Evaluation of Bayesian Forecasting Methods for Prediction of Tacrolimus Exposure Using Samples Taken on Two Occasions in Adult Kidney Transplant Recipients

BACKGROUND

Bayesian forecasting-based limited sampling strategies (LSSs) for tacrolimus have not been evaluated for the prediction of subsequent tacrolimus exposure. This study examined the predictive performance of Bayesian forecasting programs/services for the estimation of future tacrolimus area under the curve (AUC) from 0 to 12 hours (AUC0-12) in kidney transplant recipients.

METHODS

Tacrolimus concentrations were measured in 20 adult kidney transplant recipients, 1 month post-transplant, on 2 occasions one week apart. Twelve samples were taken predose and 13 samples were taken postdose at the specified times on the first and second sampling occasions, respectively. The predicted AUC0-12 (AUCpredicted) was estimated using Bayesian forecasting programs/services and data from both sampling occasions for each patient and compared with the fully measured AUC0-12 (AUCmeasured) calculated using the linear trapezoidal rule on the second sampling occasion. The bias (median percentage prediction error [MPPE]) and imprecision (median absolute prediction error [MAPE]) were determined.

RESULTS

Three programs/services were evaluated using different LSSs (C0; C0, C1, C3; C0, C1, C2, C4; and all available concentrations). MPPE and MAPE for the prediction of fully measured AUC0-12 were <15% for each program/service (with the exclusion of when only C0 was used), when using estimated AUC from data on the same (second) occasion. The MPPE and MAPE for the prediction of a future fully measured AUC0-12 were <15% for 2 programs/services (and for the third when participants who had a tacrolimus dose change between sampling days were excluded), when the occasion 1-AUCpredicted, using C0, C1, and C3, was compared with the occasion 2-AUCmeasured.

CONCLUSIONS

All 3 Bayesian forecasting programs/services evaluated had acceptable bias and imprecision for predicting a future AUC0-12, using tacrolimus concentrations at C0, C1, and C3, and could be used for the accurate prediction of tacrolimus exposure in adult kidney transplant recipients.

A PERSPECTIVE ON AUSTRALIA’S NATIONAL MEDICINES POLICY

There is international interest in Australia’s health care system for prescription medicines. The issue is particularly topical in Canada with the debate following publication of the Romanow Report into the future of health care in Canada. This Report recommended a new National Drug Agency. Australia has a National Medicines Policy with four arms – quality, safety and efficacy of medicines; equity of access; a viable and responsible pharmaceutical industry; quality use of medicines.  The  four  arms  of  the  Policy  are  interlinked  and  interdependent  for  optimal functioning. In this paper, an overview of how the prescription drug system in Australia works is presented.  The  manuscript  focuses  upon  specific  aspects  of  the  Policy,  describing  how  it functions and some of the processes integral to success, from the viewpoint of the author. The discussion includes some of the advantages of Australia’s system for pharmaceuticals as well as some of the problems, as these present opportunities for development and change

Is Conversion from Mycophenolate Mofetil to Enteric-Coated Mycophenolate Sodium Justifiable for Gastrointestinal Quality of Life?

BACKGROUND

Globally, enteric-coated mycophenolate sodium (EC-MPS) is replacing mycophenolate mofetil (MMF) in maintenance immunosuppressant regimens. The predominant reason for conversion is the purported improvement in gastrointestinal (GI) quality of life. This paper considers the level of bias associated with studies comparing EC-MPS and MMF for GI-related improvement and provides insight into whether conversion is supported by evidence.

METHODS

Using a pre-determined protocol, a literature search was conducted. Full-text review, data extraction and risk of bias analysis was conducted by two independent authors using the Cochrane domain-based evaluation of risk of bias. The review was reported according to the preferred reporting items for systematic reviews and meta-analyses.

RESULTS

Twenty-nine studies were included in risk of bias analysis. Of these, only three were deemed a low risk of bias. Across these three studies, there were no statistically significant differences in the proportion of GI-related adverse events nor was there a significant difference in the GI-related quality of life between EC-MPS- and MMF-treated patients in these data.

