A simple and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was de-veloped and validated for simultaneous determination of acetaminophen and oxycodone in human plasma. Acetaminophen-d4 and oxycodone-d3 were used as internal standards. The challenge en-countered in the method development that the high plasma concentration level of acetaminophen made the MS response saturated while the desired lower limit of quantification (LLOQ) for oxycodone was hard to reach was well solved. The analytes were extracted by protein precipitation using acetonitrile. The matrix effect of the analytes was avoided by chromatographic separation using a hydrophilic C18 column coupled with gradient elution. Multiple reaction monitoring in positive ion mode was performed on tandem mass spectrometer employing electrospray ion source. The calibration curves were linear over the concentration ranges of 40.0–8000 ng/mL and 0.200–40.0 ng/mL for acetaminophen and oxycodone, respectively. This method, which could contribute to high throughput analysis and better clinical drug monitoring, was successfully applied to a pharmacokinetic study in healthy Chinese volunteers.

OBJECTIVE: To classify the external auditory canal cholesteatoma(EACC) by high-resolution temporal bone CT scans and the clinical findings of the patients, and to discuss the clinical and imaging characteristics and the surgical management of the extensive EACC. METHOD: A retrospective study was carried out among 56 patients (58 ears) with EACC and their clinical data were carefully analyzed. We classified EACC as the extensive type and the localized type. The operation strategy depended on the extent of lesion. All cases were followed up for 1 to 6 years after surgery. RESULT: There were 31 patients with localized EACC, 2 with no bone erosion and 29 (31 ears) with bone erosion within external auditory canal, and 25 patients with extensive EACC, 16 with bone erosion of intra temporal bone and 9 with bone erosion of extra temporal bone. Among all the 25 patients with the extensive type, the most common symptoms were otorrhea, otalgia and hearing loss, with 25, 23, 22 cases, respectively. The tympanic membrane (TM) was intact in 23 patients and perforated in two. The mastoid air cells in 23 patients were involved by the lesion, as well as tympanic antrum in eight, tympanic cavity in two, sigmoid sinus bony wall in five, mastoid segment of facial canal in four, and temporomandibular joint in two patients. Twenty patients underwent modified radical mastoidectomy, only one underwent reconstruction of ossicular chain, and four underwent canaloplasty. The average time of ear dry after surgery was 29 days. The postoperative hearing was improved by an average of 15 dB. No recurrence except for one patient was found during the follow-up period. CONCLUSION It was of important clinical significance to classify EACC as the extensive type and the localized type. The extensive EACC was misdiagnosed easily because of the complicated clinical manifestations. The classification was helpful for the diagnosis and the selection of surgery strategy of EACC.
Adolescent ; Adult ; Aged ; Child ; Cholesteatoma ; classification ; diagnosis ; surgery ; Ear Canal ; Female ; Humans ; Male ; Middle Aged ; Otologic Surgical Procedures ; Retrospective Studies ; Young Adult