Medical monitoring for pharmaceutical injuries: tort law for the public's health?

A remarkable development in personal injury litigation in recent years involves attempts to expand legal claims beyond existing injuries to anticipated future harms. Attorneys have begun to sue on behalf of individuals exposed to defective pharmaceutical products who have no current injury, but who may be at risk for developing one after a latency period. This strategy seeks to make drug manufacturers pay for medical monitoring, a court-ordered program that provides diagnostic tests to exposed individuals to facilitate early detection of adverse health effects. Because medical monitoring does not depend on the existence of an actual injury and large populations may be exposed, some commentators have warned that it has the potential to spiral out of control. We examine medical monitoring in the context of 2 major cases involving diet drugs and an oral hypoglycemic drug. We conclude that this expansion of tort law should be applied sparingly, but that the performance of courts to date in these cases gives cause for optimism. Judges appear to be paying close attention to sophisticated epidemiological, clinical, and cost-effectiveness considerations. Medical monitoring arms the courts with a new mechanism for addressing harms proactively rather than reactively, which could yield new victories for public health.

Exploring the costs of a limited public sector antiretroviral treatment programme in South Africa

BACKGROUND

The role of antiretroviral treatment for adults in the pubic sector in South Africa is debated with little consideration of programme choices that could impact on the cost-effectiveness of the intervention. This study seeks to explore the impact of these programme choices at an individual level, as well as explore the total cost of a rationed national public sector antiretroviral treatment programme.

METHODS

Eight scenarios were modelled of limited national treatment programmes over the next 5 years, reflecting different programme design choices. The individual cost-effectiveness of these scenarios were compared. The total costs of the most cost-effective scenario were calculated, and the potential for savings in other areas of health care utilisation was explored.

RESULTS

The direct programme costs per life-year saved varied between scenarios from R5,923 to R11,829. All the costs of the most cost-effective scenario could potentially be offset depending on assumptions of health care access and utilisation. The total programme costs for the most cost-effective scenario in 2007 with 107,000 people on treatment are around R409 million.

CONCLUSION

Specific policy choices could almost double the number of people who could benefit from an investment in a limited national antiretroviral treatment programme. Such a programme is affordable within current resource constraints. The consideration of antiretroviral treatment calls for a unique public health approach to the rationing of health services in the public sector.

Patient self-management of oral anticoagulation

Patient self-management of oral anticoagulation is now widely practised in Germany and the USA. There are three different home-testing monitors available in the UK which are all reliable in terms of accuracy and reproducibility of results. Selected patients can be trained to perform their own International Normalized Ratio (INR) testing and dosing, with outcomes as good if not better than those from specialized anticoagulant clinics. Consensus on the frequency of testing and what quality control should be deployed is lacking. The cost-effectiveness in the UK is unproven.

Therapeutic drug monitoring: do the improved outcomes justify the costs?

In the 30 years that therapeutic drug monitoring (TDM) has moved from an abstract consideration to a routine intervention, issues remain over justifying the benefits in the light of the ever-increasing competition for budgetary resources. Resolving the issues is constrained by various methodological concerns. These include considerations such as: (i) the changed environment of knowledge and practice during the generation in which TDM has been used and evaluated; (ii) the predominance of studies using system-related rather than patient-centred outcomes; (iii) using a timeframe for analysis that is too short; (iv) a lack of rigour in many of the pharmacoeconomic analyses; and (v) excessive use of a site-specific rather than a societal perspective. Current observation suggests that the greatest benefit of TDM accrues from targeted or specialty populations: those with severely decompensated renal function, those at the extremes of age, and those using immunosuppressive, some antineoplastic, some psychotherapeutic and some anticonvulsant drugs. In these situations, safe and humane practice considers TDM a necessity without respect to cost. But for many routine situations with drugs for which TDM has commonly been used in the past, present reliance on the intervention may have become excessive in the light of today's knowledge base of practitioners.

Acetylcholinesterase treatment--modelling potential demand and auditing practice

BACKGROUND

Acetylcholinesterase inhibitors represent an entirely novel treatment option for patients with Alzheimer's disease (AD). As such they represent a significant change in practice and a significant cost pressure on funding bodies.

OBJECTIVES

To assess the impact of cholinesterase inhibitors on routine clinical practice.

METHODS

We estimated potential demand for the compounds taking into account eligibility criteria and prescribing practice agreed between clinicians and funders. We then audited actual prescribing practice assessing whether the estimated demand matched actual demand and whether practice and prescribing criteria were adhered to.

RESULTS

Over a two-year period we estimated the demand for treatment at a total of 89 patient years for the population of the audit unit. In practice only 24.5 patient years of therapy were received, the short fall apparently being due to low referral rates for treatment. Prescribing by clinicians matched practice guidelines and a high proportion of three monthly assessments using scales for cognition, function and global state were performed. Using these assessment procedures treatment successes could be differentiated from primary and secondary treatment failures and, where apparently appropriate, treatment could be stopped.

CONCLUSION

In the real world of clinical practice demand for treatment in AD is modest but likely to grow and assessment with an aim to identifying those receiving benefit from treatment can be achieved.

A pharmacoeconomic analysis of the impact of therapeutic drug monitoring in adult patients with generalized tonic-clonic epilepsy

AIMS

To carry out a retrospective pharmacoeconomic analysis of the impact of therapeutic drug monitoring (TDM) in adult patients with generalized tonic-clonic epilepsy in an academic, non profit making organization.

METHODS

Twenty-five patients who had undergone TDM were compared with 25 age, disease and duration of drug therapy matched controls who had not undergone TDM. Only direct costs were calculated. These included cost to the hospital of providing the TDM service, cost to the hospital per seizure saved, and cost to the patient per seizure saved.

RESULTS

Patients undergoing TDM had much more effective seizure control (P = 0.00032, OR 4.846, 95% confidence interval 1.29,18.3), fewer adverse events, better earning and were more likely to be married than the control group.

CONCLUSIONS

In patients with adult onset epilepsy, a minimum of two drug estimations per year offers significant benefit in terms of better seizure control, fewer adverse events and greater chances of remission.

