Evaluation of the relationship between cardiac calcification and cardiovascular disease using the echocardiographic calcium score in patients undergoing peritoneal dialysis: a cross-sectional study.

Introduction: An echocardiographic calcium score (ECS) predicts cardiovascular disease (CVD) in the general population. Its utility in peritoneal dialysis (PD) patients is unknown. Methods: This cross-sectional study assessed 125 patients on PD. The ECS (range 0-8) was compared between subjects with CVD and those without. Results: Among the subjects, 54 had CVD and 71 did not. Subjects with CVD were older (69 years vs. 56 years, P < 0.001) and had a higher prevalence of diabetes mellitus (DM) (81.5% vs. 45.1%, P < 0.001). They had lower diastolic blood pressure (72 mmHg vs. 81 mmHg, P < 0.001), lower phosphate (1.6 mmol/L vs. 1.9 mmol/L, P = 0.002), albumin (30 g/L vs. 32 g/L, P = 0.001), parathyroid hormone (34.4 pmol/L vs. 55.8 pmol/L, P = 0.002), total cholesterol (4.5 vs. 4.9, P = 0.047), LDL cholesterol (2.4 mmol/L vs. 2.8 mmol/L, P = 0.019) and HDL cholesterol (0.8 mmol/L vs. 1.1 mmol/L, P = 0.002). The ECS was found to be higher in subjects with CVD than in those without (2 vs. 1, P = 0.001). On multivariate analysis, only DM and age were independently associated with CVD. Conclusion: The ECS was significantly higher in PD patients with CVD than in those without, reflecting a higher vascular calcification burden in the former. It is a potentially useful tool to quantify vascular calcification in PD patients.

An echocardiography-derived calcium score as a predictor of major adverse cardiovascular events in peritoneal dialysis patients-A prospective cohort study.

BACKGROUND: An echocardiography-derived calcium score (ECS) has been shown to predict cardiovascular (CV) mortality in the general population but has not been utilized in the dialysis population. METHODS: We conducted a prospective cohort study including 125 prevalent PD patients. Two blinded and independent echocardiographers determined the ECS for each subject at baseline. The primary outcome was the three-point major adverse cardiovascular events (MACE) which is a composite outcome comprising CV death, non-fatal myocardial infarction and non-fatal stroke. The secondary outcome was all-cause mortality. RESULTS: The mean age was 61 ± 13 years. The median follow-up duration was 40 months (range 1-50). Seventy six (60.8%) of the subjects had diabetes mellitus (DM). The median duration of dialysis was 32 (IQR 16-54) months. The incidences of MACE and all-cause mortality were 13.0 per 100 patient-years and 18.3 per 100 patient-years. Multivariate Cox regression analysis identified the following three independent predictors of MACE: ECS (HR 1.253/unit increase in ECS, 95% CI 1.014-1.547, p = .036), DM (HR 2.467, 95% CI 1.014-6.005, p = .047) and pre-existing cardiovascular disease (CVD) (HR 2.441, 95% CI 1.261-4.728, p = .008); and the following two predictors of all-cause mortality: pre-existing CVD (HR 2.156, 95% CI 1.251-3.714, p = .006) and serum albumin (HR 0.887/g/L increase in serum albumin, 95% CI 0.839-0.937, p < .001). CONCLUSION: The ECS appears to be a significant predictor of MACE in PD patients independently of DM and pre-existing CVD.

Treatment of Severe Tumoral Calcinosis with Teriparatide in a Dialysis Patient after Total Parathyroidectomy.

