Development and Evaluation of EDTA-Treated Rabbits for Bioavailability Study of Chelating Drugs Using Levofloxacin, Ciprofloxacin, Hemiacetal Ester Prodrugs, and Tetracycline.

Laboratory rabbits are fed foods rich with cationic metals, and while fasting cannot empty gastric contents because of their coprophagic habits. This implies that, in rabbits, the oral bioavailability of chelating drugs could be modulated by the slow gastric emptying rates and the interaction (chelation, adsorption) with gastric metals. In the present study, we tried to develop a rabbit model with low amounts of cationic metals in the stomach for preclinical oral bioavailability studies of chelating drugs. The elimination of gastric metals was achieved by preventing food intake and coprophagy and administering a low concentration of EDTA 2Na solution one day before experiments. Control rabbits were fasted but coprophagy was not prevented. The efficacy of rabbits treated with EDTA 2Na was evaluated by comparing the gastric contents, gastric metal contents and gastric pH between EDTA-treated and control rabbits. The treatment with more than 10 mL of 1 mg/mL EDTA 2Na solution decreased the amounts of gastric contents, cationic metals and gastric pH, without causing mucosal damage. The absolute oral bioavailabilities (mean values) of levofloxacin (LFX), ciprofloxacin (CFX) and tetracycline hydrochloride (TC), chelating antibiotics, were significantly higher in EDTA-treated rabbits than those in control rabbits as follows: 119.0 vs. 87.2%, 9.37 vs. 13.7%, and 4.90 vs. 2.59%, respectively. The oral bioavailabilities of these drugs were significantly decreased when Al(OH)3 was administered concomitantly in both control and EDTA-treated rabbits. In contrast, the absolute oral bioavailabilities of ethoxycarbonyl 1-ethyl hemiacetal ester (EHE) prodrugs of LFX and CFX (LFX-EHE, CFX-EHE), which are non-chelating prodrugs at least in in vitro condition, were comparable between control and EDTA-treated rabbits irrespective of the presence of Al(OH)3, although some variation was observed among rabbits. The oral bioavailabilities of LFX and CFX from their EHE prodrugs were comparable with LFX and CFX alone, respectively, even in the presence of Al(OH)3. In conclusion, LFX, CFX and TC exhibited higher oral bioavailabilities in EDTA-treated rabbits than in control rabbits, indicating that the oral bioavailabilities of these chelating drugs are reduced in untreated rabbits. In conclusion, EDTA-treated rabbits were found to exhibit low gastric contents including metals and low gastric pH, without causing mucosal damage. Ester prodrug of CFX was effective in preventing chelate formation with Al(OH)3 in vitro and in vivo, as well as in the case of ester prodrugs of LFX. EDTA-treated rabbits are expected to provide great advantages in preclinical oral bioavailability studies of various drugs and dosage formulations. However, a marked interspecies difference was still observed in the oral bioavailability of CFX and TC between EDTA-treated rabbits and humans, possibly due to the contribution of adsorptive interaction in rabbits. Further study is necessary to seek out the usefulness of the EDTA-treated rabbit with less gastric contents and metals as an experimental animal.

Diagnosis by Microbial Culture, Breath Tests and Urinary Excretion Tests, and Treatments of Small Intestinal Bacterial Overgrowth.

