Effect of CYP3A and ABCB1 single nucleotide polymorphisms on the pharmacokinetics and pharmacodynamics of calcineurin inhibitors: Part II

The calcineurin inhibitors ciclosporin (cyclosporine) and tacrolimus are immunosuppressant drugs used for the prevention of organ rejection following transplantation. Both agents are metabolic substrates for cytochrome P450 (CYP) 3A enzymes - in particular, CYP3A4 and CYP3A5 - and are transported out of cells via P-glycoprotein (ABCB1). Several single nucleotide polymorphisms (SNPs) have been identified in the genes encoding for CYP3A4, CYP3A5 and P-glycoprotein, including CYP3A4 -392A>G (rs2740574), CYP3A5 6986A>G (rs776746), ABCB1 3435C>T (rs1045642), ABCB1 1236C>T (rs1128503) and ABCB1 2677G>T/A (rs2032582). The aim of this review is to provide the clinician with an extensive overview of the recent literature on the known effects of these SNPs on the pharmacodynamics of ciclosporin and tacrolimus in solid-organ transplant recipients. Literature searches were performed and all relevant primary research articles were critiqued and summarized. There is no evidence that the CYP3A4 -392A>G SNP has an effect on the pharmacodynamics of either ciclosporin or tacrolimus; however, studies have been limited. For patients prescribed ciclosporin, the CYP3A5 6986A>G SNP may influence long-term survival, possibly because of a different metabolite pattern over time. This SNP has no clear association with acute rejection during ciclosporin therapy. Despite a strong association between the CYP3A5 6986A>G SNP and tacrolimus pharmacokinetics, there is no consistent evidence of organ rejection as a result of genotype-related under-immunosuppression. This is likely to be explained by the practice of performing tacrolimus dose adjustments in the early phase after transplantation. The effect of the CYP3A5 6986A>G SNP on ciclosporin- and tacrolimus-related nephrotoxicity and development of hypertension is unclear. Similarly, the ABCB1 SNPs exert no clear influence on either ciclosporin or tacrolimus pharmacodynamics, with studies showing conflicting results in regard to the main parameters of acute rejection and nephrotoxicity. In kidney transplant patients, consideration of the donor kidney genotype rather than the recipient genotype may be more important when assessing development of nephrotoxicity. Studies with low patient numbers may account for many inconsistent results to date. The majority of studies have only evaluated the effects of individual SNPs; however, multiple polymorphisms may interact to produce a combined effect. Further haplotype analyses are likely to be useful, particularly ones that consider both donor and recipient genotype. The effects of polymorphisms associated with the pregnane X receptor, organic anion transporting polypeptides, calcineurin inhibitor target sites and immune response pathways need to be further investigated. A large standardized clinical trial is now required to evaluate the relationship between the pharmacokinetics and pharmacodynamics of CYP3A5-mediated tacrolimus metabolism, particularly in regard to the outcomes of acute rejection and nephrotoxicity. It is not yet clear whether pharmacogenetic profiling of calcineurin inhibitors will be a useful clinical tool for personalizing immunosuppressant therapy.

An intervention to improve benzodiazepine use--a new approach

OBJECTIVE

To design, implement and evaluate a novel intervention, utilizing electronic media, to improve benzodiazepine use in specific geographical areas in Australia.

METHODS

An educational intervention about benzodiazepine use, using email, a website and bookmarks, targeted consumers, GPs, nurses (in aged care facilities) and pharmacists in two areas in Australia over a 6-month period. Two control areas, which received no aspect of the intervention, were used to compare and contrast. A drug use evaluation was conducted in aged care facilities before and after the study (in the intervention areas) and after the intervention (in the control areas) to assess quality of benzodiazepine use. Benzodiazepine dispensing data were obtained for each area before, during and after the intervention to quantitate use. Interviews were conducted with nurses and pharmacists involved in the intervention and website statistics were recorded.

RESULTS

A significantly smaller number of aged care residents were on benzodiazepines for 6 months or more (P < 0.05) after the intervention compared with before. However, other indices, such as number of residents taking benzodiazepines or taking them for a long time, did not change significantly before compared to after the intervention and there were no significant differences between the control and intervention areas after the intervention. Quantitative use of benzodiazepines did not change after the intervention. Many health care professionals in the intervention areas remembered seeing the electronic educational material for benzodiazepines. The website was viewed 115 times during the study.

