APT070 inhibits complement activation during in vitro cardiopulmonary bypass.

BACKGROUND: The proteins of the complement cascade play an important role in inflammation and the immune response. They have been shown to be activated during cardiopulmonary bypass (CPB), and may be responsible for the inflammatory response to CPB. We looked at the effect of APT070, an anti-complement agent, on human blood during in vitro CPB. MATERIALS AND METHODS: Four hundred millilitres of blood was venesected from healthy human volunteers and heparinised. To the blood was added either APT070 to a concentration of 50 microg/ml (n=5) or vehicle control (n=4). The blood was entered into an in vitro CPB circuit and circulated for 90 min. RESULTS: Our results showed that after 90 min of in vitro bypass APT070 significantly inhibited the activation of compliment as demonstrated by C3a (p=0.03) and sC5b-9 (p=0.01) levels, and reduced neutrophil stimulation as measured by CD11b expression (p=0.04 at 90 min). CONCLUSION: APT070 significantly inhibits complement and neutrophil activation. This result may have considerable implications, especially if it can be shown to decrease the inflammatory sequelae of CPB.

Association between cyclosporine concentrations at 2 hours post-dose and clinical outcomes in de novo lung transplant recipients.

BACKGROUND: The objective of this study was to investigate the relationship between cyclosporine (CsA) pharmacokinetic parameters and clinical outcomes after lung transplantation. METHODS: Data from 48 lung or heart/lung transplant recipients originally recruited to a randomized, prospective clinical trial of Sandimmune vs Neoral and followed for 12 months were included in this study. CsA dosing was based on the trough concentration. CsA concentrations at 0 (C0), 2 (C2), and 6 (C6) hours post-dosing were obtained at 1, 2, 3, 4, 13, 26, 39, and 52 post-operative weeks. Based on their average C2 levels in the first post-transplant month, patients were stratified retrospectively into Low C2 (<1,000 microg/liter, n = 18), Intermediate C2 (1,000-1,500 microg/liter, n = 16) and High C2 (>1,500 microg/liter, n = 14) Groups. RESULTS: Cyclosporine C2 was the best single-point determinant (r2 = 0.934) for area-under-the-concentration-time curve (AUC(0-6 hours)) compared with C0 (r2 = 0.267) or C6 (r2 = 0.304). The mean +/- SD values of CsA C2 and AUC(0 to 6 hours) in the first year post-transplant were significantly lower in patients with >2 rejection episodes compared with those with < or =2 rejection episodes (C2: 875 +/- 546 microg/liter vs 1,114 +/- 633 microg/liter, p = 0.01; AUC(0-6 hours): 4,036 +/- 1,904 microg x hour/liter vs 4,870 +/- 2,182 microg x hour/liter; p = 0.01) whereas C0 and C6 did not differ. Patients in the Intermediate C2 Group were free from rejection episodes for a significantly longer duration (p < 0.001) and had significantly higher predicted forced expiratory volume in 1 second (%) values (p < 0.001) compared with the Low and High C2 Groups. The percentage of increase in serum creatinine concentration by the end of first month post-transplant was significantly higher in the Intermediate C2 Group (p < 0.003). CONCLUSIONS: CsA C2 concentrations correlated better with the incidence of multiple rejections after lung transplantation than did C0 or C6. C2 concentrations between 1,000 and 1,500 microg/liter within the first post-operative month may be associated with better graft outcomes and improved pulmonary function and worsened renal function.

Population pharmacokinetics of cyclosporine in cardiopulmonary transplant recipients.

A population pharmacokinetic analysis of cyclosporine (CsA) was performed, and the influence of covariates on CsA oral clearance and relative bioavailability was investigated. Data from 48 recipients of heart-lung (n = 21) or single (n = 18) or double (n = 9) lung transplant were included in the study. Patients received oral CsA as either a conventional formulation (Sandimmune) or a microemulsion (Neoral). Steady-state CsA concentrations were measured before and at approximately 2 and 6 hours after the morning dose of CsA at the end of weeks 1, 2, 3, 4, 13, 26, 39, and 52 posttransplantation. A total of 1004 CsA concentration observations were analyzed using mixed effects-modeling (NONMEM). A 1-compartment pharmacokinetic model and first-order oral absorption were used to fit the data. The absorption rate constants were fixed at 0.25 L/h for Sandimmune and 1.35 L/h for Neoral formulations. Oral clearance (CL/F) was estimated to be 22.1 L/h (95% confidence intervals [CI] 19.5-24.7 L/h). Itraconazole (ITRA), cystic fibrosis (CF), and weight (WT) were identified as significant covariates for CL/F according to the final model: CL/F = 22.1 - 11.3 x ITRA + 23.5 x CF + 0.129 x (WT - 58.7) L/h; where ITRA = 1 if the patient was taking concomitant itraconazole, otherwise 0; CF = 1 if the patient had cystic fibrosis, otherwise CF = 0; and WT is patient weight in kilograms. The relative oral bioavailability of Sandimmune to Neoral was 0.82. The bioavailability of both preparations increased during the first month posttransplantation. Age, gender, and type of transplant (single, double, or heart-lung) were not identified as significant covariates for CsA clearance. The population pharmacokinetic model developed identified some sources of variability in CsA pharmacokinetics; however, an appreciable degree of variability is still present in this patient population.

