Cost-effectiveness analysis of serum vancomycin concentration monitoring in patients with hematologic malignancies

OBJECTIVE

This study evaluates the cost-effectiveness of vancomycin serum concentration monitoring in patients with hematologic malignancies.

METHODS

The study was designed as a prospective randomized study. Seventy immunocompromised febrile patients with hematologic malignancies were randomly assigned to either a vancomycin therapeutic drug monitoring group (TDM group; n = 37) or to a control group (n = 33). Intervention in the TDM group involved patient follow-up by a clinical pharmacist to obtain and pharmacokinetically interpret serum vancomycin concentrations for dosage individualization.

RESULTS

Evaluation of all patients included global clinical response and nephrotoxicity, as well as the economic costs and effectiveness derived from the vancomycin monitoring program. There were no significant differences between the TDM and control groups in the outcome measures, except for the incidence of nephrotoxicity: the rates of minor nephrotoxicity were 33.3% and 13.5% in the control and TDM groups, respectively. The corresponding figures for moderate nephrotoxicity were 9.1% and 0%. Logistic regression analysis confirmed that TDM independently reduced the incidence of nephrotoxicity in this patient population. On the basis of this reduced nephrotoxicity, a incremental cost of $435 per case of nephrotoxicity prevented was found for vancomycin serum concentration monitoring.

CONCLUSIONS

A decreased incidence of nephrotoxicity provides evidence of a real clinical benefit to patient management in patients with hematologic malignancies. The TDM for vancomycin therapy in this high-risk population has been shown to be a cost-effective procedure.

The total process cost of parenteral antibiotic therapy: beyond drug acquisition cost

Intravenous antibiotic therapy represents a considerable expense to hospital pharmacy budgets; however, when evaluating the cost of these therapies one needs to look beyond acquisition cost and consider the total "process" cost of treatment. These additional costs include the personnel time and the materials required for drug preparation and administration, maintenance of intravenous access, waste disposal, and therapeutic drug monitoring. This paper provides an examination of the daily process costs of intravenous therapy with cefazolin, cefotaxime, ceftazidime, once-daily ceftriaxone, cefuroxime, or aminoglycoside (tobramycin or gentamicin) combination therapy, where the aminoglycoside is given once daily or in divided doses. This analysis demonstrates that the costs associated with drug preparation and administration can equal or exceed drug acquisition costs and are highly dependent on dosing frequency. On this basis, ceftriaxone, at $52.21, is the least expensive of these antibiotic regimens in terms of total daily process cost, followed by the remaining cephalosporins at $53.29 to $94.57, aminoglycoside once-daily combinations at $93.44 to $99.65, and aminoglycoside multidose combinations at $103.26 to $111.42, respectively (values are given in constant 1995 Canadian dollars). Once-daily ceftriaxone offers the potential for cost savings compared with other antibiotic regimens whose pharmacokinetics require multiple daily doses, due largely to the reduced resources required for ceftriaxone preparation and administration.

Once-daily aminoglycoside dosing: impact on requests and costs for therapeutic drug monitoring

Recently, much interest has focused on the use of once-daily aminoglycosides (ODA) in the medical literature. In late 1992, we implemented a hospital-wide ODA program for adult patients at our 850-bed community-teaching hospital. In the first phase of implementation, therapeutic drug monitoring (TDM) was accomplished with the use of a random serum concentration and a nomogram that had been developed at our institution. In the second phase, serum drug concentrations were eliminated on patients with normal renal function. The fully implemented program resulted in a 40% decrease in the request for gentamicin and tobramycin serum concentrations as compared with historic ordering patterns for conventional aminoglycoside dosing regimens. In addition, the incidence of nephrotoxicity was also reduced from 3 to 5% with conventional aminoglycoside dosing, to 1.2 and 1.3% for phases 1 and 2, respectively. Furthermore, the elimination of TDM requests totaling 300 for gentamicin and 50 for tobramycin per month is expected to result in an annual institutional savings of > $100,000.

Treatment of chronic type B and C hepatitis with interferon alfa: an economic appraisal

The aim of this study is to assess the long-term economic impact of treatment of chronic hepatitis B and C with interferon alfa. Estimates were made of the progression of the disease over a 30-year period using a transitional probability model. Cohorts of 1,000 hypothetical patients with either chronic hepatitis B or C treated with interferon alfa were compared with an untreated cohort. The costs were estimated for therapy, monitoring, and treatment of the disease, including transplantation. The cost-effectiveness of therapy was expressed in terms of cost per life saved, cost per year of life saved, and cost per quality-adjusted year of life saved. The analysis was extended to include the indirect costs to patients. The analysis included two rates of progression, two mortality rates, and discounted and undiscounted costs. Mortality in the treated group was lower, saving 18 to 31 lives in the hepatitis B virus (HBV) cohort and 13 to 22 lives in the hepatitis C virus (HCV) cohort. Fewer patients progressed to cirrhosis or decompensated cirrhosis. Discounted costs per year of life saved ranged from 2,142 pounds to 17,128 pounds. A cost-benefit analysis indicated excess benefits over costs when values for life were included in the analysis. The potential usefulness of interferon alfa on the clinical and economic outcome of treatment is indicated from the model. These findings together with the benefits that are likely to accrue from the reduction in infectious individuals suggest that this therapy has a role to play in public health policy to contain the impact of hepatitis.