CONCLUSION

There was a high risk of bias across the 29 studies investigating conversion from MMF to EC-MPS for potential improvement in GI-related quality of life. The consolidated results of the three studies with low risk of bias suggest no evidence to convert patients stabilised on MMF. If a patient experiences GI-related adverse events whilst taking MMF, other methods should be explored before conversion to EC-MPS.

Multinational Evaluation of Mycophenolic Acid, Tacrolimus, Cyclosporin, Sirolimus, and Everolimus Utilization

BACKGROUND

Increasing immunosuppressant utilization and expenditure is a worldwide challenge as more people successfully live with transplanted organs. Our aims were to characterize utilization of mycophenolate, tacrolimus, cyclosporin, sirolimus, and everolimus in Australian transplant recipients from 2007 to 2013; to identify specific patterns of usage; and to compare Australian utilization with Norwegian, Danish, Swedish, and the Netherlands use.

MATERIAL AND METHODS

Australian utilization and expenditure data were captured through national Pharmaceutical Benefits Scheme and Highly Specialized Drug administrative databases. Norwegian, Danish, Swedish, and the Netherlands utilization were retrieved from their healthcare databases. Utilization was compared as defined daily dose per 1000 population per day (DDD/1000 population/day). Data on kidney transplant recipients, the predominant patient group prescribed these medicines, were obtained from international transplant registries.

RESULTS

From 2007-2013 Australian utilization of mycophenolic acid, tacrolimus and everolimus increased 2.7-fold, 2.2-fold, and 2.3-fold, respectively. Use of cyclosporin and sirolimus decreased 20% and 30%, respectively. Australian utilization was significantly lower than European utilization (2013) but was increasing at a faster rate. Total Australian expenditure increased approximately AUD$30 million over the study period to almost AUD$100 million in 2013. Kidney transplantation rates increased across each country over this time, with Australia having the lowest rate.

CONCLUSIONS

Immunosuppressant usage and subsequent expenditure are rising in Australia and Northern Europe. With increased numbers of people living with transplants, and the observed growth potential predicted from Northern European data, this class of medicines can be expected to continue consuming an increasing share of Australian pharmaceutical expenditure into the future.

The effect of dose and type of proton pump inhibitor use on risk of fractures and osteoporosis treatment in older Australian women: A prospective cohort study

OBJECTIVES

Proton pump inhibitors (PPIs) are among the most prescribed medications worldwide, however, there is growing concern regarding potential negative effects on bone health. The aim was to examine the effect of dose and type of PPI use on subsequent use of osteoporosis medication and fractures in older Australian women.

METHODS

Data were included from 4432 participants (born 1921-26) in the 2002 survey of the Australian Longitudinal Study on Women's Health. Medication data were from the national pharmaceutical administrative database (2003-2012, inclusive). Fractures were sourced from linked hospital datasets available for four major States of Australia. Competing risk regression models used PPI exposure as a time-dependent covariate and either time to first osteoporosis medication prescription or fracture as the outcome, with death as a competing risk.

RESULTS

Of the 2328 PPI users and 2104 PPI non-users, 827 (36%) and 550 (26%) became users of osteoporosis medication, respectively. PPI use was associated with an increased risk of subsequent use of osteoporosis medication (adjusted sub-hazard ratio [SHR]=1.28; 95% confidence interval [CI]=1.13-1.44) and subsequent fracture (SHR=1.29, CI=1.08-1.55). Analysis with PPI categorized according to defined daily dose (DDD), showed some evidence for a dose-response effect (osteoporosis medication: <400 DDD: SHR=1.23, CI=1.06-1.42 and ≥400 DDD: SHR=1.39, CI=1.17-1.65, compared with non-users; SHRs were in the same range for fractures). Esomeprazole was the most common PPI prescribed (22.9%). Analysis by type of PPI use showed an increased subsequent risk for: (1) use of osteoporosis medication for rabeprazole (SHR=1.51, CI=1.08-2.10) and esomeprazole (SHR=1.48, CI=1.17-1.88); and (2) fractures for rabeprazole (SHR=2.06, CI=1.37-3.10). Users of multiple types of PPI also had increased risks for use of osteoporosis medication and fractures.