Tumoral calcinosis is a rare but debilitating condition that can affect dialysis patients. Optimal management is largely unknown. We report the clinical course, treatment, and outcome of a peritoneal dialysis (PD) patient who developed tumoral calcinosis refractory to conventional treatment but improved with teriparatide therapy. A 26-year-old lady on PD for 2 years presented to us with tumoral calcinosis involving bilateral hands. Response to surgical excision, parathyroidectomy, and conversion to hemodialysis failed to result in sustained remission, and tumoral calcinosis progressed. After total parathyroidectomy, the patient had transient but partial remission in which her calcinosis deposits remained but were asymptomatic without pain or clinical signs of inflammation. However, she later experienced a relapse with involvement of the left elbow, right shoulder, right hip, and right thigh. Tumoral calcinosis remained uncontrolled resulting in debilitation, likely attributable to poor calcium and phosphate control because of adynamic bone disease after parathyroidectomy despite treatment of superimposed tuberculosis and therapy with sodium thiosulphate and pamidronic acid. Clinical improvement was however evident after the use of teriparatide. Asymptomatic hypocalcemia occurred after teriparatide therapy but resolved after 2 months. In conclusion, teriparatide appears to be useful for treating tumoral calcinosis in the presence of adynamic bone disease. Hypocalcemia can occur in the initial months of therapy.

Risk factors and clinical course of hungry bone syndrome after total parathyroidectomy in dialysis patients with secondary hyperparathyroidism.

BACKGROUND: Hungry bone syndrome (HBS) is an important postoperative complication after parathyroidectomy for severe secondary hyperparathyroidism (SHPT). There is, however, little data in the literature on its detailed clinical course, and the associated risk factors remain controversial. METHODS: We did a single-center retrospective study on 62 consecutive dialysis patients who underwent total parathyroidectomy for SHPT to examine the risk factors, clinical course and outcome. Data on demographic characteristics, perioperative laboratory parameters including serum calcium, phosphate, alkaline phosphatase (ALP) and parathyroid hormone (PTH), drug treatment for SHPT and operative details of parathyroidectomy were collected. RESULTS: Seventeen (27.4%) patients developed severe postoperative hypocalcemia with HBS. The serum calcium dropped progressively while serum ALP rose after operation until 2 weeks later when serum calcium reached the trough and serum ALP peaked. Serum phosphate also fell but stabilized between 4 and 14 days. The total postoperative calcium and vitamin D supplementation was significantly larger, and hospital stay was significantly longer in the group with HBS as compared with those without HBS. Young age, high body weight, high preoperative ALP level, and low preoperative calcium level independently predicted the development of HBS while preoperative PTH and use of cinacalcet or paricalcitol did not. CONCLUSION: HBS was common after total parathyroidectomy in patients with SHPT, and it is important to closely monitor the postoperative serum calcium, phosphate and ALP levels in the following 2 weeks, especially for those at risk. The implications of our findings on perioperative management are discussed.

Treatment of HCV in renal transplant patients with peginterferon and ribavirin: long-term follow-up.

BACKGROUND: In addition to the observation of an increased viremia among patients with chronic hepatitis C virus (HCV) infection who undergo renal transplantation, fibrosis and necroinflammatory activity have been noted to worsen comparing pre- and post-renal transplantation liver biopsies in some of these patients. Apart from the reported reduced patient and allograft survival rates, post-transplant diabetes mellitus, de novo glomerulonephritis, and an increased overall risk of infection have been observed. However, antiviral therapy for HCV is generally considered contraindicated among patients with solid organ transplants, with the main worry being the risk of acute rejection in relation to the use of interferon. We reported the long-term outcome of four renal transplant patients with chronic HCV infection who received peginterferon-based therapy. METHODS: We collected the long-term follow-up data of four patients who completed the therapy with peginterferon in combination with ribavirin. Two of them had renal impairment at baseline. RESULTS: With treatment, they had a significant improvement in terms of serum liver transaminase level, and two patients achieved the early virological response and the other two rapid virological response. All four patients achieved sustained virological response, with neither HCV flare up nor renal dysfunction during follow-up for a mean duration of 74.3 months after therapy. CONCLUSIONS: These results suggest that sustained HCV virological response may be achieved without allograft dysfunction, in selected renal transplant patients using a peginterferon-based therapy.