Therapeutic drug monitoring for the treatment of psychiatric disorders. Clinical use and cost effectiveness

Pharmacokinetic monitoring is not routine in the treatment of psychiatric disorders, although subtherapeutic or toxic plasma concentrations of psychotropic agents can result from standard doses because of interindividual variability of drug metabolism. Therapeutic plasma concentrations have been established for several of the tricyclic antidepressants and for lithium, as well as for carbamazepine and valproic acid (valproate sodium). Despite difficulties in extrapolating from concentration-effect research, therapeutic concentrations have also been determined for some antipsychotic drugs, in particular haloperidol and clozapine. Clinicians can use therapeutic drug monitoring to optimise dosage decisions with psychotropic drugs, in order to maximise efficacy and prevent toxicity, especially when individuals are nonresponsive to treatment or vulnerable to adverse reactions with standard doses because age, disease states or drug interactions complicate therapy. Although evidence from controlled-outcome studies is unavailable, TDM-assisted psychiatric treatment is potentially useful and cost effective, particularly when applied by clinicians who are knowledgeable of pharmacokinetics and who are aware of the limitations of laboratory findings.

Appropriateness of antiepileptic drug level monitoring

OBJECTIVES

To develop explicit, reliable appropriateness criteria for antiepileptic drug level monitoring and to assess the appropriateness of monitoring in one tertiary care institution.

DESIGN

Appropriateness criteria derived from the literature and through expert opinion were used to evaluate a stratified random sample of antiepileptic drug level determinations obtained from chart review.

SETTING

Tertiary care center performing more than 10,000 antiepileptic drug level determinations per year.

PATIENTS

A total of 330 inpatients in whom antiepileptic drug levels were measured a total of 855 times.

METHODS

Drug levels were assessed at least 200 times for each of four antiepileptic drugs (phenytoin, carbamazepine, phenobarbital, and valproic acid).

MAIN OUTCOME MEASURES

The proportion of antiepileptic drug levels with an appropriate indication and, of those, the proportion sampled appropriately.

RESULTS

Overall, 27% (95% confidence interval, 24% to 30%) of levels had an appropriate indication. Interrater agreement for appropriateness was substantial (kappa = 0.61). There was no significant difference in the appropriateness rate among the four drugs (range, 25% to 29%). Of the 624 antiepileptic drug level determinations considered inappropriate (73%), only four (0.6%) were more than 20% higher than the upper limit of normal, and none of the four patients had clinical signs of drug toxicity. A median of six levels (range, one through 69) was determined per patient, and the median interval between level determinations was 24 hours. Of the 27% of level determinations with an appropriate indication, 51% were sampled correctly, resulting in an overall appropriateness rate of 14%.

CONCLUSIONS

Only 27% of antiepileptic drug level determinations had an appropriate indication, and half of these were not sampled correctly. Routine daily monitoring without pharmacological justification accounted for most of the inappropriate drug level determinations. Efforts to decrease inappropriate monitoring may result in substantial cost reductions without missing important clinical results.

The worldwide problem of osteoporosis: insights afforded by epidemiology

Osteoporosis is one of the major problems facing women and older people of both sexes. The morbid event in osteoporosis is fracture. However, the definition of osteoporosis should not require the presence of fractures but only a decrease in bone mass that is associated with an unacceptably high risk of fracture. In the USA, approximately 1.5 million fractures annually are attributable to osteoporosis: these include 700,000 vertebral fractures, 250,000 distal forearm (Colles') fractures, 250,000 hip fractures, and 300,000 fractures of other limb sites. The lifetime risk of fractures of the spine (symptomatic), hip, and distal radius is 40% for white women and 13% for white men from 50 years of age onwards. Following a hip fracture, there is a 10%-20% mortality over the subsequent 6 months, 50% of sufferers will be unable to walk without assistance, and 25% will require long-term domiciliary care. Contrary to prevailing opinion, the morbidity and suffering associated with wrist and spine fractures are also considerable. The annual cost of osteoporosis to the US healthcare system is at least $5-$10 billion with similar incidence and cost in other developed countries. These already high costs will increase further with continued aging of the population. In addition, the population explosion in underdeveloped countries will change the demography of osteoporosis; for example, the incidence of hip fracture, and, presumably, other osteoporotic fractures will increase four-fold worldwide during the next 50 years and the attendant costs will threaten the viability of the healthcare systems of many countries. Unless decisive steps for preventive intervention are taken now, a catastrophic global epidemic of osteoporosis seems inevitable.

Pharmacokinetic-pharmacodynamic and metabolite modeling with TopFit

Two examples illustrating the ease of use and powerful data fitting and simulation techniques provided by the validated program TopFit 2.0 for the PC are presented. In the first, kinetics of parent compound and metabolite for (+) and (-) enantiomers of a racemic compound X were determined during a Phase III clinical study. Four data sets were fitted simultaneously for each patient. The model could be defined by the user without programming differential equations. The fit results indicated enantiomer specific kinetics for the metabolite but not for parent compound. In the second example, a model with nonlinear elimination and an Emax-effect function was used to simultaneously fit data from six doses of compound Y in a Phase I study. The fitted parameters predicted the feasibility of a twice-daily dose regimen despite a very short plasma half-life of the compound. In conclusion, TopFit provides rapid and cost-effective support in analysis and design of clinical trials.

