Focally positive margins in breast conserving surgery: Predictors, residual disease, and local recurrence.

BACKGROUND: Re-excision after breast conserving surgery (BCS) for invasive breast cancer (IBC) can be omitted for focally positive margins in the Netherlands, but this guideline is not routinely followed. Focally positive and extensively positive margins have rarely been studied separately and compared to negative margins regarding clinicopathological predictors, residual disease incidence, and local recurrence. METHODS: All females with BCS for Tis-T3, without neo-adjuvant chemotherapy between 2005 and 2014 at one university hospital were included. Clinicopathological and follow-up information was collected from electronic patient records. Index tumor samples from all patients with re-excision were reviewed by one pathologist. Margins were classified as negative (≥2 mm width), close (<2 mm width), focally positive (≤4 mm length of tumor touching inked margin), or extensively positive (>4 mm length). RESULTS: From 499 patients included, 212 (43%) had negative, 161 (32%) had close, 59 (12%) had focally positive, and 67 (13%) had extensively positive margins. Increasingly involved margins were associated with lobular type, tumor size, and adjacent DCIS in IBC patients and lesion size in purely DCIS patients. In IBC patients, 17%, 49%, and 77% had re-excision after close, focally positive, and extensively positive margins and residual disease incidence was 55%, 50%, and 70% respectively. In purely DCIS patients, 26 (65%), 13 (87%), and 16 (94%) had re-excision after close, focally positive, and extensively positive margins and residual disease incidence was 39%, 46%, and 90% respectively. CONCLUSION: Incidence of residual disease after focally positive margins was not different from close margins, but was significantly higher after extensively positive margins. We recommend quantifying extent of margin involvement in all pathology reports.

Cell therapy for full-thickness wounds: are fetal dermal cells a potential source?

The application of autologous dermal fibroblasts has been shown to improve burn wound healing. However, a major hurdle is the availability of sufficient healthy skin as a cell source. We investigated fetal dermal cells as an alternative source for cell-based therapy for skin regeneration. Human (hFF), porcine fetal (pFF) or autologous dermal fibroblasts (AF) were seeded in a collagen-elastin substitute (Novomaix, NVM), which was applied in combination with an autologous split thickness skin graft (STSG) to evaluate the effects of these cells on wound healing in a porcine excisional wound model. Transplantation of wounds with NVM+hFF showed an increased influx of inflammatory cells (e.g., neutrophils, macrophages, CD4(+) and CD8(+) lymphocytes) compared to STSG, acellular NVM (Acell-NVM) and NVM+AF at post-surgery days 7 and/or 14. Wounds treated with NVM+pFF presented only an increase in CD8(+) lymphocyte influx. Furthermore, reduced alpha-smooth muscle actin (αSMA) expression in wound areas and reduced contraction of the wounds was observed with NVM+AF compared to Acell-NVM. Xenogeneic transplantation of NVM+hFF increased αSMA expression in wounds compared to NVM+AF. An improved scar quality was observed for wounds treated with NVM+AF compared to Acell-NVM, NVM+hFF and NVM+pFF at day 56. In conclusion, application of autologous fibroblasts improved the overall outcome of wound healing in comparison to fetal dermal cells and Acell-NVM, whereas application of fetal dermal fibroblasts in NVM did not improve wound healing of full-thickness wounds in a porcine model. Although human fetal dermal cells demonstrated an increased immune response, this did not seem to affect scar quality.

Altered morphine glucuronide and bile acid disposition in patients with nonalcoholic steatohepatitis.

The functional impact of altered drug transport protein expression on the systemic pharmacokinetics of morphine, hepatically derived morphine glucuronide (morphine-3- and morphine-6-glucuronide), and fasting bile acids was evaluated in patients with biopsy-confirmed nonalcoholic steatohepatitis (NASH) compared to healthy subjects. The maximum concentration (Cmax ) and area under the concentration-time curve (AUC0-last ) of morphine glucuronide in serum were increased in NASH patients (343 vs. 225 nM and 58.8 vs. 37.2 µM*min, respectively; P ≤ 0.005); morphine pharmacokinetics did not differ between groups. Linear regression analyses detected an association of NASH severity with increased morphine glucuronide Cmax and AUC0-last (P < 0.001). Fasting serum glycocholate, taurocholate, and total bile acid concentrations were associated with NASH severity (P < 0.006). Increased hepatic basolateral efflux of morphine glucuronide and bile acids is consistent with altered hepatic transport protein expression in patients with NASH and may partially explain differences in efficacy and/or toxicity of some highly transported anionic drugs/metabolites in this patient population.