CONCLUSION

An appropriate benefit/risk assessment should be made when prescribing PPIs, especially for esomeprazole and rabeprazole, as osteoporosis and fracture risks were increased in this cohort of elderly females subsequent to PPI prescription.

Actions following adverse drug events - how do these influence uptake and utilisation of newer and/or similar medications?

Background

Over the last decade, actions following some adverse drug events received major publicity. This study investigated changes in usage patterns of medications in Australia following two examples - rofecoxib market withdrawal (2004) and warnings about jaw necrosis following bisphosphonates (2007).

Methods

Dispensing data for COX-2 inhibitors (2000–2008) and anti-osteoporosis medications (2003–2012) were obtained from the Australian Pharmaceutical Benefits Scheme database. For bisphosphonates, data on Australian marketing expenditures were purchased from Cegedim^R.

Results

For COX-2 inhibitors, celecoxib dispensing halved after rofecoxib withdrawal, but meloxicam dispensing increased by 60 %. When lumiracoxib was introduced (2006) there was uptake of prescribing at a faster rate than meloxicam in 2002, its first year of use. For bisphosphonates, alendronate had highest use at the time of the warnings (8.3 DDD/1000/day), dropping to 4.9 DDD/1000/day by 2012. In contrast, risedronate use rose 2007–2012 from 4.1 to 4.9 DDD/1000/day. There was 49 % increase in reported annual expenditure on detailing for risedronate from 2007 to 2008 (to AUD$7.3 million) and only 29 % increase for alendronate (to AUD$3.1 million).

Conclusions

The rapid uptake of prescribing of lumiracoxib and increased use of meloxicam flagged a concern, especially after rofecoxib withdrawal due to safety issues. Bisphosphonates are useful drugs, however the dramatic rise in expenditure on detailing, followed by a rise in utilisation of risedronate could suggest that adverse publicity triggered a marketing response. These examples highlight the importance of tracking utilisation of medication classes in real time, using different data as needed, to ensure that due caution is exercised (and quick intervention provided if needed) for medications in the same class.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-015-1165-9) contains supplementary material, which is available to authorized users.

Exposure-effect relationship of mycophenolic acid and prednisolone in adult patients with lupus nephritis

AIMS

The aim was to examine relationships between total and unbound mycophenolic acid (MPA) and prednisolone exposure and clinical outcomes in patients with lupus nephritis.

METHODS

Six blood samples were drawn pre- and at 1, 2, 4, 6 and 8 h post-dose and total and unbound MPA and prednisolone pre-dose (C0 ), maximum concentration (Cmax ) and area under the concentration-time curve (AUC) were determined using non-compartmental analysis in 25 patients. The analyses evaluated drug exposures in relation to treatment response since starting MPA and drug-related adverse events.

RESULTS

Dose-normalized AUC varied 10-, 8-, 7- and 19-fold for total MPA, unbound MPA, total prednisolone and unbound prednisolone, respectively. Median values (95% CI) of total MPA AUC(0,8 h) (21.5 [15.0, 42.0] vs. 11.2 [4.8, 30.0] mg l(-1) h, P= 0.048) and Cmax (11.9 [6.7, 26.3] vs. 6.1 [1.6, 9.2] mg l(-1) , P = 0.016) were significantly higher in responders than non-responders. Anaemia was significantly associated with higher total (37.8 [14.1, 77.5] vs. 18.5 [11.7, 32.7] mg l(-1) h, P = 0.038) and unbound MPA AUC(0,12 h) (751 [214, 830] vs. 227 [151, 389] mg l(-1) h, P = 0.004). Unbound prednisolone AUC(0,24 h) was significantly higher in patients with Cushingoid appearance (unbound: 1372 [1242, 1774] vs. 846 [528, 1049] nmol l(-1) h, P = 0.019) than in those without. Poorer treatment response was observed in patients with lowest tertile exposure to both total MPA and prednisolone as compared with patients with middle and higher tertile exposure (17% vs. 74%, P = 0.023).

CONCLUSIONS

This study suggests a potential role for therapeutic drug monitoring in individualizing immunosuppressant therapy in patients with lupus nephritis.

How accurate and precise are limited sampling strategies in estimating exposure to mycophenolic acid in people with autoimmune disease?