Adaptive control of drug dosage regimens using maximum a posteriori probability Bayesian fitting

Optimal drug therapy can only be achieved if a drug is given in the right dosage regimen. Therefore the dosage regimen needs to be optimized, using the available information of the drug, the patient, and his disease. The optimization of drug therapy comprises two major steps: First, the clinician should define explicit therapeutic goals for each patient individually. Second, a strategy to achieve these goals with the greatest possible precision should be chosen. An overview of the optimization of drug therapy is presented, with special reference to maximum a posteriori probability (MAP) Bayesian fitting. Drug dosage optimization requires 1. measurement of a performance index related to the therapeutic goal, generally one or more plasma concentration measurements, 2. population pharmacokinetic parameters, including mean values, standard deviations, covariances and information on the statistical distribution, and 3. reliable software for adaptive control strategy and optimal dosage regimen calculation. The benefit of optimal drug therapy by adaptive control using MAP Bayesian fitting has been proven, resulting in improved patient outcome by improved efficacy of therapy and a reduction of adverse reactions, and in reduced costs, mainly due to a reduction of hospitalization. Newer strategies might replace the MAP Bayesian fitting procedure, if their advantage has been demonstrated convincingly, and if reliable and user-friendly software is available.

Impact of technological developments and organizational strategies on clinical laboratory cost reduction

Health care reform efforts, largely under the aegis of managed health care initiatives, have prompted clinical laboratories to increase efficiency and reduce both expenditures and test turnaround times. The adoption of newer technologies is viewed as a mechanism of achieving the latter objectives, but direct and indirect costs and outcomes are often difficult to project. Issues explored in this article include the impact on a large university hospital-based clinical microbiology laboratory following the application of various technological approaches to organism recognition and susceptibility testing and the consolidation of certain testing services. Included are applications of an automated blood culture system; radiometric detection, identification, and susceptibility testing of mycobacteria; and the use of molecular probes to identify various microorganisms. Assessment was made through retrospective review of direct costs, estimates of average test report turnaround times, work flow changes, and real or perceived outcomes. Both the application of technology per se and consolidation of an independent virology service into the general microbiology laboratory enabled improvement in test report times and led to direct or indirect cost reduction. Managerial strategies to bring about organization changes throughout all clinical laboratories in response to a major hospital-wide cost reduction program are also presented together with financial outcomes achieved.

Are serum levels of vancomycin useful in the first week of therapy?

Controversy exists regarding the need to monitor serum concentrations of vancomycin with some investigators recommending measurement of peak and trough concentrations in the first week of therapy and regularly thereafter, whereas others contend that empiric dosing produces safe and effective drug concentrations so that testing is unnecessary. Since vancomycin concentrations are measured, routinely in our hospital in the first week of therapy, we conducted a 12 month study to assess their clinical value in patients who were treated when gram positive cocci were detected in blood culture smears. One-hundred-five patients had gram positive cocci on blood culture smears. These bacteria were pathogens in 15 patients with Staphylococcus aureus and in 18 with coagulase negative staphylococci based on microbiologic criteria and a chart review confirming their clinical significance. Ten patients with S. aureus and 8 patients with coagulase negative staphylococci that were pathogens and 10 patients with coagulase negative staphylococci that were contaminants were treated with vancomycin. Serum peak and trough concentrations of vancomycin obtained within the first 5 days of therapy in these 28 patients were 14 to 40 micrograms/ml and 4.8 to 20 micrograms/ml. These concentrations were much above the MIC's of the microorganisms (< 4 micrograms/ml). Five patients had increases of serum creatinine of more than 0.6 mg% and in each patient the increases were attributable to other causes-shock, heart failure, and preexisting renal failure. Fifty five peak and trough concentrations 19 of which were drawn in patients with contaminated cultures were measured at a cost of $2,475.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of therapeutic drug monitoring in improving the cost effectiveness of anticonvulsant therapy

When monitoring of the plasma concentrations of anticonvulsant drugs first came into use 25 years ago, it appeared to have a major impact on improving the effectiveness and safety of anticonvulsant therapy. However, as time has passed, prescribers have absorbed many of the lessons to be learned from the monitoring, and now apply this knowledge without necessarily monitoring plasma anticonvulsant concentrations as frequently as in the past. Therefore, the effect of the drug concentration monitoring on the cost effectiveness of anticonvulsant therapy is probably not as significant now as it originally was. In theory, drug concentration monitoring is often unlikely to decrease the cost of contemporary anticonvulsant drug therapy, but it may enhance the efficacy of the therapy. Thus, monitoring may reveal unrecognised under- or overdosage, detect failure of compliance or drug-drug interactions, or indicate when there is little point in persisting with a particular anticonvulsant drug. Despite a good deal of anecdotal testimony, surprisingly little has been published demonstrating the benefits of anticonvulsant therapeutic drug monitoring in epileptic populations. However, one study did show better rates of seizure control rates in patients monitored in the first 6 months of their epileptic disorder; but not if the monitoring began later than this.(ABSTRACT TRUNCATED AT 250 WORDS)

