Hepatic Recovery Ratio Research Articles

Pharmacokinetic Characteristics and Hepatic Distribution of IH-901, a Novel Intestinal Metabolite of Ginseng Saponin, in Rats

We investigated the pharmacokinetic characteristics of 20- O-(beta-D-glucopyranosyl)-20(S)-protopanaxadiol (IH-901), a metabolite that is formed by intestinal bacteria, after its intravenous (i.v.) or oral administration in rats. We developed an LC/MS/MS-based method to analyze IH-901 levels in plasma, bile, urine and tissue homogenates and validated its use in a pharmacokinetic study. After i.v. administration of 3 - 30 mg/kg IH-901, it disappeared rapidly from the plasma at alpha phase followed by slow disappearance at beta phase (t(1/2,)(alpha) of 0.042 - 0.055 h and t (1/2,)(beta) of 6.98 - 10.6 h, respectively). The oral route slightly prolongs IH-901 plasma levels (terminal phase t(1/2) of 26.1 h) yet leads to a bioavailability of only 4.54 %. Of the various organs tested, the liver contained the majority of the i.v. bolus or orally administered IH-901, and liver IH-901 levels shortly after i.v. administration were 6-fold higher than the initial plasma concentration. The R(h) (hepatic recovery ratio) was calculated to be 0.417, and the uptake clearance (CL(uptake)) for i.v. administered IH-901 was 0.401 mL.min(-1).g liver(-1). Additionally, IH-901 is mostly excreted into the bile, since 40.5 % of the i.v.-administered dose (30 mg/kg) was recovered in the bile within 6 h, and only 15 % was found in the urine. Moreover, at steady state after i. v. infusion of IH-901, C(ss,liver) was about 11.3-fold higher than C(ss,plasma), whereas C(ss,bile) was about (1/2)-fold lower than C(ss,liver). These results indicated that the liver is largely responsible for removing IH-901 from the circulation. Oral administration of IH-901 leads to a low bioavailability; thus, the parenteral route may be the suitable way to deliver IH-901 for clinical applications.

Evaluation of capacity-limited first-pass effect through liver by three-points sampling in portal and hepatic veins and systemic artery.

The three-points method was newly developed by sampling the portal and hepatic veins and systemic artery. A model of hepatic local disposition with the Michaelis-Menten elimination was proposed to explain the concentration dependency of the hepatic recovery ratio (F(H)). 5-fluorouracil (5-FU) was selected as a model drug. 5-FU was administered orally 90 min after its intraarterial dose. Blood specimens in both femoral artery and hepatic vein were sampled after intraarterial dose, and blood specimens in both femoral artery and portal vein were taken after oral administration. It was shown that F(H) increased with an increase in the input drug concentration into the liver. The mean absorption time (MAT) estimated by nonlinear analysis agreed with the mean local absorption time (t(n)) whereas MAT by linear analysis was significantly smaller than t(a). The three-points method was newly developed, and the proposed nonlinear model explained well the capacity-limited elimination of 5-FU through the liver. MAT by the nonlinear analysis was in good agreement with t(a).

Introduction of Recirculatory Analysis into Portal and Systemic Concentration Difference Method.

Recirculatory analysis was introduced into the portal and systemic concentration difference method with double dosing (PS-DD method), which is an evaluation system for the local intestinal and hepatic first-pass effect. 5-Fluorouracil (5-FU) and cephalexin (CEX) were selected as model drugs. A new recirculatory system was constructed to predict the time courses of a drug concentration in the systemic and portal bloods. Bioavailability (F), local absorption ratio (Fa), hepatic recovery ratio (FH), and local mean absorption time (ta) estimated by recirculatory analysis were close to those calculated by moment analysis with numerical integration. Using recirculatory analysis, the sampling period was considerably shortened and the sampling number was also reduced, which demonstrates that recirculatory analysis is useful in PS-DD method.

Dose‐Dependency in Local Disposition of 5‐Fluorouracil under Non‐Steady‐State Condition in Rat Liver

Dose‐dependency in local disposition of 5‐fluorouracil (5‐FU) was evaluated using the rat liver in the once‐through perfusion system under the non‐steady‐state condition. A curve‐fitting program based on Finite Element Method, MULTI(FEM), was adopted to evaluate the capacity‐limited elimination in the hepatic local disposition of 5‐FU, which is described by a nonlinear dispersion model with a pulse input. The dose of 5‐FU was increased from 10.4 to 208 μg for rat livers at five dose levels. Two nonlinear models, two‐compartment dispersion models with Michaelis–Menten elimination from the central compartment or from the peripheral compartment, were employed for comparison. The hepatic recovery ratio, FH, increased from 13.1% to 68.3% and the mean transit time, t-H, increased from 5.1 to 13.1s with an increase in the dose. It was found that the hepatic local disposition of 5‐FU was well represented by the peripheral elimination model. Vmax and Km in the model with peripheral Michaelis–Menten elimination were estimated to be 9.04 mg/h and 2.88 mg/L, respectively. Vmax estimated by the present investigation in situ was about seven times greater than that in vitro, whereas Kmin situ was close to that in vitro. This result suggests that the elimination activity by the hepatocytes in vitro may be lowered, compared with that in situ. © 2000 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89: 100–107, 2000

Effect of pentobarbital anaesthesia on intestinal absorption and hepatic first-pass metabolism of oxacillin in rats, evaluated by portal-systemic concentration difference.