Population pharmacokinetics of azithromycin in whole blood, peripheral blood mononuclear cells, and polymorphonuclear cells in healthy adults.

Azithromycin's extensive distribution to proinflammatory cells, including peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs), may be important to its antimicrobial and anti-inflammatory properties. The need to simultaneously predict azithromycin concentrations in whole blood ("blood"), PBMCs, and PMNs motivated this investigation. A single-dose study in 20 healthy adults was conducted, and nonlinear mixed effects modeling was used to simultaneously describe azithromycin concentrations in blood, PBMCs, and PMNs (simultaneous PK model). Data were well described by a four-compartment mamillary model. Apparent central clearance and volume of distribution estimates were 67.3 l/hour and 336 l (interindividual variability of 114 and 122%, respectively). Bootstrapping and visual predictive checks showed adequate model performance. Azithromycin concentrations in blood, PBMCs, and PMNs from external studies of healthy adults and cystic fibrosis patients were within the 5th and 95th percentiles of model simulations. This novel empirical model can be used to predict azithromycin concentrations in blood, PBMCs, and PMNs with different dosing regimens.

Effect of Ritonavir on (99m)Technetium-Mebrofenin Disposition in Humans: A Semi-PBPK Modeling and In Vitro Approach to Predict Transporter-Mediated DDIs.

A semiphysiologically based pharmacokinetic (semi-PBPK) model was developed to describe a unique blood, liver, and bile clinical data set for the hepatobiliary imaging agent (99m)Technetium-mebrofenin ((99m)Tc-mebrofenin), and to simulate sites/mechanisms of a (99m)Tc-mebrofenin-ritonavir drug-drug interaction (DDI). The transport inhibitor ritonavir (multiple-dose: 2 × 300 mg) significantly increased systemic (99m)Tc-mebrofenin exposure as compared with control (4,464 ± 1,861 vs. 1,970 ± 311 nCi min/ml; mean ± SD), without affecting overall hepatic exposure or biliary recovery. A novel extrahepatic distribution compartment was required to characterize (99m)Tc-mebrofenin disposition. Ritonavir inhibited (99m)Tc-mebrofenin accumulation in human sandwich-cultured hepatocytes (SCH) (half maximal inhibitory concentration (IC50) = 3.46 ± 1.53 µmol/l). Despite ritonavir accumulation in hepatocytes, intracellular binding was extensive (97. 6%), which limited interactions with multidrug resistance protein 2 (MRP2)-mediated biliary excretion. These in vitro data supported conclusions from modeling/simulation that ritonavir inhibited (99m)Tc-mebrofenin hepatic uptake, but not biliary excretion, at clinically relevant concentrations. This integrated approach, utilizing modeling, clinical, and in vitro data, emphasizes the importance of hepatic and extrahepatic distribution, assessment of inhibitory potential in relevant in vitro systems, and intracellular unbound concentrations to assess transporter-mediated hepatic DDIs.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e20; doi:10.1038/psp.2012.21; advance online publication 2 January 2013.

Consequences of polyparasitism on anaemia among primary school children in Zimbabwe.

The effect of concomitant infection with schistosomes, Plasmodium falciparum and soil transmitted helminths (STHs) on anaemia was determined in 609 Zimbabwean primary school children. P. falciparum, haemoglobin levels and serum ferritin were determined from venous blood. Kato Katz, formal ether concentration and urine filtration techniques were used to assess prevalence of Schistosoma mansoni, STHs and Schistosoma haematobium infections. The prevalence of S. haematobium, S. mansoni, P. falciparum, hookworm, Trichuris trichiura and Ascaris lumbricoides were 52.3%, 22.7%, 27.9%, 23.7%, 2.3% and 2.1%, respectively. The overall prevalence of anaemia and iron deficiency anaemia (IDA) were 48.4% (277/572) and 38.1% (181/475). Haemoglobin levels among children who had P. falciparum, S. haematobium and hookworm were lower than negative individuals, p<0.001, p<0.001 and p=0.030, respectively. The prevalence of anaemia and IDA in co-infections was almost double that in single infection. Children with P. falciparum/STHs/schistosome and schistosomes/P. falciparum co-infections recorded higher prevalence of anaemia and IDA (80.8% and 57.4%, respectively) than other combinations, p<0.001. Logistic regression revealed that, age group > or = 14 years, P. falciparum, S. haematobium light and heavy infections, and S. mansoni moderate and heavy infection, hookworm light infection were predictors of anaemia. This study suggests that integrated school based de-worming and malaria control have the potential to reduce the burden of anaemia.