Implementation of pharmaceutical care in acute medical cardiovascular patients

All inpatients who were admitted to one designated cardiologist at a private community hospital were followed by a pharmacist. The pharmacist prospectively evaluated the patients' medications in order to identify, resolve, and prevent any medication related problems. Recommendations concerning these medication related problems were made to the physician involved. In addition, the pharmacist documented medication information questions, medication dosing consultations, and patient medication counseling consults. Ninety-seven percent of the recommendations were accepted by the prescriber. The most common categories of recommendations were for drugs belonging to cardiovascular (40.3%) and anti-infective (18.4%) classes. Improper medication selection (19.6%), untreated indication (17.4%), overdosage (16.3%), and medication given without an indication (13%) were the most common medication related problems and accounted for over two-thirds of the total accepted recommendations. Sixty-six percent of the recommendations were considered significant and 4% were considered extremely significant. Based on the pharmacist's interventions, an annual patient medication charge savings of $17,576.00 was estimated.

[Leponex: experience of the hospital pharmacist]

Clozapine's monitoring, with a co-responsibility between psychiatrists and pharmacists, was very efficient for the prevention of neutropenia's side effects. This intensive drug safety has lowered the agranulocytosis' cases in France to a 0.5% prevalence. However the cost of clozapine led to a strict estimation for Health expenditures. Our study, trained in an university department of psychiatry in Sainte-Anne Hospital (Paris), has included 14 patients treated with clozapine during at least 12 months and has displayed a decrease of 10% in their annual global cost, comparing to the same group of patients treated by classical neuroleptics during the preceding year. This global cost includes the treatment, the blood monitoring and the cost of different hospital or community cares. Quality of life, in clozapine group, was much improved as illustrated by lowing full time hospitalization relayed earlier by community care and precocious social readaptation.

The total costs of drug therapy for rheumatoid arthritis. A model based on costs of drug, monitoring, and toxicity

OBJECTIVE

We created a model to estimate the total medication costs of treating patients with rheumatoid arthritis with 6 second-line agents for the first 6 months of treatment.

METHODS

Drug costs were obtained from a survey of pharmacies; monitoring costs were calculated from utilization information obtained in a survey of rheumatologists; toxicity costs were obtained using decision trees to represent the evaluation and treatment of potential toxicities. Monitoring and toxicity costs were estimated using costs from the Boston University Medical Center or, for hospitalizations, using appropriate diagnosis-related group categories. The sum of the 3 components determined the total medication costs.

RESULTS

The least expensive medication was penicillamine, at $10.62/week, and the most expensive was injectable gold, at $30.89/week. In terms of monitoring costs, methotrexate had the highest costs associated with necessary laboratory tests and office visits. Hydroxychloroquine had the lowest monitoring costs for office visits, and oral gold had the lowest for laboratory costs. Hematologic toxicities were the largest component of toxicity costs for all 6 medications, and renal toxicities were costly for patients taking oral gold, penicillamine, and injectable gold. Total medication costs revealed oral gold as the least expensive medication and injectable gold as the most expensive. The combination of monitoring and toxicity costs accounted for more than 60% of the total costs for all medications except injectable gold. In all cases, the cost of treating toxicities was the smallest of the 3 components.

CONCLUSION

When calculating the costs of drug therapy, it is important to consider not only the price of the drug, but also the costs of monitoring and treating the toxicities that might occur. Failure to do so will result in underestimating the true costs of treatment with these medications.

Adjusting dosage intervals of intermittent intravenous ranitidine according to creatinine clearance: a cost-minimization analysis

To provide effective ranitidine therapy at the lowest possible cost to institutions and patients, the main study objectives were to develop a dosage intervention strategy for intermittent intravenous ranitidine and to document the resultant cost savings through cost-minimization analysis. During a 6-week baseline phase, a pharmacy resident prospectively monitored all patients in the intensive care unit receiving intravenous ranitidine and evaluated appropriateness of dose according to creatinine clearance. Staff pharmacists collected identical data during the 6-week intervention phase but also made recommendations for dosage interval adjustment. In patients with creatinine clearance rates less than 50 mL per minute, the mean number of doses per patient treatment-day was reduced from 2.33 +/- 0.81 during baseline phase to 1.56 +/- 0.70 during intervention phase (P < 0.001). The hospital cost per patient treatment-day was decreased by 33%, from $5.29 +/- 1.83 to $3.54 +/- 1.59 (P < 0.001). Thus a program of prospective monitoring and verbal interventions by pharmacists effectively reduced the number of inappropriate ranitidine doses and hospital cost.

Microsampling homogeneous immunoassay with Cedia digoxin reagents on the Technicon CHEM 1 chemistry analyzer

We report the determination of digoxin concentration in serum with Microgenics Cedia digoxin reagents on the Technicon CHEM 1. The Technicon CHEM 1 clinical chemistry analyzer has a throughput of 720 tests per hour and uses only 7 microliters each of two reagents. A 100 test kit can perform 2,640 tests. The within-run coefficient of variation (CV) range is 2.3-0.9% and the total CV is 6.3-2.9% at concentrations tested ranging from 1.10 to 2.94 ng/ml. The results of the Technicon CHEM 1 (y) assay correlated well with those by the Technicon RA 1000 system (x) with 31 clinical serum samples (y = -0.03 + 1.11x, r = 0.96). We concluded that the Cedia digoxin assay on the Technicon CHEM 1 provides a very cost-effective, precise, rapid, and accurate means to determine digoxin concentration in serum.

