Four-year study of lamivudine and adefovir combination therapy in lamivudine-resistant hepatitis B patients: influence of hepatitis B virus genotype and resistance mutation pattern

To investigate the efficacy of long-term lamivudine (3TC) and adefovir dipivoxil (ADV) combination therapy in 3TC-resistant chronic hepatitis B virus (HBV) infected patients, we analysed 28 3TC-resistant patients treated with the combination therapy during 47 months (range, 9-75). At 12, 24, 36, and 48 months, the rates of virological response with undetectable HBV DNA (≤ 2.6 log copies/mL) were 56, 80, 86, and 92%, respectively. Among 17 hepatitis B e antigen (HBeAg)-positive patients, HBeAg disappeared in 24% at 12 months, 25% at 24 months, 62% at 36 months, and 88% at 48 months. When HBV genotypes were compared, patients with genotype B achieved virological response significantly more rapidly than those with genotype C (P=0.0496). One patient developed virological breakthrough after 54 months, and sequence analysis of HBV obtained from the patient was performed. An rtA200V mutation was present in the majority of HBV clones, in addition to the 3TC-resistant mutations of rtL180M+M204V. The rtN236T ADV-resistant mutation was observed in only 25% clones. In vitro analysis showed that the rtA200V mutation recovered the impaired replication capacity of the clone with the rtL180M+M204V mutations and induced resistance to ADV. Moreover, rtT184S and rtS202C, which are known entecavir-resistant mutations, emerged in some rtL180M+M204V clones without rtA200V or rtN236T. In conclusion, 3TC+ADV combination therapy was effective for most 3TC-resistant patients, especially with genotype B HBV, but the risk of emergence of multiple drug-resistant strains with long-term therapy should be considered. The mutation rtA200V with rtL180M+M204V may be sufficient for failure of 3TC+ADV therapy.

Metabolism of ipecac alkaloids cephaeline and emetine by human hepatic microsomal cytochrome P450s, and their inhibitory effects on P450 enzyme activities

In this study, we identified the metabolites and the CYP forms that are specifically involved in emetine O-demethylation in human liver microsomes, and cleared the inhibitory potential of cephaeline and emetine on the activity of the major drug-metabolizing CYP enzymes. Incubation of emetine with human liver microsomes yielded three metabolites identified by using HPLC by comparison of the retention time with the authentic sample of cephaeline, 9-O-demethylemetine and 10-O-demethylemetine. CYP3A4 and CYP2D6 were able to metabolize emetine to cephaeline and 9-O-demethylemetine, and CYP3A4 also participated in metabolizing emetine to 10-O-demethylemetine. Cephaeline and emetine inhibited probe substrates metabolism. IC50 for cephaeline against CYP2D6 and CYP3A4 were 121 and 1000 microM, respectively. For the emetine, CYP2D6 and CYP3A4 were 80 and 480 microM, respectively. Inhibition constants (Ki) for both compounds on the CYP2D6 and CYP3A4 activities were determined by graphic analysis of Dixon plots at various concentrations. The obtained Ki values of cephaeline for CYP2D6 and CYP3A4 were 54 and 355 microM, respectively, and the values of emetine were 43 and 232 microM, respectively. We concluded that these in vitro inhibitions of cephaeline and emetine would hardly increase plasma concentrations of co-administered drugs in clinical therapy.

Simultaneous determination of byak-angelicin and oxypeucedanin hydrate in rat plasma by column-switching high-performance liquid chromatography with ultraviolet detection

A simple and sensitive column-switching HPLC method was developed for the simultaneous determination of two furocoumarin compounds, byak-angelicin and oxypeucedanin hydrate, which are the main components of hot water extract of Angelica dahurica root (AE), in rat plasma. Plasma sample was simply deproteinated with perchloric acid. After centrifugation, the supernatant was injected into a column-switching HPLC system consisting of a clean-up column (Symmetry Shield RP 8, 20x3.9 mm I.D.) and analytical column (Symmetry C18, 75x4.6 mm I.D.) which were connected with a six-port switching valve. The flow-rate of the mobile phase (acetonitrile-water, 20:80) was maintained at 1 ml/min. Detection was carried out at wavelength 260 nm with a UV detector. The column temperature was maintained at 40 degrees C. The calibration curves of byak-angelicin and oxypeucedanin hydrate were linear over the ranges 19.6 to 980 ng/ml (r2>0.997). The accuracy of these analytes was less than 4.4%. The intra- and inter-day relative standard deviations of byak-angelicin and oxypeucedanin hydrate were within 12.0% and 12.7%, respectively. The present method was applied for the analysis of plasma concentration from rats after administration of AE.

