title: High-performance liquid chromatographic analysis of trimethoprim and sulfamethoxazole in microliter volumes of chinchilla middle ear effusion and serum.
abstract: A reversed-phase high-performance liquid chromatographic procedure was developed to analyze 25-microliters volumes of chinchilla middle ear effusion and 50-microliters volumes of serum for trimethoprim and sulfamethoxazole. The small sample volumes were dictated by the chinchilla model of otitis media and our need to collect multiple samples over a 12-h drug dosing interval. The drugs were separated on a cyanopropylsilane column using acetonitrile-40 mM sodium phosphate, (16:84, v/v), pH 4.8. Trimethoprim and the internal standard were detected at 230 nm while sulfamethoxazole was detected at 250 nm. Middle ear effusion and serum samples were extracted with ethyl acetate-dichloromethane (25:75, v/v). The limit of quantitation was 0.5 micrograms/ml for sulfamethoxazole and 0.1 micrograms/ml for trimethoprim (coefficient of variation less than 20%), the limit of detection 0.25 and 0.05 micrograms/ml, respectively. Middle ear and serum samples of chinchilla with experimentally induced otitis media receiving 10 mg/kg trimethoprim and 50 mg/kg sulfamethoxazole intramuscularly were collected over a 12-h period and analyzed. All statistics that validate the analytic method are reported.
authors.affiliation: Department of Pharmacy Practice, College of Pharmacy, University of Minnesota, Minneapolis 55455.
authors.forename: G R
authors.initials: GR
authors.lastname: Erdmann
authors.forename: D M
authors.initials: DM
authors.lastname: Canafax
authors.forename: G S
authors.initials: GS
authors.lastname: Giebink
mesh_terms: D000818:Animals; D002682:Chinchilla; D002851:Chromatography, High Pressure Liquid; D010033:Otitis Media / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013420:Sulfamethoxazole / Q000032:analysis* / Q000097:blood; D014295:Trimethoprim / Q000032:analysis* / Q000097:blood
chemical_list: D014295:Trimethoprim; D013420:Sulfamethoxazole