Long-term outcomes of corrective osteotomy for the treatment of distal radius malunion.

Corrective osteotomy is an established but challenging treatment for distal radius malunion. Short- and intermediate-term results have been previously published while long-term results have not. The long-term results of 22 patients treated with corrective osteotomy for symptomatic distal radius malunion are presented (range 6-24 years, mean 13 years). All patients completed the DASH questionnaire and the modified Gartland and Werley, and Green and O'Brien scores postoperatively. Wrist alignment was assessed through standard wrist radiographs. Average wrist flexion-extension was 72.5% of the contralateral limb. Grip strength averaged 71%. The DASH score averaged 16 points corresponding to mild perceived disability. Results were categorized as fair on both the Gartland and Werley score (average 9 points) and the modified Green and O'Brien score (average 67 points). Wrist alignment was maintained over time but 13 patients presented mild to moderate symptomatic wrist arthritis. The outcome presented may be a reflection of the use of stricter evaluation instruments or reflect the development of post-traumatic arthritis.

The burden of polyparasitism among primary schoolchildren in rural and farming areas in Zimbabwe.

A cross-sectional study was conducted in Zimbabwe among 1303 primary schoolchildren from a rural (53.3%) and a commercial farming area (46.7%) to determine the prevalence of co-infection by helminths and Plasmodium falciparum. Urine was examined on three successive days using the filtration method. Two stool specimens were processed using the Kato-Katz method and a third specimen was processed using the sedimentation method. Plasmodium falciparum was diagnosed from thick blood films. The prevalence of Schistosoma haematobium in the rural and farming areas was 66.8% and 52.3%, respectively, and for S. mansoni the prevalence was 12.4% and 22.7%, respectively. Plasmodium falciparum, hookworms, Ascaris lumbricoides and Trichuris trichiura occurred only in the farming area, with a prevalence of 27.9%, 23.7%, 2.1%, 2.3%, respectively. Co-infection and triple infection with schistosomes, P. falciparum and soil-transmitted helminths occurred in the commercial farming area only. Hookworm and S. mansoni infections were associated with P. falciparum malaria (P<0.001, OR=2.48, 95% CI 1.56-3.93 and P=0.005, OR=1.85, 95% CI 1.20-2.87, respectively). Overlap of helminths with malaria is a concern among primary schoolchildren and incorporating helminth control in programmes aiming to control malaria will improve funding and increase the efficiency of control for neglected tropical diseases in identified co-endemic settings.

Serum-free transient protein production system based on adenoviral vector and PER.C6 technology: high yield and preserved bioactivity.

Stable E1 transformed cells, like PER.C6, are able to grow at scale and to high cell densities. E1-deleted adenoviruses replicate to high titer in PER.C6 cells whereas subsequent deletion of E2A from the vector results in absence of replication in PER.C6 cells and drastically lowers the expression of adenovirus proteins in such cells. We therefore considered the use of an DeltaE1/DeltaE2 type 5 vector (Ad5) to deliver genes to PER.C6 cells growing in suspension with the aim to achieve high protein yield. To evaluate the utility of this system we constructed DeltaE1/DeltaE2 vector carrying different classes of protein, that is, the gene coding for spike protein derived from the Coronavirus causing severe acute respiratory syndrome (SARS-CoV), a gene coding for the SARS-CoV receptor or the genes coding for an antibody shown to bind and neutralize SARS-CoV (SARS-AB). The DeltaE1/DeltaE2A-vector backbones were rescued on a PER.C6 cell line engineered to constitutively over express the Ad5 E2A protein. Exposure of PER.C6 cells to low amounts (30 vp/cell) of DeltaE1/DeltaE2 vectors resulted in highly efficient (>80%) transduction of PER.C6 cells growing in suspension. The efficient cell transduction resulted in high protein yield (up to 60 picogram/cell/day) in a 4 day batch production protocol. FACS and ELISA assays demonstrated the biological activity of the transiently produced proteins. We therefore conclude that DeltaE1/DeltaE2 vectors in combination with the PER.C6 technology may provide a viable answer to the increasing demand for high quality, high yield recombinant protein.

