[CYTOREDUCTIVE SURGERY AND HYPERTHERMIC INTRAPERITONEAL CHEMOTHERAPY FOR PERITONEAL CARCINOMATOSIS OF COLORECTAL ORIGIN - FIRST 100 CASES]

BACKGROUND

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is an effective treatment for selected patients with peritoneal carcinomatosis of colorectal origin. We present our experience with the first 100 consecutive cases of this combined treatment.

METHODS

CRS/HIPEC procedures were performed between 4/2009-8/2016. HIPEC was initially delivered using the "Open" abdomen technique; beginning in January 2014, HIPEC was delivered using the "Closed" technique. As a chemotherapeutic agent we used Mitomycin-C, perfused for duration of 90 minutes at 41 degrees Celsius.

RESULTS

A total of 100 procedures were performed in 94 patients (64% females, median age 62 (22-83) years) with colon (n=89) or rectal (n=5) cancer. Complete cytoreduction (CC score≤1) was achieved in 91 procedures. The average duration of surgery was 7.5±2.3 hours, the median number of organs resected was 2 (0-6) and the median length of hospital stay was 9 (5-101) days. Postoperative complications occurred in 54% of procedures and the incidence of major complications (Clavien-Dindo 3-4) was 12%. Three patients (3%) died within 90 days postoperatively. Higher peritoneal cancer index (PCI) score, higher number of organs resected/anastomoses created and longer duration of surgery were associated with perioperative morbidity (all p≤0.05). The median follow-up period was 2.1 years during which 50 patients died. The median overall survival (OS) and disease free survival were 3.1 years and 10.7 months, respectively; 7 patients survived ≥5 years after surgery. Higher PCI score and occurrence of major postoperative complications were associated with poorer OS.

CONCLUSIONS

CRS/HIPEC for peritoneal carcinomatosis of colorectal cancer origin is feasible and safe. This treatment may benefit selected patients in terms of OS.

Correlation Between Intraoperative and Pathological Findings for Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

BACKGROUND

This study aimed to examine the correlation between intraoperative and pathological findings for patients undergoing cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) and to determine their prognostic significance.

METHODS

Pathological reports of all colorectal cancer (CRC) patients undergoing CRS/HIPEC between 2009 and 2016 were retrospectively reviewed. Pathological specimens lacking tumor cells were defined as negative pathological specimens (NPS). The intraoperative peritoneal cancer index (PCI) and pathological PCI (excluding NPS) were calculated separately. Receiver operating characteristic (ROC) curves were applied to compare the prognostic value of intraoperative and pathological scoring systems.

RESULTS

For 108 CRC patients, 113 CRS/HIPEC procedures were performed. Of 959 pathological specimens examined, 178 (18.6%) were NPS. Overall, 78 procedures (69%) showed NPS. In 52 procedures (46%), the pathological PCI differed from the intraoperative PCI (∆PCI > 0). The ROC areas for intraoperative PCI and pathological PCI were similar in predicting 1-year overall survival (OS), 2-year OS, and 1-year disease-free survival (all p values not significant). However, for the patients with NPS, the number of positive specimens (containing tumor tissue) was superior to intraoperative PCI in predicting 2-year OS (ROC under the curve areas, 0.69 vs. 0.58, respectively; p = 0.012). In addition, a subgroup of 15 patients with a high ∆PCI (≥ 3) had a more favorable median OS than a matched group of 30 patients with similar intraoperative PCI and a ∆PCI of 0 (median survival not reached vs. 21.6 months, respectively; p = 0.05).

CONCLUSIONS

In the majority of CRC CRS/HIPEC procedures, NPS may be found. Among patients with NPS, pathological correlation may have a prognostic significance.

The Antiaggregating Activity of Clopidogrel Is due to a Metabolic Activation by the Hepatic Cytochrome P450-1A

Clopidogrel and ticlopidine are two well known selective anti-ADP agents which are inactive in vitro and must be administered in vivo to fully exhibit their antiaggregating and antithrombotic effects. Since previous studies have clearly demonstrated that the activation steps take place in the liver, we examined the effect of specific induction or inhibition of cytochrome P450 subfamilies on the antiaggregating activity of clopidogrel. SKF 525-A, a global cytochrome P450 inhibitor, dramatically decreased the antiaggregating effect of clopidogrel, therefore indicating that cytochrome P450 enzymes are involved in the hepatic activation of clopidogrel. The efficacy of clopidogrel was increased in animals pretreated with 3-methylcholanthrene and (3-naphthoflavone, indicating that the cytochrome P450-1A subfamily pathway was mainly involved in the activating metabolism of clopidogrel. The use of specific antibodies directed against the various cytochrome P450 subfamilies ascertained this observation.