Saliva versus blood sampling for therapeutic drug monitoring in children: patient and parental preferences and an economic analysis

The objective of this study was to conduct an assessment of patient and parental preferences and an economic analysis of hospital costs in sampling blood and saliva for therapeutic drug monitoring (TDM). Costs and preferences were evaluated in the course of a study, which compared anticonvulsant concentrations in blood routinely drawn for therapeutic monitoring and in saliva in infants and children attending a pediatric neurology clinic. Parents of 84.8% of children, and half of the children, indicated a preference for saliva sampling over venous blood drawing. Children who had been on medications that required therapeutic monitoring for < 2 years were more likely to prefer saliva sampling as compared to those who were under treatment for > or = 2 years. Computation, based upon a basic assumption that a registered nurse obtained blood and a medical technician or a registered nurse assistant sampled saliva, indicated that for every 1,000 cases of changing from blood to saliva sampling, total cost savings would amount to $1,930 for cooperative children and $1,660 for infants and uncooperative children. This saving is equivalent to approximately 100 h of a registered nurse's initial salary. The important contributions to the differential cost were derived from the requirements for more highly trained individuals to take the blood sample and from the doubling time required for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors associated with preventable adverse drug reactions

Factors associated with preventable adverse drug reactions (ADRs) in a community hospital patient population were studied. The following data were collected by concurrent review of all ADRs reported from July 1992 through January 1993: patient demographics, ADR variables, length of stay, and preventability of ADR. These data were analyzed to determine factors associated with preventable ADRs. Of the 203 ADRs reported, 38 (19%) were identified as preventable. The only significant difference found between preventable and nonpreventable ADRs was in severity (preventable ADRs were more severe). Length of stay (LOS) for patients who experienced ADRs was longer than the national average for patients in the same diagnosis-related group. Most of the preventable ADRs involved (1) a documented allergy to medication ordered or to similar medications, (2) anticoagulants or thrombolytics, (3) that required serum drug concentration monitoring (in the absence of pharmacokinetics service involvement), and (4) renally eliminated drugs for which dosage adjustments were not made in patients with impaired renal function. Strategies for minimizing ADRs were developed based on these factors. An ADR reporting program helped in identifying preventable ADRs, determining factors associated with preventable ADRs, and developing strategies for preventing ADRs in a community hospital patient population.

Educational effort and CQI program improves ordering of serum digoxin levels

In a 289-bed, acute-care, non-tertiary-care regional referral center, a continuous quality improvement educational effort successfully improved ordering of serum digoxin levels. Following a determination that physicians were not requesting serum digoxin levels correctly, the P & T Committee issued a letter describing appropriate wording of orders for serum digoxin levels. The number of incorrectly ordered serum digoxin levels requested dropped significantly over a 49-month period as a result of the intervention described below, which also resulted in cost savings.

Cost considerations in therapeutic drug monitoring of aminoglycosides

Aminoglycoside antibiotics are very important in the treatment of Gram-negative infections and as synergistic agents for the treatment of staphylococcal and streptococcal (group B streptococci and enterococci) infections. However, these agents have a narrow therapeutic index. Thus, a number of new antibiotics have been introduced in an attempt to reduce the number of patients treated with aminoglycosides. Unfortunately, these new antibiotics tend to be costly, and are often associated with development of resistance and treatment failure. Data suggest that a pharmacokinetic/pharmacodynamic relationship exists for some aspects of efficacy and toxicity of aminoglycosides. Serum drug concentrations and/or tissue accumulation are related to the development of nephrotoxicity, and individualised pharmacokinetic monitoring may decrease rates of nephrotoxicity. Peak serum drug concentrations and the ratio of peak serum drug concentration to minimum inhibitory concentration appear to correlate with clinical efficacy in the treatment of patients with bacteraemia or pneumonia. Therapeutic drug monitoring (TDM) has been used to optimise aminoglycoside therapy and reduce toxicity. Cost-effective approaches to drug selection and TDM are important considerations in the proper use of aminoglycosides.

The use of concentration measurements of parent drug and metabolites during clinical trials

The need for well-designed pharmacokinetic (PK) and pharmacodynamic (PD) studies early in the development of new drugs is described. In this review we illustrate the application and cost-effectiveness of optimal sampling theory in PK study design for ongoing clinical trial studies of ethyol, a chemoprotector drug. The importance of careful selection of the appropriate biological fluid in which to measure drug concentration at the earliest possible stage of new drug development is described in the context of the development of new immunosuppressive drugs. We focus on the requirement for well-validated analytical methodology in PK-PD studies, described in a discussion of the analytical methodology in use in clinical trials of two immunosuppressive agents, cyclosporin G and RS-61443 (mycophenolate mofetil).