Alpha-fetoprotein microheterogeneity: a potential biochemical marker for Down's syndrome

Our purpose was to examine the utility of analyzing alpha-fetoprotein (AFP) microheterogeneity assessed by lectin affinity in Down's syndrome (DS) screening. Maternal sera and amniotic fluids were collected from 18 women who were carrying DS fetuses and 70 unaffected pregnancies around 16 weeks of gestation. The percentages of AFP which reacted with Lens culinaris agglutinin (AFP-L2,3) were determined by lectin affinity electrophoresis. AFP-L2,3 levels were significantly increased (P<0.0001) in both maternal serum and amniotic fluid from DS-affected versus unaffected pregnancies. The fractional areas under the receiver operating characteristic curves were 0.835 and 0.700 (P=0.106) for AFP-L3 and AFP MoM (multiples of the median) in maternal serum. No correlation was found between AFP-L3 and AFP MoM in maternal serum (r=0.006). Our data suggest that the measurement of AFP-L3 in maternal serum is a potential biochemical marker for DS.

Baicalin, the predominant flavone glucuronide of scutellariae radix, is absorbed from the rat gastrointestinal tract as the aglycone and restored to its original form

When baicalin was orally administered to conventional rats, it was detected in their plasma for 24 h after administration, but baicalein, the aglycone of baicalin, was not detected. However, when baicalin was given to germ-free rats, only a small amount of baicalin was detected in their plasma within 2 h after the administration, its AUC0-lim (the area under the concentration-time curve from 0 to last determination time) being 12.0% of that in conventional rats. Subsequently, a considerable amount (55.1 +/- 6.2%) of baicalin was recovered from the gastrointestinal tract even 4 h after administration. When baicalein was orally administered to conventional rats, however, baicalin appeared rapidly in their plasma at an AUC0-lim value similar to that obtained after oral administration of baicalin, despite the absence of baicalein in plasma. When intestinal absorption was evaluated by the rat jejunal loop method, baicalein was absorbed readily, but only traces of baicalin were absorbed. Moreover, in conventional rats a small amount (13.4 +/- 3.1%) of baicalin and an appreciable amount (21.9 +/- 3.4%) of baicalein were recovered from the gastrointestinal tract even 4 h after oral administration of baicalin, but only a small amount (3.93 +/- 1.43%) of baicalein was detected in the intestinal tract 1 h after administration of baicalein. Baicalin was transformed to baicalein readily by the rat gastric and caecal contents. When baicalin was administered orally to conventional rats, an appreciable amount of baicalein was recovered in their gastrointestinal tracts. Moreover, baicalein was efficiently conjugated to baicalin in rat intestinal and hepatic microsomes. These results indicate that baicalin itself is poorly absorbed from the rat gut, but is hydrolysed to baicalein by intestinal bacteria and then restored to its original form from the absorbed baicalein in the body.