Small intestinal bacterial overgrowth (SIBO) is characterized as the increase in the number and/or alteration in the type of bacteria in the upper gastrointestinal tract and accompanies various bowel symptoms such as abdominal pain, bloating, gases, diarrhea, and so on. Clinically, SIBO is diagnosed by microbial culture in duodenum/jejunum fluid aspirates and/or the breath tests (BT) of hydrogen/methane gases after ingestion of carbohydrates such as glucose. The cultural analysis of aspirates is regarded as the golden standard for the diagnosis of SIBO; however, this is invasive and is not without risk to the patients. BT is an inexpensive and safe diagnostic test but lacks diagnostic sensitivity and specificity depending on the disease states of patients. Additionally, the urinary excretion tests are used for the SIBO diagnosis using chemically synthesized bile acid conjugates such as cholic acid (CA) conjugated with para-aminobenzoic acid (PABA-CA), ursodeoxycholic acid (UDCA) conjugated with PABA (PABA-UDCA) or conjugated with 5-aminosalicylic acid (5-ASA-UDCA). These conjugates are split by bacterial bile acid (cholylglycine) hydrolase. In the tests, the time courses of the urinary excretion rates of PABA or 5-ASA, including their metabolites, are determined as the measure of hydrolytic activity of intestinal bacteria. Although the number of clinical trials with this urinary excretion tests is small, results demonstrated the usefulness of bile acid conjugates as SIBO diagnostic substrates. PABA-UDCA disulfate, a single-pass type unabsorbable compound without the hydrolysis of conjugates, was likely to offer a simple and rapid method for the evaluation of SIBO without the use of radioisotopes or expensive special apparatus. Treatments of SIBO with antibiotics, probiotics, therapeutic diets, herbal medicines, and/or fecal microbiota transplantation are also reviewed.

Study on the method to avoid infusion-site adverse events following chemotherapeutic treatment with epirubicin and fosaprepitant using immortalized human umbilical vein endothelial cells.

The combination of intravenous Proemend® containing fosaprepitant meglumine, a prodrug for fosaprepitant (FAP), and Tween 80 and chemotherapy with anthracyclines, such as epirubicin (EPI), can cause infusion-site adverse events in clinical practice. In immortalized human umbilical vein endothelial (HUEhT-1) cells, the cytotoxic effects of FAP, EPI, diluted Proemend with culture medium and Tween 80 alone, and a combination of FAP and EPI, were evaluated using the WST-1 cell viability assay. FAP, EPI and diluted Proemend exhibited cytotoxicity in a concentration-dependent manner and marked synergic cytotoxicity was observed between FAP and EPI. The washing of the cell surface following incubation with diluted Proemend containing FAP and Tween-80 eliminated the synergic cytotoxicity of EPI applied thereafter. These results indicated that washing of the infusion-site vascular tissue following intravenous Proemend administration via intravenous tube flushing with an efficient amount of saline may reduce the infusion-site adverse events, which are caused by the combined use of FAP and EPI.

Study on the infusion-site adverse events and vascular distribution of epirubicin in chemotherapy with epirubicin and fosaprepitant.

In breast cancer patients on a fluorouracil-epirubicin (EPI)-cyclophosphamide (FEC) regimen and intravenous fosaprepitant (FAP) during chemotherapy, infusion-site adverse events such as vascular pain and induration and/or phlebitis are observed. In the present study, adverse events induced by the FEC regimen and FAP, a prodrug of aprepitant (AP), were studied based on the vascular tissue distribution of EPI in rats. Rats were treated with intravenous FAP (3 mg/kg, 10 min-constant rate infusion) or oral AP (3 mg/kg) and then intravenous EPI (1 mg/kg, 5 min-constant rate infusion) as follows: FAP-S Group, FAP and then EPI was infused from the same site on the jugular vein; FAP-D Group, FAP and then EPI was infused from different jugular veins (left and right); and AP Group, AP was administered orally and EPI was infused from the jugular vein. Concentrations of EPI in vascular tissue at the EPI infusion sites and opposite sites of the jugular vein (left and right, respectively) were measured at 30 min and 24 h after EPI infusion. Histological observation of the EPI infusion site was also made separately. In rats, the tissue concentrations of EPI at the infusion site in the FAP-S group were higher than those in the FAP-D and AP groups. Inflammation and necrosis were observed at the EPI infusion-site vascular tissue of the FAP-S group, but not of the FAP-D and AP groups. These findings could aid the development of an approach to avoid infusion-site adverse events in anthracycline-based chemotherapy in the clinical practice.