Hospital readmission rates and risk factors for readmission following cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for peritoneal surface malignancies

BACKGROUND

Cytoreductive surgery and Hyperthermic intra-peritoneal chemotherapy (CRS/HIPEC) for peritoneal surface malignancies is associated with high morbidity. The increased numbers of patients undergoing CRS/HIPEC in recent years mandates risk analysis and quality assurance. However, only scarce data exist regarding causative parameters for readmission. The aim of this study was to assess readmission rates and risk factors associated with readmission.

METHODS

A retrospective-cohort study including patients from two high-volume centers who underwent CRS/HIPEC surgery between the years 2007-2016 was performed. Patients' demographics, peri-operative data and readmission rates were recorded.

RESULTS

223 patients were included in the study. The 7 and 30-day readmission rates were 3.5% (n = 8) and 11% (n = 25), respectively. Late readmission rates (up to 90 days) were 11% (n = 25). The most common causes of readmission were surgical related infections (35%), small bowel obstruction (17.5%) and dehydration (14%). Post-operative complications were associated with higher readmission rates (p = 0.0001). PCI score was not associated with higher rates of readmission.

CONCLUSION

Readmissions following CRS/HIPEC occur mainly due to infectious complications and dehydrations. Patients following CRS/HIPEC should be discharged after careful investigation to a community based continuing care with access for IV fluid replacement or antibiotics administration when required.

Extrahepatic metastasectomy for hepatocellular carcinoma: Predictors of long-term survival

INTRODUCTION

We report our institutional experience with extrahepatic metastasectomy (EM) in a cohort of hepatocellular carcinoma (HCC) patients with focus on predictors of survival.

METHODS

All patients diagnosed with metastatic HCC from 2001 to 2014 were retrospectively reviewed to identify those who underwent EM with therapeutic intent. Associations among multiple clinicopathological variables and survival after EM were analyzed by univariate and multivariate analyses.

RESULTS

Out of 440 metastatic HCC cases, we identified 85 patients (mean age 58.8 ± 11.7 years, 81.2% males) who underwent lung (n = 36), peritoneal (n = 22), lymph node (n = 19), musculoskeletal (n = 18), and adrenal (n = 9) metastasectomy. Most patients (84.7%) underwent metachronous EM following primary liver resection or transplantation. The median follow-up period was 20.9 months, during which 55 patients (64.7%) died. The 1-/2-/5-year overall survival rates after EM were 77.4, 53.1, and 25.1%, respectively. On multivariate analysis, number of metastases resected >2 correlated independently with poor survival (HR = 2.058, P = 0.0099). EM patients had superior median survival compared to all (n = 194) metastatic HCC patients treated with sorafenib without EM during the study period (27.2 vs. 7.4 months, P < 0.001).

CONCLUSION

Long-term survival may be achieved in highly selected HCC patients following EM. The presence of greater than two extrahepatic lesions correlates independently with poor survival. J. Surg. Oncol. 2016;114:469-474. © 2016 Wiley Periodicals, Inc.

Colonoscopy after the first episode of acute diverticulitis: challenging management paradigms

BACKGROUND

Colonoscopy is commonly recommended after the first episode of acute diverticulitis to exclude colorectal neoplasia. Recent data have challenged this paradigm due to insufficient diagnostic yield. The aim of this study was to assess whether colonoscopy after the first episode of acute diverticulitis is needed to exclude colorectal neoplasia.

METHODS

We performed a retrospective cohort analysis of medical records of patients admitted for the first episode of acute diverticulitis between January 2008 and December 2012. Ambulatory colonoscopy was routinely recommended at discharge. Clinical follow-up and telephone surveys were used for data collection.

RESULTS

Four hundred and twenty-five patients with a mean age of 62.6 years (range 21-98 years) were admitted during the 5-year period. Three hundred and ten (72.9 %) patients underwent colonoscopy at median time of 3.2 months after discharge. Five patients (1.6 %) of the 310 available for evaluation had malignant findings in colonoscopy. Of those, one patient had rectal carcinoma away from the inflamed site and one had colonic lymphoma. None of the 95 patients <50 years of age was found to have adenocarcinoma of the colon.