Safety of a clinical surveillance protocol with 3- and 6-week warfarin prophylaxis after total joint arthroplasty

The charts of 1869 patients were reviewed for the occurrence of deep venous thrombosis (DVT) and pulmonary embolism after total hip or knee arthroplasty. Prophylaxis consisted of 3 (group 1; n=1235) or 6 (group 2; n=634) weeks low-dose warfarin, pneumatic compression boots worn by patients in the hospital, mobilization on the first postoperative day, and a clinical surveillance protocol. Venous ultrasound or ventilation/perfusion lung scintigraphy (V/Q) was performed only if patients became symptomatic. patients. Twenty-three (1.8%) patients were positive for DVT. Ventilation/perfusion lung scintigraphy was performed on 25 patients, and 5 (0.4%) patients were positive for pulmonary embolism. In group 2, 117 patients were evaluated for DVT, and 19 (3%) patients had positive results determined by ultrasound. Twenty-five patients were evaluated with V/Q and only 1 (0.16%) patient was positive for pulmonary embolism. No patient developed a fatal pulmonary embolism or postphlebitic syndrome. This prophylaxis protocol is an efficient and cost-effective method for the prevention of significant events after surgery.

Implementation and pharmacoeconomic analysis of a clinical staff pharmacist practice model

The implementation and pharmacoeconomic analysis of a clinical staff pharmacist (CSP) practice model are described. Staff pharmacists at a large, tertiary care, academic medical center were selected and trained to perform clinical pharmacy services under the direction of clinical pharmacy specialist mentors. Clinical interventions by these CSP practitioners were evaluated in terms of direct cost savings (the difference in actual acquisition costs between therapies) and cost avoidance (the dollar value of adverse drug events [ADEs] avoided). The CSPs performed a total of 4959 interventions during a 12-month period. The interventions provided direct cost savings of $92,076 and an estimated cost avoidance of $488,436. Comparing cost savings and cost avoidance with the expenses of providing these services indicated a net economic benefit of $392,660. A new model of pharmacy practice that integrates staff pharmacists into existing clinical practice has the potential to minimize the risks, decrease the costs, and improve the outcomes associated with drug therapy.

[Simultaneous quantitative determination of amprenavir and indinavir in human plasma by high-performance liquid chromatography]

A reversed-phase high-performance liquid chromatographic assay for the determination of the HIV protease inhibitors amprenavir (Agenerase) and indinavir (Crixivan) in human plasma is described, using a mobile phase consisting of 0.50 M phosphate buffer (adjusted to pH 5,5) - Milli-Q water - acetonitrile (120: 1,080: 800, v/v/v). A solid-phase extraction using C18 extraction columns (Discovery columns 100 mg, 1 ml Supelco) and a liquid-liquid extraction with 0.5 ml hydrogenocarbonate/carbonate buffer (adjusted to pH 10.6) and 6 ml methyl ter-butyl ether have been compared. The liquid-liquid extraction has been chosen to be easier and cheaper. The method has been validated over the range of 60 to 3,000 ng/ml for amprenavir and 20 to 3,000 ng/ml for indinavir using a 0.5 ml sample volume. The specificity, linearity, accuracy and precision have been studied. The limit of detection was respectively for amprenavir and indinavir 15 and 4 ng, and the limit of quantification was 60 and 20 ng/ml. Stability tests under various conditions were performed. This assay can readily be used in a hospital laboratory for the routine monitoring of plasma concentrations of amprenavir in HIV-infected patients. The trough plasma concentrations average has been determined in patients treated by amprenavir and indinavir for seven months.

Costs of outpatient anticoagulant treatment in patients with cerebral and peripheral arterial occlusive disease

BACKGROUND AND OBJECTIVE

Knowledge of the costs of oral anticoagulant (AC) treatment may be relevant for resource allocation. Also, the incremental costs may be compared with other treatments for health care policy decisions. In this report, we have assessed actual costs of anticoagulant therapy in anticoagulation clinics (AC-clinic) in three different settings in the Netherlands.

METHODS

Costs of anticoagulant drug supply and costs as a result of INR-adjustment procedures were estimated. We compared the total costs of treatment in patients treated after minor cerebral ischaemia in the Stroke Prevention in Reversible Ischemia Trial (SPIRIT) and in patients treated because of peripheral arterial occlusive disease in the Dutch Bypass Oral anticoagulants or Aspirin Trial (BOA).

RESULTS

Costs of monitoring ranged between Euro 6.44 and Euro 9.87 per visit for monitoring at the AC-clinic and at home, respectively. The annual costs of administering anticoagulant drugs ranged between Euro 83 (phenprocoumon) and 107 (acenocoumarol). Variation in the overall actual annual costs of AC treatment was caused by the number of monitoring visits, the distribution of home and clinic visits and, to a lesser extent, the medication used. Annual costs of AC therapy for patients in SPIRIT was Euro 239 and for patients in BOA Euro 312. Overall costs of anticoagulant therapy were about 3 to 4-fold higher than standard treatment with aspirin.

CONCLUSIONS

Although the actual costs of anticoagulant therapy may be substantially higher than that of other antithrombotic therapies, its cost-effectiveness depends highly on efficacy.

Clinical and economic impact of ambulatory care clinical pharmacists in management of dyslipidemia in older adults: the IMPROVE study. Impact of Managed Pharmaceutical Care on Resource Utilization and Outcomes in Veterans Affairs Medical Centers

We examined the impact of ambulatory care clinical pharmacist interventions on clinical and economic outcomes of 208 patients with dyslipidemia and 229 controls treated at nine Veterans Affairs medical centers. This was a randomized, controlled trial involving patients at high risk of drug-related problems. Only those with dyslipidemia are reported here. In addition to usual medical care, clinical pharmacists were responsible for providing pharmaceutical care for patients in the intervention group. The control group did not receive pharmaceutical care. Seventy-two percent of the intervention group and 70% of controls required secondary prevention according to the National Cholesterol Education Program guidelines. Significantly more patients in the intervention group had a fasting lipid profile compared with controls (p=0.021). The absolute change in total cholesterol (17.7 vs 7.4 mg/dl, p=0.028) and low-density lipoprotein (23.4 vs 12.8 mg/dl, p=0.042) was greater in the intervention than in the control group. There were no differences in patients achieving goal lipid values or in overall costs despite increased visits to pharmacists. Ambulatory care clinical pharmacists can significantly improve dyslipidemia in a practice setting designed to manage many medical and drug-related problems.