CONCLUSIONS

The study was easy and inexpensive to administer and attracted high participation rates by health care professionals. There was a change in the use of benzodiazepines in aged care facilities (less long-term benzodiazepine use) in the intervention areas. The electronic educational materials (emails and website) were read and informations (especially the key messages) were able to be recalled after the intervention. However, no large changes in benzodiazepine overall use (either between control and intervention areas or before and after the intervention) were recorded.

Effect of CYP3A and ABCB1 single nucleotide polymorphisms on the pharmacokinetics and pharmacodynamics of calcineurin inhibitors: Part I

The calcineurin inhibitors ciclosporin (cyclosporine) and tacrolimus are immunosuppressant drugs used for the prevention of organ rejection following transplantation. Both agents are metabolic substrates for cytochrome P450 (CYP) 3A enzymes--in particular, CYP3A4 and CYP3A5--and are transported out of cells via P-glycoprotein (ABCB1). Several single nucleotide polymorphisms (SNPs) have been identified in the genes encoding for CYP3A4, CYP3A5 and P-glycoprotein, including CYP3A4 -392A>G (rs2740574), CYP3A5 6986A>G (rs776746), ABCB1 3435C>T (rs1045642), ABCB1 1236C>T (rs1128503) and ABCB1 2677G>T/A (rs2032582). The aim of this review is to provide the clinician with an extensive overview of the recent literature on the known effects of these SNPs on the pharmacokinetics of ciclosporin and tacrolimus in solid-organ transplant recipients. Literature searches were performed, and all relevant primary research articles were critiqued and summarized. Influence of the CYP3A4 -392A>G SNP on the pharmacokinetics of either ciclosporin or tacrolimus appears limited. Variability in CYP3A4 expression due to environmental factors is likely to be more important than patient genotype. Influence of the CYP3A5 6986A>G SNP on the pharmacokinetics of ciclosporin is also uncertain and likely to be small. CYP3A4 may play a more dominant role than CYP3A5 in the metabolism of ciclosporin. The CYP3A5 6986A>G SNP has a well established influence on the pharmacokinetics of tacrolimus. Several studies in kidney, heart and liver transplant recipients have reported an approximate halving of tacrolimus dose-adjusted trough concentrations and doubling of tacrolimus dose requirements in heterozygous or homozygous carriers of a CYP3A5*1 wild-type allele compared with homozygous carriers of a CYP3A5*3 variant allele. Carriers of a CYP3A5*1 allele take a longer time to reach target blood tacrolimus concentrations. Influence of ABCB1 3435C>T, 1236C>T and 2677G>T/A SNPs on the pharmacokinetics of ciclosporin and tacrolimus remains uncertain, with inconsistent results. Genetic linkage between the three variant genotypes suggests that the pharmacokinetic effects are complex and not related to any one ABCB1 SNP. It is likely that these polymorphisms exert a small but combined effect, which is additive to the effects of the CYP3A5 6986A>G SNP. In liver transplant patients, recipient and donor liver genotypes may act together in determining overall drug disposition, hence the importance of assessing both. Studies with low patient numbers may account for many inconsistent results to date. Meta-analyses of the current data should help resolve some discrepancies. The majority of studies have only evaluated the effects of individual SNPs; however, multiple polymorphisms may interact to produce a combined effect. Further haplotype analyses are likely to be useful. It is not yet clear whether pharmacogenetic profiling of calcineurin inhibitors will be a useful clinical tool for personalizing immunosuppressant therapy.

The Queensland experience of participation in a national drug use evaluation project, Community-Acquired Pneumonia Towards Improving Outcomes Nationally (CAPTION)

Background

Multicentre drug use evaluations are described in the literature infrequently and usually publish only the results. The purpose of this paper is to describe the experience of Queensland hospitals participating in the Community-Acquired Pneumonia Towards Improving Outcomes Nationally (CAPTION) project, specifically evaluating the implementation of this project, detailing benefits and drawbacks of involvement in a national drug use evaluation program.

Methods

Emergency departments from nine hospitals in Queensland, Australia, participated in CAPTION, a national quality improvement project, conducted in 37 Australian hospitals. CAPTION was aimed at optimising prescribing in the management of Community-Acquired Pneumonia according to the recommendations of the Australian Therapeutic Guidelines: Antibiotic 12th edition. The project involved data collection, and evaluation, feedback of results and a suite of targeted educational interventions including audit and feedback, group presentations and academic detailing.

