Bridging the gap: ageing, pharmacokinetics and pharmacodynamics

Apixaban plasma concentrations before and after catheter ablation for atrial fibrillation

BACKGROUND

Catheter ablation in patients with atrial fibrillation is associated with a transient increase in thromboembolic risk and adequate anticoagulation is highly important. When patients are anticoagulated with apixaban, monitoring of plasma concentrations of the drug is not routinely performed. This study aimed to assess the influence of clinical patient characteristics, concomitant drug treatment and self-reported adherence on apixaban concentrations, and to describe the intra- and inter-individual variability in apixaban concentrations in this group of patients. Method Apixaban concentrations from 141 patients were measured in plasma one week before ablation and two, six and ten weeks after ablation, employing ultra-high performance liquid chromatography coupled with tandem mass spectrometry. In samples not obtained at trough, apixaban concentrations were adjusted to trough levels. Self-reported adherence was registered by means of the 8-item Morisky Medication Adherence Scale before and after ablation.

RESULTS

There were statistically significant, positive correlations between apixaban concentrations and increased age, female sex, lower glomerular filtration rate, higher CHA2DS2-VASc score, use of cytochrome P450 3A4 and/or p-glycoprotein inhibitors, and use of amiodarone. Self-reported adherence was generally high. The mean intra-individual and inter-individual coefficients of variation were 29% and 49%, respectively.

CONCLUSION

In patients undergoing catheter ablation for atrial fibrillation, age, sex, renal function, interacting drugs and cerebrovascular risk profile were all associated with altered plasma apixaban concentration. In this group of patients with a generally high self-reported adherence, intra-individual variability was modest, but the inter-individual variability was substantial, and similar to those previously reported in other patient apixaban-treated populations. If a therapeutic concentration range is established, there might be a need for a more flexible approach to apixaban dosing, guided by therapeutic drug monitoring.

The Pharmacokinetics, Safety, and Tolerability of Rimegepant 75 mg Are Similar in Elderly and Nonelderly Adults: A Phase 1, Open-Label, Parallel-Group, Single-Dose Study

Rimegepant is a small-molecule calcitonin gene-related peptide receptor antagonist approved for the acute treatment of migraine ± aura and preventive treatment of migraine in adults. The pharmacokinetics of rimegepant in elderly and nonelderly subjects were evaluated. In an open-label Phase 1 study, 14 elderly (aged 65 years or older) and 14 nonelderly (aged 18 to less than 45 years) subjects each received a single oral dose of rimegepant 75 mg. Blood samples were collected before dosing and through 96 hours after dosing. The pharmacokinetic parameters of rimegepant after a single dose were similar in both age groups. Geometric least-squares mean ratios (elderly/nonelderly) of the natural log-transformed maximum observed plasma concentration and natural log-transformed area under the plasma concentration-time curve from time 0 extrapolated to infinity were 96.6 and 104.6, respectively. Eight (28.6%) subjects (4 elderly, 4 nonelderly) experienced 1 or more adverse events (AEs); all AEs were mild in intensity, and no serious AEs or AEs leading to discontinuation were reported. Following a single 75-mg dose of oral rimegepant, pharmacokinetic parameters were similar in elderly and nonelderly adults; no dose adjustment is warranted in elderly subjects.

Direct Oral Anticoagulants in Octogenarians With Atrial Fibrillation: It Is Never Too Late

Atrial fibrillation is the most common arrhythmia in clinical practice, and age is one of the strongest predictors/risk factors for ischemic stroke in patients with atrial fibrillation. Elderly patients, in particular patients aged 80 years and older, are at higher risk of both ischemic and bleeding events compared with younger patients. Vitamin K antagonists (VKAs) reduce the risk of ischemic stroke, especially in the elderly, but increase the bleeding risk. In addition, frequent international normalized ratio monitoring is needed to ensure the optimal level of anticoagulation. Furthermore, VKAs have multiple drug and food interactions. Direct oral anticoagulants (DOACs) have recently emerged as alternatives to VKAs and are gradually increasing their popularity mainly because of their fewer drug and food interactions and ease of use. Their effectiveness and safety have been well-established in the general population, but the benefit in the very elderly (≥80 years old) is still unclear. Data about the safety and the effectiveness of DOACs in patients older than 75 years are available in literature, but the evidences of the use of DOACs in patients aged 80 years and older are lacking. This review aims to give light to the differences, in terms of benefits and safety, of the DOACs in this subset of patients.