Monitoring depression in patients undergoing alpha-interferon and ribavirin therapy for hepatitis C

Individuals with hepatitis C virus (HCV) constitute a growing segment of the US population, with most new infections attributable to intravenous drug use. Commonly, there is a 10- to 30-year delay from time of infection to diagnosis. Current treatment is with interferon, alone or in combination with ribavirin. A concerning side effect of both monotherapy and combination therapy is depression, which can become severe and lead to suicide. In patients with liver disease and those who have used intravenous drugs, depression is highest among those who are also positive for HCV. Use of a standardized short form depression self-rating tool would provide the advantages of increased accuracy in patient assessment, improved documentation, and cost-effective monitoring of depression in patients with HCV receiving interferon/ribavirin therapy. This article discusses the importance of screening and monitoring patients for depression as they undergo treatment for HCV infection with interferon alone or in combination therapy with ribavirin.

Anticoagulation clinics and patient self-testing for patients on chronic warfarin therapy: A cost-effectiveness analysis

This study was intended to evaluate the cost-effectiveness of anticoagulation clinic care and self-testing for the management of patients on chronic warfarin therapy. Using a 5-year Markov model, we evaluated the health and economic outcomes associated with each of three different anticoagulation management approaches: (1) usual care, (2) anticoagulation clinic testing with a capillary monitor, and (3) patient self-testing with a capillary monitor. Data available in the published literature and data from a large health system were used to develop model assumptions. Model results indicate that over a 5-year period, compared with usual care, anticoagulation clinic testing results in a total of 1.7 fewer thromboembolic events and 2.0 less hemorrhagic events per 100 patients. Another 4.0 thromboembolic events and 0.8 hemorrhagic events are avoided with patient self-testing compared with anticoagulation clinic testing. In addition to the health advantages of these strategies, both also have cost advantages. When the costs incurred by provider organizations and patients are considered, patient self-testing is the most cost-effective alternative, resulting in an overall cost saving.

Optimization of inpatient warfarin therapy: impact of daily consultation by a pharmacist-managed anticoagulation service

OBJECTIVE

To determine the effect of daily consultation by a team of hospital pharmacists on the accuracy and rapidity of optimizing warfarin therapy.

DESIGN

Comparison of a historical control cohort with a prospective cohort matched for treatment indication.

SETTING

A 400-bed university teaching hospital.

PATIENTS

Sixty consecutive patients hospitalized in 1992 and starting warfarin for the first time, with anticoagulation therapy managed by physicians, were compared with 60 patients matched for warfarin indication hospitalized in 1995, but with anticoagulation therapy managed with pharmacy consultation.

RESULTS

Pharmacist management of initial warfarin therapy resulted in a significant reduction in the length of hospitalization compared with physician dosing, from 9.5 +/- 5.6 days to 6.8 +/- 4.4 days (p = 0.009). The number of patients and patient-days with international normalized ratio (INR) values >3.5 were reduced by pharmacist dosing from 37 patients and 142 days to 16 patients and 29 days, respectively (p < 0.001). Similarly, the number of patients and patient-days with INR >6.0 were reduced from 20 patients and 50 days to two patients and six days, respectively (p < 0.001). There were six documented bleeding complications in 1992 compared with one in 1995 (p = 0.11). The mean INR at discharge was significantly lower in the pharmacy surveillance group, 2.6 +/- 0.58, compared with the physician cohort, 3.3 +/- 2.1 (p = 0.07). Readmissions after discharge due to bleeding or recurrent thrombosis were reduced from five (at 1 mo) and 10 (at 3 mo) to two and five readmissions, respectively, by pharmacist intervention (p = 0.43). The number of patients with concurrently prescribed drugs known to significantly interact with warfarin was significantly lower (6 vs. 13; p = 0.02) in the pharmacy surveillance group.

CONCLUSIONS

Among patients starting warfarin for the first time, daily consultation by a pharmacist significantly decreased the length of hospital stay and the number of patients who received excessive anticoagulation therapy. These findings translate into improved quality of care and potentially significant cost savings.

Therapeutic drug monitoring of selective serotonin reuptake inhibitors influences clinical dosing strategies and reduces drug costs in depressed elderly patients

OBJECTIVE

This study was initiated in order to describe and evaluate the effects of a therapeutic drug monitoring (TDM) routine of selective serotonin reuptake inhibitors (SSRIs) on treatment strategies and drug costs in depressed elderly patients.

METHOD

Blood samples were drawn from elderly depressed patients and analysed for steady-state trough serum concentrations of citalopram (n = 48), paroxetine (n = 48) or sertraline (n = 39). A global efficacy evaluation was made at baseline and after 6-9 months. Antidepressant drug costs before and after TDM were estimated.

RESULTS

Eight samples were excluded due to technical problems or noncompliance. In 65 of the 127 (51.2%) remaining cases, the treatment strategy was changed according to the TDM outcome, in most a reduction of the prescribed dose. Bioanalytical TDM costs included the antidepressant drug costs after TDM were reduced by 10.2%.

CONCLUSION

The results support the utility of TDM in the search for the individual minimum effective SSRI dose in the elderly.

Pharmacoeconomics of therapeutic drug monitoring in transplantation

Immunosuppressive drugs have contributed significantly to the success of organ transplantation. Therapeutic drug monitoring is an integral part of transplant protocols. However, there is little information concerning its positive contribution to pharmacoeconomics. Before developing studies to demonstrate the potential benefits of TDM, consideration must be given to the type of TDM to be evaluated. It is argued that, given that the lymphocyte in the central compartment is the target for immunosuppressants, Area-Under-the-Curve monitoring may be a better reflection of control and toxicity than traditional trough monitoring.

Narrowing the gap: access to HIV treatments in developing countries. A pharmaceutical company's perspective

The advent of new antiretroviral medicines means that the effects of HIV can now be curbed, but only one in twenty infected people have so far benefited. For those living in developing countries, the new treatments are practically unattainable. Governments, UNAIDS and pharmaceutical companies recognise this only too well and have rethought established assumption in order to try and overcome the challenges posed by cost, inadequate health services and unreliable local supply of medicines.

Incidence and costs of adverse drug reactions during hospitalisation: computerised monitoring versus stimulated spontaneous reporting

OBJECTIVE

To implement a computer-based adverse drug reaction monitoring system and compare its results with those of stimulated spontaneous reporting, and to assess the excess lengths of stay and costs of patients with verified adverse drug reactions.

DESIGN

A prospective cohort study was used to assess the efficacy of computer-based monitoring, and case-matching was used to assess excess length of stay and costs.

SETTING

This was a study of all patients admitted to a medical ward of a university hospital in Germany between June and December 1997.