Alternating Mupirocin/Gentamicin is Associated with Increased Risk of Fungal Peritonitis as Compared with Gentamicin Alone - Results of a Randomized Open-Label Controlled Trial.

UNLABELLED: ♦ BACKGROUND AND OBJECTIVES: Catheter-related infection, namely exit-site infection (ESI) and peritonitis, is a major infectious complication and remains a main cause of technique failure for patients receiving peritoneal dialysis (PD). Topical application of antibiotic cream might reduce catheter-related infection but emergence of resistant or opportunistic organisms could be a concern. Optimal topical agents and regimens remain to be determined. We did a study to examine the effect of an alternating topical antibiotic regimen in preventing catheter-related infection. ♦ METHOD: We performed a single-center, randomized, open-label study to compare daily topical application of gentamicin cream with a gentamicin/mupirocin alternate regimen to the exit site. Patients randomized to alternating regimen were asked to have daily application of gentamicin cream in odd months and mupirocin cream in even months. Primary outcomes were ESI and peritonitis. Secondary outcomes were catheter removal or death caused by catheter-related infection. A total of 146 patients (71, gentamicin group; 75, alternating regimen group) were enrolled with a total follow-up duration of 174 and 181 patient-years for gentamicin and alternating groups, respectively. All patients were followed up until catheter removal, death, transfer to another unit, transplantation or the end of the study on March 31, 2014. There were no significant differences in the age, sex, dialysis vintage, and rate of diabetes, helper-assisted dialysis and methicillin-resistant Staphylococcus aureus (MRSA) carriage state. ♦ RESULTS: No difference was seen in the time to first ESI or peritonitis. However, the time to first gram-negative peritonitis seemed longer for the gentamicin group (p = 0.055). The 2 groups showed a similar rate of ESI (0.17/yr vs 0.19/yr, p = 0.93) but P. aeruginosa ESI was less common in the gentamicin group (0.06/yr vs 0.11/yr, p < 0.001). There was no difference in the incidence of ESI due to non-tuberculous mycobacteria. Peritonitis rate was significantly lower in the gentamicin group (0.22/yr vs 0.32/yr, p < 0.001), with a striking decrease in gram-negative peritonitis (0.08/yr vs 0.14/yr, p < 0.001), and fungal peritonitis (0.006/yr vs 0.03/yr, p < 0.001), which was all antibiotics-related episodes with antecedent use of systemic antibiotics for the treatment of catheter-related infections. There was no significant difference in the catheter loss or death related to catheter-related infection. ♦ CONCLUSION: Alternating gentamicin/mupirocin cream application appeared as effective as gentamicin alone in preventing ESI except for P. aeruginosa. However, it was inferior to gentamicin in the prevention of peritonitis episodes, especially for those caused by gram-negative organisms. It was also not useful in reducing catheter-related infection due to opportunistic organisms but instead associated with a higher incidence of antibiotic-related fungal peritonitis.

Persistent sterile peritoneal inflammation after catheter removal for refractory bacterial peritonitis predicts full-blown encapsulating peritoneal sclerosis.