Determination of total mycophenolic acid and its glucuronide metabolite using liquid chromatography with ultraviolet detection and unbound mycophenolic acid using tandem mass spectrometry.

Two simple, sensitive and reproducible methods for determination of total mycophenolic acid (MPA) and its glucuronide metabolite (MPAG) as well as unbound MPA (fMPA) was developed by the use of HPLC-UV and LC-MS/MS methods, respectively. For the total MPA/MPAG method, the analytes were extracted using Isolute C(2) solid-phase extraction (SPE) cartridges and analyzed at 254 nm over a Zorbax Rx C(8) column (150 mm x 4.6 mm, 5 microm). The mobile phase was a gradient mixture of methanol and water (containing 0.1% (v/v) phosphoric acid). The total run time was 18 min and the extraction recovery was 77% for MPA and 84% for MPAG. The method was precise and accurate with a lower limit of quantification (LLOQ) of 0.5 mg/l for MPA and 5.0 mg/l for MPAG. For the fMPA method, plasma was subjected to ultrafiltration followed by SPE using C(18) cartridges. Analytical column was the same as the HPLC-UV method and the mobile phase was a gradient composition of methanol:0.05% formic acid with a flow rate of 0.6 ml/min for the first 3 min and 0.7 ml for the last 4 min. The chromatographic method separated MPA from its metabolites MPAG and Acyl-MPAG. Mass transitions in negative ionization mode for MPA and the internal standard, indomethacin were m/z: 319-->190.9 and m/z: 356-->312.2, respectively. The assay was linear in the concentration range of 1-1000 microg/l for fMPA with a LLOQ of 1 microg/l and an accuracy of >95%. The two methods reported have an adequate degree of robustness and dynamic concentration range for the measurement of MPA, MPAG and fMPA for therapeutic drug monitoring purposes or pharmacokinetics investigations.

Immunosuppression, eotaxin and the diagnostic changes in eosinophils that precede early acute heart allograft rejection.

Peripheral blood eosinophil counts (EOS) are undetectable in 40% blood samples sent for routine haematology at Papworth Hospital during the first 3 months after heart transplantation (HTx). Increases in EOS usually precede the development of allograft rejection by a median of 4 days. We compared the effects of cyclosporin (dose and total blood concentration), prednisolone (dose and both total and unbound plasma concentrations) and azathioprine, as well as plasma concentrations of the CCR-3 chemokines, eotaxin and RANTES, on changes in EOS in 47 consecutive HTx recipients, with a median follow-up of 90 (IQR 85-95) days. Multivariate analysis confirmed the independent association between both prednisolone dose (P<0.0001) and eotaxin (P<0.0001) and changes in EOS. The plasma eotaxin concentration was, in turn, most closely associated with the cyclosporin dose (P<0.001) and plasma prednisolone concentration (P=0.022). The blood cyclosporin concentration (P=0.028), EOS (P=0.012) and prednisolone dose (P=0.015) were all independently associated with the risk of treated acute rejection. When prednisolone pharmacokinetic parameters were substituted for the prednisolone dose in this multivariate model, only the pharmacokinetic parameter retained a significant association with the risk of rejection. Changes in EOS preceding cardiac allograft rejection are directly associated with plasma eotaxin concentrations and indirectly with prednisolone dosage. Cyclosporin may also indirectly influence these changes by inhibiting eotaxin production. EOS, prednisolone dose and blood cyclosporin concentrations were independently associated with the risk of acute rejection. The total and unbound fractions of prednisolone in plasma appear to be even more closely related to rejection but are difficult to measure. Monitoring EOS, as a surrogate measure of prednisolone immunosuppression, may be more cost-effective for controlling rejection than conventional cyclosporin monitoring in the first 6 weeks after HTx.

The perennial problem with potassium.

BACKGROUND: The problem of spurious hyperkalaemia in blood samples delivered to hospitals from local general practitioners' (GP) surgeries remains a source of diagnostic confusion and potential danger to patients. We have carried out retrospective and prospective audits of serum potassium measurements to assess the influences of blood sample delivery time and temperature during transit from GP surgeries to a centralized laboratory on the risk of spurious serum potassium measurements. METHOD: The retrospective audit included serum potassium measurements made by the pathology laboratory at Addenbrooke's Hospital on 51 843 patients attending either the hospital itself or one of 62 local GP surgeries during the months August 2001 to February 2002 (i.e. summer through to winter). The probability of spurious potassium measurements on GP patients relative to blood sample delivery time and temperature was modelled by least-squares multiple linear regression. The prospective audit included serum potassium measurements made on 40 patients presenting early in the day at the Sutton GP surgery near Ely, Cambridgeshire, during the months February to May 2002. RESULTS: Low blood sample delivery temperature had a greater impact on the probability of spurious potassium measurements than long delivery time. Low delivery temperature also had a greater impact on the probability of spurious hyperkalaemia than it had on the probability of spurious normokalaemia. At temperatures below 20.3 degrees C, the probabilities of both spurious hyper- and normokalaemia for samples delivered from the most distant and closest GP surgeries to Addenbrooke's increased significantly. CONCLUSIONS: Maintaining blood sample delivery temperatures a few degrees above 20 degrees C will minimize the risk of spurious serum potassium measurements on samples from GP patients.