A baseline audit and two drug use evaluation cycles were conducted during the 2-year project. The implementation of the project was evaluated using feedback forms after each phase of the project (audit or intervention). At completion a group meeting with the hospital coordinators identified positive and negative elements of the project.

Results

Evaluation by hospitals of their participation in CAPTION demonstrated both benefits and drawbacks. The benefits were grouped into the impact on the hospital dynamic such as; improved interdisciplinary working relationships (e.g. between pharmacist and doctor), recognition of the educational/academic role of the pharmacist, creation of ED Pharmacist positions and enhanced involvement with the National Prescribing Service, and personal benefits. Personal benefits included academic detailing training for participants, improved communication skills and opportunities to present at conferences. The principal drawback of participation was the extra burden on already busy staff members.

Conclusion

A national multicentre drug use evaluation project such as CAPTION allows hospitals which would otherwise not undertake such projects the opportunity to participate. The Queensland arm of CAPTION demonstrated benefits to both the individual participants and their hospitals, highlighting the additional value of participating in a multicentre project of this type.

A comparison of mycophenolate use in Australia and Northern Europe, and the impact on the pharmaceutical benefits scheme

PURPOSE

The aim of this study was to characterise utilisation of mycophenolate in Australian transplant recipients from 2001 to 2007; to identify specific patterns of mycophenolate mofetil and enteric-coated mycophenolate sodium usage; to examine expenditure on mycophenolate prescription and to compare Australian usage with Danish, Finish and Netherlands populations.

METHODS

Data on mycophenolate usage were obtained from Medicare Australia, Finish and Danish Medicines Agency and Netherlands Healthcare Insurance Board databases. Utilisation of mycophenolate was described as daily defined dose (DDD/per 1000 population/day).

RESULTS

From 2001 to 2007, utilisation of mycophenolate in Australia increased approximately 30-fold. In 2007, mycophenolate sodium accounted for 8.3% of mycophenolate total DDDs. In 2007, AUD$4,890,000 was spent on mycophenolate prescription. In 2006, utilisation of mycophenolate was five- to eight-fold higher in Northern Europe compared to Australia. Renal transplant rates per 1000 population/year were similar across countries.

CONCLUSIONS

Differences in the rate of mycophenolate utilisation between Northern Europe and Australia exist and may be due to differences in approved indications between countries, prescribing habits, or because of a more mature market in Europe. If the Australian market increases to that of North Europe the cost of prescribing mycophenolate will eventually be in the vicinity of AUD$20-80 million.

Systematic Review of Interventions to Improve Prescribing

Objective:

To update 2 comprehensive reviews of systematic reviews on prescribing interventions and identify the latest evidence about the effectiveness of the interventions.

Data Sources:

Systematic searches for English-language reports of experimental and quasi-experimental research were conducted in PubMed(1951–May 2007). EMBASE (1974–March 2008), International Pharmaceutical Abstracts (1970–March 2008), and 11 other bibliographic databases of medical, social science, and business research. Following an initial title screening process and after selecting 6 specific intervention categories (identified from the previous reviews) in community settings, 2 reviewers independently assessed abstracts and then full studies for relevance and quality and extracted relevant data using formal assessment and data extraction tools. Results were then methodically incorporated into the findings of the 2 earlier reviews of systematic reviews.

Data Selection And Synthesis:

Twenty-nine of 26,314 articles reviewed were assessed to be of relevant, high-quality research. Audit and feedback, together with educational outreach visits, were the focus of the majority of recent, high-quality research into prescribing interventions. These interventions were also the most effective in improving prescribing practice. A smaller number of studies included a patient-mediated intervention; this intervention was not consistently effective. There is insufficient recent research into manual reminders to confidently update earlier reviews and there remains insufficient evidence to draw conclusions regarding the effectiveness of local consensus processes or multidisciplinary teams.

Conclusions:

Educational outreach as well as audit and feedback continue to dominate research into prescribing interventions. These 2 prescribing interventions also most consistently show positive results. Much less research is conducted into other types of interventions and there is still very little effort to systematically test why interventions do or do not work.

