Clinical effectiveness, tolerability and cost-effectiveness of newer drugs for epilepsy in adults: a systematic review and economic evaluation

OBJECTIVES

To examine the clinical effectiveness, tolerability and cost-effectiveness of gabapentin (GBP), lamotrigine (LTG), levetiracetam (LEV), oxcarbazepine (OXC), tiagabine (TGB), topiramate (TPM) and vigabatrin (VGB) for epilepsy in adults.

DATA SOURCES

Electronic databases. Internet resources. Pharmaceutical company submissions.

REVIEW METHODS

Selected studies were screened and quality assessed. Separate analyses assessed clinical effectiveness, serious, rare and long-term adverse events and cost-effectiveness. An integrated economic analysis incorporating information on costs and effects of newer and older antiepileptic drugs (AEDs) was performed to give direct comparisons of long-term costs and benefits.

RESULTS

A total of 212 studies were included in the review. All included systematic reviews were Cochrane reviews and of good quality. The quality of randomised controlled trials (RCTs) was variable. Assessment was hampered by poor reporting of methods of randomisation, allocation concealment and blinding. Few of the non-randomised studies were of good quality. The main weakness of the economic evaluations was inappropriate use of the cost-minimisation design. The included systematic reviews reported that newer AEDs were effective as adjunctive therapy compared to placebo. For newer versus older drugs, data were available for all three monotherapy AEDs, although data for OXC and TPM were limited. There was limited, poor-quality evidence of a significant improvement in cognitive function with LTG and OXC compared with older AEDs. However, there were no consistent statistically significant differences in other clinical outcomes, including proportion of seizure-free patients. No studies assessed effectiveness of AEDs in people with intellectual disabilities or in pregnant women. There was very little evidence to assess the effectiveness of AEDs in the elderly; no significant differences were found between LTG and carbamazepine monotherapy. Sixty-seven RCTs compared adjunctive therapy with placebo, older AEDs or other newer AEDs. For newer AEDs versus placebo, a trend was observed in favour of newer drugs, and there was evidence of statistically significant differences in proportion of responders favouring newer drugs. However, it was not possible to assess long-term effectiveness. Most trials were conducted in patients with partial seizures. For newer AEDs versus older drugs, there was no evidence to assess the effectiveness of LEV, LTG or OXC, and evidence for other newer drugs was limited to single studies. Trials only included patients with partial seizures and follow-up was relatively short. There was no evidence to assess effectiveness of adjunctive LEV, OXC or TPM versus other newer drugs, and there were no time to event or cognitive data. No studies assessed the effectiveness of adjunctive AEDs in the elderly or pregnant women. There was some evidence from one study (GBP versus LTG) that both drugs have some beneficial effect on behaviour in people with learning disabilities. Eighty RCTs reported the incidence of adverse events. There was no consistent or convincing evidence to draw any conclusions concerning relative safety and tolerability of newer AEDs compared with each other, older AEDs or placebo. The integrated economic analysis for monotherapy for newly diagnosed patients with partial seizures showed that older AEDs were more likely to be cost-effective, although there was considerable uncertainty in these results. The integrated analysis suggested that newer AEDs used as adjunctive therapy for refractory patients with partial seizures were more effective and more costly than continuing with existing treatment alone. Combination therapy, involving new AEDs, may be cost-effective at a threshold willingness to pay per quality-adjusted life year (QALY) greater than 20,000 pounds, depending on patients' previous treatment history. There was, again, considerable uncertainty in these results. There were few data available to determine effectiveness of treatments for patients with generalised seizures. LTG and VPA showed similar health benefits when used as monotherapy. VPA was less costly and was likely to be cost-effective. The analysis indicated that TPM might be cost-effective when used as an adjunctive therapy, with an estimated incremental cost-effectiveness ratio of 34,500 pounds compared with continuing current treatment alone.