CONCLUSIONS

Cancer is rarely detected in colonoscopy following the first episode of acute diverticulitis. These results question this indication for colonoscopy, especially in patients under 50.

The effect of locoregional therapies in patients with advanced hepatocellular carcinoma treated with sorafenib

BACKGROUND & AIMS

It is unknown whether the addition of locoregional therapies (LRTx) to sorafenib improves prognosis over sorafenib alone in patients with advanced hepatocellular carcinoma (HCC). The aim of this study was to assess the effect of LRTx in this population.

METHODS

A retrospective analysis was performed of patients with advanced HCC as defined by extrahepatic metastasis, lymphadenopathy >2 cm, or gross vascular invasion. Sorafenib therapy was required for inclusion. Survival of patients who received LRTx after progression to advanced stage was compared to those who did not receive LRTx.

RESULTS

Using an intention to treat analysis of 312 eligible patients, a propensity weighted proportional hazards model demonstrated LRTx as a predictor of survival (HR = 0.505, 95% CI: 0.407-0.628; P < 0.001). The greatest benefit was seen in patients with the largest tumor burden (HR = 0.305, 95% CI: 0.236-0.393; P < 0.01). Median survival in the sorafenib arm was 143 days (95% CI: 118-161) vs. 247 days (95% CI: 220-289) in the sorafenib plus LRTx arm (P < 0.001).

CONCLUSIONS

These results demonstrate a survival benefit with the addition of LRTx to sorafenib for patients with advanced HCC. These findings should prompt a prospective clinical trial to further assess the role of LRTx in patients with advanced HCC.

Disentangling the effects of race and socioeconomic factors on liver transplantation rates for hepatocellular carcinoma

INTRODUCTION

Liver transplantation is the most effective treatment for hepatocellular carcinoma (HCC) in eligible patients, but is not accessed equally by all. We explored the effects of race and socioeconomic factors on transplantation for HCC while controlling for stage, resection status, and transplant candidacy.

PATIENTS AND METHODS

All HCC patients, 2003-2013, were retrospectively analyzed using multivariate analysis to explore differences in transplantation rates among cohorts.

RESULTS

Of 3078 HCC patients, 754 (24%) were considered transplant eligible. Odds of transplantation were significantly higher for those with commercial insurance (OR = 1.99, 95% CI [1.42, 2.79]) and lower for black patients (OR = 0.55, 95% CI [0.33, 0.91]). Asians were more likely to be resected than white patients with similarly staged tumors and transplant criteria (p < 0.001). Patients not listed for transplantation for non-medical reasons were more likely to be government-insured (p = 0.02) and not white (p = 0.05). No step along the transplantation pathway was identified as the dominant hurdle.

DISCUSSION

Patients who are black or government-insured are significantly less likely to undergo transplantation for HCC despite controlling for tumor stage, resection status, and transplant eligibility. Asian patients have higher rates of hepatic resection, but also appear to have lower transplantation rates beyond this effect.

Prophylactic hyperthermic intraperitoneal chemotherapy in patients with epithelial appendiceal neoplasms

Background Prophylactic hyperthermic intraperitoneal chemotherapy (HIPEC) is a promising approach for preventing peritoneal carcinomatosis in high-risk patients. We report our initial experience with prophylactic HIPEC in a series of patients with appendiceal neoplasms. Methods We retrospectively reviewed our prospectively maintained database to identify patients who underwent HIPEC in the absence of peritoneal disease. Patients with previously documented peritoneal surface disease were excluded. Data regarding clinical, operative and pathological features were analysed. Results Out of 322 HIPEC procedures performed between March 2007and August 2015, we identified 16 patients who underwent surgery with prophylactic intent. Primary diagnoses included high-grade and low-grade appendiceal neoplasms. Most patients presented originally with appendiceal perforation; all patients underwent initial surgery during which the appendix or right colon were resected. Following a median time interval of 2.2 months, a second surgery performed at our institution consisted of completion of omentectomy, partial colectomy and oophorectomy, with administration of prophylactic HIPEC (using mitomycin C). A totally laparoscopic approach was attempted and achieved in 11 patients in whom the median duration of surgery, estimated intraoperative blood loss and length of hospitalisation were 251 min, 100 cm(3) and 4 days, respectively. There were no cases of major perioperative morbidity or mortality. Conclusions Prophylactic HIPEC for appendiceal neoplasms is feasible, safe and may be performed laparoscopically. Larger studies with long-term follow-up are needed to determine whether a survival benefit is associated with this treatment.