Reduction in the rate of postoperative delirium by switching from famotidine to omeprazole in Japanese hepatectomized recipients.

BACKGROUND: Hepatectomy is a highly invasive procedure with a high probability of postoperative delirium. Treatment with antiulcer drugs is indispensable after hepatectomy for anastomotic ulcer management. The clinical pathway for hepatectomy was reviewed and the antiulcer drug used was switched from famotidine, a H2-receptor antagonist, to omeprazole, a proton pump inhibitor, owing to the pharmacist's intervention. METHODS: Hepatectomized recipients over 65 years of age, except in the cases of laparoscopic surgery and intensive care unit entry, were treated with famotidine injections (10 patients) or omeprazole injections (11 patients), and the incidence rates and severity of delirium were compared between the famotidine and omeprazole groups. The delirium after hepatectomy was assessed using the Japanese version of the NEECHAM confusion scale. RESULTS: The incidence rates of delirium were 90% in the famotidine group and 27.3% in the omeprazole group. Four out of 9 recipients in the famotidine group were injected with haloperidol to treat for delirium, but no recipients needed this treatment in the omeprazole group. CONCLUSIONS: Compared with famotidine, the use of omeprazole was found to be effective in reducing the incidence rate and severity of postoperative delirium in patients undergoing hepatectomy. Pharmacists should actively strive to mitigate the risks of delirium.

Dosage Adjustment of Dabigatran Etexilate Based on Creatinine Clearance in Patients With Cardioembolic Stroke or Atrial Fibrillation.

BACKGROUND: A recommendation for dosage adjustment of dabigatran etexilate, a prodrug of dabigatran, seems to be desirable based on creatinine clearance to avoid bleeding and stroke. METHODS: Outpatients and inpatients having a history of cardioembolic stroke or atrial fibrillation were included. After taking dabigatran etexilate orally (75-150 mg twice daily) for at least 1 week, plasma trough concentration (Ctrough, ng/mL) of dabigatran and creatinine clearance (CLcr, mL/min) of patients according to Cockcroft and Gault equation were determined. RESULTS: Among the 38 patients studied, Ctrough of dabigatran and CLcr were scattered in a range from 31.4 to 329.5 ng/mL and 15.4-133.4 mL/min, respectively. Temporal CLtotal (Temp-CLtotal) of dabigatran, estimated by dividing the daily absorbed amount of dabigatran etexilate with Ctrough of dabigatran, was linearly correlated with CLcr of patients (P = 0.0018). Based on the findings, the daily dose of dabigatran etexilate that provides Ctrough of dabigatran at approximately 70 ng/mL was estimated. CONCLUSIONS: A linear relationship was found between Temp-CLtotal of dabigatran and CLcr of patients. Depending on CLxr of patients, we recommend 4 different dosages of dabigatran etexilate to obtain Ctrough of dabigatran at approximately 70 ng/mL.

Interaction of magnesium oxide with gastric acid secretion inhibitors in clinical pharmacotherapy.

PURPOSE: Magnesium oxide (MgO), a short-term osmotic laxative, is converted into MgCl2 under acidic condition in the stomach and then Mg(HCO3)2 in the intestinal tract, where Mg(HCO3)2 induces the water exudation into the intestine. This indicates that the laxative effect of MgO could be attenuated under the suppressed gastric acid secretion. In this study, the possible interaction of MgO with gastric acid secretion inhibitors was evaluated by using electronic patient records of MgO dosage levels. METHODS: Defecation was controlled with MgO alone in some patients after colon surgery (n = 67) and after total gastric resection (n = 4). Some other patients were treated with a combination use of MgO and H2 receptor antagonist (H2RA) (n = 14) or proton pump inhibitor (PPI) (n = 27). The possible drug interaction of MgO with H2RA or PPI was evaluated by comparing dosage levels of MgO used in controlling defecation. RESULTS: In controlling defecation, the daily dosage levels of MgO in patients taking H2RA or PPI and patients with total gastric resection were significantly higher than those patients taking MgO alone after colon surgery. The ratios of good constipation control (controlled well at the dosing level of 1,000 mg MgO) in patients taking H2RA or PPI were significantly lower than that in patients treated with MgO alone. In an in vitro study, the solubility of MgO at pH 4.5 was quite low, as compared with that at pH 1.2. CONCLUSIONS: When patients received H2RA or PPI, the laxative effect of MgO is decreased possibly due to the low solubility of MgO at the higher gastric pH and less generation of MgCl2 and Mg(HCO3)2. Higher dosing level of MgO or another laxative should be used in patients taking H2RA or PPI, as well as the case of patients with total gastric resection.