CONCLUSIONS

There was little good-quality evidence from clinical trials to support the use of newer monotherapy or adjunctive therapy AEDs over older drugs, or to support the use of one newer AED in preference to another. In general, data relating to clinical effectiveness, safety and tolerability failed to demonstrate consistent and statistically significant differences between the drugs. The exception was comparisons between newer adjunctive AEDs and placebo, where significant differences favoured newer AEDs. However, trials often had relatively short-term treatment durations and often failed to limit recruitment to either partial or generalised onset seizures, thus limiting the applicability of the data. Newer AEDs, used as monotherapy, may be cost-effective for the treatment of patients who have experienced adverse events with older AEDs, who have failed to respond to the older drugs, or where such drugs are contraindicated. The integrated economic analysis also suggested that newer AEDs used as adjunctive therapy may be cost-effective compared with the continuing current treatment alone given a QALY of about 20,000 pounds. There is a need for more direct comparisons of the different AEDs within clinical trials, considering different treatment sequences within both monotherapy and adjunctive therapy. Length of follow-up also needs to be considered. Trials are needed that recruit patients with either partial or generalised seizures; that investigate effectiveness and cost-effectiveness in patients with generalised onset seizures and that investigate effectiveness in specific populations of epilepsy patients, as well as studies evaluating cognitive outcomes to use more stringent testing protocols and to adopt a more consistent approach in assessing outcomes. Further research is also required to assess the quality of life within trials of epilepsy therapy using preference-based measures of outcomes that generate cost-effectiveness data. Future RCTs should use CONSORT guidelines; and observational data to provide information on the use of AEDs in actual practice, including details of treatment sequences and doses.

Cost effectiveness of photodynamic therapy with verteporfin for age related macular degeneration: the UK case

AIM

To estimate the potential cost effectiveness of photodynamic therapy (PDT) with verteporfin in the UK setting.

METHODS

Using data from a variety of sources a Markov model was built to produce estimates of the cost effectiveness (incremental cost per quality adjusted life year (QALY) and incremental cost per vision year gained) of PDT for two cohorts of patients (one with starting visual acuity (VA) of 20/40 and one at 20/100) with predominantly classic choroidal neovascular disease over a 2 year and 5 year time horizon. A government perspective and a treatment cost only perspective were considered. Probabilistic and one way sensitivity analyses were undertaken.

RESULTS

From the government perspective, over the 2 year period, the expected incremental cost effectiveness ratios range from 286 000 (starting VA 20/100) to 76 000 UK pounds (starting VA 20/40) per QALY gained and from 14 000 (20/100) to 34 000 UK pounds (20/40) per vision year gained. A 5 year perspective yields incremental ratios less than 5000 UK pounds for vision years gained and from 9000 (20/40) to 30 000 UK pounds (20/100) for QALYs gained. Without societal or NHS cost offsets included, the 2 year incremental cost per vision year gained ranges from 20 000 (20/100) to 40 000 UK pounds (20/40), and the 2 year incremental cost per QALY gained ranges from 412 000 (20/100) to 90 000 UK pounds (20/40). The 5 year time frame shows expected costs of 7000 (20/40) to 10 000 UK pounds (20/100) per vision year gained and from 38 000 (20/40) to 69 000 UK pounds (20/100) per QALY gained.

CONCLUSION

This evaluation suggests that early treatment (that is, treating eyes at less severe stages of disease) with PDT leads to increased efficiency. When considering only the cost of therapy, treating people at lower levels of visual acuity would probably not be considered cost effective. However, a broad perspective that incorporates other NHS treatment costs and social care costs suggests that over a long period of time, PDT may yield reasonable value for money.

Progress towards an OMERACT-ILAR guideline for economic evaluations in rheumatology

A working report from the OMERACT Health Economics Group. The group is working towards creating common standards for economic evaluation in rheumatology and also towards improving the scientific underpinning of economic evaluation, particularly pertaining to the rheumatic diseases. Preliminary recommendations for "reference cases" in osteoporosis, rheumatoid arthritis, and osteoarthritis are proposed.

The cost-effectiveness of population Helicobacter pylori screening and treatment: a Markov model using economic data from a randomized controlled trial

BACKGROUND

Economic models have suggested that population Helicobacter pylori screening and treatment may be a cost-effective method of reducing mortality from gastric cancer. These models are conservative as they do not consider that the programme may reduce health service peptic ulcer and other dyspepsia costs. We have evaluated the economic impact of population H. pylori screening and treatment over 2 years in a randomized controlled trial and have incorporated the results into an economic model exploring the impact of H. pylori eradication on peptic ulcer disease and gastric cancer.