BACKGROUND: Encapsulating peritoneal sclerosis (EPS) is the most serious complication of peritoneal dialysis, having high morbidity and mortality. To improve outcomes, early diagnosis is needed to direct treatment during the early inflammatory phase. However, in the early inflammatory phase, clinical features are nonspecific, and no reliable diagnostic criteria have been established. Because bacterial peritonitis and termination of dialysis are two important risk factors triggering the progression of EPS, patients with refractory bacterial peritonitis necessitating dialysis catheter removal are at particularly high risk of developing EPS. Many of these patients might indeed experience non-resolving sterile peritonitis (probably the inflammatory phase of EPS) before progression to full-blown disease (that is, the presence of intestinal obstruction). We undertook a retrospective study to compare, in this particular situation, the clinical characteristics of patients with or without sterile peritoneal inflammation, assessing their clinical outcomes in terms of short-term mortality and the chance of developing full-blown EPS. METHODS: Our retrospective review included 62 patients whose dialysis catheter was removed because of refractory peritonitis between January 2005 and December 2010. RESULTS: Of the 62 patients identified, 39 (63%) had persistent sterile peritoneal inflammation ("high-risk" group, n = 39), and 23 (37%) had resolution of inflammation without significant intra-abdominal collection after catheter withdrawal ("control" group, n = 23). Compared with the control group, the high-risk group had a significantly longer PD duration (71.6 ± 43.3 months vs 42.3 ± 29.9 months, p = 0.003), a higher dialysate-to-plasma ratio (D/P) of creatinine (0.768 ± 0.141 vs 0.616 ± 0.091, p = 0.004), and a higher computed tomography score for EPS (7.69 ± 2.98 vs 1.00 ± 1.00, p < 0.001). During the 6-month study period, the high-risk group had a higher chance of developing full-blown EPS (31% vs 0%, p = 0.002) and a higher 6-month all-cause mortality (36% vs 4.3%, p = 0.004). CONCLUSIONS: Persistent sterile peritoneal inflammation was common after dialysis catheter removal for refractory bacterial peritonitis, and the patients with such inflammation were at high risk of progression to full-blown EPS.

Atypical mycobacterial exit-site infection and peritonitis in peritoneal dialysis patients on prophylactic exit-site gentamicin cream.

We report 9 cases of exit-site infection and continuous ambulatory peritoneal dialysis peritonitis associated with atypical mycobacteria. All patients had been using topical gentamicin cream as prophylaxis for exit-site infection before the onset of these infections. Gentamicin cream is postulated to be a potential risk factor for atypical mycobacterial infection because of selective pressure on other micro-organisms. The microbiology of atypical mycobacteria and the treatment for atypical mycobacterial infections are discussed.

Efficacy of enteric-coated mycophenolate sodium in patients with active lupus nephritis.

BACKGROUND: The ideal treatment of lupus nephritis has yet to be defined. Both cyclophosphamide and mycophenolate mofetil have been used with encouraging results, but adverse events are frequently seen. There are no data on the use of enteric-coated mycophenolate sodium. METHODS: We retrospectively reviewed 12 patients with active forms of lupus nephritis (1 class III, 7 class IV and 4 class V) treated with enteric-coated mycophenolate sodium combined with corticosteroids. RESULTS: The mean age of the patients was 32.3 +/- 11.2 years and the average length of follow up was 25.9 +/- 8.9 months. The mean serum creatinine clearance was 93 +/- 30.1 mL/min per 1.73 m(2) and the mean proteinuria level was 4.5 +/- 3.6 g/day. All had features that warranted aggressive treatment. Mycophenolate sodium was given for 12.9 +/- 9.7 months with an averaged starting dose of 1350 +/- 163 mg/day. Six patients attained complete remission and six attained partial remission with treatment. The mean interval to attain first remission (complete or partial) was 8.3 +/- 5.7 weeks. At last follow up, all patients were in complete or partial remission. Apart from herpes zoster that developed in one patient, no other significant side-effects were encountered. CONCLUSION: Enteric-coated mycophenolate sodium was effective and well-tolerated in the treatment of active lupus nephritis.

Treatment of fungal peritonitis with a combination of intravenous amphotericin B and oral flucytosine, and delayed catheter replacement in continuous ambulatory peritoneal dialysis.