PATIENTS AND PARTICIPANTS

379 patients were included, most of whom had infectious, gastrointestinal or liver diseases, or sleep apnoea syndrome. Patients admitted because of adverse drug reactions were excluded.

METHODS

All automatically generated laboratory signals and reports were evaluated by a team consisting of a clinical pharmacologist, a clinician and a pharmacist for their likelihood of being an adverse drug reaction. They were classified by severity and causality. For verified adverse drug reactions, control patients with similar primary diagnosis, age, gender and time of admission but without adverse drug reactions were matched to the cases in order to assess the excess length of hospitalisation caused by an adverse drug reaction.

RESULTS

Adverse drug reactions were detected in 12% of patients by the computer-based monitoring system and stimulated spontaneous reporting together (46 adverse reactions in 45 patients) during 1718 treatment days. Computer-based monitoring identified adverse drug reactions in 34 cases, and stimulated spontaneous reporting in 17 cases. Only 5 adverse drug reactions were detected by both methods. The relative sensitivity of computer-based monitoring was 74% (relative specificity 75%), and that of stimulated spontaneous reporting was 37% (relative specificity 98%). All 3 serious adverse drug reactions were detected by computer-based monitoring, but only 2 out of the 3 were detected by stimulated spontaneous reporting. The percentage of automatically generated laboratory signals associated with an adverse drug reaction (positive predictive value) was 13%. The mean excess length of stay was 3.5 days per adverse drug reaction. 48% of adverse reactions were predictable and detected solely by computer-based monitoring. Therefore, the potential for savings on this ward from the introduction of computer-based monitoring can be calculated as EUR56 200/year ($US59 600/year) [ 1999 values].

CONCLUSION

Computer monitoring is an effective method for improving the detection of adverse drug reactions in inpatients. The excess length of stay and costs caused by adverse drug reactions are substantial and might be considerably reduced by earlier detection.

Anti-coagulant monitoring service delivery: a comparison of costs of hospital and community outreach clinics

Anti-coagulated patients are monitored at regular intervals to ensure that their warfarin dosage is appropriate for their target International Normalized Ratio. The traditional setting for this monitoring has been the hospital clinic. Technological advances allow-- and with growing numbers of anti-coagulated patients, are leading to-- greater provision of monitoring clinics outside the hospital, at a more convenient location nearer patients' homes. This paper discusses the differences in organization between a hospital clinic and one set in the community (although provided by the hospital), and compares their costs. The comparison demonstrates the greater average cost per appointment in outreach of pound sterling 13.12 under current arrangements. Estimates are presented of incremental cost per appointment of pound sterling 3.93 and pound sterling 15.88 for a 10% increase in weekly patient numbers put through hospital and outreach clinics, respectively. Cost estimates are also presented for suggested alterations to hospital clinics that may reduce patient inconvenience, and the conditions under which outreach provision might be expanded at comparable cost to hospital provision are also examined.

The cost-effectiveness of different management strategies for patients on chronic warfarin therapy

OBJECTIVE

To examine the cost-effectiveness of moving from usual care to more organized management strategies for patients on chronic warfarin therapy.

DESIGN

Using information available in the scientific literature, supplemented with data from a large health system and, when necessary, expert opinion, we constructed a 5-year Markov model to evaluate the health and economic outcomes associated with each of three different anticoagulation management approaches: usual care, anticoagulation clinic testing with a capillary monitor, and patient self-testing with a capillary monitor.

PATIENTS

Three hypothetical cohorts of patients beginning long-term warfarin therapy were used to generate model results.

MAIN RESULTS

Model results indicated that moving from usual care to anticoagulation clinic testing would result in a total of 1.7 thromboembolic events and 2.0 hemorrhagic events avoided per 100 patients over 5 years. Another 4.0 thromboembolic events and 0.8 hemorrhagic events would be avoided by moving to patient self-testing. When direct medical care costs and those incurred by patients and their caregivers in receiving care were considered, patient self-testing was the most cost-effective alternative, resulting in an overall cost saving.

CONCLUSIONS

Results illustrate the potential health and economic benefits of organized care management approaches and capillary monitors in the management of patients receiving warfarin therapy.

The procedure of new drug application and the philosophy of critical rationalism or the limits of quality assurance with good clinical practice

K.R. Popper's philosophy of critical rationalism is concerned with the detection and removal of error. Fundamental contradictions exist between Popper's theory of knowledge and the present-day practice of the clinical investigation of new drugs. Currently, the public authorities concerned with the licensing of drugs pass judgment on trials, which are closely linked by the one-sponsor problem: the assertions made by the sponsor are not independently confirmed. This lack leads to excessive documentation and to costly monitoring and auditing, which are intended to ensure the credibility of results. In Popper's view, confirmatory trials, independent of the sponsor and supervised by the regulatory bodies, would be a better way to achieve reliable knowledge. The consequence would, among other things, be a reorganization of phase III of the clinical investigation of new drugs by dividing it into independent parts, one under the control of the sponsor and one under the control of the public authority. The implementation of this suggestion would lead to a more scientific manner of dealing with new drugs and to savings in terms of unproductive measures during the application process.

Therapeutic drug monitoring of antidepressants: cost implications and relevance to clinical practice

Despite evidence to support its potential benefit in clinical practice, therapeutic drug monitoring (TDM) is under-utilised and underdeveloped in the field of psychiatry. In antidepressant pharmacotherapy drug dose is emphasised as the critical treatment variable. However, dose in, and of, itself can be a strikingly misleading predictor of drug concentration and, hence, treatment effect. For antidepressant drugs, plasma concentrations at a given dose have been shown to vary in excess of 40-fold. The clinical relevance of this variability is that at a standard antidepressant dosage only some patients will have tissue drug concentrations associated with an optimal response whereas others will have either low, ineffective drug concentrations or unnecessarily high concentrations which may be poorly tolerated. Among clinicians and healthcare agencies there is an under-appreciation of the degree of pharmacokinetic variability found in patients and how that might impact on the patients response to pharmacotherapy. Hence there is a perception that TDM is an unnecessary, complicated and costly procedure. This is actually unfounded. There are data to suggest that TDM can favourably affect the outcome of antidepressant treatment by providing a rational alternative to the inherently slower, trial and error practice of dosage titration based on clinical response. It is unlikely that TDM will become a standard of care for all antidepressant agents and all patients. Therefore the question becomes for which antidepressant agents, for which patients and under what circumstances, is TDM more cost-effective than traditional dose titration. The use of TDM to optimise the efficient use of selected antidepressant agents could potentially free up healthcare resources to fund other equally deserving treatments. This article provides a discussion of the major classes of antidepressant drugs with regard to their pharmacological features that predict the utility of TDM in clinical practice. Recommendations are made for the practical application of TDM and the directions for further research.