METHODS

Subjects between the ages of 40 and 49 years were randomly invited to attend their local primary care centre. H. pylori status was evaluated by (13)C-urea breath test and infected individuals were randomized to receive omeprazole, 20 mg b.d., clarithromycin, 250 mg b.d., and tinidazole, 500 mg b.d., for 7 days or identical placebos. Economic data on health service costs for dyspepsia were obtained from a primary care note review for the 2 years following randomization. These data were incorporated into a Markov model comparing population H. pylori screening and treatment with no intervention.

RESULTS

A total of 2329 of 8407 subjects were H. pylori positive: 1161 were randomized to receive eradication therapy and 1163 to receive placebo. The cost difference favoured the intervention group 2 years after randomization, but this did not reach statistical significance (11.42 ponds sterling per subject cost saving; 95% confidence interval, 30.04 ponds sterling to -7.19 pounds sterling; P=0.23). Analysis by gender suggested a statistically significant dyspepsia cost saving in men (27.17 ponds sterling per subject; 95% confidence interval, 50.01 pounds sterling to 4.32 pounds sterling; P=0.02), with no benefit in women (-4.46 per subject; 95% confidence interval, -33.85 pounds sterling to 24.93 pounds sterling). Modelling of these data suggested that population H. pylori screening and treatment for 1,000,000 45-year-olds would save over 6,000,000 pounds sterling and 1300 years of life. The programme would cost 14, 200 pounds sterling per life year saved if the health service dyspepsia cost savings were the lower limit of the 95% confidence intervals and H. pylori eradication had only a 10% efficacy in reducing mortality from distal gastric cancer and peptic ulcer disease.

CONCLUSIONS

Modelling suggests that population H. pylori screening and treatment are likely to be cost-effective and could be the first cost-neutral screening programme. This provides a further mandate for clinical trials to evaluate the efficacy of population H. pylori screening and treatment in preventing mortality from gastric cancer and peptic ulcer disease.

When is it cost-effective to change the behavior of health professionals?

Because of the workings of health care systems, new, important, and cost-effective treatments sometimes do not become routine care while well-marketed products of equivocal value achieve widespread adoption. Should policymakers attempt to influence clinical behavior and correct for these inefficiencies? Implementation methods achieve a certain level of behavioral change but cost money to enact. These factors can be combined with the cost-effectiveness of treatments to estimate an overall policy cost-effectiveness. In general, policy cost-effectiveness is always less attractive than treatment cost-effectiveness. Consequently trying to improve the uptake of underused cost-effective care or reduce the overuse of new and expensive treatments may not always make economic sense. In this article, we present a method for calculating policy cost-effectiveness and illustrate it with examples from a recent trial, conducted during 1997 and 1998, of educational outreach by community pharmacists to influence physician prescribing in England.

A proactive approach to assessing men for eating disorders

Assessment guidelines for nurses on the subject of eating disorders (EDs) focus primarily on evaluating the severity and progress of the problem for females who have already received a formal ED diagnosis. We argue that, because there is scant research into men with eating disorders and men strive to conceal this health problem, nurses should be equipped with information that will support earlier detection of EDs among men and boys before they manifest as a serious health problem. We advocate the use of epidemiological data to identify groups of men most at risk and the use of qualitative interview data as a means of grounding the nurse on the issues these men face when seeking to modify their body image.

Properties of the Escherichia coli rhodanese-like protein SseA: contribution of the active-site residue Ser240 to sulfur donor recognition

The product of Escherichia coli sseA gene (SseA) was the subject of the present investigation aimed to provide a tool for functional classification of the bacterial proteins of the rhodanese family. E. coli SseA contains the motif CGSGVTA around the catalytic cysteine (Cys238). In eukaryotic sulfurtransferases this motif discriminates for 3-mercaptopyruvate:cyanide sulfurtransferase over thiosulfate:cyanide sulfurtransferases (rhodanese). The biochemical characterization of E. coli SseA allowed the identification of the first prokaryotic protein with a preference for 3-mercaptopyruvate as donor substrate. Replacement of Ser240 with Ala showed that the presence of a hydrophobic residue did not affect the binding of 3-mercaptopyruvate, but strongly prevented thiosulfate binding. On the contrary, substitution of Ser240 with an ionizable residue (Lys) increased the affinity for thiosulfate.