Mycophenolic acid (MPA) is a potent immunosuppressant agent, which is increasingly being used in the treatment of patients with various autoimmune diseases. Dosing to achieve a specific target MPA area under the concentration-time curve from 0 to 12 h post-dose (AUC12) is likely to lead to better treatment outcomes in patients with autoimmune disease than a standard fixed-dose strategy. This review summarizes the available published data around concentration monitoring strategies for MPA in patients with autoimmune disease and examines the accuracy and precision of methods reported to date using limited concentration-time points to estimate MPA AUC12. A total of 13 studies were identified that assessed the correlation between single time points and MPA AUC12 and/or examined the predictive performance of limited sampling strategies in estimating MPA AUC12. The majority of studies investigated mycophenolate mofetil (MMF) rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation of MPA. Correlations between MPA trough concentrations and MPA AUC12 estimated by full concentration-time profiling ranged from 0.13 to 0.94 across ten studies, with the highest associations (r (2) = 0.90-0.94) observed in lupus nephritis patients. Correlations were generally higher in autoimmune disease patients compared with renal allograft recipients and higher after MMF compared with EC-MPS intake. Four studies investigated use of a limited sampling strategy to predict MPA AUC12 determined by full concentration-time profiling. Three studies used a limited sampling strategy consisting of a maximum combination of three sampling time points with the latest sample drawn 3-6 h after MMF intake, whereas the remaining study tested all combinations of sampling times. MPA AUC12 was best predicted when three samples were taken at pre-dose and at 1 and 3 h post-dose with a mean bias and imprecision of 0.8 and 22.6 % for multiple linear regression analysis and of -5.5 and 23.0 % for maximum a posteriori (MAP) Bayesian analysis. Although mean bias was less when data were analysed using multiple linear regression, MAP Bayesian analysis is preferable because of its flexibility with respect to sample timing. Estimation of MPA AUC12 following EC-MPS administration using a limited sampling strategy with samples drawn within 3 h post-dose resulted in biased and imprecise results, likely due to a longer time to reach a peak MPA concentration (t max) with this formulation and more variable pharmacokinetic profiles. Inclusion of later sampling time points that capture enterohepatic recirculation and t max improved the predictive performance of strategies to predict EC-MPS exposure. Given the considerable pharmacokinetic variability associated with mycophenolate therapy, limited sampling strategies may potentially help in individualizing patient dosing. However, a compromise needs to be made between the predictive performance of the strategy and its clinical feasibility. An opportunity exists to combine research efforts globally to create an open-source database for MPA (AUC, concentrations and outcomes) that can be used and prospectively evaluated for AUC target-controlled dosing of MPA in autoimmune diseases.

Pharmacology and toxicology of mycophenolate in organ transplant recipients: an update

This review aims to provide an update of the literature on the pharmacology and toxicology of mycophenolate in solid organ transplant recipients. Mycophenolate is now the antimetabolite of choice in immunosuppressant regimens in transplant recipients. The active drug moiety mycophenolic acid (MPA) is available as an ester pro-drug and an enteric-coated sodium salt. MPA is a competitive, selective and reversible inhibitor of inosine-5'-monophosphate dehydrogenase (IMPDH), an important rate-limiting enzyme in purine synthesis. MPA suppresses T and B lymphocyte proliferation; it also decreases expression of glycoproteins and adhesion molecules responsible for recruiting monocytes and lymphocytes to sites of inflammation and graft rejection; and may destroy activated lymphocytes by induction of a necrotic signal. Improved long-term allograft survival has been demonstrated for MPA and may be due to inhibition of monocyte chemoattractant protein 1 or fibroblast proliferation. Recent research also suggested a differential effect of mycophenolate on the regulatory T cell/helper T cell balance which could potentially encourage immune tolerance. Lower exposure to calcineurin inhibitors (renal sparing) appears to be possible with concomitant use of MPA in renal transplant recipients without undue risk of rejection. MPA displays large between- and within-subject pharmacokinetic variability. At least three studies have now reported that MPA exhibits nonlinear pharmacokinetics, with bioavailability decreasing significantly with increasing doses, perhaps due to saturable absorption processes or saturable enterohepatic recirculation. The role of therapeutic drug monitoring (TDM) is still controversial and the ability of routine MPA TDM to improve long-term graft survival and patient outcomes is largely unknown. MPA monitoring may be more important in high-immunological recipients, those on calcineurin-inhibitor-sparing regimens and in whom unexpected rejection or infections have occurred. The majority of pharmacodynamic data on MPA has been obtained in patients receiving MMF therapy in the first year after kidney transplantation. Low MPA area under the concentration time from 0 to 12 h post-dose (AUC0-12) is associated with increased incidence of biopsy-proven acute rejection although AUC0-12 optimal cut-off values vary across study populations. IMPDH monitoring to identify individuals at increased risk of rejection shows some promise but is still in the experimental stage. A relationship between MPA exposure and adverse events was identified in some but not all studies. Genetic variants within genes involved in MPA metabolism (UGT1A9, UGT1A8, UGT2B7), cellular transportation (SLCOB1, SLCO1B3, ABCC2) and targets (IMPDH) have been reported to effect MPA pharmacokinetics and/or response in some studies; however, larger studies across different ethnic groups that take into account genetic linkage and drug interactions that can alter a patient's phenotype are needed before any clinical recommendations based on patient genotype can be formulated. There is little data on the pharmacology and toxicology of MPA in older and paediatric transplant recipients.