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in patients with liver involvement

BACKGROUND

We examined outcomes of patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) combined with liver resection.

METHODS

All patients undergoing CRS/HIPEC between 2007 and 2014 were retrospectively reviewed: patients who underwent synchronous liver resection (group 1) were compared with those who did not (group 2) in terms of perioperative and long-term results.

RESULTS

Group 1 included 103 patients with colorectal cancer (CRC, n = 28), appendiceal cancer (n = 34), and other malignancies. Compared with group 2 (n = 166), group 1 had higher number of organs resected, increased intraoperative blood loss, and longer hospital stay (all P ≤ 0.004) but similar major morbidity (24.3% vs. 18.1%, P = 0.22) and perioperative mortality rates. Two patients from group 1 developed liver resection-related complications. A comparison between patients who underwent parenchymal liver resection (n = 42) and matched pairs from group 2 with similar extent of cytoreduction did not yield significant differences in morbidity/mortality. CRC patients from group 1 had poorer median overall survival (45.1 vs. 73.5 months from stage IV diagnosis, P = 0.009).

CONCLUSIONS

Liver involvement denotes high peritoneal carcinomatosis burden, which often requires resection of multiple organs in order to achieve optimal cytoreduction. However, liver resection-related morbidity is low and overall morbidity/mortality rates are comparable to other extensive CRS/HIPEC procedures. J. Surg. Oncol. 2016;113:432-437. © 2016 Wiley Periodicals, Inc.

A case series of congenital hepatic hilar cyst: recommendations for diagnosis and management

BACKGROUND

Congenital hepatic hilar cysts are rare. Some are simple and do not require intervention, but some biliary cystic malformations impose the risk of morbidity and mortality.

OBJECTIVES

To assess a series of five patients presenting with congenital hepatic hilar cysts.

METHODS

We retrospectively reviewed all cases presenting to our pediatric surgical service between January 2010 and December 2012 and found to have a congenital hepatic hilar cyst. Data regarding clinical, radiological, operative and pathological features were analyzed.

RESULTS

Five children with congenital cyst of the hepatic hilum were identified; four of them were diagnosed prenatally. Four children had undergone surgical intervention: one with intrahepatic choledochal cyst, one with epidermoid cyst, and two with biliary atresia and an associated cyst of the common bile duct. In another case of choledochal cyst the treatment was conservative. All children except one had a good prognosis; one child with biliary atresia required liver transplantation.

CONCLUSIONS

The differential diagnosis of congenital hepatic hilar cyst includes a broad spectrum of pathologies. It is essential to diagnose biliary atresia as early as possible. Signs such as smaller cysts in association with a hypoplastic gallbladder and direct hyperbilirubinemia may be suggestive of biliary atresia.

[Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for peritoneal carcinomatosis of colorectal and appendiceal origin]

BACKGROUND

We report our initial experience combining cytoreductive surgery (CRS) plus intraperitoneal chemotherapy with hyperthermia (HIPEC) in a selected group of patients presenting with disseminated peritoneal carcinomatosis (PC) of colorectaL or appendiceaL origin at a single tertiary referral institution.

METHODS

The study included patients who underwent CRS with HIPEC at the Sheba Medical Center between April 2009 and December 2011. The HIPEC technique was administered with the open Coliseum technique reaching a steady state of mitomycin-C delivery at 410 C for perfusion duration of 90 minutes.

RESULTS

AnaLysis included 45 patients (18 males) incorporating 42 cases of primary colorectal cancer (CRC) or appendiceal cancer and 3 cases of pseudomyxoma peritonei. Thirty-seven patients (82%) underwent CC-0 resections with a median overall hospital stay of 8 days (range 5-43). There was one perioperative death at 90 days. The perioperative complication rate was 31.1%. The median follow-up was 12 months (range 2-36) during which 13 patients died. Among the CRC and appendiceal cancer group the median overall survival was 20.2 months and the median progression free survival was 16.4 months (Kaplan-Meier analysis). During follow-up, 23 patients experienced disease progression.

CONCLUSION

The selective use of cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy for patients with peritoneal carcinomatosis from colorectal or appendiceal origin is safe with acceptable morbidity and low mortality.