Efficacy and side effects of praziquantel treatment against Schistosoma haematobium infection among primary school children in Zimbabwe.

We examined the efficacy of praziquantel against Schistosoma haematobium among primary school children during a school-based deworming programme in the Burma Valley commercial farming area and the Nyamaropa rural areas in Zimbabwe, where the disease is highly endemic. Among 767 individuals infected with S. haematobium, 675 (88.0%) received treatment. Two single oral doses of 40mg/kg praziquantel were given 6 weeks apart. Of the 675 participants, heavy infection intensity was more common in males than females (chi(2)=6.61, P=0.010). Six weeks later, 624 participants (92.4%) were successfully followed up. The overall cure rate was 88.5% and the egg reduction rate was 98.2%. The highest cure rate was among those individuals with light infection. Seventy-two individuals remained infected at 6 weeks post treatment, among which 3 and 69 individuals had heavy and light infection, respectively. Forty-six of these children resolved following a second round of treatment at 6 weeks follow-up. Of the remaining children successfully followed-up, 22 resolved after a third round of treatment 6 months later. A wide range of observed mild and transient side effects were not associated with egg intensity. The parasitological cure rate was not associated with gender or age. Our study demonstrates that praziquantel is efficacious against S. haematobium in Zimbabwe, although low levels of persistent infection warrant further investigation.

Pitfalls in determining knee alignment: a radiographic cadaver study.

Full-length anteroposterior (AP) radiographs provide the basis for evaluating leg alignment. A cadaver study was performed to determine the effect of knee flexion and hip rotation on projected angles on full-length AP radiographs. The outcomes were verified mathematically. The results of the cadaver study were similar to the mathematical results. Flexion of the knee without rotation of the lower extremity has little effect on angles as projected on full-length AP radiographs. Rotation of the lower extremity without flexion of the knee also has little effect. Simultaneous flexion of the knee and rotation of the leg, however, cause large changes in projected angles. Full-length radiographs can be taken without fluoroscopic control as long as the knee can be fully extended. In flexion contracture, a full-length AP radiograph taken under lateral fluoroscopic control is necessary to obtain accurate determination of the mechanical axis.

Randomized clinical trial of the impact of early enteral feeding on postoperative ileus and recovery.

BACKGROUND: Postoperative convalescence is mainly determined by the extent and duration of postoperative ileus. This randomized clinical trial evaluated the effects of early oral feeding on functional gastrointestinal recovery and quality of life. METHODS: One hundred and twenty-eight patients undergoing elective open colorectal or abdominal vascular surgery participated in the trial. Of these, 67 were randomized to a conventional return to diet, and 61 to a regimen allowing resumption of an oral diet as soon as tolerated (free diet group). RESULTS: Reinsertion of a nasogastric tube was necessary in 20 per cent of the free diet group and 10 per cent of the conventional group (P = 0.213). The complication rate was similar for both groups, as was return of gastrointestinal function. A normal diet was tolerated after a median of 2 days in the free diet group compared with 5 days in the conventional group (P < 0.001). Quality of life scores were similar in both groups. CONCLUSION: Early resumption of oral intake does not diminish the duration of postoperative ileus or lead to a significantly increased rate of nasogastric tube reinsertion. Tolerance of oral diet is not influenced by gastrointestinal functional recovery. As there is no reason to withhold oral intake following open colorectal or abdominal vascular surgery, postoperative management should include early resumption of diet.

Randomized clinical trial of patient-controlled versus fixed regimen feeding after elective abdominal surgery.

BACKGROUND: Although studies have shown that early oral feeding after abdominal surgery is feasible, many surgeons still advocate a careful, slow introduction of postoperative oral feeding. This study was conducted to investigate whether patient-controlled postoperative feeding is possible in patients undergoing colonic or aortic surgery. METHODS: A randomized clinical trial compared patient-controlled postoperative oral feeding (PC group) with a fixed regimen (FR group). Patients in the PC group (n = 56) received oral feeding when they requested it; patients in the FR group (n = 49) started a normal diet on day 5. Endpoints were time to tolerance of a diet similar to the preoperative diet, reinsertion of a nasogastric tube, complications and duration of hospitalization. RESULTS: Median time to resumption of a normal diet was 3 days in the PC group and 5 days in the FR group (P < 0.001). Reinsertion of a nasogastric tube was required in nine patients in each group (P not significant). The incidence of complications was similar in both groups: 12 of 56 in the PC group and 13 of 49 in the FR group. There was no significant difference in duration of hospital stay between the groups. CONCLUSION: Most patients tolerate a normal diet on the third day after operation. Patient-controlled postoperative feeding is safe and leads to earlier resumption of a normal diet.