Differences in utilisation of gastroprotective drugs between 2001 and 2005 in Australia and Nova Scotia, Canada

PURPOSE

This study aimed to compare use of histamine H2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs), 2001-2005, in the elderly and social security beneficiaries in Australia (AUS) and Nova Scotia, Canada (NS).

METHODS

Prescription dispensing data were collected for all subsidised H2RAs and PPIs. In AUS, dispensing data for concession beneficiaries were obtained from the Pharmaceutical Benefits Scheme database. In NS, data were sourced from the Pharmacare database. Relevant population data were used to convert to World Health Organisation Anatomic Therapeutic Chemical defined daily doses (2005) per 1000 beneficiaries per day (DDD/1000/day).

RESULTS

Overall use of gastroprotective agents was similar and rising in NS and AUS (100-160 DDD/1000/day) over this 5-year time window. However, the proportion of this use accounted for by PPIs was far higher in AUS (over 85% by 2005) than in NS (23% rising to 35% over the 5 years). In AUS, PPI use rose from 50 to about 140 DDD/1000/day over the 5 years, whereas PPI use in NS rose slowly to less than 60 DDD/1000/day by 2005. H2RA use in NS was always high (over 100 DDD/1000/day), whereas in AUS, H2RA use fell from 54 to around 24 DDD/1000/day over this period.

CONCLUSIONS

AUS had much higher use of PPIs than NS over 2001-2005. The proportion of PPIs in all gastroprotective agents rose in AUS to be nearly 90%. The differences in utilisation during this time window could lead to differences in health outcomes from either lower gastro-intestinal bleeding risk or higher long-term adverse effects of PPIs.

Validity of self-reported osteoporosis in mid-age and older women

The validity of self-reported osteoporosis is often questioned, but validation studies are lacking. We validated self-reported prevalence and incidence of osteoporosis against self-reported and administrative data on medications. The concurrent validity was moderate to good for self-reported prevalent osteoporosis, but only poor to moderate for self-reported incident osteoporosis in mid-age and older women, respectively. Construct validity was acceptable for self-reported prevalent but not for incident osteoporosis.

INTRODUCTION

The validity of self-reported osteoporosis is often questioned, but validation studies are lacking. The aim was to examine the validity of self-reported prevalence and incidence of osteoporosis against self-reported and administrative data on medications.

METHODS

Data were from mid-age (56-61 years in 2007) and older (79-84 years in 2005) participants in the Australian Longitudinal Study on Women's Health. Self-reported diagnosis was compared with medication information from (1) self-report (n(mid) = 10,509 and n(old) = 7,072), and (2) pharmaceutical prescription reimbursement claims (n(mid) = 6,632 and n(old) = 4,668). Concurrent validity of self-report was examined by calculating agreement, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Construct validity was tested by examining associations of self-reported diagnosis with osteoporosis-related characteristics (fracture, weight, bodily pain, back pain, and physical functioning).