BACKGROUND: Fungal peritonitis (FP) is associated with significant mortality and high risk of peritoneal failure. The optimum treatment for peritoneal dialysis (PD)-associated FP remains unclear. Since January 2000 we have been treating FP with a combination of intravenous amphotericin B and oral flucytosine, together with deferred catheter replacement. We examined the clinical course and outcome of the FP patients treated with this approach (study group). An outcome comparison was also made to an alternatively treated historic cohort (control group). METHODS: This was a single-center retrospective study. The clinical course and outcome of 13 consecutive episodes of FP occurring in 13 patients treated between January 2000 and April 2005 with the study approach were examined. The patients were treated with an incremental dose of intravenous amphotericin B to a target dose of 0.75 - 1 mg/kg body weight/day, and oral flucytosine 1 g/day upon a diagnosis of FP at 3.77 +/- 0.93 days from presentation. Replacement of the peritoneal catheter was intended after complete clearing of effluent, after which, antifungal chemotherapy was continued for another 1 - 2 weeks. Their outcome was compared with 14 historic controls that were treated between April 1995 and December 1999. RESULTS: Mean age of the study group was 58.7 +/- 13.2 years; male-to-female ratio was 2:11; 6 (46.1%) were diabetic. All FP were caused by Candida species (C. albicans, 2; C. parapsilosis, 8; C. glabrata, 3). Two (15.4%) patients died before resolution of the peritonitis. The dialysate effluent cleared in 11 patients (84.6%) after 13.2 +/- 3.3 days of treatment, but 2 patients died of acute myocardial infarction before catheter replacement. Nine patients had their catheters replaced at day 26.7 +/- 7.7 of treatment; all 9 returned to PD after a total of 31 +/- 12.2 days of antifungal chemotherapy. Reversible liver dysfunction was common with this regimen. When compared with the 14 cases in the historic control group (Candida species, 13; Trichosporon, 1), who were treated with amphotericin B, fluconazole, or a combination of the two, and the majority (78.6%) of whose catheters were removed before day 10 of presentation, the study group appeared to have a lower technique failure rate (30.8% vs 78.6%, p = 0.013) and similar all-cause mortality (30.7% vs 28.5%, p = NS), FP-related mortality (15.4% vs 28.5%, p = NS), and length of hospitalization (48.5 +/- 30.2 vs 57.0 +/- 37.7 days, p = NS). However, a significantly earlier commencement of antifungal treatment in the study group (3.8 +/- 0.9 vs 5.8 +/- 2.4 days, p = 0.012) could be an important confounder of outcome. CONCLUSIONS: Combination of intravenous amphotericin B and oral flucytosine with deferred catheter replacement appears to be associated with a relatively low incidence of PD technique failure, without affecting mortality in patients suffering from FP due to yeasts in this preliminary study. Nonetheless, drug-induced hepatic dysfunction was common; close monitoring during treatment is of paramount importance. The reasons accounting for the observed distinctive outcome remain unclear and further study is required to confirm the results and to investigate for the underlying mechanism.

Prevention of fungal peritonitis with nystatin prophylaxis in patients receiving CAPD.

OBJECTIVE: Fungal peritonitis (FP) is a serious complication of continuous ambulatory peritoneal dialysis (CAPD), being associated with significant morbidity and mortality. The role of nystatin prophylaxis during antibiotic therapy in the prevention of FP remains controversial, especially in programs with a modest or low baseline FP rate. The aim of the present study was to evaluate the effect of nystatin prophylaxis on the occurrence of FP in programs with a relatively modest baseline FP rate. PATIENTS AND METHODS: Incident and prevalent patients receiving CAPD between April 1995 and April 2005 at our center were included and divided into 2 groups. The control group included 320 patients (total follow-up 8875 patient-months) being treated without nystatin before October 1999; the nystatin group included 481 patients (total follow-up 13725 patient-months) being treated after October 1999. Nystatin tablets (500,000 units, 4 times per day) were given orally during whatever use of antibiotics to cover the whole course of antibiotic therapy. Occurrence of FP and antibiotic-related FP (AR-FP) in patients with and without nystatin prophylaxis was compared. RESULTS: The two groups were of similar age but the nystatin group had a significantly higher percentage of diabetics. In addition, the nystatin group had a higher proportion of patients using disconnecting twin-bag exchange systems and had a significantly lower peritonitis rate compared with the control. There were 13 and 14 episodes of FP in the nystatin and control groups respectively. The fungal peritonitis rate of the nystatin group was slightly lower than that of the control group (0.011 vs 0.019 per patient-year) but it did not reach statistical significance. There was, however, a significant decrease in the incidence and proportion of AR-FP in the nystatin group compared with the control group, which persisted even after adjustment for the peritonitis rate. Kaplan-Meier analysis further demonstrated significantly better AR-FP-free survival in the nystatin group compared with the control group. No significant side effects were observed for nystatin. Subgroup analyses in patients of the 2 different connecting systems revealed a similar but nonsignificant trend toward reduction of AR-FP in patients given nystatin prophylaxis. CONCLUSION: Oral nystatin prophylaxis might prevent the occurrence of AR-FP in CAPD patients, resulting in a trend toward reduction in the incidence of FP even in programs with a modest baseline FP rate. A large scale, prospective, randomized controlled trial is needed to further examine this issue.