Why is the use of clopidogrel increasing rapidly in Australia? An exploration of geographical location, age, sex and cardiac stenting rates as possible influences on clopidogrel use

PURPOSE

To explore clopidogrel use within Australia, investigating geography, age, sex and cardiac stenting rates.

METHODS

Data for clopidogrel supply (Pharmaceutical Benefits Scheme (PBS) and Repatriation Pharmaceutical Benefits Scheme (RPBS)) and cardiac stenting procedures (State Health Departments) were obtained for four different geographic regions (very remote/remote and major city in two Australian states). General linear modelling and correlation analyses were used to test for associations and chi2 analyses for proportions.

RESULTS

Clopidogrel supply increased rapidly in Australia since introduction, from 1.2 to 9.0 Defined Daily Doses (DDD)/1000 population/day. Among concessional and veteran populations use was much higher. Analysis of geographical area data confirmed an association between clopidogrel supply rates and cardiac stenting rates (r = 0.8-0.9 Spearman's rho, p < 0.01). Sex, age and geographical location were associated with both rates when considered together and when considered independently. Further modelling indicated that between 30 and 73% of clopidogrel supply could be accounted for by people receiving cardiac stents.

CONCLUSIONS

The supply of clopidogrel increases with age, male sex and living in a major city. These same demographic variables were important for cardiac stenting, an indication which is currently not approved for subsidy by the Australian government, but which modelling indicated could account for between one-third and three quarters of clopidogrel use. A review may be required to ensure subsidised indications reflect current evidence and cost-effective use.

Non-steroidal anti-inflammatory drugs, Cyclooxygenase-2 inhibitors and paracetamol use in Queensland and in the whole of Australia

BACKGROUND

Cross national drug utilization studies can provide information about different influences on physician prescribing. This is important for medicines with issues around safety and quality of use, like non selective non-steroidal anti-inflammatory drugs (ns-NSAIDs) and cyclo-oxygenase-2 (COX-2) inhibitors. To enable comparison of prescription medicine use across different jurisdictions with a range of population sizes, data first need to be compared within Australia to understand whether use in a smaller sub-population may be considered as representative of the total use within Australia. The aim of this study was to compare the utilization of non selective NSAID, COX-2 inhibitors and paracetamol between Queensland and Australia.

METHOD

Dispensing data were obtained for concession beneficiaries for Australia for ns-NSAIDs, COX-2 inhibitors and paracetamol subsidized by the PBS over the period 1997-2003. The same data were purchased for Queensland. Data were converted to Defined Daily Dose (DDD)/1000 beneficiaries/day (World Health Organization anatomical therapeutic chemical classification, 2005).

RESULTS

Total NSAID and paracetamol consumption were similar in Australia and Queensland. Ns-NSAID use decreased sharply with the introduction of COX-2 inhibitors (from approximately 80 to 40 DDD/1000 beneficiaries/day). Paracetamol was constant (approximately 45 DDD/1000 beneficiaries/day). COX-2 inhibitors consumption was initially higher in Queensland than in the whole of Australia.

CONCLUSION

Despite initial divergence in celecoxib use between Queensland and Australia, the use of ns-NSAIDs, COX-2 inhibitors and paracetamol overall, in concession beneficiaries, was comparable in Australia and Queensland.

A comparison of benzodiazepine and related drug use in Nova Scotia and Australia

OBJECTIVE

Benzodiazepines can be a problem if used for long periods, or in at-risk populations, such as the elderly. We compared the use of benzodiazepine and related prescription medicines in Nova Scotia and Australia.

METHODS

The Nova Scotia Pharmacare Program and the Pharmaceutical Benefits Scheme in Australia were used to obtain dispensing data in comparable populations for all publicly subsidized benzodiazepines and related compounds. Usage was compared from 2000 to 2003, using the World Health Organization anatomical therapeutic chemical and defined daily dosage (DDD) system. We also determined differences in the types of benzodiazepines prescribed.

RESULTS

The use of benzodiazepines increased at a steady but comparable rate in both areas. However, the use of benzodiazepines in Nova Scotia was more than double that of Australia in 2000 (123 and 48 DDD/1000 beneficiaries per day, respectively) through 2003 (138 and 57 DDD/1000 beneficiaries per day, respectively). Eight different benzodiazepines made up 90% of the drug use in Nova Scotia by contrast to only 4 different benzodiazepines in Australia.