RESULTS

Agreement, sensitivity and PPV of self-reported prevalent diagnosis were higher when compared with medication claims (mid-age women: kappa = 0.51, 95% confidence interval [CI] = 0.46-0.56; older women: kappa = 0.65, 95% CI = 0.63-0.68) than with self-reported medication (mid-age women: kappa = 0.41, 95% CI = 0.37-0.45; older women: kappa = 0.57, 95% CI = 0.55-0.59). Sensitivity, PPV and agreement were lower for self-reported incident diagnosis (mid-age women: kappa = 0.39, 95% CI = 0.32-0.47; older women: kappa = 0.55, 95% CI = 0.51-0.61). Statistically significant associations between self-reported diagnosis and at least four of five characteristics were found for prevalent diagnosis in both age groups and for incident diagnosis in older women.

CONCLUSIONS

The concurrent validity was moderate to good for self-reported prevalent osteoporosis, but only poor to moderate for self-reported incident osteoporosis in mid-age and older women, respectively. Construct validity was acceptable for self-reported prevalent but not for incident osteoporosis.

Innovation in hospital quality improvement activities--acute postoperative pain management (APOP) self-help toolkit audits as an example

It is often difficult to maintain quality improvement change. Many behavioral strategies have been used to improve uptake of new practices and knowledge. One effective way of changing medication prescribing is audit and feedback with specific educational feedback. The challenge however is to maintain ongoing quality improvement activities. In Australia, unique downloadable "toolkits" are now available to assist hospitals to maintain prescribing quality improvement activities. The first designed to improve the management of acute postoperative pain (APOP toolkit) has been piloted. The toolkit includes data collection and educational tools, an automated feedback report on key indicators, with complete instructions for use. The APOP toolkit has been used in 73 hospitals, in two facilitated "snapshot" audits. There was continued improvement in performance, assessed by increases in the percentage of patients with measured pain and sedation scores and in those with documented pain management plans at discharge, compared with earlier APOP project audits. Using this example of the APOP toolkit and "snapshot" audits, we have now demonstrated that hospitals nationwide are able to undertake quality improvement activities voluntarily to maintain optimal performance. Encouragement, guidance, and availability of ready-made tools developed by a national team facilitate opportunities for ongoing quality improvements.

Quality Use of Medicines--medication safety issues in naming; look-alike, sound-alike medicine names

OBJECTIVE

To review current literature with the objective of developing strategies and recommendations to enhance patient safety and minimise clinical issues with look-alike, sound-alike medication names.

METHODS

A comprehensive search of the PubMed database and an Australian online repository of Quality Use of Medicines projects was conducted to identify publications addressing look-alike, sound-alike medication problems. Author networks, grey literature and the reference lists of published articles were also used to identify additional material.

KEY FINDINGS

Thirty-two publications describing the extent of the specific problem and recommending solutions were identified. The majority of these publications provided a qualitative assessment of the issues, with few quantitative estimates of the severity of the problem and very little intervention research. As a result, most recommendations for addressing the problem are the result of expert deliberations and not experimental research. This will affect the capacity of the recommendations to ameliorate and resolve problems caused by look-alike, sound-alike medication names. Themes identified from articles included the nature and causes of look-alike, sound-alike problems, potential solutions and recommendations.

CONCLUSIONS

There are many existing medications which can potentially cause clinical issues due to mix-ups because of similar sounding or looking medication names. This confusion can be lethal for some medication errors. A multifaceted, integrated approach involving all aspects of the medication use process, from initial naming of INN through to consumer education, is suggested to minimise this issue for medication safety.

Consumers' experiences and values in conventional and alternative medicine paradigms: a problem detection study (PDS)

Background

This study explored consumer perceptions of complementary and alternative medicine (CAM) and relationships with CAM and conventional medicine practitioners.

A problem detection study (PDS) was used. The qualitative component to develop the questionnaire used a CAM consumer focus group to explore conventional and CAM paradigms in healthcare. 32 key issues, seven main themes, informed the questionnaire (the quantitative PDS component - 36 statements explored using five-point Likert scales.)