A multicenter study of the pharmacokinetics of lisinopril in pediatric patients with hypertension.

The pharmacokinetic (PK) parameters of lisinopril were obtained in 46 children aged 6 months to 15 years. A lisinopril suspension (0.15 mg/kg per day) was administered to patients <6 years of age; the remaining children received lisinopril tablets, the daily dose being adjusted according to body weight, i.e., 2.5 mg if <25 kg, 5 mg if 25-45 kg, and 10 mg if >45 kg. Blood was drawn predose and on eight occasions postdose in children aged 4-15 years, and on five occasions in those aged <4 years. PK data are reported for the 46 children in terms of age groups: Group I (n=9), aged 6-23 months; Group II (n=8), aged 2-5 years; Group III (n=12), aged 6-11 years; Group IV (n=17), aged 12-15 years. The dose of lisinopril ranged from 3.07 mg/m(2) per day in Group I to 4.78 mg/m(2) per day in Group IV. C(max) of lisinopril, which occurred 5-6 h postdose, varied from 22 ng/ml in Groups I and II to 44 ng/ml in Groups III and IV; AUC(0-24 h) ranged from 301-311 ng.h/ml in Groups I and II to 550-570 ng.h/ml in Groups III and IV. No serious adverse events related to lisinopril were reported.

Stabilization and determination of a PPAR agonist in human urine using automated 96-well liquid-liquid extraction and liquid chromatography/tandem mass spectrometry.

Two stability challenges were encountered during development of an urine assay for a proliferator-activated receptor (PPAR) agonist, I (2-{[5,7-dipropyl-3-(trifluoromethyl)-1,2-benzisoxazol-6-yl]oxy}-2-methyl propionic acid), indicated for the treatment of Type II diabetes. First, the analyte was lost in urine samples due to adsorption on container surface which is a common problem during clinical sample handling. Secondly, the acylglucuronide metabolite (III), a major metabolite of I, displayed limited stability and effected the quantitation of parent drug due to the release of I through hydrolysis. Therefore, a clinical collection procedure was carefully established to stabilize I and its acylglucuronide metabolite, III, in human urine. The metabolite was not quantitated with this method. The urine samples are treated with bovine serum albumin (BSA) equal to 1.75% of the urine volume and formic acid equal to 1% of urine volume. Compound (I) and internal standard (II) were extracted from urine with 1 mL ethyl acetate using a fully automated liquid-liquid extraction in 96-well plate format. The analytes are separated by reverse phase high-performance liquid chromatography (HPLC) with tandem mass spectrometry in multiple-reaction-monitoring (MRM) mode used for detection. The urine method has a lower limit of quantitation (LLOQ) of 0.05 ng/mL with a linearity range of 0.05-20 ng/mL using 0.05 mL of urine. The method was validated and used to assay urine clinical samples.

Vibrio vulnificus peritonitis after handling of seafood in a patient receiving CAPD.