CONCLUSIONS

Large differences exist between the type and rate of benzodiazepine prescribing in Nova Scotia and Australia, with Nova Scotia reporting more than twice as much use. Benzodiazepine use in both jurisdictions is increasing. The Canadian findings are especially concerning as benzodiazepine use in the Atlantic provinces has been reported to be less than other provinces. The variations between the 2 jurisdictions may be due to factors such as fewer benzodiazepines available in Australia, differences in prescriber, patient attitudes and behaviours, or different initiatives to influence benzodiazepine use.

Development of a sufficient design for estimation of fluconazole pharmacokinetics in people with HIV infection

AIMS

To assess an optimal design that is sufficient to gain precise estimates of the pharmacokinetic (PK) parameters for fluconazole in people with HIV infection.

METHODS

Two studies were identified, the first in healthy volunteers and the second in HIV patients. The investigators (J.F.R. and S.B.D.) were blinded to the second study results. The healthy volunteer study was modelled and a design was found to estimate the PK parameters. The design was evaluated by comparison of the standard errors of the parameters and the predictive performance of the optimal design. The predictive performance was assessed by comparing model predictions against observed concentrations for two models. The first model, termed 'sufficient design', was developed from data extracted from the HIV study that corresponded to the optimal design. The second model, termed 'HIV outcome model', by modelling all the data from the HIV study.

RESULTS

An optimal design HIV study was developed which had considerably fewer blood samples and dosing arms compared with the actual HIV study. The optimized design performed as well as the actual HIV study in terms of parameter precision. The performance of the design, described as the precision (mg l(-1))(2) (95% confidence interval) of the predicted concentrations to the actual concentrations for the 'sufficient design' and 'HIV outcome model' models were: 0.63 (0.40, 0.87) and 0.56 (0.32, 0.79), respectively.

CONCLUSION

This study demonstrates how data from healthy volunteers can be utilized via optimal design methodology to design a successful study in the target population.

A Bayesian approach for population pharmacokinetic modelling of sirolimus

AIMS

To explore a Bayesian approach for the pharmacokinetic analysis of sirolimus concentration data arising from therapeutic drug monitoring (poorly informative concentration-time point design), and to explore possible covariate relationships for sirolimus pharmacokinetics.

METHODS

Sirolimus concentration-time data were available as part of routine clinical care from 25 kidney transplant recipients. Most samples were taken at or near the trough time point at steady state. The data were analyzed using a fully conditional Bayesian approach with PKBUGS (v 1.1)/WinBUGS (v 1.3). Features of the data included noncompliance and missing concentration measurements below the limit of sensitivity of the assay. Informative priors were used.

RESULTS

A two-compartment model with proportional residual error provided the best fit to the data (consisting of 315 sirolimus concentration-time points). The typical value for the apparent clearance (CL/F ) was 12.5 l h(-1) at the median age of 44 years. Apparent CL was found to be inversely related to age with a posterior probability of a clinically significant effect of 0.734.

CONCLUSIONS

A population pharmacokinetic model was developed for sirolimus using a novel approach. Bayesian modelling with informative priors allowed interpretation of a significant covariate relationship, even using poorly informative data.

Clinical pharmacokinetics and pharmacodynamics of mycophenolate in solid organ transplant recipients