Sirolimus inhibits oxidative burst activity in transplant recipients.

Increased susceptibility to bacterial infection is a recognized side-effect of sirolimus treatment after transplantation, which could be caused by inhibition of neutrophil activation. Blood from 24 healthy subjects was equilibrated with 0 to 50 ng/mL sirolimus or 60 microg/mL propofol. Blood was also collected from 23 transplant recipients (13 kidney, 10 liver) with renal impairment, randomized to remain on calcineurin inhibitors (n=12) or to be switched to sirolimus monotherapy (n=11). Phorbol myristate acetate (PMA)-stimulated oxidative burst was measured by flow cytometry at 0 and 3 months after randomization. There was a linear relationship between inhibition of neutrophil activation in vitro and sirolimus concentrations spanning the therapeutic range (P=0.01). Neutrophil activation was decreased significantly in transplant recipients 3 months after switching from calcineurin inhibitors to sirolimus therapy (mean percentage change -24.4%; 95% confidence interval -7.5, -41.2%, P=0.009), but no changes were observed in patients who remained on calcineurin inhibitors.

Distribution of cyclosporin in organ transplant recipients.

Cyclosporin is an immunosuppressive agent with a narrow therapeutic index. The total concentration of cyclosporin in blood is usually monitored to guide dosage adjustment and to compensate for substantial interindividual and intraindividual variability in cyclosporin pharmacokinetics. Cyclosporin is a highly lipophilic molecule and widely distributes into blood, plasma and tissue components. It mainly accumulates in fat-rich organs, including adipose tissue and liver. In blood, it binds to erythrocytes in a saturable fashion that is dependent on haematocrit, temperature and the concentration of plasma proteins. In plasma, it binds primarily to lipoproteins, including high-density, low-density and very-low-density lipoprotein, and, to a lesser extent, albumin. The unbound fraction of cyclosporin in plasma (CsA(fu)) expressed as a percentage is approximately 2%. It has been shown that both the pharmacokinetic and pharmacodynamic properties of cyclosporin are related to its binding characteristics in plasma. Furthermore, there is some evidence to indicate that the unbound concentration of cyclosporin (CsA(U)) has a closer association with both kidney and heart allograft rejection than the total (bound + unbound) concentration. However, the measurement of CsA(fu) is inherently complex and cannot easily be performed in a clinical setting. Mathematical models that calculate CsA(fu), and hence CsA(U), from the concentration of plasma lipoproteins may be a more practical option, and should provide a more accurate correlate of effectiveness and toxicity of this drug in transplant recipients than do conventional monitoring procedures. In conclusion, the distribution characteristics of cyclosporin in blood, plasma and various tissues are clinically important. Further investigations are needed to verify whether determination of CsA(U) improves the clinical management of transplant recipients.

Risk factors for the development and progression of dyslipidemia after heart transplantation.

BACKGROUND: Hyperlipidemia is an important complication after organ transplantation and contributes to the development of posttransplant accelerated coronary artery diseases. METHODS: We have retrospectively evaluated the relative contribution of various risk factors associated with the development and progression of hyperlipidemia in 194 heart transplant recipients by the use of mixed effects multiple linear regression analysis. The demographic characteristics evaluated were primary diagnosis of ischemic heart disease (IHD), gender, and age. Postoperative characteristics included number of treated rejections, dosage of cyclosporine (CYA), tacrolimus (TAC), prednisolone and azathioprine, and concentration of serum creatinine and glucose. The effects of administration of antihypertensive agents, diuretics, and lipid lowering agents were also studied. RESULTS: The total cholesterol concentration increased significantly in the first 3 months posttransplant but gradually decreased thereafter. Total cholesterol and the ratio of low density lipoprotein (LDL) cholesterol to high density lipoprotein (HDL) cholesterol (LDL-C/HDL-C) increased to a greater extent in patients with IHD although female transplant recipients had a greater increase in the total cholesterol concentration. Each episode of rejection increased serum cholesterol by 0.306 mmol/liter (0.258, 0.355) [mean (95% C.I.)] and serum triglyceride by 0.164 mmol/liter (0.12, 0.209) although switching to TAC improved total cholesterol and LDL-C/HDL-C. Administration of frusemide, increased the total cholesterol and LDL-C/HDL-C whereas administration of bumetanide or metolazone increased the concentration of serum triglyceride. Serum glucose was associated with hypertriglyceridemia whereas serum creatinine was associated with increases in the total cholesterol, LDL-C/HDL-C and triglyceride. CONCLUSIONS: We have identified demographic and postoperative covariables that predispose heart transplant recipients to hyperlipidemia. Some of these risk factors, such as the effect of diuretics, have not been identified before in this group of patients and may be amenable to modification or closer control. TAC rather than CYA may be the immunosuppressive of choice for patients who are at greater risk of developing hyperlipidemia.