Tricuspid valve regurgitation after orthotopic heart transplantation: prevalence and etiology

Background. Tricuspid valve regurgitation (TR) after orthotopic heart transplantation (OHT) is common. The aims of this study were to determine the prevalence of TR after OHT, to examine the correlation between its development and various variables, and to determine its outcomes. Methods. All 163 OHT patients who were followed up between 1988 and 2009 for a minimal period of 12 months were divided into those with no TR/mild TR and those with at least mild-moderate TR, as assessed by doppler echocardiography. These groups were compared regarding preoperative hemodynamic variables, surgical technique employed, number of endomyocardial biopsies, number of acute cellular rejections, incidence of graft vasculopathy, and clinical outcomes. Results. At the end of the followup (average 8.2 years) significant TR was evident in 14.1% of the patients. The development of late TR was found by univariate, but not multivariate, analysis to be significantly correlated with the biatrial surgical technique (P < 0.01) and the presence of graft vasculopathy (P < 0.001). TR development was found to be correlated with the need for tricuspid valve surgery but not with an increased mortality. Conclusions. The development of TR after OHT may be related to the biatrial anastomosis technique and to graft vasculopathy.

Ethylene glycol and amino acid derivatives of 5-aminolevulinic acid as new photosensitizing precursors of protoporphyrin IX in cells

Protoporphyrin IX (PpIX) is used as a photosensitizing agent in photodynamic detection and therapy (PDT) of cancer and is synthesized intracellularly from aminolevulinic acid (ALA) precursors. To evaluate means to specifically target ALA derivatives to defined cells, we have synthesized and characterized ethylene glycol esters and amino acid pseudodipeptide derivatives of ALA as potential specific substrates for cellular esterases and aminopeptidases, respectively. The PpIX formation induced by these products was investigated using cultures of human and rat cell lines of carcinoma and endothelial origins. The cytotoxicity of these compounds in the absence of light was also controlled. The results have shown that ethylenglycol esters can induce high levels of PpIX and are useful at concentrations below their cytotoxicity threshold. From the ALA-amino acid derivatives which were evaluated, the highest PpIX production was obtained using ALA derivatives of neutral amino acids, as compared to acidic or basic amino acids.

Very slow chiral inversion of clopidogrel in rats: a pharmacokinetic and mechanistic investigation

Clopidogrel hydrogen sulfate, a thienopyridine derivative, is an ADP receptor antagonist that inhibits platelet aggregation. Clopidogrel is an enantiopure carboxylic ester of S-configuration. The R-enantiomer is devoid of antithrombotic activity and can provoke convulsions at high doses in animals. During preclinical safety evaluation, the possible chiral inversion of clopidogrel has, therefore, been investigated in vivo after repeated oral administration of different dose levels of clopidogrel to male and female rats. Due to rapid metabolism in the liver and low plasma levels of unchanged drug, possible chiral inversion was assessed by monitoring the plasma concentrations of the carboxylic acid metabolites, i.e., the (S)- and (R)-acid, by means of a stereoselective assay. The production of 4 to 8% of (R)-acid was observed. This could be the result of chiral inversion of either clopidogrel or its main metabolite, the (S)-acid. Thus, the possibility of nonenzymatic and enzymatic inversion of clopidogrel and its carboxylic acid metabolite was studied in vitro by chiral HPLC and (1)H NMR. Nonenzymatic chiral inversion of clopidogrel at 37 degrees C in 0.1 M phosphate buffers could be observed but was found to be slow, with estimated half-lives of 7 to 12 days, depending on the pH. The (S)-acid was configurationally fully stable up to 45 days in phosphate buffers. Neither clopidogrel nor its carboxylic acid metabolites were subject to enzymatic chiral inversion in isolated rat hepatocyte suspensions. We conclude that the nonenzymatic inversion of clopidogrel accounts for the 4 to 8% of chiral inversion seen in vivo in the rat.