This review aims to provide an extensive overview of the literature on the clinical pharmacokinetics of mycophenolate in solid organ transplantation and a briefer summary of current pharmacodynamic information. Strategies are suggested for further optimisation of mycophenolate therapy and areas where additional research is warranted are highlighted. Mycophenolate has gained widespread acceptance as the antimetabolite immunosuppressant of choice in organ transplant regimens. Mycophenolic acid (MPA) is the active drug moiety. Currently, two mycophenolate compounds are available, mycophenolate mofetil and enteric-coated (EC) mycophenolate sodium. MPA is a potent, selective and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), leading to eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil and EC-mycophenolate sodium are essentially completely hydrolysed to MPA by esterases in the gut wall, blood, liver and tissue. Oral bioavailability of MPA, subsequent to mycophenolate mofetil administration, ranges from 80.7% to 94%. EC-mycophenolate sodium has an absolute bioavailability of MPA of approximately 72%. MPA binds 97-99% to serum albumin in patients with normal renal and liver function. It is metabolised in the liver, gastrointestinal tract and kidney by uridine diphosphate gluconosyltransferases (UGTs). 7-O-MPA-glucuronide (MPAG) is the major metabolite of MPA. MPAG is usually present in the plasma at 20- to 100-fold higher concentrations than MPA, but it is not pharmacologically active. At least three minor metabolites are also formed, of which an acyl-glucuronide has pharmacological potency comparable to MPA. MPAG is excreted into the urine via active tubular secretion and into the bile by multi-drug resistance protein 2 (MRP-2). MPAG is de-conjugated back to MPA by gut bacteria and then reabsorbed in the colon. Mycophenolate mofetil and EC-mycophenolate sodium display linear pharmacokinetics. Following mycophenolate mofetil administration, MPA maximum concentration usually occurs in 1-2 hours. EC-mycophenolate sodium exhibits a median lag time in absorption of MPA from 0.25 to 1.25 hours. A secondary peak in the concentration-time profile of MPA, due to enterohepatic recirculation, often appears 6-12 hours after dosing. This contributes approximately 40% to the area under the plasma concentration-time curve (AUC). The mean elimination half-life of MPA ranges from 9 to 17 hours. MPA displays large between- and within-subject pharmacokinetic variability. Dose-normalised MPA AUC can vary more than 10-fold. Total MPA concentrations should be interpreted with caution in patients with severe renal impairment, liver disease and hypoalbuminaemia. In such individuals, MPA and MPAG plasma protein binding may be altered, changing the fraction of free MPA available. Apparent oral clearance (CL/F) of total MPA appears to increase in proportion to the increased free fraction, with a reduction in total MPA AUC. However, there may be little change in the MPA free concentration. Ciclosporin inhibits biliary excretion of MPAG by MRP-2, reducing enterohepatic recirculation of MPA. Exposure to MPA when mycophenolate mofetil is given in combination with ciclosporin is approximately 30-40% lower than when given alone or with tacrolimus or sirolimus. High dosages of corticosteroids may induce expression of UGT, reducing exposure to MPA. Other co-medications can interfere with the absorption, enterohepatic recycling and metabolism of mycophenolate. Most pharmacokinetic investigations of MPA have involved mycophenolate mofetil rather than EC-mycophenolate sodium therapy. In population pharmacokinetic studies, MPA CL/F in adults ranges from 14.1 to 34.9 L/h (ciclosporin co-therapy) and from 11.9 to 25.4 L/h (tacrolimus co-therapy). Patient bodyweight, serum albumin concentration and immunosuppressant co-therapy have a significant influence on CL/F. The majority of pharmacodynamic data on MPA have been obtained in patients receiving mycophenolate mofetil therapy in the first year after kidney transplantation. Low MPA AUC is associated with increased incidence of biopsy-proven acute rejection. Gastrointestinal adverse events may be dose related. Leukopenia and anaemia have been associated with high MPA AUC, trough concentration and metabolite concentrations in some, but not all, studies. High free MPA exposure has been identified as a risk factor for leukopenia in some investigations. Targeting a total MPA AUC from 0 to 12 hours (AUC12) of 30-60 mg.hr/L is likely to minimise the risk of acute rejection and may reduce toxicity. IMPDH monitoring is in the early experimental stage. Individualisation of mycophenolate therapy should lead to improved patient outcomes. MPA AUC12 appears to be the most useful exposure measure for such individualisation. Limited sampling strategies and Bayesian forecasting are practical means of estimating MPA AUC12 without full concentration-time profiling. Target concentration intervention may be particularly useful in the first few months post-transplant and prior to major changes in anti-rejection therapy. In patients with impaired renal or hepatic function or hypoalbuminaemia, free drug measurement could be valuable in further interpretation of MPA exposure.

Diagnostic accuracy of cystatin C compared to serum creatinine for the estimation of renal dysfunction in adults and children--a meta-analysis

OBJECTIVES

To perform a systematic review comparing the diagnostic accuracy of CysC with SCr.

METHODS

MEDLINE and EMBASE (January 1984-February 2006) were searched. Studies included i) evaluated CysC against a recognised 'gold standard' method for determining GFR using a receiver operating characteristics (ROC) curve analysis and ii) included data that could be extracted into a 2x2 table.