Usefulness of one-point plasma SN-38G/SN-38 concentration ratios as a substitute for UGT1A1 genetic information after irinotecan administration.

BACKGROUND: It was recently reported that genetic polymorphisms of UDP glucuronyltransferase-1 polypeptide A1 (UGT1A1), a glucuronidation enzyme, were associated with irinotecan (CPT-11) metabolism. The active metabolite of CPT-11, 7-ethyl-10-hydroxycamptothecin (SN-38) was glucuronidated (SN-38G) by UGT1A1. Genetic polymorphisms of UGT1A1 were associated with potentially serious adverse events, including neutropenia. Several studies have suggested that the dose of CPT-11 should be decreased in patients homozygous for UGT1A1*6 or UGT1A1*28, or double heterozygotes (*6/*28). However, the reference dose for patients with these genetic polymorphisms is unclear. METHODS: We investigated the relationship between the SN-38G/SN-38 concentration ratio and the dose of CPT-11 in 70 patients with colorectal cancer who received FOLFIRI-based regimens, by measuring the plasma concentrations of CPT-11, SN-38, and SN-38G. RESULTS: The SN-38G/SN-38 concentration ratio was lower in patients who were homozygous for UGT1A1*6, heterozygous for UGT1A1*6 or UGT1A1*28, or were double heterozygotes compared with patients with wild-type genes. The relative decreases in the SN-38G/SN-38 concentration ratio in patients homozygous for UGT1A1*6 and in double heterozygotes were greater than in patients heterozygous for UGT1A1*6 or UGT1A1*28. Interestingly, decreases in the SN-38G/SN-38 concentration ratio were associated with decreases in the neutrophil count and the final infusion dose of CPT-11. CONCLUSION: Our results suggest that the SN-38G/SN-38 concentration ratio is an important factor for guiding dose adjustments, even in patients with wild-type genes. Therefore, the SN-38G/SN-38 concentration ratio, as an index of the patient's metabolic capacity, is useful for assessing dose adjustments of CPT-11.

Correlation between plasma concentration ratios of SN-38 glucuronide and SN-38 and neutropenia induction in patients with colorectal cancer and wild-type UGT1A1 gene.

In irinotecan (CPT-11)-based chemotherapy, neutropenia and diarrhea are often induced. In the present study, the clinical significance of the concentration ratios of 7-ethyl-10-hydroxycamptothecin (SN-38) glucuronide (SN-38G) and SN-38 in the plasma in predicting CPT-11-induced neutropenia was examined. A total of 17 patients with colorectal cancer and wild-type UDP-glucuronosyltransferase (UGT)1A1 gene were enrolled and treated with CPT-11 as part of the FOLFIRI regimen [CPT-11 and fluorouracil (5-FU)]. Blood was taken exactly 15 min following a 2-h continuous infusion of CPT-11. Plasma concentrations of SN-38, SN-38G and CPT-11 were determined by a modified high-performance liquid chromatography (HPLC) method. The median, maximum and minimum values of plasma SN-38G/SN-38 ratios were 4.25, 7.09 and 1.03, respectively, indicating that UGT activities are variable among patients with the wild-type UGT1A1 gene. The plasma SN-38G/SN-38 ratios decreased with an increase in the trial numbers of chemotherapy (r=0.741, p=0.000669), suggesting that CPT-11 treatment suppresses UGT activity, and the low plasma SN-38G/SN-38 ratios resulted in the induction of greater neutropenia. However, in this analysis, 2 clearly separated regression lines were observed between plasma SN-38G/SN-38 ratios and neutropenia induction. In conclusion, UGT activity involved in SN-38 metabolism is variable among patients with the wild-type UGT1A1 gene, and each CPT-11 treatment suppresses UGT activity. One-point determination of the plasma SN-38G/SN-38 ratio may provide indications for the prediction of CPT-11-induced neutropenia and adjustment of the optimal dose, although further studies are required.