Expression and induction of CYP1A1/1A2, CYP2A6 and CYP3A4 in primary cultures of human hepatocytes: a 10-year follow-up

1. The aims were to refine experimental conditions (using 76 human hepatocyte preparations) in terms of the selection of enzyme inducers and their optimal concentration, the treatment duration with inducers and the choice of specific cytochrome P450 isoform(s) probes to optimize the use of primary hepatocytes for predicting the potential induction by new chemical entities of cytochrome P450 isoforms in vivo in man. 2. In the absence of any inducer, basal cytochrome P450 isoform(s)-mediated activities decreased to 20% of their initial activity (end of the seeding period) by 72-96 h. In contrast, UGT-dependent enzyme activities remained at a constant level (+/- 20%) up to the fifth day of culture. 3. Beta-naphthoflavone, at an optimal concentration of 50 microM and after a 3-day treatment, specifically and potently induced 7-ethoxyresorufin (10.4 +/- 10.4-fold, n = 74) and phenacetin (6.6 +/- 6.4-fold, n = 60) O-deethylation processes, markers for CYP1A1 and CYP1A2 isoforms respectively. Only a 2-fold increase was noted following treatment with 2 mM phenobarbitone, whereas dexamethasone and rifampicin had no effect at all. 4. A 3-day treatment of human hepatocytes with 50 microM dexamethasone was associated with a major induction of both coumarin 7-hydroxylation (9.4 +/- 11.4-fold, n = 49) and nifedipine dehydrogenation (4.7 +/- 3.8-fold, n = 61), markers for CYP2A6 and CYP3A4 respectively. Phenobarbitone, however, exhibited a broad but moderate inducing effect on 7-ethoxyresorufin (2.2 +/- 1.5-fold, n = 55) and phenacetin (1.7 +/- 0.9-fold, n = 54) O-deethylation, coumarin 7-hydroxylation (3.9 +/- 9.2-fold, n = 50) and nifedipine dehydrogenation (2.1 +/- 2.0-fold, n = 47). 5. Km obtained for the different cytochrome P450 isoform substrates in untreated hepatocytes were in the same range of magnitude that those determined on human hepatic microsomal fractions. Enzyme induction processes were characterized by a large increase in apparent Vmax whereas apparent Km were not affected. 6. These studies demonstrate that human hepatocytes in primary culture can respond specifically and quantitatively to model inducers. This in vitro system offers a useful approach to study the regulation of human hepatic biotransformation activities and should facilitate the demand for a reproducible method for addressing cytochrome P450 induction.

Disposition of irbesartan, an angiotensin II AT1-receptor antagonist, in mice, rats, rabbits, and macaques

Metabolism and disposition of irbesartan, an angiotensin II AT(1) receptor antagonist, were investigated in mice, rats, rabbits, and macaques. In both rats and macaques, irbesartan was characterized by a rapid oral absorption, a large volume of distribution, a low plasma clearance, and a long terminal half-life. The oral bioavailability in macaques was notably higher than in rats. Irbesartan was highly protein bound in rats and macaques. A lower binding rate was found in mice and rabbits. In distribution studies performed in rats, mice, and rabbits, irbesartan was rapidly distributed into most organs and tissues including brain, intrauterine area, and milk. No retention of radioactivity in tissues other than liver and kidney was noted. Irbesartan was the main circulating compound in rats, rabbits, and macaques representing a maximum of 67, 68, and 80% of plasma radioactivity, respectively. The drug was metabolized mainly by glucuronidation (primarily on the tetrazole ring), hydroxylation, and additional oxidation. The overall pathways within the different species generated 18 metabolites identified from bile, urine, and feces samples. Irbesartan did not significantly induce or inhibit most of the isoenzymes commonly associated with drug metabolism in either rats or macaques after oral administration for 1 month. In most species irbesartan and its metabolites were mainly excreted in feces with more than 80% of a radioactive dose recovered within 24 or 48 h. Enterohepatic circulation was demonstrated in rats and macaques.

Disposition of tiludronate (Skelid) in animals

The disposition of tiludronate in mouse, rat, rabbit, dog and monkey has been studied after oral and intravenous doses. Like other bisphosphonates, tiludronate was characterized by poor absorption from the gastrointestinal tract. Peak plasma concentrations appeared shortly (0.5-1 h) after dosing, except for the baboon (4.5 h). Food intake highly impaired intestinal absorption The affinity of tiludronate for bone and the slow release from this deep compartment could account for the large volume of distribution and the low plasma clearance found in all species. Tiludronate has low affinity for red blood cells and binds moderately to serum proteins, mainly to serum albumin. Calcified tissues appeared to be the main target for deposition. Distribution into bone was not homogenous, with higher levels in the trabecular bone than in the corticol part of the long bones. The uptake of tiludronate into bone was unequivocally less in the older animal. No metabolism occurred in the tested animal species. The major route of elimination of the absorbed drug is urine. Preclinical observations made with tiludronate, like with other bisphosphonates, were predictive of results obtained in clinical investigation.