Use of therapeutic drug monitoring in pharmacoeconomics

The use of therapeutic drug monitoring (TDM) for drugs with a narrow therapeutic range has contributed substantially to the literature. The pharmacoeconomics of this service for hospitalized patients has demonstrated significant hospital savings. Appropriate use of this pharmacy-based service has demonstrated savings, reduction in total length of hospitalization, and cost avoidance with aminoglycoside-induced nephrotoxicity. Use of a Clinical Pharmacokinetic Service (CPS) for inpatient theophylline therapy and outpatient anticonvulsant therapy documents the pharmacoeconomic benefits provided by this service to both in- and outpatients. This report will discuss current literature with regard to pharmacoeconomics and cost-benefit analysis of TDM.

Reducing the cost of phenytoin assays with in-house TDx reagents

The Abbott TDx is frequently used for therapeutic drug monitoring of phenytoin concentrations, but reagent costs are high. In an attempt to reduce these costs, we investigated the preparation of in-house reagents. A commercial antiserum was available at reasonable cost and the fluorescent tracer was easily prepared. We describe the preparation of these reagents and their application to the TDx system. Substantially reduced costs were obtained using the in-house reagents.

Therapeutic drug monitoring in ambulatory care

There is a growing emphasis on developing ambulatory care services in an attempt to minimize healthcare costs through preventive medicine and outpatient therapeutic management. This creates an environment that can greatly benefit from a pharmacist-managed ambulatory TDM service. The implementation of a pharmacist-managed TDM service can improve patient care, contain the cost of healthcare, and enhance the education of pharmacy/medical students and physicians. The opportunity exists for further development of clinical pharmacy services to positively influence patient care in the ambulatory care setting. This development, however, may be hindered by inadequate reimbursement for services and lack of documentation to support the beneficial impact of clinical pharmacy services on patient outcome. Methods of documenting clinical pharmacists' interventions and outcome must be developed in order to obtain reimbursement for these services.

The way towards adverse event monitoring in clinical trials

Different approaches to the monitoring of adverse reactions to drugs have been used over the years, with the aim of preventing catastrophes like the thalidomide episode and to rationalise drug usage. In the 1960s, the use of national and international adverse event monitoring was first suggested by the British statistician, David Finney. According to Finney, the method was well suited for the postmarketing surveillance of drugs. The idea was rejected by the World Health Organization (WHO) but was later taken up by the Prescription Event Monitoring Event System in the UK. Subsequent to problems with practolol in the 1970s it was suggested that adverse event monitoring could also be useful in clinical trials to detect adverse reactions before a drug is launched. The idea of adverse event monitoring has been tested by Astra Hässle in Sweden in clinical trials with felodipine and omeprazole, and is now the standard method within the company. Adverse event monitoring is an expensive and time-consuming method seen from a short term perspective. However, such monitoring offers an opportunity to optimise the use of clinical trials in safety monitoring, and its ability to predict possible adverse drug reactions is superior to other methods.

Aminoglycoside dosing: a randomized prospective study

Although clinical benefits for aminoglycoside dosing services have been suggested, this has not been clearly documented in a prospective fashion. Therefore, we randomly assigned patients to be dosed (1) by their physician (Physician dosing method), (2) by predicting an initial dosage (Predictive dosing method), or (3) by calculating an initial dosing regimen by measuring the pharmacokinetics for the individual patients after a loading dose (Individual dosing method). The patients' clinical response and nephrotoxicity were then evaluated. The individual dosing method resulted in erratic aminoglycoside levels, necessitating its elimination from the study. This group was not included in the final analysis. Of the 164 patients entering the study, 41 had a documented gram-negative infection, received aminoglycosides for more than 2 days, and had serum aminoglycoside levels measured. The predictive dosing method in these 41 patients produced statistically significant higher peak and lower trough levels, but there was no difference in the incidence of nephrotoxicity or clinical response. The 95% confidence intervals precluded any major clinical benefit in these patients with documented gram-negative infections. We question the previous findings of increased efficacy and decreased nephrotoxicity with the use of an aminoglycoside dosing service and suggest that larger studies be done.

Clinical safety and cost of heparin titration using bedside activated clotting time

OBJECTIVE

To evaluate the clinical safety of heparin titration and the procedural cost of anticoagulation measurement using bedside low-range activated clotting time.

DESIGN

Quasi-experimental study using data gathered through retrospective record review.

SETTING

Coronary care, medical intensive care and telemetry units of a community hospital.

SUBJECTS

Sample of 102 patients undergoing elective percutaneous transluminal coronary angioplasty.

INTERVENTION

Intravenous heparin therapy was titrated using low-range activated clotting time in 51 percutaneous transluminal coronary angioplasty patients. Data from this group were compared to a matched sample of 51 angioplasty patients whose intravenous heparin therapy was titrated using activated partial thromboplastin time.

RESULTS

No differences in procedural, early or late complications were found between the groups. The cost of managing heparin therapy with low-range activated clotting time was less than with activated partial thromboplastin time.

CONCLUSION

These results suggest that titrating heparin therapy based on bedside low-range activated clotting time for the angioplasty patients in this sample was as safe as with activated partial thromboplastin time. Use of bedside low-range activated clotting time saved money for the hospital.