Evaluation of clinical efficacy of Maeda's nomogram for vancomycin dosage adjustment in adult Japanese MRSA pneumonia patients.

The clinical efficacy of Maeda's nomogram for vancomycin dosage adjustment was evaluated by comparison with a standard dosage regimen (package insert information: vancomycin dose reduced in elderly patients and patients with renal dysfunction, with Moellering's nomogram used for renal-dysfunction patients) in adult Japanese MRSA pneumonia patients. Using Maeda's nomogram, the vancomycin dose is fixed at 1,000 mg while the dosing interval is varied in accordance with individual creatinine clearance. Using a standard dosage regimen, 5 patients out of 27 (18.5%) achieved target plasma levels of vancomycin (25-40 microg/mL for peak and 5-15 microg/mL for trough) within 2-6 days. Using Maeda's nomogram, 38 patients out of 53 (71.7%) achieved target levels in that time. A higher clinical response (complete resolution of all signs and symptoms of MRSA infection) to vancomycin therapy was also obtained with Maeda's nomogram when evaluated approximately 2-weeks after discontinuation of vancomycin therapy (43.4% versus 18.5% for the standard regimen). In conclusion, the Maeda's nomogram regimen with a 1,000 mg vancomycin dose was shown to achieve target plasma levels of vancomycin at a higher rate and provide higher clinical efficacy in vancomycin therapy of MRSA pneumonia patients, as compared with the currently available standard dosage regimen.

Increased erythrocyte distribution of valproic acid in pharmacokinetic interaction with carbapenem antibiotics in rat and human.

Carbapenem antibiotics cause pharmacokinetic interaction with valproic acid (VPA) in clinical pharmacotherapy. Here, we investigated the mechanism of interaction from the viewpoint of erythrocyte distribution of VPA in rats and humans. Imipenem or panipenem was administered intravenously and then VPA intravenously or into the intestinal lumen in rats. Both imipenem and panipenem significantly decreased plasma VPA levels. In contrast, these antibiotics did not affect, or rather increased, VPA levels in whole blood, and increased the erythrocyte distribution of VPA in vivo. In clinical, two patients receiving VPA were given imipenem intravenously, because of intractable infectious diseases. Imipenem lowered plasma VPA levels by approximately 40%-60% of original levels, and increased the erythrocyte distribution of VPA, as observed in rats. In conclusion, the pharmacokinetic interaction between VPA and carbapenem antibiotics, in which plasma VPA levels were markedly reduced, may partly be derived from the increased erythrocyte distribution of VPA.

Prevention of irinotecan-induced diarrhoea by oral carbonaceous adsorbent (Kremezin) in cancer patients.