Monitoring unfractionated heparin therapy with antifactor Xa activity results in fewer monitoring tests and dosage changes than monitoring with the activated partial thromboplastin time

STUDY OBJECTIVE

To determine how much more costly it is to monitor unfractionated heparin (UFH) therapy by antifactor Xa heparin activity (HA) than by activated partial thromboplastin time (aPTT).

DESIGN

Prospective, randomized, unmasked, cohort, single-center study.

SETTING

A 625-bed, adults-only, private teaching hospital.

PATIENTS

Two hundred sixty-eight patients with a variety of indications for UFH therapy.

INTERVENTIONS

Patients were treated with UFH based on ideal weight (75 U/kg bolus, 20 U/kg initial infusion) and monitored by either HA or aPTT, MEASUREMENTS AND MAIN RESULTS: After adjusting for gender, groups were equivalent in patient characteristics and UFH dosage. The HA group had fewer monitoring tests and dosage changes/24 hours than the aPTT group. These reductions neutralized much of the increased cost of the HA assay itself.

CONCLUSION

Monitoring UFH therapy over 96 hours with an HA assay costs $4.37 more than monitoring with aPTT. This modest increase may be acceptable given other advantages of the HA assay.

Impact of goal-oriented and model-based clinical pharmacokinetic dosing of aminoglycosides on clinical outcome: a cost-effectiveness analysis

The benefits of a pharmacy-based, active therapeutic drug monitoring (TDM) service (ATM) on outcomes were examined in a prospective study at four hospitals. ATM involved pharmacokinetic dosage optimization at the start of treatment, subsequent Bayesian adaptive control, and frequent patient evaluation. Cost-effectiveness was calculated based on real costs. The ATM group comprised 105 patients and 127 patients with nonguided TDM who were followed up as controls. Forty-eight of the ATM and 62 of the nonguided TDM patients had an infection on admission. Peak concentrations in ATM patients were significantly higher (10.6+/-2.9 mg/L; nonguided TDM, 7.6+/-2.2 mg/L; p < 0.01). Trough levels in the ATM group were significantly lower (p < 0.01). There was a trend toward lower mortality in the ATM group (nine of 105 versus 18 of 127; p = 0.26) that was significant for patients with an infection on admission (one of the 48 ATM patients died versus nine of the 62 nonguided TDM patients; p = 0.023). ATM reduced the length of hospital stay for all patients in the study (20.0+/-1.4 days; nonguided TDM, 26.3+/-2.9 days; p = 0.045) and for patients admitted with an infection (12.6+/-0.8 days; nonguided TDM, 18.0+/-1.4; p < 0.001). The incidence of nephrotoxicity was reduced from 13.4% (nonguided TDM) to 2.9% (p < 0.01). With ATM, total costs were lower for all patients (Dutch guilders [DFL], 13,125+/-9,267; nonguided TDM, DFL 16,862+/-17,721; p < 0.05) and for patients admitted with an infection (DFL 8,883+/-3,778; nonguided TDM, DFL 11,743+/-7,437; p < 0.01). Goal-oriented, model-based dosing of aminoglycosides resulted in higher antibiotic efficacy, shorter hospitalization, and reduced incidence of nephrotoxicity. By combining efficacy with savings, ATM offered a significant alternative to usual care.

Point-of-care (POC) measurement of coagulation after cardiac surgery

OBJECTIVE

Two different point-of-care (POC) systems for the monitoring of coagulation variables at the bedside were evaluated with regard to practicability, accuracy and costs.

DESIGN

Prospective, descriptive study.

SETTING

Single-institutional, clinical investigation on an intensive care unit (ICU) of an urban, university-affiliated hospital.

PATIENTS

Eighty cardiac surgery patients were studied postoperatively.

INTERVENTIONS

Arterial blood samples were drawn postoperatively on the ICU at different data points.

MEASUREMENTS AND RESULTS

Activated partial thromboplastin time (aPTT) and prothrombin time (PT) were measured using two POC systems (Thrombolytic Assessment System [TAS] and CoaguCheck Plus). At the same time coagulation parameters were measured by the central laboratory of the hospital. Measurements were carried out at different data points after cardiac surgery on the ICU. The direct and indirect costs of measuring aPTT/PT were also assessed. Bias analyses revealed good agreement of the POC-based monitoring of aPTT/PT with laboratory-based monitoring of coagulation (e. g. aPTT CoaguCheck: bias of -2.8 s with +/- 2 SD [limits of agreement] of +13.7 and -19.1 s). Mean turn-around time (TAT; time from blood sampling until availability of data for the ICU physicians) was significantly longer for the central laboratory-based coagulation monitoring (130 +/- 38 min) than for the two POC systems (aPTT-TAS: 9.6 +/- 2.7 min; aPTT-CoaguCheck: 6.5 +/- 1.9 min). Blood sampling at unfavorable times increased the TAT for laboratory-based measurements considerably. The direct costs for measuring aPPT and PT were significantly higher using both POC systems (aPTT-TAS: $4.84; aPTT-CoaguCheck: $4.34) than for the central laboratory ($1.59). Costs for transportation increased the laboratory-based monitoring considerably ($3.77).

CONCLUSIONS

Both POC analyzers may reduce the potential for preanalytical errors associated with coagulation measurements at the central laboratory, hasten TAT significantly and may improve patient therapy by reducing inappropriate administration of blood products.