Carboplatin and gemcitabine in metastatic transitional cell carcinoma of the urothelium: effective treatment of patients with poor prognostic features

PURPOSE

To evaluate the activity and toxicity of gemcitabine and carboplatin in consecutive patients presenting with locally advanced or metastatic transitional cell carcinoma of the urothelium (TCC).

PATIENTS AND METHODS

Seventeen consecutive patients referred to a single institution with locally advanced or metastatic TCC were treated with carboplatin AUC 5 on day 1 and gemcitabine 1000 mg/m2 on day 1 and 8 of a 21-day cycle. All patients were assessable for response and toxicity. Minimal eligibility criteria were used to minimize patient selection.

RESULTS

Seventeen patients with measurable stage IV TCC of the urothelium were treated. The median age was 69 years (range 54-78), the median creatinine clearance was 56 ml/min (range 34-90) and 30% of patients had an ECOG performance score of two. Nine patients (53%) had visceral metastases and the majority of patients had multiple sites of metastases. There were three complete responses, seven partial responses, for an overall response rate of 58.8%. Responses were seen at all sites including the liver. One patient had a response within a previously irradiated field and three patients with prior chemotherapy had responses. Median overall survival was 10.5 months and median time to progression was 4.6 months. Toxicity was primarily haematologic with six patients having grade 3 neutropenia and six patients with grade 4 neutropenia. There were five cases of grade 3 and three cases of grade 4 thrombocytopenia. There were no episodes of febrile neutropenia and only one patient required admission for management of toxicity. Thirteen patients required dose reduction or delay due to neutropenia or thrombocytopenia. There were no treatment-related deaths.

CONCLUSION

The combination of carboplatin and gemcitabine is active in metastatic transitional cell carcinoma of the urothelium with manageable toxicity in a relatively elderly group of patients with some poor prognostic features.

Introducing economic and quality of life measurements into clinical studies

Although the collection of cost and quality of life data alongside clinical studies generates detailed patient level data in a timely fashion, it also raises practical and methodological challenges. These include the fact that the settings and patients enrolled in trials may not be typical of those found in regular clinical practice, that costs and quality of life may be influenced by the trial protocol, that the clinical alternatives compared in trials may not be the most relevant for cost-effectiveness assessments, that the length of follow-up may be too short to observe changes in cost and quality of life, and that adding these data will increase the overall measurement burden in the trial. This paper discusses these challenges and the ways in which they might be overcome, focussing particularly on preference-based measures of quality of life. In particular, recommendations are given for choosing the range of quality of life instruments, sample size calculations for quality of life measurement and the measurement of quality of life in multinational studies.

Two-hybrid analysis of domain interactions involving NtrB and NtrC two-component regulators

Signal transduction by two-component regulatory systems involves phosphorylation of the receiver domain of a response regulator by the transmitter domain of the cognate histidine kinase. In the NtrBC system, phosphorylation of NtrC by NtrB results in transcriptional activation of nitrogen-regulated genes. We have used the yeast two-hybrid system to probe interactions between domains of the NtrB and NtrC proteins from Klebsiella pneumoniae. We constructed fusions from each of a series of proteins or protein domains to the activation and the DNA-binding domains of GAL4 and analysed expression of GAL1:lacZ and GAL1:HIS3 reporters in yeast. The DNA-binding domain of NtrC and the so-called sensor domain of NtrB appeared to provide the major determinants for dimerization of the fusion proteins. A strong and specific interaction was also shown between NtrB and NtrC, localized to the HN region of the NtrB transmitter module and to the NtrC receiver domain, whereas other domains of these proteins do not appear to contribute to the recognition specificity. The results presented here indicate that communication between two-component partners also involves protein-protein interactions that can be detected in vivo, suggesting that the yeast two-hybrid system is a powerful genetic tool for identifying functional partners of prokaryotic signal transduction pathways.