RESULTS

The search identified 27 population groups in 24 studies (n=2007) that compared the diagnostic accuracy of CysC with SCr. The diagnostic odds ratios (DORs) (95% CI) of predicting renal dysfunction derived from a Moses-Littenberg linear regression model were 3.99 (3.41-4.57) for CysC and 2.79 (2.12-3.46) for SCr.

CONCLUSION

The diagnostic accuracy for impaired renal function favours CysC. However, the confidence intervals for the pooled DORs for the biomarkers overlap. The ability of CysC (cut-off values between 0.9 and 1.4 mg/L) to rule in renal impairment (as measured by inulin-determined GFR of 60-79 mL/min/1.73 m2) in persons in whom this is suspected is large and conclusive.

What happened to the prescribing of other COX-2 inhibitors, paracetamol and non-steroidal anti-inflammatory drugs when rofecoxib was withdrawn in Australia?

OBJECTIVES

To analyse how the prescribing of cyclooxygenase-2 (COX-2) inhibitors, non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs) and paracetamol (acetaminophen) changed when rofecoxib was withdrawn in 2004.

METHOD

COX-2 inhibitors, paracetamol and ns-NSAID's use was measured using dispensing data for concession beneficiaries subsidized by the Australian Pharmaceutical Benefit Scheme (PBS) for the period of 1997-2005. Data were downloaded from the Medicare Australia website and converted, according to the World Health Organization (WHO) Anatomical Therapeutic Chemical (ATC)/Defined Daily Dose (DDD) (2005), to DDD/1000 concession beneficiaries/day.

RESULTS

In the period 2000-2004, the use of COX-2 inhibitors was progressively increased. Overall NSAID's use changed from approximately 80 to 105 DDD/1000 concession beneficiaries/day while a decrease of ns-NSAIDs from about 70 to 40 DDD/1000 concession beneficiaries/day was observed. Following rofecoxib withdrawal, the overall NSAIDs use declined. In 2005, celecoxib prescription declined (23%) while prescription of meloxicam increased by 62%. Use of paracetamol was steady over the period 1997-2004 (around 40 DDD/1000 concession beneficiaries/day). In April 2005, a slight increase in paracetamol use was observed.

CONCLUSION

Our analysis showed that COX-2 inhibitors prescribing markedly influenced the overall NSAIDs prescribing in Australia. When COX-2 inhibitors were introduced their uptake was rapid and extensive. Following rofecoxib withdrawal, the total overall dispensing of NSAIDs returned to a similar value as before COX-2 inhibitors' introduction. The decrease was due both to rofecoxib withdrawal and to a reduction in celecoxib prescribing. However, meloxicam use increased. Paracetamol prescribing was steady, between 1997 and 2005 and was not affected when the COX-2 inhibitors were introduced on to the market and after rofecoxib withdrawal, rather than increasing as might have been anticipated after rofecoxib withdrawal.

How is leflunomide prescribed and used in Australia? Analysis of prescribing and adverse effect reporting

PURPOSE

To evaluate the use of leflunomide in the Australian community since introduction in 2000. Trends in adverse drug reaction (ADR) reporting were also studied.

METHODS

Annual Australian prescription and dispensing statistics were analysed. Drug utilisation was estimated as defined daily doses (DDD)/1000 inhabitants/day. ADR data from the Therapeutic Goods Administration's Adverse Drug Reactions Advisory Committee (ADRAC) national monitoring system were compared with the World Health Organisation (WHO) Vigibase records.

RESULTS

Leflunomide use in Australia (dispensing data) increased from 0.2 in 2000 to 0.4 DDD/1000 inhabitants/day in 2002. The same overall pattern was observed in the 'authority to prescribe' data. From 2000-2002, prescribing of the starter pack (3 x 100 mg loading dose plus 30 x 20 mg tablets) declined (down 74%); likewise for the 20 mg (30 tablets) pack. Gradual increases were noted for the 10 mg (30 tablets) pack (up 40%). Approximately 135 reports, detailing about 370 individual ADR, were generated annually. Gastro-intestinal disorders predominated, accounting for 24% of reactions reported to ADRAC. Skin and appendages disorders constituted 14% of reported reactions. Deaths in leflunomide users were attributed to a combination of haematological and gastro-intestinal complications, but it was not possible to ascertain other medication usage or contributing factors. Trends observed with the ADRAC reports were consistent with the WHO database.