The problem of underdosing with direct-acting oral anticoagulants in elderly patients with nonvalvular atrial fibrillation

Unless contraindicated, anticoagulant therapy should be prescribed to elderly patients with atrial fibrillation. Direct-acting oral anticoagulants (DOACs) are superior to vitamin K antagonists for preventing stroke. This, together with their higher net clinical benefit, makes DOACs the treatment of choice in this population. However, due to the concerns about bleeding and the need for dose adjustment based on clinical variables, underdosing of DOACs is common and the risk of stroke high. Drugs with more easily adjusted doses are likely associated with a lower risk of dosing errors and, therefore, a greater protective effect. Correct dosing can ensure a maximal net benefit of DOACs in elderly patients with atrial fibrillation.

Impact of age and CYP2D6 genetics on exposure of aripiprazole and dehydroaripiprazole in patients using long-acting injectable versus oral formulation: relevance of poor and intermediate metabolizer status

PURPOSE

Tailoring medication dosing for the individual patient is complex, and many factors can influence drug exposure. We investigated the effect of age and CYP2D6 genotype on aripiprazole and dehydroaripiprazole exposure in patients using long-acting injectable (LAI) or oral aripiprazole.

METHODS

Matched data on serum concentration of aripiprazole and CYP2D6 genotype of patients using oral or LAI aripiprazole were included retrospectively from a therapeutic drug monitoring service. The patients were divided into the following CYP2D6 genotype-defined categories: poor metabolizers (PMs), intermediate metabolizers (IMs), normal metabolizers (NMs), and ultrarapid metabolizers (UMs). Linear mixed model analyses were used to evaluate the impact of CYP2D6 genotype on dose-adjusted serum concentrations of the active moiety of aripiprazole+dehydroaripiprazole in relation to age and formulation.

RESULTS

We identified 635 patients (mean age = 40.1 years, 9.4% ≥ 65 years, 53.7% females) using LAI (n = 166) or oral formulation (n = 469). The genotype-predicted CYP2D6 phenotype subgroups were 2.4% UMs, 82.0% NMs, 8.0% IMs, and 7.2% PMs. Age did not significantly affect exposure of the active moiety of aripiprazole+dehydroaripiprazole in the LAI (p = 0.071) or oral (p = 0.14) subgroups. Compared with CYP2D6 NMs, PMs and IMs had significantly increased exposure of the active moiety of aripiprazole+dehydroaripiprazole in the LAI (1.7-fold higher, p < 0.001, and 1.5-fold higher, p < 0.001) and oral (1.7-fold higher, p < 0.001, and 1.6-fold higher, p < 0.001) subgroups.

CONCLUSIONS

In conclusion, doses should be adjusted according to CYP2D6 genotype when initiating treatment with aripiprazole LAI or tablets, while advanced age do not affect the exposure of the active moiety of aripiprazole treatment regardless of formulation.

Real-Life Peak and Trough Dabigatran Plasma Measurements over Time in Hospitalized Geriatric Patients with Atrial Fibrillation

BACKGROUND

Few geriatric patients were included in studies on direct oral anticoagulants and data on dabigatran concentration and safety are needed in this population. Our objectives were to evaluate peak and trough dabigatran plasma concentrations over time in a geriatric population and to identify factors associated with dabigatran plasma concentrations and to assess the relationship with bleeding events.

METHODS

Peak and trough dabigatran plasma concentration were performed 4,8,15,30,45 days after inception of dabigatran treatment in 68 consecutive patients ≥75 years old hospitalized in a geriatric hospital with atrial fibrillation. Bleeding events were monitored for 1 year.

RESULTS

Mean age was 85.8(5.1) years old and 76.5% were women. Overall, 541 dabigatran plasma measurements (270 peak, 271 trough) were performed. Mean dabigatran concentrations of the 5 sequential measurements ranged 106-146ng/mL for peak and 66-84ng/mL for trough. Renal failure was associated with high peak and trough dabigatran concentration. Inter- and intra-individual coefficients of variation were 59.5% and 44.7% for peak and 74.5% and 44.6% for trough. Participants in the lower two tertiles of dabigatran concentration at day 8 (D8) remained below the 90th percentile (243.9ng/ml) on the next measurements. Bleeding events were associated with high trough dabigatran concentrations. Trough dabigatran concentration at D8>243.9ng/mL significantly predicted bleeding.

CONCLUSION

In this geriatric population, renal function and low albumin were associated with dabigatran concentrations. Despite large variability, participants in the lower two tertiles of dabigatran concentration at D8 remained below the 90th percentile on the following measurements. D8 dabigatran trough concentration≥243.9ng/mL identified patients at risk of bleeding.