Issues of consensus and debate for economic evaluation in rheumatology

We report initial attempts at developing standards for the conduct of economic evaluations in rheumatology. We surveyed 25 clinicians and economists with an interest in rheumatology regarding the design and reporting of economic evaluations, with particular reference to 4 clinical scenarios relating to treatment for rheumatoid arthritis, osteoarthritis, and osteoporosis. The results demonstrated widespread agreement on a number of methodological issues such as statement of funding source, perspective, discounting, and allowance for uncertainty. However, there was lack of consensus over clinical variables including sources of data for efficacy estimates, specific clinical outcomes, methods of assessing quality of life, and choice of comparators. Some of the disagreement reflects lack of consensus in current general methodological guidelines. Consensus regarding the disease-specific clinical variables is crucial to standardizing analysis and facilitating comparisons within clinical scenarios.

The U.K. NHS economic evaluation database. Economic issues in evaluations of health technology

OBJECTIVE

The U.K. NHS Economic Evaluation Database (EED) project is commissioned to identify papers on economic evaluations of health technologies and to disseminate their findings to NHS decision makers by means of structured abstracts that are available through a public database and the Cochrane Library. This paper discusses current issues relating to the economic aspects of producing NHS EED abstracts.

METHODS

A review of NHS EED was undertaken between 1994 and 1999 to determine the methodologies adopted and issues that influence the usefulness of economic evaluations. Methods adopted to improve the quality of NHS EED abstracts are also reported.

RESULTS

Eighty-five percent of NHS EED abstracts are cost-effectiveness analyses (CEAs), 9.3% are cost-utility analyses (CUAs), and only 1.4% are cost-benefit analyses (CBAs). Of the total abstracts, 65.9% are based on single studies, 19.5% on reviews, 3.9% on estimates of effectiveness, and 10.7% on combinations of these sources. Models are utilized in 16.7% of CEAs, 60.2% of CUAs, and 20% of CBAs. Analyses of CBA studies reveal a degree of misuse of well-established definitions. NHS EED internal control mechanisms are reported that provide a means of ensuring that abstracts are based on sound academic principles.

CONCLUSIONS

Most economic evaluations are conducted by means of CEA, followed by CUA, while CBA accounts for an extreme minority of cases. Single studies form the principal source of effectiveness data, although models are widely used, principally in CUA. The structure of NHS EED abstracts provides decision makers with the principal results and an interpretation of the relative strengths and weaknesses of economic evaluations.

Developing guidance for budget impact analysis

The role of economic evaluation in the efficient allocation of healthcare resources has been widely debated. Whilst economic evidence is undoubtedly useful to purchasers, it does not address the issue of affordability which is an increasing concern. Healthcare purchasers are concerned not just with maximising efficiency but also with the more simplistic goal of remaining within their annual budgets. These two objectives are not necessarily consistent. This paper examines the issue of affordability, the relationship between affordability and efficiency and builds the case for why there is a growing need for budget impact models to complement economic evaluation. Guidance currently available for such models is also examined and it is concluded that this guidance is currently insufficient. Some of these insufficiencies are addressed and some thoughts on what constitutes best practice in budget impact modelling are suggested. These suggestions include consideration of transparency, clarity of perspective, reliability of data sources, the relationship between intermediate and final end-points and rates of adoption of new therapies. They also include the impact of intervention by population subgroups or indications, reporting of results, probability of re-deploying resources, the time horizon, exploring uncertainty and sensitivity analysis, and decision-maker access to the model. Due to the nature of budget impact models, the paper does not deliver stringent methodological guidance on modelling. The intention was to provide some suggestions of best practice in addition to some foundations upon which future research can build.

Low doses vs. high doses of the angiotensin converting-enzyme inhibitor lisinopril in chronic heart failure: a cost-effectiveness analysis based on the Assessment of Treatment with Lisinopril and Survival (ATLAS) study. The ATLAS Study Group

OBJECTIVE

A cost-effectiveness analysis of high and low doses of the angiotensin-converting enzyme (ACE) inhibitor lisinopril in the treatment of chronic heart failure.

METHODS

A cost-effectiveness analysis using data from a randomized controlled trial, ATLAS, where 3164 patients with chronic heart failure were allocated to a high-dose (daily target dose 32.5-35 mg) or low-dose strategy (daily target dose 2.5-5.0 mg) of lisinopril. Differential costs were based on resource use data collected in the trial costed using UK unit costs. Cost-effectiveness analysis related differential costs to differential life-years during a 4-year trial follow-up.