Interaction of drugs and Chinese herbs: pharmacokinetic changes of tolbutamide and diazepam caused by extract of Angelica dahurica

The inhibitory effects of Angelica dahurica root extract on rat liver microsomal cytochrome P450 and drug-drug interactions were studied. The 2alpha- and 16alpha-hydroxylase activity of testosterone were most strongly inhibited, with 17.2% and 28-5% of their activity remaining, respectively, after oral administration of A. dahurica extract at a 1 g kg(-1) dose. 6beta-Hydroxylase activity was also inhibited, with 70% of its activity remaining, under the same conditions. In addition, treatment with the extract inhibited the metabolism of tolbutamide, nifedipine and bufuralol. These results showed that the extract inhibited the various isoforms of cytochrome P450 such as CYP2C, CYP3A and CYP2D1. The A. dahurica extract delayed elimination of tolbutamide after intravenous administration at a 10 mg kg(-1) dose to rats. Thus, the extract altered the liver intrinsic clearance. It had little effect, however, on the pharmacokinetic parameters of diazepam after intravenous administration at 10 mg kg(-1). Since diazepam showed high clearance, it underwent hepatic blood flow rate-limited metabolism. Therefore, the change of intrinsic clearance had little effect on hepatic clearance. However, the Cmax value after oral administration of diazepam with extract treatment was four times that with non-treatment. It was suggested that the first-pass effect was changed markedly by the extract. High-dose (1 g kg(-1)), but not low dose (0.3 g kg(-1)), administration of A. dahurica extract increased significantly the duration of rotarod disruption following intravenous administration of diazepam at 5 mg kg(-1). It was concluded that administration of A. dahurica extract has the potential to interfere with the metabolism, by liver cytochrome P450, of other drugs.

A study on the lectin reactivity of alpha-fetoprotein produced by hepatoid adenocarcinomas and yolk sac tumors

The carbohydrate structure of glycoproteins is considered to be tissue-specific or cell type-specific, but there have been no reports on the differences of the carbohydrate structure of alpha-fetoproteins (AFPs) produced by histologically identical tumors in different tissues. The lectin affinity electrophoresis of hepatoid adenocarcinomas and yolk sac tumors from different organs suggested that either the tumor heterogeneity or the tissue specificity is possibly involved, the lectin reactivity of the AFP sugar chain structure produced by the tumors in different tissues.

In-vivo assessment of extrahepatic metabolism of paeoniflorin in rats: relevance to intestinal floral metabolism

The extraction ratios of paeoniflorin in gut wall (EG), liver (EH) and lung (EL) were assessed by comparing AUCs after various routes of its administration to estimate the first-pass effects and the metabolism by intestinal flora. Pulmonary extraction ratio of paeniflorin was assessed by comparing AUCs calculated from venous and arterial plasma concentrations after its intravenous administration (0.5 mg kg-1). The mean pulmonary extraction ratio was estimated to be 0.06. The hepatic extraction ratio (EH was assessed by comparing AUCs after intraportal and intravenous administrations (0.5 and 5 mg kg-1). The plasma concentration profiles of paeoniflorin after intraportal administration were very close to those after intravenous administration, suggesting a negligible hepatic extraction ratio of paeoniflorin. The AUC value after intraperitoneal administration (0.5 mg kg-1) was greater than that after intraportal or intravenous administration. This finding suggests that paeoniflorin is not metabolized in the gut wall. The transference of paeoniflorin from the serosal side to the mucosal side was evaluated by the in-vitro everted sac method. The low intestinal permeability (19.4% at 60 min) was demonstrated by the comparison with phenobarbital (63.1% at 60 min). We conclude that paeoniflorin is not metabolize by gut wall, liver and lung, its poor absorption from the intestine results in extremely low bioavailability and the unabsorbed fraction of paeoniflorin is degraded by the intestinal flora.

Antiarrhythmic effects of an aconitine-like compound, TJN-505, on canine arrhythmia models

We examined the effects of an aconitine-like compound, TJN-505 (1alpha-16beta-dimethoxy-20-ethyl-14alpha-(4-methox ybenzoyloxy)-aconitan-8,13-diol hydrochloride), on canine arrhythmias provoked by digitalis, two-stage coronary ligation, adrenaline, programmed electrical stimulation, or aconitine. TJN-505 (2-2.5 mg/kg i.v.) suppressed digitalis-, two-stage coronary ligation- and adrenaline-induced ventricular arrhythmias. The antiarrhythmic plasma concentrations (IC50) of TJN-505 for these arrhythmia models were 1.26, 0.94 and 1.31 microg/ml, respectively. TJN-505 (2 mg/kg i.v. followed by the infusion of 0.1 mg/kg per min) prolonged PR, QRS, QTc and JTc intervals and the ventricular effective refractory period and reduced the incidence of programmed electrical stimulation-induced arrhythmias in dogs with 7-day-old myocardial infarction (P < 0.05). TJN-505 (2 mg/kg i.v.) also suppressed the aconitine-induced atrial arrhythmias. In conclusion, TJN-505 suppressed various canine ventricular and atrial arrhythmias and seems to act as a blocker of multiple channels.

