Rapid and sensitive HPLC-MS/MS method for pharmacokinetic assessment of ribavirin in healthy Chinese.

A rapid and sensitive quantitative assay method was developed for determining ribavirin pharmacokinetic in human plasma. The chromatographic separation was achieved within 4.5 min using a SinoChrom ODS-BP column (4.6 x 150 mm, 5 microm) with acetonitrile-water (1 mmol/L ammonium acetate buffer, 0.1% formic acid; 15:85, v/v) at a constant flow rate of 0.8 mL/min. The MRM pairs were m/z 245.2 --> m/z 113.1 for ribavirin and m/z 226.1 --> m/z 152.1 for acyclovir (internal standard), respectively, with dwell times of 200 ms for each transition. The results showed calibration curve for ribavirin was linear over a concentration range of 1-1000 ng/mL. The lower limit of quantification (LLOQ) was 1 ng/mL ribavirin. Twenty healthy volunteers received a 300 mg oral dose of ribavirin. Blood samples were then collected up to 120 h postdosing. All plasma data were comodeled for ribavirin by using noncompartmental modeling. The single dose of ribavirin was well tolerated and no serious adverse effects occurred. The mean time to maximum concentration was about 1.25 h. The mean maximum concentration of drug in plasma for oral ribavirin was 250 ng/mL. The mean elimination half-life was 43.6 h. The present study describes a simple, specific, sensitive HPLC-MS/MS method for measuring plasma drug concentration and analyzing human pharmacokinetics of ribavirin.

[Association of polymorphism on HLA-DRB1*04 alleles with outcome of hepatitis B virus infection].

OBJECTIVE: To investigate the relation between the alleles of HLA-DRB1*04 and outcome of HBV infection. METHODS: The alleles of HLA-DRB1*04 were detected by polymerase chain reaction-sequence specific primer (PCR-SSP). The frequency of allele of HLA-DRB1*04 in four groups[106 asymptomatic HBsAg carriers (group ASC), 93 chronic hepatitis B patients (group CHB), 77 patients with hepatitis B cirrhosis and 102 cases of spontaneous recovery after HBV infection (control group)] were studied, and the frequency of that in different replication of HBV was also studied. RESULTS: The frequency of allele of HLA-RB1*04 in groups ASC, CHB and hepatitis B cirrhosis was markedly higher than that of control group (25.94%, 26.34%, 27.92% respectively versus 14.22%, P< 0.01); the frequency of HLA-DRB1*0401 in groups ASC, CHB and hepatitis B cirrhosis was also higher than that of control group (20.91%, 24.49%, 22.09% respectively versus 8.62%, P< 0.05, P< 0.01,P< 0.05 respectively); the frequency of HLA-DRB1*0405 in groups ASC, CHB and hepatitis B cirrhosis was lower than that of control group (3.64%, 2.04%, 3.49% respectively versus 15.52%, P< 0.01, P< 0.01, P< 0.05 respectively ). There was no statistical significance in the allele frequency of HLA-DRB1*04 among groups ASC, CHB and hepatitis B cirrhosis (P> 0.05), and the same result was observed in different replication of HBV (P> 0.05). CONCLUSION: HLA-DRB1*04 gene is one of the factors which determine the outcomes of HBV infection, while it has no influence on HBV replication.

A rapid and simple high-performance liquid chromatography method for the determination of human plasma levofloxacin concentration and its application to bioequivalence studies.

A high-performance liquid chromatography method with fluorescence detection (HPLC-FLD) for the determination of levofloxacin in human plasma is described. Neutralized with phosphate buffer (pH 7.0), the sample (0.1 mL) was extracted with dichlormethane (1 mL). After voltex-mixing and centrifuged at 3000g for 6 min at 4 degrees C, the upper aqueous layer was aspirated using a micro vacuum pump and the organic layer was directly transferred to a clean test tube without pipetting. The organic solvent was evaporated and the residues were reconstituted with the mobile phase. Levofloxacin and terazosin (internal standard, IS) were chromatographically separated on a C(18) column with a mobile phase containing phosphate buffer (pH 3.0, 10 mm), acetonitrile and triethylamine (76:24:0.076, v/v/v) at a flow rate of 1 mL/min. The analytes were detected using fluorescence detection at an excitation and emission wavelength of 295 and 440 nm, respectively. The linear range of the calibration curves was 0.0521-5.213 microg/mL for levofloxacin with a lower limit of quantitation (0.0521 microg/mL). The retention times of levofloxacin and terazosin were 2.5 and 3.1 min, respectively. Within- and between-run precision was less than 12 and 11%, respectively. Accuracy ranged from -6.3 to 4.5%. The recovery ranged from 86 to 89% at the concentrations of 0.0521, 0.5213 and 5.213 microg/mL. The present HPLC-FLD method is sensitive, efficient and reliable. The method described herein has been successfully used for the pharmacokinetic and bioequivalence studies of a levofloxacin formulation product after oral administration to healthy Chinese volunteers.