CONCLUSIONS

Leflunomide was the first registered DMARD in Australia in over a decade and its use has increased within the community. The ADR reports might have contributed to Australian rheumatologists gradually abandoning loading patients with high doses of leflunomide in favour of starting therapy at lower doses.

Relationships between sirolimus dosing, concentration and outcomes in renal transplant recipients

AIM

To explore relationships between sirolimus dosing, concentration and clinical outcomes.

METHODS

Data were collected from 25 kidney transplant recipients (14 M/11 F), median 278 days after transplantation. Outcomes of interest were white blood cell (WBC) count, platelet (PLT) count, and haematocrit (HCT). A naive pooled data analysis was performed with outcomes dichotomized (Mann-Whitney U-tests).

RESULTS

Several patients experienced at least one episode when WBC (n = 9), PLT (n = 12), or HCT (n = 21) fell below the lower limits of the normal range. WBC and HCT were significantly lower (P < 0.05) when sirolimus dose was greater than 10 mg day(-1), and sirolimus concentration greater than 12 microg l(-1). No relationship was shown for PLT and dichotomized sirolimus dose or concentration.

CONCLUSIONS

Given this relationship between sirolimus concentration and effect, linked population pharmacokinetic-pharmacodynamic modelling using data from more renal transplant recipients should now be used to quantify the time course of these relationships to optimize dosing and minimize risk of these adverse outcomes.

Perceptions of the influence of prescription medicine samples on prescribing by family physicians

BACKGROUND

The provision of free prescription medicine samples is a common and traditional marketing strategy used by pharmaceutical companies, but concerns have been raised about their influence on physician prescribing behavior and patient safety.

OBJECTIVE

We sought to investigate the knowledge, attitudes, and behaviors of Australian family physicians regarding the use of sample prescription medications.

METHODS

Qualitative and quantitative techniques were used, including (1) mailed questionnaires to family physicians, (2) semistructured interviews with family physicians, and (3) sample cupboard inventories.

RESULTS

A number of issues about samples were identified by the questionnaires (208) and interviews (17 doctors), including insufficient labeling, poor record keeping, diversion of stock (personal use by doctors, their families, practice staff and pharmaceutical representatives), and wasting of expired stock. Prescription medicine samples also influenced prescribing behavior. Australian doctors were less likely to provide samples to patients on financial grounds compared with a previous study in the United States on medical residents. Six sample cupboards were inventoried. Median wholesale value of sample cupboards was AUD Dollars 4959 (range Dollars 2395-Dollars 8709), with 6% of stock expired. Very little generic medicine was included in the sample cupboards.

CONCLUSIONS

Better methods are needed to meet legislative requirements and to ensure quality use of medicines (and optimal public health) with respect to prescription medicine samples. Doctors and practice staff require training on the appropriate handling and storage of prescription medications. Alternative ways for distribution of sample medications need to be investigated.

Relationships of tacrolimus pharmacokinetic measures and adverse outcomes in stable adult liver transplant recipients

BACKGROUND AND OBJECTIVES

Alternative measures to trough concentrations [non-trough concentrations and limited area under the concentration-time curve (AUC)] have been shown to better predict tacrolimus AUC. The aim of this study was to determine if these are also better predictors of adverse outcomes in long term liver transplant recipients.

METHODS

The associations between tacrolimus trough concentrations (C(0)), non-trough concentrations (C(1), C(2), C(4), C(6/8)), and AUC(0-12) and the occurrence of hypertension, hyperkalaemia, hyperglycaemia and nephrotoxicity were assessed in 34 clinically stable liver transplant patients.

RESULTS AND DISCUSSION

The most common adverse outcome was hypertension, prevalence of 36%. Hyperkalaemia and hyperglycaemia had a prevalence of 21% and 13%, respectively. A sequential population pharmacokinetic/pharmacodynamic approach was implemented. No significant association between predicted C(0), C(1), C(2), C(4), C(6/8) or AUC(0-12) and adverse effects could be found. Tacrolimus concentrations and AUC measures were in the same range in patients with and without adverse effects.

CONCLUSIONS

Measures reported to provide benefit, preventing graft rejection and minimizing acute adverse effects in the early post-transplant period, were not able to predict adverse effects in stable adult liver recipients whose trough concentrations were maintained in the notional target range.