RESULTS

The mean total number of hospital in-patient days per patient was 18. 5 in the high dose group and 22.5 in the low dose group. Over the whole duration of the trial, the mean (S.D.) daily dose of lisinopril in the high-dose group was 22.5 mg (15.7 mg) compared to 3.2 mg (2.5 mg) in the low-dose group. The mean difference in cost per patient was pound sterling 397 lower in the high-dose group [95% CI (high-dose-low-dose) - pound sterling 1263 to pound sterling 436]. Mean life-years per patient were 0.085 years higher in the high-dose group [95% CI (high-dose-low-dose) -0.0074 to 0.1706). Based on mean costs and life-years, high-dose therapy dominates low-dose (less costly and more effective). Allowing for uncertainty in mean costs and life-years, the probability of high-dose therapy being less costly than low dose was 82%. If a decision maker is willing to pay at least pound sterling 3600 per life-year gained, the probability of high-dose being more cost-effective was 92%.

CONCLUSIONS

The ATLAS Study showed that the treatment of heart failure with high-doses of lisinopril has a high probability of being more cost-effective than low-dose therapy.

Implementing the findings of health technology assessments. If the CAT got out of the bag, can the TAIL wag the dog?

OBJECTIVE

To explore whether more could be done to increase the implementation of health technology assessment (HTA) findings.

METHODS

A literature review was undertaken to identify the main barriers to implementation, the mechanisms that influence the diffusion and use of health technologies, and evidence of the successful implementation of findings.

RESULTS

Numerous barriers to the implementation of HTA findings exist at the public policy, healthcare professional, and general public levels. Several mechanisms for influencing the use of health technologies exist, and there are some examples of findings being implemented through these mechanisms. However, there are also concerns about the aggressive implementation of findings. A balanced approach to the implementation of HTAs is required.

CONCLUSION

The main elements of a successful implementation strategy are: a) defining a clear policy question; b) defining a clear research question; c) making recommendations commensurate with the evidence; d) identifying the implementation mechanism; e) paying attention to incentives and disincentives; and f) clarifying the roles and responsibilities of the various parties. Further research is also required into several aspects of implementation.

Prioritizing investments in health technology assessment. Can we assess potential value for money?

OBJECTIVE

The objective was to develop an economic prioritization model to assist those involved in the selection and prioritization of health technology assessment topics and commissioning of HTA projects.

METHODS

The model used decision analytic techniques to estimate the expected costs and benefits of the health care interventions that were the focus of the HTA question(s) considered by the NHS Health Technology Assessment Programme in England. Initial estimation of the value for money of HTA was conducted for several topics considered in 1997 and 1998.

RESULTS

The results indicate that, using information routinely available in the literature and from the vignettes, it was not possible to estimate the absolute value of HTA with any certainty for this stage of the prioritization process. Overall, the results were uncertain for 65% of the HTA questions or topics analyzed. The relative costs of the interventions or technologies compared to existing costs of care and likely levels of utilization were critical factors in most of the analyses. The probability that the technology was effective with the HTA and the impact of the HTA on utilization rates were also key determinants of expected costs and benefits.

CONCLUSIONS

The main conclusion was that it is feasible to conduct ex ante assessments of the value for money of HTA for specific topics. However, substantial work is required to ensure that the methods used are valid, reliable, consistent, and an efficient use of valuable research time.

The basis of ammonium release in nifL mutants of Azotobacter vinelandii

In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations in nifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator of nif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination of nifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifH mRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH(4)(+) uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen.

A randomized trial of Evidence-based OutReach (EBOR): rationale and design

There is increasing interest in evaluating the methods used to implement the findings from medical research. This paper describes the Evidence-based OutReach (EBOR) trial, which is the first large randomized study in the United Kingdom that will evaluate the effectiveness and efficiency of educational outreach visits by trained pharmacists who are delivering messages derived from four evidence-based clinical practice guidelines. General practices form the unit of allocation and analysis. The study design addresses important factors that may influence the effectiveness of the intervention, such as the pharmacist who delivers the messages, the health authority in which practices are located, and the size of a practice.