL. Drug concentration in treated skin was relatively high, with low concentration in other tissues. Thus, topical CAP gel had strong local effects and weaker systemic effects.
authors.affiliation: Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang, 110016, People's Republic of China; Beijing Institute of Pharmacology and Toxicology, 27 Taiping Road, Beijing, 100850, People's Republic of China.
authors.forename: Dimin
authors.initials: D
authors.lastname: Wang
authors.forename: Fanhua
authors.initials: F
authors.lastname: Meng
authors.forename: Lin
authors.initials: L
authors.lastname: Yu
authors.forename: Lu
authors.initials: L
authors.lastname: Sun
authors.forename: Lili
authors.initials: L
authors.lastname: Sun
authors.forename: Jifen
authors.initials: J
authors.lastname: Guo
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004355:Drug Stability; D007668:Kidney / Q000737:chemistry; D008099:Liver / Q000737:chemistry; D008168:Lung / Q000737:chemistry; D008297:Male; D010949:Plasma / Q000737:chemistry; D011817:Rabbits; D012680:Sensitivity and Specificity; D013154:Spleen / Q000737:chemistry; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014018:Tissue Distribution
chemical_list: D002211:Capsaicin; C012906:dihydrocapsaicin
keywords: LC-MS/MS; capsaicin; dihydrocapsaicin; pharmacokinetic; tissue distribution