Irinotecan (CPT-11) treatments induce severe diarrhoea at a rate of >40%. In clinical trials, we evaluated the preventing effects of oral alkalization, which has been reported previously, and oral carbonaceous adsorbent (Kremezin trade mark ) on diarrhoea possibly induced by CPT-11. Evaluation was made by counting the maximum number of bowel motions in each patient. Five patients out of 7 treated with CPT-11 had bowel motions of >5 times daily, and maximum number of bowel motions reached 20 times in 1 patient. Oral alkalization (2 g sodium bicarbonate, 2 g magnesium oxide and 300 mg ursodeoxycholic acid daily for 4 days) decreased bowel motions from 20 to 8 thereafter in the patient. Maximum number of bowel motions in other 3 patients treated in a combination of CPT-11 and oral alkalization was <3. Oral adsorbent (2 g Kremezin x 3 times, during and after CPT-11 treatment) also decreased maximum number of bowel motions from 7 (without oral adsorbent) to 3 in 1 patient. Also, the maximum number of bowel motions in other 3 patients treated with oral adsorbent was <3 (p<0.05, vs CPT-11 alone). Effect of oral Kremezin on plasma concentrations of CPT-11 and its related compounds after a 1-h CPT-11 infusion, evaluated in a patient, was small. These results suggested that the oral Kremezin is effective in ameliorating CPT-11-induced diarrhoea without decreasing much the plasma clearance of CPT-11.

Dosage adjustment of ribavirin based on renal function in Japanese patients with chronic hepatitis C.

The daily dose of ribavirin is currently determined based on body weight. In the present study, the authors examined factors influencing total plasma clearance (CL(total)) and the toxic level on red blood cells of ribavirin in such body weight-based dosage adjustment in Japanese chronic hepatitis C patients (13 male and 6 female). Patients received ribavirin (600 or 800 mg/d) orally, depending on their body weights, together with interferon alpha-2b (6 million units) intramuscularly. A steady-state trough plasma concentration (C(pss)) was achieved approximately 4 weeks after the initiation of treatment, but the value was scattered among patients in a range from 1100 to 4200 ng/mL. The high C(pss) of ribavirin of approximately 4000 ng/mL decreased hemoglobin concentrations to less than 8.5 g/dL. The individual CL(total), estimated by dividing dose normalized by body weight by C(pss), of ribavirin correlated significantly with the patient's creatinine clearance. In contrast, no relationship was observed with other parameters such as age, body weight, serum creatinine concentration, alanine aminotransferase (ALT) concentration, or aspartate aminotransferase (AST) concentration, though ALT and AST concentrations decreased with ribavirin treatment in most patients. These results indicate that CL(total) of ribavirin is dependent on renal function (creatinine clearance), and hemolysis is induced by high ribavirin concentrations in plasma. Dosage adjustment of ribavirin based on renal function and body weight would provide effective and safer treatment without causing hemolysis.

Possible mechanism for pharmacokinetic interaction between lidocaine and mexiletine.

OBJECTIVE: Our objective was to elucidate the mechanism of pharmacokinetic interaction between lidocaine and mexiletine, because an unexpected increase in plasma lidocaine concentration accompanied by severe side effects was observed when mexiletine was administered to a patient with dilated cardiomyopathy. METHODS: Plasma concentrations of lidocaine, its major metabolites, and mexiletine were measured in a patient with dilated cardiomyopathy. The lidocaine-mexiletine interaction was evaluated by examination of the effects of mexiletine on plasma concentration and the tissue distribution of lidocaine in rabbits in vivo, as well as on the in vitro lidocaine binding to phosphatidylserine, a binding constituent for weakly basic drugs. RESULTS: Plasma lidocaine concentrations increased significantly when the oral dose of mexiletine was increased. This pharmacokinetic interaction was not attributable to a metabolic interaction as evaluated by plasma lidocaine metabolites concentrations. In rabbits, mexiletine seemed to decrease the total plasma clearance of lidocaine, resulting in increased plasma lidocaine concentrations. Mexiletine significantly reduced the tissue distribution of lidocaine to the kidneys and lungs. A strong displacing effect of mexiletine on the binding of lidocaine to phosphatidylserine was observed in vitro. CONCLUSIONS: A drug interaction derived from the displacement of lidocaine from tissue binding sites by mexiletine that resulted in the increased plasma lidocaine concentrations was shown. This observation had implications for loading doses and acute effects of lidocaine in the concurrent therapy of lidocaine and mexiletine.