The Effects of Yoga on Pain, Mobility, and Quality of Life in Patients with Knee Osteoarthritis: A Systematic Review

Objective. To systematically assess the effects of yoga on pain, mobility, and quality of life in patients with knee osteoarthritis. Methods. Pubmed, Medline, EMBASE, the Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), and other sources were searched systematically in this study. Two reviewers identified eligible studies and extracted data independently. Downs and Black's Quality Index were used to evaluate the methodological quality of the included studies. Results. A total of 9 articles (6 studies) involving 372 patients with knee osteoarthritis met the inclusion criteria. The most common yoga protocol is 40~90 minutes/session, lasting for at least 8 weeks. The effect of yoga on pain relief and function improvement could be seen after two-week intervention. Conclusion. This systematic review showed that yoga might have positive effects in relieving pain and mobility on patients with KOA, but the effects on quality of life (QOL) are unclear. Besides, more outcome measure related to mental health of yoga effects on people with KOA should be conducted.

Effects of age and sex on the single-dose pharmacokinetics and pharmacodynamics of apixaban

BACKGROUND AND OBJECTIVES

The effects of age and sex on apixaban pharmacokinetics and pharmacodynamics were studied.

METHODS

This was an open-label, single-dose, 2 × 2 factorial study. Healthy young (aged 18-40 years) and elderly (aged ≥ 65 years) male and female subjects received a single oral 20 mg dose of apixaban. Blood and urine samples were collected for pharmacokinetic and pharmacodynamic (blood only) analyses. Subjects were monitored for adverse events throughout the study.

RESULTS

Seventy-nine subjects were enrolled into four groups: young males (n = 20), elderly males (n = 20), young females (n = 20) and elderly females (n = 19). Age did not affect the maximum observed plasma concentration (C max). The mean area under the concentration-time curve from time zero extrapolated to infinite time (AUC∞) was 32% greater in elderly subjects than in young subjects. The mean C max and AUC∞ values were 18 and 15% higher, respectively, in females than in males. The time course of the mean international normalized ratio (INR), modified prothrombin time (mPT) and anti-Xa activity tracked the apixaban concentration-time curve. All three pharmacodynamic measures exhibited a positive linear correlation with the plasma apixaban concentration. Differences in the mean INR, mPT and anti-Xa activity between age and sex groups were small (<15% at the maximum mean values) and were generally related to pharmacokinetic differences. However, anti-Xa activity demonstrated less variability than the INR or mPT, and may have utility as a bioassay for apixaban. Apixaban was well tolerated, with no serious adverse events.

CONCLUSION

There were no clinically meaningful age- or sex-related differences in the pharmacokinetics and pharmacodynamics of apixaban that would require dose modification on the basis of age or sex alone.

Clinical and epidemiological profile of elderly patients with Chagas disease followed between 2005-2013 by pharmaceutical care service in Ceará State, Northeastern Brazil

By controlling the transmission of Chagas disease, the challenge of providing assistance to millions of infected patients that reach old age arises. In this study, the socioeconomic, demographic and comorbidity records of all elderly chagasic patients followed at the Pharmaceutical Care Service of the Chagas Disease Research Laboratory were assessed. The information related to the clinical form of the disease was obtained from medical records provided by the Walter Cantídio University Hospital. The profile of the studied population was: women (50.5%); mean age of 67 years; retired (54.6%); married (51.6 %); high illiteracy rate (40.2%); and family income equal to the minimum wage (51.5%). The predominant clinical forms of Chagas disease were cardiac (65.3%) and indeterminate (14.7%). The main electrocardiographic changes were the right bundle branch block (41.0%), associated or not with the anterosuperior left bundle branch block (27.4%). The average number of comorbidities per patient was 2.23 ± 1.54, with systemic arterial hypertension being the main one found (67.0%). It was found that the elderly comprise a vulnerable group of patients that associate aging with cardiac and/or digestive disorders resulting from the evolution of Chagas disease and other comorbidities, which requires special attention from health services to ensure more appropriate medical and social care.

The impracticality of biomedical rejuvenation therapies: translational and pharmacological barriers

The notion that it is possible to eradicate age-related degeneration and live a life with a negligible rate of senescence solely by using a physical "repair-oriented" approach is flawed on a number of fronts. Here, I will argue that there are so many unknown variables embedded in this line of thinking that make the final result impossible to predict. Two relatively easy-to-research areas are the search for successful cross-link breakers and an effective lysosomal degradation therapy. A more complex and speculative strategy is whole-body interdiction of lengthening of telomeres (WILT). Highlighting these as examples, I argue that it is unlikely that such rejuvenation biotechnologies will be used meaningfully by the general public. The discussion assumes that although such therapies may in theory one day be developed in the laboratory, and even possibly be formulated as physical clinical therapies, these will be unusable in practical terms when applied upon humans at large. Due to inherent characteristics of our biological, evolutionary, and psychological heritage, it is implausible that curing aging will occur by using physical interventions alone.

Effect of integrated yoga therapy on pain, morning stiffness and anxiety in osteoarthritis of the knee joint: A randomized control study

Aim:

To study the effect of integrated yoga on pain, morning stiffness and anxiety in osteoarthritis of knees.