Bioavailability study of glycyrrhetic acid after oral administration of glycyrrhizin in rats; relevance to the intestinal bacterial hydrolysis

To clarify the metabolic fate of glycyrrhizin when orally ingested, we investigated the bioavailability of glycyrrhetic acid, the aglycone of glycyrrhizin, after intravenous or oral administration of glycyrrhetic acid (5.7 mg kg-1, equimolar to glycyrrhizin) or glycyrrhizin (10 mg kg-1) at a therapeutic dose in rat. Plasma concentration of glycyrrhetic acid rapidly decreased after its intravenous administration, with AUC of 9200 +/- 1050 ng h mL-1 and MRT of 1.1 +/- 0.2 h. The AUC and MRT values after oral administration were 10600 +/- 1090 ng h mL-1 and 9.3 +/- 0.6 h, respectively. After oral administration of glycyrrhizin, the parent compound was not detectable in plasma at any time, but glycyrrhetic acid was detected at a considerable concentration with AUC of 11700 +/- 1580 ng h mL-1 and MRT of 19.9 +/- 1.3 h, while glycyrrhetic acid was not detected in plasma of germ-free rats at 12 h after oral administration of glycyrrhizin. The AUC value of glycyrrhetic acid after oral administration of glycyrrhizin was comparable with those after intravenous and oral administration of glycyrrhetic acid, indicating a complete biotransformation of glycyrrhizin to glycyrrhetic acid by intestinal bacteria and a complete absorption of the resulting glycyrrhetic acid from intestine. Plasma glycyrrhizin rapidly decreased and disappeared in 2 h after intravenous administration. AUC and MRT values were 2410 +/- 125 micrograms min mL-1 and 29.8 +/- 0.5 min, respectively. Plasma concentration of glycyrrhetic acid showed two peaks a small peak at 30 min and a large peak at 11.4 h, after intravenous administration of glycyrrhizin, with an AUC of 15400 +/- 2620 ng h L-1 and an MRT of 18.8 +/- 1.0 h. The plasma concentration profile of the latter large peak was similar to that of glycyrrhetic acid after oral administration of glycyrrhizin, which slowly appeared and declined. The difference of MRT values (19.9 and 9.3 h) for plasma glycyrrhetic acid after oral administration of glycyrrhizin and glycyrrhetic acid suggests the slow conversion of glycyrrhizin into glycyrrhetic acid in the intestine.

Determination of schizandrin in human plasma by gas chromatography-mass spectrometry

Schizandrin (SZ) is one of the lignan components from Schisandra fruits. A highly sensitive and precise method for the determination of SZ in human plasma was developed involving selected-ion monitoring with gas chromatography-mass spectrometry using a fused-silica capillary column. A 0.1-ml plasma sample was used for solid-phase extraction. A good linear relationship was obtained in the concentration range studied (2.0-500 ng/ml) and the method was sufficiently accurate and precise to support clinical pharmacokinetic studies. After oral administration of SZ at a dose of 15 mg to healthy male subjects, the average value of the maximum plasma concentration of SZ was 96.1 +/- 14.1 ng/ml. The plasma concentration of this substance could be monitored for 8 h after administration.