The true cost of monitoring antibiotic levels

Antibiotic assays are most often ordered for the purpose of toxicity monitoring, which usually involves determination of peak and trough antibiotic concentrations in the blood. The cost of monitoring antibiotic levels is probably higher than is commonly appreciated. Factors that contribute to the cost of this service include staffing the microbiology laboratory with appropriate personnel, who are responsible for determining the adequacy of sample collection and related patient information; analyzing the specimens in a timely manner; and taking action to modify drug dosage and dosage intervals in light of the test results. There are also costs related to the reagents, consumables, and equipment used in the assay, as well as to revenue and capital overheads. Additional clinical and laboratory costs can be incurred in the event of litigation pursuant to antibiotic-induced toxicity. With hospital and government policymakers devoting increasing attention to the escalating costs of health care, pressure to move away from the routine use of drugs having dose-related toxicity may increase, the objective being to save on assay costs.

Evolution of a neonatal gentamicin dosing protocol in a small community hospital

The effects of conventional dosage of gentamicin of 2.5 mg/kg given every 12 hours was retrospectively investigated in a small community hospital. Consistent with previous results in large hospitals, the conventional dosage of gentamicin commonly resulted in serum concentrations associated with toxicosis. Results were compared with those obtained prospectively according to a gentamicin dosing protocol that used a formula based on gestational age. The gestational age regimen provided similar peak and significantly lower trough serum concentrations; statistical analysis indicated no demographic differences in the compared groups. Very few neonates who received gentamicin according the gestational age formula were exposed to gentamicin serum concentrations associated with an increased risk of toxicosis. An absence of any significant differences in mean peak and trough serum concentrations in subgroups of neonates treated according to the gestational age formula suggested that use of the gentamicin dosing protocol was appropriate for all neonates. The dose of 3.5 mg/kg used in the gestational age formula was predicted to have resulted in initial gentamicin peak serum concentrations > 5 micrograms/ml in nearly 90% of neonates. The experience obtained with the gestational age formula allowed revision of the gentamicin dosing protocol to provide for more cost-responsible serum concentration monitoring.

A model for planning optimal follow-up for outpatients on warfarin anticoagulation. Warfarin Optimal Outpatient Follow-up Study Group

Patients taking warfarin for long-term anticoagulation require frequent clinic visits to monitor the prothrombin time ratio (PTR), a measure of blood clotting. A dynamic stochastic model using nonlinear optimization was developed to select follow-up visit intervals that minimize the overall costs of patient care. Assuming that fluctuations in a patient's PTR behave as a random diffusion process, future PTR fluctuations are unknown, except as revealed by past PTRs. To determine the incidence and costs of complications in relation to PTR, the authors reviewed the charts of 216 patients who had 719 patient-years of follow-up with 695 trivial, significant, life-threatening, or fatal complications. They modeled the relationship between costs of complications and deviation of the PTR from the therapeutic target as a fourth-order convex polynomial. The model is used to compute the interval to the next follow-up visit to minimize accumulated potential costs. Variables in the optimization are the cost of a monitoring visit and the expected costs of complications. The latter are derived from the current PTR, the variability of the patient's past PTR values, the number of past PTRs available, and the target PTR for the patient. No attempt is made to predict the level of the next PTR or suggest adjustments in the warfarin dose. Shorter follow-up is recommended for patients who have histories of large fluctuations in past PTRs and for patients with few prior PTR determinations. As visits accumulate, the patient's degree of variability can be estimated more accurately and visit intervals adjusted accordingly. The scheduling method balances costs to the health care system of monitoring each patient against the expected costs of complications. This approach has the potential to reduce the number of monitoring visits necessary for safe management of anticoagulated patients with stable PTRs and to improve control among unstable patients.

A utilization and cost-benefit analysis of an aminoglycoside kinetics monitoring service

Utilization and cost-benefit analysis of an aminoglycoside kinetics monitoring service were performed. Utilization was reviewed for 161 patients using the service between May 1, 1986 and April 30, 1987. The cost-benefit analysis used a cohort of 48 matched patients for the same time period. Pharmacy-based dosing recommendations were compared to physician-based dosing recommendations. According to specific guidelines, most pharmacy-based dosing recommendations were acceptable (91%) and followed either in full (76%) or in part (13.6%). According to specified criteria, gentamicin could have been substituted for tobramycin in 29.4% of courses of therapy. No statistically significant benefits (p less than 0.05) were associated with pharmacy-based recommendations, which cost $47.43 each, or $26.48 more than a physician-based recommendation. Although the service yields appropriate recommendations and is well received, our results suggest that further studies must be conducted to define methods by which a cost-benefit ratio greater than one may be realized.

Clinical significance of hypergastrinaemia: relevance to gastrin monitoring during omeprazole therapy

During the early experience with omeprazole, it was recommended that plasma gastrin levels be monitored to identify patients with 4-5-fold increases above baseline. Such patients were thought to be at an increased risk of developing gastric carcinoid tumours. Studies have established that plasma gastrin levels usually rise 2-4-fold during omeprazole therapy, there being considerable inter- and intra-individual variation. Approximately 3.3% of patients have plasma gastrin levels above 400 pg/ml when treated continuously for 1 year. In clinical practice, it is not cost-effective to screen all patients to detect such a small percentage, particularly given the paucity of realistic treatment options in such patients, and the growing evidence that hypergastrinaemia during omeprazole treatment is of little, if any, clinical significance.