Vibrio vulnificus is a marine bacterium and opportunistic human pathogen. Associated infections have contributed to the majority of seafood-related deaths in the United States. In patients with such predisposed clinical conditions as chronic liver disease, immunocompromised state, and end-stage renal disease, this organism has been associated with the development of life-threatening primary septicemia and severe wound infection. However, continuous ambulatory peritonitis dialysis (CAPD)-related peritonitis caused by V vulnificus has not been reported. We describe a patient receiving CAPD who developed peritonitis caused by V vulnificus after handling seafood. This case highlights the importance of strict aseptic technique during CAPD exchanges and calls for an effort in educating our dialysis patients on precautions about seafood handling.

Fully automated liquid-liquid extraction for the determination of a novel insulin sensitizer in human plasma by heated nebulizer and turbo ionspray liquid chromatography-tandem mass spectrometry.

I, 2-{[5,7-dipropyl-3-(trifluoromethyl)-1,2-benzisoxazol-6-yl]oxy}-2-methyl propionic acid is an alpha peroxisome proliferator-activated receptor (PPAR) agonist with some gamma activity being investigated for potential use in the treatment of Type II diabetes mellitus and dyslipidemia. Two automated liquid-liquid extraction methods were developed and validated for the determination of I in human plasma. Concentrations of I were determined over a wide range of clinical doses. For Method A, plasma was acidified and extracted with ethyl acetate using a fully automated procedure. Analysis was performed by LC-MS/MS with a turbo ionspray source in negative ion mode. For Method B, a larger volume of plasma was extracted and a heated nebulizer source was used on the mass spectrometer. Method A was linear from 0.05 to 50 ng/mL and Method B from 0.2 to 1000 ng/mL. Validation procedures showed that both methods were robust, specific and reproducible.

Quantitative determination of a novel dual PPAR alpha/gamma agonist using on-line turbulent flow extraction with liquid chromatography-tandem mass spectrometry.

Turbulent flow chromatograph (TFC) is a technique for the direct and efficient analysis of drugs and metabolites in biological matrices. We report here TFC on-line with an HPLC-MS/MS assay for the determination of 5-[2,4-dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[(4-trifluoromethyl)phenyl]methyl]benzamide (I, MK-0767, KRP297, Fig. 1) in plasma. Samples were transferred using an automated system followed by the addition of internal standard (II), prepared in 0.1 M ammonium acetate (pH 4.0). The plasma samples were directly injected onto a C18 turbulent flow column on-line with an HPLC-MS/MS system, and the analytical column used was a ThermoHypersil Keystone C18. Detection was achieved by MS/MS, using positive ionization on a TurboIonSpray probe, operated in multiple reaction monitoring (MRM) mode. The linear range was 4-2000 ng/mL for I when using 50 microL of plasma. The method exhibited good linearity and reproducibility. The method also showed good selectivity and ruggedness when applied to clinical samples, and was successfully cross-validated with a conventional off-line SPE, LC-MS/MS method.

Determination of MK-0767 enantiomers in human plasma by normal phase LC-MS/MS.

A sensitive and selective analytical method for the enantioselective determination of MK-0767, a dual peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonist, in human plasma has been developed and validated. The chromatography is based on normal-phase chiral separation on a Kromasil, 5 microm, CHI-DMB 250 mm x 4.6 mm column. The detection involves the direct introduction of the normal phase eluent into MS/MS without the addition of a post-column reagent. Atmospheric pressure chemical ionization (APcI) mode was selected as the ion source in this method. With proper sample handling and processing procedures, ex vivo interconversion of the enantiomers was kept to minimum during sample collection, preparation and short term storage of frozen human plasma samples. The method was successfully utilized to determine the concentrations of MK-0767 enantiomers in human plasma to support pharmacokinetic investigation in man.

Quantitative determination of MK-0767, a dual alpha/gamma peroxisome proliferator-activated receptor (PPAR) agonist, in human plasma by liquid chromatography-tandem mass spectrometry.