Absorption and excretion of paeoniflorin in rats

The absorption and excretion of paeoniflorin after intravenous and oral administration was studied in rats to evaluate the significance of paeoniflorin in the pharmacological action of Paeony root. The plasma concentration of paeoniflorin after intravenous administration at the doses of 0.5, 2.0 and 5.0 mg kg-1 rapidly decreased, simulated by a biexponential curve, with mean terminal half-lives of 11.0, 9.9 and 12.6 min, respectively. The Vdss values were 0.332, 0. 384 and 0.423 L kg-1 and the CLtot values were 26.1, 31.2 and 30.3 mL min-1 kg-1 at each dose. When given orally at the same doses, the absolute bioavailability values (F) determined by the AUC were 0.032, 0.033 and 0.038, respectively. The cumulative urinary and faecal excretions of paeoniflorin at the dose of 5 mg kg-1 after intravenous administration were 50.5 and 0.22% of the dose within 72 h, and 1.0 and 0.08% of the dose after oral administration within 48 h, respectively. Cumulative biliary excretion after intravenous or oral administration at a dose of 0.5 mg kg-1 was 6.9 and 1.3% of the dose within 24 h, respectively. The total CLR and CLB value after intravenous dosing was less than the CLtot value. These findings suggest that paeoniflorin is metabolized in other organs as well as in the liver. We conclude that paeoniflorin absorbed is excreted mainly in urine, it has a low bioavailability and the metabolites may be involved in the pharmacological action of Paeony root.

Determination of baicalin and baicalein in rat plasma by high-performance liquid chromatography with electrochemical detection

A rapid and sensitive method, using electrochemical detection, has been developed for the determination of baicalin and baicalein, the flavonoid of Scutellariae radix, in rat plasma. Following separation by high-performance liquid chromatography, baicalin and baicalein were oxidized at a glassy carbon electrode to permit selective electrochemical detection. Absolute detection limits were found to be 5 ng/ml from 50 microliters of plasma for baicalin and 2 ng/ml from 100 microliters of plasma for baicalein. The resulting assays were suitable for pharmacokinetic studies of baicalin and baicalein in rats.

[Determination of gomisin A (TJN-101) and its metabolite in rat serum by gas chromatography-mass spectrometry]

Gomisin A (TJN-101) is one of the lignan components isolated from Schisandra Fruits. A high sensitive and precise method for the determination of TJN-101 and its major metabolite (Met. B) in the rat serum was developed by selected ion monitoring (SIM) with gas chromatography-mass spectrometry (GC/MS) using a fused silica capillary column (SPB-1, Supelco). A 100 microliter serum sample was used for the solid phase extraction. The calibration curves of TJN-101 and Met.B both showed a good linearity between 2.0 and 2000.0 ng/ml. The analytical precision (intra-assay, C.V. less than 4.7%), recoveries (98.4 +/- 10.1%), and detection limit (2 ng/ml) of TJN-101 indicated that this system was suited for the determination of TJN-101 in biological fluid. In case of Met.B, the same results as TJN-101, were obtained. After oral administration of TJN-101 at a dose of 10 mg/kg to male rats, the average values of the maximal serum concentration of TJN-101 and Met.B were 1446.1 +/- 131.8 and 317.4 +/- 18.5 ng/ml, respectively. The serum concentrations of these substances could be monitored sufficiently for 8 h after dosing.

[Effects of Shosaiko-to-go-keishikashakuyaku-to (TJ-960) on the valproic acid induced anomalies of rat fetuses]

Shosaiko-to-go-keishikashakuyaku-to (TJ-960) is an extract of nine herbal drugs (Paeoniae radix, Cinna momi cortex, Bupleuri radix, Zingiberis rhizoma, Glycyrrhizae radix, Ginseng radix, Scutellariae radix, Pinelliae tuber and Zizyphi fructus) that has a potent anticonvulsant action. The rat fetuses treated orally with TJ-960 during the organogenesis period (days 7-17 of gestation) revealed no anomalies (up to 3000 mg/kg/day). When TJ-960 was co-administered with sodium valproate (VPA, 400 mg/kg) during the organogenesis period, embryonic resorption, fetal body weight, ossification and skeletal variation or anomalies induced by VPA were markedly reduced. The maternal plasma and embryonic concentration of VPA with TJ-960, however, were not significantly different from VPA alone. These results suggest that TJ-960 has protective effects against the teratogenicity of VPA.