An algorithm for drug waste reduction using pharmacokinetic principles

When delivering several intravenous drug doses from a single bag, it is generally necessary to throw away any drug that remains in the bag, if the amount is insufficient to deliver the next dose. An algorithm has been developed to allow all of the drug in a bag to be used. Based on standard pharmacokinetic equations, the algorithm calculates the time when the remainder should be given, so that a desired peak serum drug concentration is achieved on the next dose. The algorithm requires as inputs the time limit on the bag, the dosing interval and the size of the dose. This algorithm applies only to drugs that obey single compartment, first-order linear kinetics (e.g. aminoglycosides), but is easily modified for other situations. In conjunction with computer-assisted infusion, use of the algorithm may potentially reduce the cost of aminoglycoside administration by reducing clinical drug waste.

Effect of individualized pharmacokinetic dosing on patient outcome

OBJECTIVE

To study the effect of individualized pharmacokinetic dosing of aminoglycosides on patient outcome.

DESIGN

Prospective, randomized study.

SETTING

Tertiary care hospital.

PATIENTS

Ninety-five patients with documented Gram-negative infections received 97 courses of aminoglycoside therapy.

INTERVENTIONS

Patients were randomized between pharmacokinetic dose adjustment and monitoring or traditional physician-directed techniques. Patients were stratified by severity of underlying illness before randomization.

MEASUREMENT AND MAIN RESULTS

Sixty-two courses of treatment were satisfactorily completed. Patients in the severely ill group (eight kinetic, eight traditional) had significantly (p less than .05) better survival (7 kinetic, 3 traditional) when managed with pharmacokinetic consultation. The kinetic arm received greater doses (156 +/- 59 mg/dose; 2.4 +/- 0.6 mg/kg) than the traditional arm (81 +/- 27 mg/dose; 1.5 +/- 0.6 mg/kg) (p less than .001). In addition, the dose per day (mg/kg) was greater in the kinetic arm (4.1 +/- 1.5) than the traditional arm (3.2 +/- 1.3) (p less than .001). The improved survival was achieved by attaining therapeutic peak serum concentrations earlier in the course of the infection and by administering more total aminoglycoside without increasing toxicity.

CONCLUSIONS

We conclude that pharmacokinetic management of aminoglycoside dosing may improve the outcome of severely ill patients.

Multilevel model to assess appropriateness of pediatric serum drug concentrations

A multilevel model reviewing four assessment levels for pediatric serum drug concentrations was developed. Criteria for appropriate indication, sample collection, documentation, and utilization were based on therapeutic drug monitoring principles. The model was applied to 222 pediatric serum drug concentrations. Inadequate documentation was a major problem, but it occurred at a lower rate (37%) than previously reported. The rates of inappropriateness for indication (15%), sample collection (16%), and utilization (10%) were well within reported ranges but were significantly lower with pharmacy input. Overall, 48.2% of drug concentrations were inappropriate. Digoxin, phenobarbital, and aminoglycosides had the highest error rates. The annualized cost of inappropriate serum drug concentrations was $12,325. The described method allows for targeting of educational programs with defined areas for improvement. The findings of this study also support the involvement of clinical pharmacists in the therapeutic drug monitoring process.

Making digoxin therapeutic drug monitoring more effective

Digoxin is an important drug in the treatment of patients with either congestive heart failure or atrial arrhythmia. Because of its narrow therapeutic range, digoxin serum concentrations are commonly monitored in both inpatients and outpatients. However, with the costs of health care skyrocketing, there is debate whether such therapeutic drug monitoring (TDM) is cost-effective. To reduce the number of samples drawn too soon after a previous dose and in an effort to improve digoxin TDM at this teaching hospital, a new dosing and monitoring policy was initiated. This policy involved uniform digoxin dosing at 5 p.m. (1700 h) for all inpatients and serum drug measurements at 7 a.m. (0700 h) the next day. By coordinating the time of dosing to be greater than 12 h prior to serum digoxin analysis, the number of inappropriate digoxin serum determinations have been reduced. This new protocol has increased the effectiveness of the toxicology laboratory and enhanced the efficiency of the house staff. Other issues concerning digoxin TDM are also addressed. These findings can be generalized to all drugs that are monitored at any hospital and can result in a significant cost savings and decrease the time spent analyzing inappropriate data.

Evaluation of an imipenem/cilastatin target drug program

This article describes an imipenem/cilastatin (I/C) target drug program. The program, developed following completion of a drug usage evaluation study, was designed to improve I/C dosing, reduce central nervous system (CNS) adverse effects, and reduce antibiotic costs. Following completion of an inservice education program for the medical and pharmacy professional staffs, ongoing monitoring of I/C usage was accomplished through the pharmacy-based drug-dosing service. Pharmacists evaluated I/C dosage based upon culture/sensitivity results and indicators of renal function. If deemed inappropriate, the pharmacist contacted the prescribing physician with a dosage recommendation. Two hundred ten courses of I/C therapy were prescribed in the nine-month period following implementation of the target drug program; 26 cases (12 percent) required dosage adjustment. The incidence of CNS adverse effects including seizures decreased from 15 to 1 percent (p = 0.0015). A $6033 drug cost avoidance also resulted from pharmacist intervention.