Pharmacokinetic and pharmacodynamic implications of P-glycoprotein modulation.

P-glycoprotein (P-gp) is a cell membrane-associated protein that transports a variety of drug substrates. Although P-gp has been studied extensively as a mediator of multidrug resistance in cancer, only recently has the role of P-gp expressed in normal tissues as a determinant of drug pharmacokinetics and pharmacodynamics been examined. P-glycoprotein is present in organ systems that influence drug absorption (intestine), distribution to site of action (central nervous system and leukocytes), and elimination (liver and kidney), as well as several other tissues. Many marketed drugs inhibit P-gp function, and several compounds are under development as P-gp inhibitors. Similarly, numerous drugs can induce P-gp expression. While P-gp induction does not have a therapeutic role, P-gp inhibition is an attractive therapeutic approach to reverse multidrug resistance. Clinicians should recognize that P-gp induction or inhibition may have a substantial effect on the pharmacokinetics and pharmacodynamics of concomitantly administered drugs that are substrates for this transporter.

Induction of P-glycoprotein and cytochrome P450 3A by HIV protease inhibitors.

P-Glycoprotein (Pgp) and cytochrome P450 3A (CYP3A) are important enzymes affecting the disposition of HIV protease inhibitors (HIV PIs). After multiple dosing experiments in rats, decreases in the plasma concentrations and area under plasma concentration-time curve (AUC) for HIV PIs have been observed. The purpose of these studies was to determine the changes in Pgp and CYP3A expression and HIV PI plasma exposure after multiple doses of HIV PIs. Male rats were orally dosed with an amprenavir prodrug (450 mg/kg/day amprenavir-equivalent) or nelfinavir (175 mg/kg/day) for 1 or 14 days. Relative to day 1, the C(max) and the AUC for amprenavir at day 14 were decreased by 33 and 51%, respectively. Similarly, the plasma concentration of nelfinavir at 1 h after the last dose (C(max)) was reduced by 52% after multiple doses. Compared with controls, dosing of amprenavir for 14 days increased intestinal Pgp and hepatic CYP3A protein levels by 59 and 151%, respectively, but did not alter intestinal CYP3A protein levels. In contrast, amprenavir treatment did not result in an increase in hepatic CYP3A activity. Nelfinavir treatment increased expression of intestinal Pgp and hepatic CYP3A levels by 83 and 85%, respectively, but not hepatic Pgp or intestinal CYP3A. HIV PIs also induced Pgp expression in the LS174T human intestinal cell line. These results indicate that HIV protease inhibitors induce both intestinal Pgp and hepatic CYP3A and suggest that induction of Pgp and CYP3A is a possible mechanism reducing drug exposure after multiple doses.

Increased oral bioavailability of paclitaxel by GF120918 in mice through selective modulation of P-glycoprotein.

Previous studies in mice with disrupted mdr1a P-glycoprotein genes have shown that the oral bioavailability of paclitaxel is very low because of the presence of this drug-transporting protein in the intestinal wall. Additional studies with cyclosporin A have shown that this P-glycoprotein-inhibiting agent is able to increase the bioavailability of paclitaxel in mouse models and in patients. However, the potential immune-suppressive side effects of cyclosporin A renders this compound less suitable for chronic use in cancer patients. In this paper we present the results obtained with GF120918, an experimental P-glycoprotein inhibitor, on the oral bioavailability of paclitaxel in both wild-type and mdrlab knockout mice. GF120918 (25 mg/kg) was administered p.o. by gavage 15 min or 2 h before oral or i.v. dosing of paclitaxel, respectively. Paclitaxel plasma levels were quantified by high-performance liquid chromatography. GF120918 increased the plasma values for areas under the concentration-time curve of oral paclitaxel in wild-type mice by 6.6-fold from 408 to 2701 ng x ml(-1) h. Calculated relative to their respective values for area under the concentration-time curve after i.v. administration, GF120918 increased the oral bioavailability of paclitaxel in wild-type mice from 8.5 to 40.2%. The plasma pharmacokinetics of paclitaxel in mdr1ab knockout mice was not altered by GF120918, whereas the pharmacokinetics of paclitaxel in wild-type mice receiving GF120918 became comparable with mdr1ab knockout mice. This result indicates that GF120918 at this dose-level selectively and completely blocks P-glycoprotein in the intestines and does not notably interfere in the elimination of paclitaxel by metabolism or other transporters. On the basis of this result, GF120918 has been selected for additional study in humans.