The effects of anaesthesia on intestinal drug absorption and hepatic first-pass metabolism in rats were investigated by observing the difference in the drug concentration between portal and systemic bloods. Oxacillin and pentobarbital were selected as a model drug and as an anaesthetic, respectively. Rats were divided into a conscious control group and an anaesthetized group. All rats were cannulated simultaneously in the portal vein and in the femoral artery, and oxacillin was orally administered after its intra-arterial injection (double dosing). For the anaesthetized group, pentobarbital was intrasubcutaneously administered twice, first before intra-arterial injection and again before oral administration of oxacillin. The arterial blood alone was sampled from the cannula in the femoral artery before oral administration, whereas the arterial and portal bloods were simultaneously sampled from both cannulated sites after oral administration. Oxacillin concentrations in plasma were assayed by HPLC. The anaesthesia increased the absolute bioavailability (F), the mean absorption time (MAT) and the hepatic recovery ratio (F(H)), but caused little change in the local absorption ratio into the portal system (Fa) and the total clearance (CL). The hepatic clearance (CL(H)) was significantly decreased, resulting in an apparent small change in CL-CL(H) which is considered to be renal clearance. By this method, it was shown directly that an increase in F due to pentobarbital anaesthesia was attributable to the significant increase in F(H). It is expected that the method is useful not only to evaluate the effect of anaesthesia on the first-pass effect, but also to assess the effect of co-administration of drugs on first-pass metabolism.

Pharmacokinetic analysis program based on tank-in-series model, MULTI(TIS), for evaluation of capacity-limited local disposition.

A pharmacokinetic analysis program based on a tank-in-series model, MULTI(TIS), was developed for the evaluation of dose-dependency in the local disposition of a drug. The program written in FORTRAN was constructed by expanding MULTI(RUNGE). The reliability of MULTI(TIS) was verified by analyzing the experimental data based on linear and nonlinear tank-in-series models. Linear one- and two-compartment tank-in-series models were adopted to analyze outflow time profiles in single-pass hepatic perfusion following a pulse input of 5'-deoxy-5-fluorouridine (DFUR). The estimated parameters agreed well with those by MULTI(FILT) which is widely used for linear kinetic analysis. The nonlinear models adopted were one-compartment model with Michaelis-Menten elimination and two-compartment models with Michaelis-Menten elimination from central and peripheral compartments. Oxacillin was used as a model drug, because time courses of oxacillin show a capacity-limited hepatic disposition following a pulse input in high doses to the liver (300, 1000, 3000 and 5000 microg). The hepatic recovery ratio (F(H)) of oxacillin increased with dose, whereas the mean transit time (tH) was almost constant. The maximum elimination rate constant (Vmax) and Michaelis constant (Km) of oxacillin were estimated to be 1980 microg/ml/min and 54.1 microg/ml, respectively. Thus, the reliability of MULTI(TIS) was demonstrated for the analysis of nonlinear local disposition, especially, capacity-limited elimination in the liver.

Local disposition of a new xanthine oxidase/xanthine dehydrogenase inhibitor, BOF-4272, in rat liver.

The local hepatic disposition of BOF-4272, a newly developed xanthine oxidase (XO)/xanthine dehydrogenase (XDH) inhibitor, was evaluated in the rat perfusion system following pulse input of the drug into the portal vein. The elution time profiles from the liver into the hepatic vein were analyzed by dispersion models. The disposition of BOF-4272 through the rat liver was represented by a two-compartment dispersion model based on the Akaike's Information Criterion (AIC). The area under the concentration time curve (aucH) of BOF-4272 was proportional to the dosing amount, and the mean transit time was constant from 62.5 up to 500 micrograms/liver, which demonstrates that the local hepatic disposition of BOF-4272 is linear in this dosing range. The local disposition parameters were precisely estimated at the dosing amount of 250 micrograms/liver using several rats. These parameters in the dispersion model were correlated to the local moment characteristics. The hepatic recovery ratio (FH) was 22.8 +/- 3.2% and the mean transit time (tH) was 0.112 +/- 0.008 min, which show that the influx of BOF-4272 into the liver is efficiently large.