5-[2,4-Dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[(4-trifluoromethyl)-phenyl]methyl]benzamide (I, MK-0767 or KRP-297, Fig. 1), is a dual alpha/gamma peroxisome proliferator-activated receptor (PPAR) agonist. A LC-MS/MS method for the determination of I in human plasma has been successfully developed, validated and applied to clinical programs. The analyte and internal standard (II) are extracted from 0.05 mL plasma via solid phase extraction (SPE). HPLC is used for the separation of I and II from possible co-extracted endogenous and other compounds. Detection is by MS/MS in multiple reaction monitoring (MRM) mode using a TurboIonSpray probe. The whole sample preparation is automated by using a Packard Multiprobe liquid handling system. The linear range is 4-2000 ng/mL in plasma. Recoveries were 71.1% and 69.4% for I and II, respectively. The method exhibited good linearity, reproducibility and sensitivity, selectivity and robustness when used for the analysis of clinical samples.

Quantitative determination of a novel insulin sensitizer and its para-hydroxylated metabolite in human plasma by LC-MS/MS.

I, 5-[3-[3-(4-phenoxy-2-propylphenoxy)-propoxy]-phenyl]-2,4-thiazolidinedione sodium salt, is a dual alpha/gamma peroxisome proliferator-activated receptor (PPAR) agonist for potential use in diabetic patients. The compound has a para-hydroxylated metabolite, II, which has also been shown to exhibit PPAR activity. An LC-MS/MS method for the simultaneous determination of I and its active metabolite (II) in human plasma has been successfully developed. The method consists of treating 0.5 ml plasma with ammonium acetate (pH 9.6; 50mM) and extracting I, II and internal standard (III, Fig. 2) with 5 ml ethyl acetate. The ethyl acetate is evaporated and the samples are reconstituted in 0.1 ml acetonitrile:0.1% formic acid (65:35, v/v). The entire extraction procedure, as well as sample collection, was performed in glass tubes and vials to overcome the analytes adherence to polypropylene. A linear HPLC gradient was used to separate the analyte, metabolite, internal standard, and other interfering, non-quantitated metabolites. Detection was by negative ionization MS/MS on a turbo ionspray probe. Precursor-->product ion combinations were monitored in multiple reaction monitoring (MRM) mode. The linear range is 0.05-20 ng/ml for I and 0.1-20 ng/ml for II. Recoveries were 59.4, 90.1 and 56.8% for I, II and III, respectively. Intraday variation using this method was <==7.0% for I and <==9.2% for II. The method exhibits good linearity and reproducibility for each analyte and good sensitivity, selectivity and robustness when used for the analysis of clinical samples.

Simultaneous determination of losartan and EXP3174 in human plasma and urine utilizing liquid chromatography/tandem mass spectrometry.

Losartan is an orally active angiotensin II receptor antagonist indicated for the treatment of hypertension. EXP3174 is an active metabolite, which contributes to the overall activity of losartan. Analytical methods for the simultaneous determination of losartan and its active metabolite EXP3174 in human plasma and urine with limited plasma sample size have been developed and validated to support a pediatric clinical program. In both methods, analytes are extracted from the matrixes by liquid-liquid extraction and separated using reverse phase high-performance liquid chromatography (HPLC). A tandem mass spectrometer (MS/MS) with a Turbo ionspray (TIS) interface in multiple-reaction-monitoring (MRM) mode is used for detection of the analytes in both methods. The plasma method has a lower limit of quantitation (LOQ) of 1 ng/ml with a linearity range of 1-500 ng/ml for losartan and EXP3174 using 100 microl of plasma. For the urine method, the LOQ for both losartan and EXP3174 is 2 ng/ml using 0.5 ml of urine, and the linearity range for both analytes is 2-1000 ng/ml. Validation procedures have proven that both methods are robust, accurate, and reproducible. Both methods have been used to assay clinical samples and provided satisfactory results.