Altered hepatobiliary disposition of acetaminophen glucuronide in isolated perfused livers from multidrug resistance-associated protein 2-deficient TR(-) rats.

Previous studies have demonstrated that phenobarbital treatment impairs the biliary excretion of acetaminophen glucuronide (AG), although the transport system(s) responsible for AG excretion into bile has not been identified. Initial studies in rat canalicular liver plasma membrane vesicles indicated that AG uptake was stimulated modestly by ATP, but not by membrane potential, HCO(3)(-), or pH gradients. To examine the role of the ATP-dependent canalicular transporter multidrug resistance-associated protein 2 (Mrp2)/canalicular multispecific organic anion transporter (cMOAT) in the biliary excretion of AG, the hepatobiliary disposition of acetaminophen, AG, and acetaminophen sulfate (AS) was examined in isolated perfused livers from control and TR(-) (Mrp2-deficient) Wistar rats. Mean bile flow in TR(-) livers was approximately 0.3 microl/min/g of liver ( approximately 4-fold lower than control). AG biliary excretion was decreased (>300-fold) to negligible levels in TR(-) rat livers, indicating that AG is an Mrp2 substrate. Similarly, AS biliary excretion in TR(-) livers was decreased ( approximately 5-fold); however, concentrations were still measurable, suggesting that multiple mechanisms, including Mrp2-mediated active transport, may be involved in AS biliary excretion. AG and AS perfusate concentrations were significantly higher in livers from TR(-) compared with control rats. Pharmacokinetic modeling of the data revealed that the rate constant for basolateral egress of AG increased significantly from 0.028 to 0.206 min(-1), consistent with up-regulation of a basolateral organic anion transporter in Mrp2-deficient rat livers. In conclusion, these data indicate that AG biliary excretion is mediated by Mrp2, and clearly demonstrate that substrate disposition may be influenced by alterations in complementary transport systems in transport-deficient animals.

Phase I trial of a 96 h paclitaxel infusion with filgrastim support in refractory solid tumor patients.

A phase I study of a 96 h paclitaxel infusion with filgrastim support was performed to determine the toxicity, maximum-tolerated dose (MTD) and pharmacokinetics in patients with refractory solid tumors. In this phase I trial, the initial paclitaxel dose was 140 mg/m2/96 h followed by filgrastim (5 microg/kg/day s.c.) beginning 24 h after the paclitaxel and continued until granulocyte recovery. Cycles were repeated every 21 days. Patients with refractory solid tumors were eligible; however, only one previous chemotherapy regimen was allowed. The dose of paclitaxel was escalated by 20 mg/m2/96 h in subsequent cohorts until dose-limiting toxicity (DLT) occurred. Pharmacokinetic analysis was performed by quantitating paclitaxel concentrations at baseline, 24, 48, 72 and 96 h after the start of the paclitaxel infusion. Twenty-one patients were entered into this trial of which 19 were evaluable. A total of 52 treatment cycles were administered. DLT was seen in two of four patients at 200 mg/m2/96 h, and consisted of diarrhea, mucositis and granulocytopenic infection. The MTD of the 96 h paclitaxel infusion was 180 mg/m2 with filgrastim support. Mucosal and granulocyte toxicity were correlated with steady-state paclitaxel concentrations (Css) greater than 0.100 micromol/l. In the presence of liver function test 1.5 times or lower than normal, metastatic liver disease did not alter paclitaxel Css. Objective responses were observed in non-small cell lung cancer, small cell lung cancer and melanoma. The recommended phase II dose of paclitaxel infused over 96 h with filgrastim support is 180 mg/m2. Paclitaxel Css correlate with mucosal and granulocyte toxicity. In the presence of normal enzymatic function, metastatic liver disease does not affect paclitaxel clearance.

Partial maintenance of taurocholate uptake by adult rat hepatocytes cultured in a collagen sandwich configuration.