Economic impact of aminoglycoside toxicity and its prevention through therapeutic drug monitoring

Therapeutic drug monitoring (TDM) of aminoglycoside antibacterials with the goal of minimising toxicity and maximising effectiveness has become routine. Successful management of serious infections requires the ability to achieve therapeutic peak concentrations, while maintaining low trough concentrations will assist in avoiding nephrotoxicity. Reported nephrotoxicity rates range from 1.7 to 58% and depend on the definition used, the patient group studied, concomitant drug therapy used and whether TDM services have been provided. TDM services have been shown to reduce aminoglycoside nephrotoxicity. The costs of providing TDM averages $US301.87 (1997 values) per patient and the cost for each use of nephrotoxicity is estimated at $US4583 (1997 values). In order for the costs of providing a TDM service to 100 patients ($US30,187) to be offset by cost savings due to decreasing nephrotoxicity, the service would need to be able to reduce nephrotoxicity by 6.6%, resulting in a saving of $US30,248. The ability to achieve this saving is dependent on the characteristics of the population in which aminoglycoside therapy is used. In populations where high rates of nephrotoxicity (e.g. > 15%) would be expected, TDM services are cost justified. In populations where nephrotoxicity is low (e.g. < 5%), TDM service is not justified for this purpose. In order to provide a cost-efficient approach to TDM, resources should be focused on providing service to high risk patient groups.

Economic and outcome issues for therapeutic drug monitoring in medicine

Outcome and economic studies pertaining to the use of therapeutic drug monitoring (TDM) are summarized. The studies were classified by a 2 x 2 matrix comprised of process, outcome, system-related variables, and patient-centered variables. Two hundred forty-seven studies conducted from 1974 to 1994, culled from eight summary sources, were reviewed. Almost 75% of the studies reported system-related, not patient-centered, measures for assessing the value of TDM; nearly the same percentage evaluated processes as opposed to outcome measures. Studies comparing TDM to non-TDM populations generally showed that TDM as an intervention reduced the rate of undesirable system-related variables by 50% and increased the rate of desirable system-related variables by 100%. For patient-centered variables, TDM was less dramatic, decreasing the rate of undesirable variables by 15% to 50%. Only 8% of the studies examined economic variables. TDM-influenced changes in process variables resulted in a projected mean annual savings of $37,000. The few studies available of cost-benefit analysis focused on aminoglycosides and showed that TDM yielded a range from 4:1 to 52:1 in benefit-to-cost ratio. Most studies have limitations that include small sample size, short study periods to predict long-term outcomes, no long-term follow-up, and designs for noncontrolled study.

Pharmacokinetics of once-daily gentamicin dosing in pediatric patients

BACKGROUND/PURPOSE

To achieve cost-effective health care in adults, once-daily aminoglycosides administration has been used and judged to be safe and efficacious. A similar strategy in children requires the characterization of pharmacokinetic parameters and the development of a therapeutic monitoring protocol for this antibiotic regimen.

METHODS

A prospective, controlled, randomized (2:1) study was undertaken in 50 pediatric patients between June 1995 and September 1997. Children between 6 months and 18 years who required gentamicin therapy based on independent clinical assessment were eligible if they had normal renal function, no aminoglycoside allergies, were not neutropenic, or did not have cystic fibrosis. Measurements included a peak, 4-hour, 8-hour, and trough gentamicin levels to determine volume of distribution (Vd) and elimination constant (Ke). Ototoxicity and nephrotoxicity were monitored by pre- and postaudiology examinations and serial calculated creatinine clearance determinations, respectively.

RESULTS

Thirty-three patients received 7.5 mg/kg every 24 hours, and 17 patients received 2.5 mg/kg every 8 hours. Most frequent indications for treatment were ruptured appendicitis (n = 19) followed by wound infections caused by trauma (n = 4), but the spectrum of treatment was broad including enteric, genitourinary, central nervous system, biliary, ophthalmologic, and orthopedic infections. Pharmacokinetic data indicated that 24-hour dosing resulted in higher peak levels compared with 8-hour dosing (20.4 +/- 45.4 v 7.2 +/- 6.2 mg/L, P < .0001) and lower trough levels (0.29 +/- .02 v 0.69 +/- 0.13, P < .0001), whereas rate of elimination constant and volume of distribution were not significantly different. No nephrotoxicity or ototoxicity has been noted in either group.

CONCLUSIONS

These data confirm that once-daily dosing of gentamicin is a safe method of treatment that provides equivalent pharmacokinetics compared with traditional dosing and enhances bactericidal effect based on higher peak levels, avoids toxicity, and allows cost savings.

[Medico-economic study of Léponex (clozapine) in the Bordeaux Charles Perrens Hospital Center]

Schizophrenia disorders afflict approximately 1% of the population during their lifetime. Conventional antipsychotic agents show therapeutic limitations because of their side-effects and inefficacy among some patients. A novel antipsychotic class, named atypical neuroleptics, among Léponex is the leader, constitutes a hope in treatment-resistant schizophrenia. However, because the drug involves a 1% to 2% risk of agranulocytosis, an haematological oversees has been established. Moreover, the acquisition cost of clozapine is high in comparison with that of standard antipsychotics. The purpose of this study was to observe the management of 72 patients suffering from resistant schizophrenia, to assess the cost of this treatment in medical and social terms, and to realize cost-effectiveness study in Charles Perrens Hospital (Bordeaux). The survey based on three questionnaires (Clinical informations, Quality of Life, Epidemiological information) was sent to psychiatrists practising in this hospital. The results confirm efficacy (overall functioning measured by CGI which is significant, p < 0.0001) and tolerance of Léponex (no side effects in 33.3% patients, no agranulocytosis, only one neutropenia and only 4.2% neurologic side effects). We found a significant reduction of the annual mean number of days of full time hospitalization (214 days versus 135 after two years, p < 0.0005) associated with the significant reduction of direct cost mainly related to shorter length of hospitalization; and 45.8% versus 8.3% adjust to life in the community (p < 0.0004). Clozapine produced a marked improvement (p < 0.0001) in Quality of Life measured by two self-rating scales (SWN and TEAQV). The estimated total two-years cost decreased from 31,108 Francs/month/patient to 22,950 Francs/month/patient, a saving of 8,158 Francs/month/patient (a decrease of 26.2%). Although the acquisition cost of clozapine is high, cost effectiveness estimates in patients with treatment resistant schizophrenia suggest that the clinical benefits (improved psychopathology, social functioning and quality of life) of this drug may confer medium to long term economic benefits, primarily by reducing the need for psychiatric hospital service.

[Pharmaco-economic aspects of antibiotic therapy in hospitals]

Amongst medications used in hospitals, antibiotics represent the most expensive therapeutic group; their use is constantly growing. Beyond acquisition costs, antibiotherapy costs must be approached at a broader level, including costs of preparation, administration, efficacy or inefficacy, monitoring, side effects treatment, and long-term costs resulting bacteria resistance. An attempt to cost containment in antibiotherapy can only result from a global, multidisciplinary strategy, with at all levels, as main objectives, the improvement of the quality and effectiveness of treatment adequate relevance of drug selection and therapy assessment.