Results

Of 300 questionnaires distributed (Brisbane, Australia), 83 consumers responded. Results indicated that consumers felt empowered by using CAM and they reported positive relationships with CAM practitioners. The perception was that CAM were used most effectively as long-term therapy (63% agreement), but that conventional medicines would be the best choice for emergency treatment (81% agreement). A majority (65%) reported that doctors appeared uncomfortable about consumers' visits to CAM practitioners. Most consumers (72%) believed that relationships with and between health practitioners could be enhanced by improved communication. It was agreed that information sharing between consumers and healthcare practitioners is important, and reported that "enough" information is shared between CAM practitioners and consumers. Consumers felt comfortable discussing their medicines with pharmacists, general practitioners and CAM practitioners, but felt most comfortable with their CAM practitioners.

Conclusions

This PDS has emphasized the perceived importance of open communication between consumers, CAM and conventional providers, and has exposed areas where CAM consumers perceive that issues exist across the CAM and conventional medicine paradigms. There is a lot of information which is perceived as not being shared at present and there are issues of discomfort and distrust which require resolution to develop concordant relationships in healthcare. Further research should be based on optimisation of information sharing, spanning both conventional and CAM fields of healthcare, due to both the relevance of concordance principles within CAM modalities and the widespread use of CAM by consumers.

Maximum a posteriori Bayesian estimation of mycophenolic Acid area under the concentration-time curve: is this clinically useful for dosage prediction yet?

This review seeks to summarize the available data about Bayesian estimation of area under the plasma concentration-time curve (AUC) and dosage prediction for mycophenolic acid (MPA) and evaluate whether sufficient evidence is available for routine use of Bayesian dosage prediction in clinical practice. A literature search identified 14 studies that assessed the predictive performance of maximum a posteriori Bayesian estimation of MPA AUC and one report that retrospectively evaluated how closely dosage recommendations based on Bayesian forecasting achieved targeted MPA exposure. Studies to date have mostly been undertaken in renal transplant recipients, with limited investigation in patients treated with MPA for autoimmune disease or haematopoietic stem cell transplantation. All of these studies have involved use of the mycophenolate mofetil (MMF) formulation of MPA, rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation. Bias associated with estimation of MPA AUC using Bayesian forecasting was generally less than 10%. However some difficulties with imprecision was evident, with values ranging from 4% to 34% (based on estimation involving two or more concentration measurements). Evaluation of whether MPA dosing decisions based on Bayesian forecasting (by the free website service https://pharmaco.chu-limoges.fr) achieved target drug exposure has only been undertaken once. When MMF dosage recommendations were applied by clinicians, a higher proportion (72-80%) of subsequent estimated MPA AUC values were within the 30-60 mg · h/L target range, compared with when dosage recommendations were not followed (only 39-57% within target range). Such findings provide evidence that Bayesian dosage prediction is clinically useful for achieving target MPA AUC. This study, however, was retrospective and focussed only on adult renal transplant recipients. Furthermore, in this study, Bayesian-generated AUC estimations and dosage predictions were not compared with a later full measured AUC but rather with a further AUC estimate based on a second Bayesian analysis. This study also provided some evidence that a useful monitoring schedule for MPA AUC following adult renal transplant would be every 2 weeks during the first month post-transplant, every 1-3 months between months 1 and 12, and each year thereafter. It will be interesting to see further validations in different patient groups using the free website service. In summary, the predictive performance of Bayesian estimation of MPA, comparing estimated with measured AUC values, has been reported in several studies. However, the next step of predicting dosages based on these Bayesian-estimated AUCs, and prospectively determining how closely these predicted dosages give drug exposure matching targeted AUCs, remains largely unaddressed. Further prospective studies are required, particularly in non-renal transplant patients and with the EC-MPS formulation. Other important questions remain to be answered, such as: do Bayesian forecasting methods devised to date use the best population pharmacokinetic models or most accurate algorithms; are the methods simple to use for routine clinical practice; do the algorithms actually improve dosage estimations beyond empirical recommendations in all groups that receive MPA therapy; and, importantly, do the dosage predictions, when followed, improve patient health outcomes?

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.