Drug resistance of infectious pathogens after liver transplantation.

BACKGROUND: Infection in liver recipients is related to high risk of transplantation failure and mortality. Infectious agents isolated from 55 liver recipients from January 2003 through June 2005 were studied to improve the anti-infectious therapy. METHODS: Pathogens were isolated from routine culture. K-B method was used to examine the drug susceptibility. Extended spectrum beta-lactamase, AmpC beta-lactamase and Van gene in E.coli were examined by the agar-dilution susceptibility test and Nitrocefin test. RESULTS: Thirty-nine of the 55 recipients got infection. The 513 strains of pathogens isolated from 1861 specimens were predominantly Gram negative bacteria and over 40% of them showed resistance to more than 4 drugs. The positive rates of extended spectrum beta-lactamse and AmpC beta-lactamse production in E.cloacae were 32.4% and 36.8%, in E.coli were 33.8% and 10.5%, but the rates of these 2 bacteria producing both lactamses were 24.3% and 7.0%. The beta-lactamse production rates of Enterococcus faecalis and Enterococcus faecium were 8.8% and 11.1%, and the resistance rates to vancomycin were 11.2% and 18.5%, respectively. CONCLUSIONS: Infectious pathogens isolated from liver recipients are potent and multiple drug resistant. ESBLs and AmpC beta-lactamases are the major factors associated with Gram negative drug resistance. The infection of Enterococcal species presents as a particular challenge.

Multiple dose pharmacokinetics of risperidone and 9-hydroxyrisperidone in Chinese female patients with schizophrenia.

AIM: To study the multiple dose clinical pharmacokinetics of risperidone and its main active metabolite, 9-hydroxyrisperidone, in Chinese female patients with schizophrenia. METHODS: The subjects were 23 Chinese female inpatients aged 18-65 years who met the CCMD-III (third revision of the Chinese Criteria of Mental Disorders) criteria for schizophrenia. Subjects were tested after 17 d of treatment with 2 mg risperidone twice daily. Plasma concentrations of risperidone and 9-hydroxy-risperidone were assayed by using validated high performance liquid chromatography-mass spectrometry (HPLC-MS) methods. RESULTS: Risperidone was rapidly absorbed (Tmax was 1.6 h) and its T1/2 in plasma was short (3.2 h). 9-hydroxy-risperidone was quickly metabolized from the parent drug with a mean Tmax of 2.5 h. It had a long half-life of 24.7 h. The C(ss)(av) of risperidone and 9-hydroxy-risperidone were 36.9+/-33.1 and 110.6+/-30.5 microg x h x L(-1), respectively, and the AUC(ss)0-12 were 443.2+/- 397.4 and 1327.2+/- 402.3 microg x h x L(-1), respectively. CL/F and V/F of risperidone were 8.7+/- 6.2 L/h and 34.1+/- 24.3 L, respectively. Interindividual variations for pharmacokinetic parameters were quite large for risperidone. All 23 subjects experienced high prolactin levels when treated with risperidone. However there was no correlation between prolactin level and the concentration of risperidone, 9-hydroxy-risperidone, or the active moiety. CONCLUSION: Risperidone showed large interindividual variations in pharmacokinetics. Administration of risperidone resulted in high serum prolactin levels. The results indicate that systemic exposure to risperidone and 9-hydroxy-risperidone in female Chinese schizophrenic patients is higher relative to published data for white Caucasian patients. Larger studies regarding the PK/PD relationship may be required to develop a reasonable clinical dosage regimen for Chinese female patients.

[Pathogenic characters of infected bacteria after liver transplantation].

OBJECTIVE: To analyze the main pathogens of infection after the liver transplantation and their antibiotic resistant patterns. METHODS: The main pathogens of infection after the liver transplantation were retrospectively analyzed. Using 3-dimensional tests, ESBLs (extended-spectrum beta-lactamase), and AmpC were detected among the Gram negative bacilli. beta-Lactamase and Van gene in Enterococcus were determined by the standard agar dilution susceptibility tests and Nitrocefin respectively. RESULTS: The main infected strains were Enterococcus faecalis (15.0%), Enterobacter cloacae (13.9%), fungus (13.3%), and Escherichia coli (10.7%) after the liver transplantation. Among them, 32.4% of Enterobacter cloacae and 36.8% of Escherichia coli produced ESBLs; 33.8% of Enterobacter cloacae and 10.5% of Escherichia coli. produced AmpC beta-lactamases. The detectable rate of VanA gene in Enterococcusfaecalis and Enterococcus faecium was 7.5% and 11.1%; VanB was 3.8% and 7.4%; VanC was 1.3% and 0, respectively. CONCLUSION: The infection mainly occurs in the intestinal tract after the liver transplantation. The production of ESBLs and AmpC beta-lactamases is the main mechanism of antibiotic resistance. The increased detectable rate of vancomycin-resistant Enterococcus should be paid attention to.