[Risks, benefits and costs of hormone replacement therapy in menopause]

Hormone replacement therapy (HRT) acts both as an effective treatment of menopausal symptoms and genital atrophy, and as an effective prevention of osteoporosis. It is also probably cardioprotective and potentially preventing cerebrovascular disease. The risk of oestrogen-induced endometrial cancer is eliminated by the addition of a progestin. An increase in breast cancer risk is however possible after 10 years or more of HRT use. This multifactorial risk-benefit balance altogether with other variables (numerous and expensive hormonal therapies, low compliance of postmenopausal women, need for monitoring, therapy-related adverse events) explain why so few global pharmaco-economic appraisals have been devoted to HRT. Computer model studies have been set up to study hypothetical cohorts of menopausal women treated for 5-10 years or more, comprising hysterectomized women (receiving an estrogen alone) and non hysterectomized women (receiving an oestrogen-progestogen therapy) compared with untreated controls. Treatment of hysterectomized women as well as non hysterectomized symptomatic menopausal women appears relatively cost-effective. In terms of mortality and morbidity, a reduction in cardiovascular disease risk and, to a smaller extent, in osteoporosis has a strikingly greater impact than the small increase in breast cancer risk related to HRT use. A significant increase in life expectancy seems associated with long-term use and the quality-adjusted life years gain, is particularly impressive, as quality of life appears distinctly improved by HRT utilization. In the future, this beneficial cost-effectiveness equation will probably be optimized thanks to the introduction of alternative and innovative replacement therapies allowing longer treatment periods without increasing the risk of breast cancer.

Total testing process applied to therapeutic drug monitoring: impact on patients' outcomes and economics

The Total Testing Process (TTP) refers to the sequence of 11 steps of laboratory testing, beginning with a clinical question prompted by the patient-clinician encounter and concluding with the impact of the test result on patient care. TTP when applied to therapeutic drug monitoring (TDM) emphasizes that TDM must be considered a process involving a series of steps and interrelated activities and not viewed simply as a numerical value for a serum drug concentration. TTP is also an ideal format for organizing and identifying the system-related and patient-centered variables used in outcomes assessment of TDM, as well as providing a template for collecting the cost data needed for economic analyses. Examples are provided for improving application of TDM by practitioners, clinical laboratories, and educators.

Routine monitoring of gentamicin serum concentrations in pediatric patients with normal renal function is unnecessary

OBJECTIVE

Due to increasing demands for cost containment within the healthcare system, we evaluated the need for routine gentamicin concentrations (i.e., peak and trough with third dose).

DESIGN

Single-institution study performed concurrently with hospitalization.

SETTING

A 225-bed pediatric teaching hospital.

PARTICIPANTS

The study population consisted of 150 hospitalized pediatric patients (53% medicine, 47% surgical patients) from 3 months to 15 years old with normal serum creatinine.

OUTCOME MEASURES

If the administered dose produced diagnoses-appropriate peak concentrations of at least 4 micrograms/mL or 5 micrograms/mL in bacteremia/septicemia and at least 6 micrograms/mL or 8 micrograms/mL in patients with pneumonia if trough serum gentamicin concentrations were less than 2 micrograms/mL, if the patient was noted by the attending physician to be clinically responding as well as objectively having a decreased white blood cell count and was afebrile, and if there was not an increase of 0.5 mg/dL or more in serum creatinine during the course of therapy.

RESULTS

Patients received a mean dose of gentamicin 2.51 +/- 0.14 mg/kg i.v. q8h, which resulted in a mean peak concentration of 6.1 +/- 1.7 micrograms/mL (range 2.4-11.7) and a mean trough concentration of 0.5 +/- 0.3 microgram/mL (range 0.1-1.8). Peak and trough concentrations were at least 4 micrograms/mL and less than 2 micrograms/mL in 96% and 100% of patients, respectively. No patient required a dosage change due to lack of clinical response.

CONCLUSIONS

Our data do not support the routine monitoring of gentamicin concentrations in pediatric patients older than 3 months of age who are receiving appropriate standard doses of gentamicin and have normal renal function.

Analytic performance of digoxin laboratory monitoring

Since therapeutic drug monitoring is rapidly becoming a widely-used tool in clinical medicine we prospectively assessed 547 control samples over a period of 18 months using fluorescence polarization immunoassay, calibrators and control samples to determine the analytical performance of Abbott TDx in measuring serum digoxin levels. Recovery of the controls (within-run and between-run coefficient of variation) evaluated at the low, target therapeutic and intoxication ranges was 14%, 8% and 7% and precision was -3.57, -7.02, -3.38, respectively. Our clinical utility analysis showed that the prescribed dose provided serum digoxin levels within, above and below the targeted therapeutic range for 50.2%, 38.4% and 11.4% of the patients, respectively. The discrepancy between the calibrators and the controls, the tendency towards lower prescription dosage and patient noncompliance with the prescribed dose all account for these findings. The direct costs for digoxin serum concentration monitoring amount to 10 US $. A closer collaboration between the laboratory and the prescribing physician will undoubtedly form the basis of a more effective cost-efficacy strategy of digoxin serum monitoring as an indispensable tool and cornerstone of clinical decision-making.

Pharmacoeconomics and therapeutic drug monitoring

The ever increasing rate of inflation and the reality that resources for medical care are limited has led to significant changes in the reimbursement for health care services. These influences have convinced health care policy makers to closely evaluate innovative health services in terms of the benefits and costs. New pharmaceutical services must be economically justified in order to exist in the future. This is crucial to the expansion and adoption of pharmaceutical services. Application of economic evaluations is not new to the health care sector. Until recently, there were no incentives to transfer this interest into widespread use. As health care expenditures have escalated over the past two decades, the number of applications of these techniques has increased. Especially significant are cost-benefit and cost-effectiveness evaluations of medical practice, pharmaceuticals, and other health care technologies. Pharmacoeconomic analysis is an important tool to assist in the evaluation of new pharmaceutical services and technologies. Essentially, economic analytical methods are used to weigh the positive and negative consequences of alternative courses of action. The usefulness of pharmacoeconomic analyses is in resource allocation, with the purpose of achieving the highest return on investment or accomplishing a given objective in the least costly manner. Unfortunately, very few pharmacy programs have been evaluated using pharmacoeconomic techniques. The purpose of this article is to present various methods to assess the economic value of therapeutic drug monitoring services in society and for specific patient populations. Additionally, this article will review the previous attempts and various issues surrounding the economic justification of therapeutic drug monitoring.