PURPOSE: This study was designed to characterize taurocholate uptake properties in primary cultures of rat hepatocytes maintained under different matrix conditions. METHODS: Hepatocytes isolated from male Wistar rats (230-280 g) were cultured on a simple collagen film, on a substratum of gelled collagen or between two layers of gelled collagen (sandwich configuration). Hepatocyte morphology, taurocholate uptake properties, and expression of the sinusoidal transport protein. Na+/taurocholate-cotransporting polypeptide (Ntcp) were examined in these cultures at day 0 and day 5. RESULTS: By day 5, monolayer integrity had deteriorated in simple collagen cultures. In contrast, cell morphology was preserved in hepatocytes maintained in a sandwich configuration. At day 5, taurocholate accumulation at 5 min in hepatocytes cultured on a simple collagen film, on a substratum of gelled collagen, and in a sandwich configuration was approximately 13%, 20% and 35% of day-0 levels, respectively, and occurred predominately by a Na+-dependent mechanism. The initial taurocholate uptake rate vs. concentration (1-200 microM) profile was best described by a combined Michaelis-Menten and first-order function. In all cases, the estimated apparent Km values were comparable for day-0 and day-5 hepatocytes (3241 microM). In contrast, the Vmax values of hepatocytes cultured on a simple collagen film, on gelled collagen and in a sandwich configuration were approximately 5, 6 and 14% of the values at day 0, respectively; values for the first-order rate constant were 5-, 3- and 2-fold lower, respectively. Immunoblot analysis indicated that at day 5 Ntcp expression in hepatocytes cultured in a sandwich configuration was greater than in hepatocytes cultured on a simple collagen film. CONCLUSIONS: A collagen sandwich configuration reestablishes normal morphology and partially restores bile acid uptake properties in primary cultures of rat hepatocytes.

Effect of multidrug resistance modulators on the hepatobiliary disposition of doxorubicin in the isolated perfused rat liver.

P-Glycoprotein (P-gp)-mediated multidrug resistance (MDR) in cancer cells may be modulated by competitive inhibitors of P-gp. In the liver, P-gp is localized on the canalicular membrane of hepatocytes. Quinidine and GF120918 inhibit the transport of P-gp substrates, including doxorubicin. Competitive inhibition of P-gp transport may alter biliary excretion of substrates. This study was designed to examine the effects of MDR modulators on the hepatobiliary disposition of doxorubicin and to elucidate the site(s) of drug-modulator interaction using pharmacokinetic modeling techniques. Livers from male Sprague Dawley rats were isolated and perfused for 2 h at 37 degrees C with recirculating male rat blood. MDR modulator (16.8-480 microg of GF120918 or 0.3-3.0 mg of quinidine) or vehicle (buffer or DMSO, respectively) was administered as a bolus to the perfusate reservoir 5 min prior to the addition of doxorubicin (464 microg). Perfusate and bile were collected during the perfusion, the liver was homogenized after the perfusion, and samples were analyzed by high-pressure liquid chromatography for doxorubicin and the major metabolite doxorubicinol. In the presence of GF120918, the biliary excretion of doxorubicin and doxorubicinol was decreased significantly without alterations in doxorubicin perfusate concentrations or doxorubicin and doxorubicinol liver concentrations. In the presence of quinidine, the biliary excretion of doxorubicin was reduced significantly; however, doxorubicinol recovery in bile was not altered. The perfusate and liver concentrations of doxorubicin were not altered by quinidine; doxorubicinol liver concentrations were increased. A series of pharmacokinetic models were evaluated incorporating perfusate, liver, and bile compartments to describe the disposition of doxorubicin and doxorubicinol in the isolated perfused rat liver. The model that best described these data, based on goodness-of-fit criteria, included first-order rate constants for all disposition processes. On the basis of this model, the rate-limiting process for doxorubicin and doxorubicinol elimination was biliary excretion. In the presence of GF120918, rate constants associated with doxorubicin and doxorubicinol canalicular egress were decreased, and other doxorubicinol disposition pathways were increased slightly. Quinidine was associated with a decrease in doxorubicin canalicular egress, doxorubicinol formation, and other doxorubicinol pathways. Pharmacokinetic modeling of the data supported the hypothesis that decreased biliary excretion of doxorubicin in the isolated perfused rat liver, as determined by mass-balance analysis, was due to interactions at the canalicular membrane. The present study further supports the utility of pharmacokinetic modeling in identifying sites of drug interactions within the hepatobiliary system. This approach may be particularly useful in predicting the effects of perturbations in hepatic translocation processes on the hepatobiliary disposition of drugs and derived metabolites.