A rapid cost-effective high-performance liquid chromatographic (HPLC) assay of serum lamotrigine after liquid-liquid extraction and using HPLC conditions routinely used for analysis of barbiturates

Lamotrigine (lamictal) is a new anticonvulsant drug approved by the FDA for clinical use. Therapeutic monitoring of lamotrigine is useful for patient management and avoidance of toxicity. The suggested therapeutic range is 1 to 4 micrograms/ml. The authors describe a simple high-performance liquid chromatographic (HPLC) method for analysis of lamotrigine from serum. Serum (0.5 ml) was alkalinized with borate buffer (pH 9.8). Lamotrigine and the internal standard thiopental were extracted with 10 ml of chloroform. After evaporation of the extract, the residue was reconstituted in the mobile phase (prepared by mixing 750 ml of potassium dihydrogen phosphate, 550 ml of deionized water, 430 ml of methanol, and 100 microliters of triethylamine as an ion pairing reagent) and injected into an LC-18 column (15 cm x 4.6 mm). The authors use this HPLC system routinely in their laboratory for the analysis of barbiturates. They demonstrated that the same system can be used for the analysis of lamotrigine. The within-run and between-run precisions of the lamotrigine assay were 1.63% (mean = 3.05, SD = 0.05 microgram/ml, n = 6) and 3.7% (mean = 2.97 micrograms/ml, SD = 0.11, n = 8). The assay was linear for serum lamotrigine concentrations of 0.5 microgram/ml to 20 micrograms/ml with a detection limit of 0.5 microgram/ml. The authors observed excellent correlation between serum lamotrigine concentrations measured by their assay and a reference laboratory in six patients receiving lamotrigine. Their assay is free from interferences from common tricyclic antidepressants, benzodiazepines, other common anticonvulsants, salicylate, and acetaminophen.

Demand for warfarin anticoagulation monitoring in Tayside, Scotland

AIM

The aim of this study was to assess the demand for warfarin prescribing and monitoring, and to identify patients with atrial fibrillation who might benefit from warfarin therapy. The study was carried out in the population of Tayside, Scotland (400,000 people) using patient-specific dispensed prescribing and hospitalisation data from the Medicines Monitoring Unit at the University of Dundee.

METHODS

The incidence and prevalence of digoxin and warfarin prescribing were calculated between 1989 and 1993. Patients dispensed digoxin in 1993 were assumed to have atrial fibrillation and they were stratified into high risk groups for an adverse thromboembolic event based on past medical history. The numbers of patients at high risk who were judged to be possible candidates for warfarin were calculated.

RESULTS

The prevalence of warfarin prescribing is increasing in Tayside and is mainly for elderly patients. There were also many patients assumed to have atrial fibrillation who were at particularly high risk for an adverse thromboembolic event, who had no record of warfarin prescribing. Only 35% received warfarin. Even given the methodological limitations of this study, and the use of aspirin as an alternative prophylactic agent, it is likely that these patients have been a source of increased prevalence of warfarin prescribing since 1993 and will be in the future. Other indications for warfarin prescribing are also increasing.

CONCLUSION

It is anticipated that there will be increasing demands for anticoagulant monitoring, which will need to be met either by increasing the capacity of existing clinics, or by increasing the role of primary care.

Initiation of clinical pharmacy in Greece

INTRO

There was neither Clinical Pharmacy practice in Greece nor Hospital Formularies. Clinical Pharmacy (CP) services started experimentally during a 3-month period (February 1995-April 1995) at the 2nd surgical Department of "Apostle Paul-KAT" Hospital in Athens. Since then there has been a strategy plan for further CP development. Our aim is to give information about these first steps in introducing CP in Greece.

METHOD

The work at the Department was based on the prescription monitoring of every patient, realizing the prescribing trends and giving priority to certain prescribing problems. Eventually there was a focus on antibiotics and respiratory system drugs.

RESULTS

250 patients 91 interventions for alternative drug treatment and the duration of antibiotic treatment 25 interventions for individualization of drug dosage. 15 cases of monitoring adverse effects. 12 discussions with patients consulting them about their drug treatment 4 educational presentations. High acceptance by the medical staff. Comparison of 2 months (pre and post CP services) revealed 50.7% reduction in antibiotics and respiratory system drugs. Total cost saving 1,034120 drs-->E 2,787 for one month.

CONCLUSIONS

The results of the 1st experimental 3-month period are indicative for the consequences of CP services both for the quality of pharmaceutical care and pharmaco-economics. Implementation of CP services by organizing a CP dept or Unit will influence the pharmaceutical policy of the Hospital and lead to institutional changes, such as a Hospital Formulary.

Cost-effectiveness of clozapine monitoring after the first 6 months

BACKGROUND

Clozapine is effective in treating patients with schizophrenia who do not respond to conventional neuroleptic drugs. The drug is unique in that it is available only with a US Food and Drug Administration-mandated system for weekly monitoring of patients' white blood cell counts. No study has been conducted to evaluate the cost-effectiveness of this mandatory monitoring system.

METHODS

A benchmark case was established by utilizing cumulative incidence rates of agranulocytosis from a recent study with a large sample of clozapine-treated patients. We assumed a 20% mortality among patients with agranulocytosis, $30.61 in monitoring costs each week, and 14.4 years of remaining life expectancy after detection of agranulocytosis. Based on these bench-mark assumptions, cost-effectiveness ratios in dollars per quality-adjusted life-year were calculated for the first, second, and third 6-month periods during which a patient was receiving clozapine. Sensitivity analyses were performed with more conservative assumptions in 5 alternative scenarios.

RESULTS

In the benchmark case, costs per quality-adjusted life-year gained were $61,694, $925,418, and $420,644 for the first, second, and third 6-month periods of clozapine treatment, respectively. In the alternative scenarios, these costs ranged from $7923 to $46,056 for the first 6-month period and from $54,025 to $690,850 for the second and third 6-month periods.

CONCLUSIONS

While the costs of monitoring patients with schizophrenia in the first 6-month period of clozapine treatment seem to be justifiable, monitoring thereafter may not be cost-effective because of the very low incidence of agranulocytosis in the later periods.