Materials and Methods:

Two hundred and fifty participants with OA knees (35–80 years) were randomly assigned to yoga or control group. Both groups had transcutaneous electrical stimulation and ultrasound treatment followed by intervention (40 min) for two weeks with follow up for three months. The integrated yoga consisted of yogic loosening and strengthening practices, asanas, relaxation, pranayama and meditation. The control group had physiotherapy exercises. Assessments were done on 15^th (post 1) and 90^th day (post 2).

Results:

Resting pain (numerical rating scale) reduced better (P<0.001, Mann–Whitney U test) in yoga group (post 1=33.6% and post 2=71.8%) than control group (post 1=13.4% and post 2=37.5%). Morning stiffness decreased more (P<0.001) in yoga (post 1=68.6% and post 2=98.1%) than control group (post 1=38.6% and post 2=71.6%). State anxiety (STAI-1) reduced (P<0.001) by 35.5% (post 1) and 58.4% (post 2) in the yoga group and 15.6% (post 1) and 38.8% (post 2) in the control group; trait anxiety (STAI 2) reduced (P<0.001) better (post 1=34.6% and post 2=57.10%) in yoga than control group (post 1=14.12% and post 2=34.73%). Systolic blood pressure reduced (P<0.001) better in yoga group (post 1=−7.93% and post 2=−15.7%) than the control group (post 1=−1.8% and post 2=−3.8%). Diastolic blood pressure reduced (P<0.001) better in yoga group (post 1=−7.6% and post 2=−16.4%) than the control group (post 1=−2.1% and post 2=−5.0%). Pulse rate reduced (P<0.001) better in yoga group (post 1=−8.41% and post 2=−12.4%) than the control group (post 1=−5.1% and post 2=−7.1%).

Conclusion:

Integrated approach of yoga therapy is better than physiotherapy exercises as an adjunct to transcutaneous electrical stimulation and ultrasound treatment in reducing pain, morning stiffness, state and trait anxiety, blood pressure and pulse rate in patients with OA knees.

Use of benzodiazepines, depressive symptoms and cognitive function in old age

OBJECTIVE

Benzodiazepine use is more frequently observed in depressive and cognitively impaired subjects. The temporal relation behind this association is unknown. Here, we studied whether benzodiazepine use is associated with depressive symptoms and cognitive function and what the temporal relation underlying the associations is.

METHODS

Within the Leiden 85-plus Study, a prospective population based study of 599 subjects aged 85 years at baseline, we assessed benzodiazepine use, depressive symptoms, and cognitive function annually during a 5-year follow-up period.

RESULTS

Benzodiazepine users were more likely to be female, be institutionalized, and have a low education. Benzodiazepine users scored 0.76 points higher on the 15-item Geriatric Depression Scale than non-users (95% CI: 0.27-1.25, p = 0.002). They were 1.6-fold more likely to develop new depressive symptoms in 1 year when compared to non-users (95% CI: 1.05-2.55, p = 0.028). Benzodiazepine use did not associate with cognitive function, but discontinued benzodiazepine users had a 4.0 points lower Mini Mental State Examination (MMSE) score in the year before discontinuation than continued benzodiazepine users (95% CI: 1.31-6.73, p = 0.004).

CONCLUSIONS

In old age the use of benzodiazepines is associated with depressive symptoms and the use of benzodiazepines may precede the development of depressive symptoms. Treating physicians seem to be aware of the detrimental effects of benzodiazepines on cognitive function. However, they should be cautious in prescribing a new benzodiazepine in old age and monitor elderly benzodiazepine users for development of depressive symptoms.

Cellular senescence, ageing and disease

Cellular senescence is the irreversible growth arrest of individual mitotic cells, which as a consequence display a radically altered phenotype that is thought to impair tissue function and predispose tissues to disease development and/or progression as they gradually accumulate. However, in the past, research into mechanisms of ageing has commonly been researched and treated separately from disease development. This may partly be due to the lack of understanding concerning mechanisms of ageing and the difficulty in implementing what was known into models of disease development. Only in the last 10 years, with increasing knowledge of the senescent phenotype and the ability to detect senescent cells in human tissues, have biologists been able to investigate the relationship between cellular senescence and disease. This review therefore brings together and discusses recent findings which suggest that cellular senescence does contribute to ageing and the development/progression of disease.

Opioids for nonmalignant pain

Pain is the most common symptom in the world for which patients seek professional help. Opioids offer an appropriate and safe treatment for some but not all patients with nonmalignant chronic pain. Potential risks, including drug abuse and intolerable side effects, appear to be manageable or even preventable in most cases. Patients with persistent rheumatic pain who have failed traditional treatments should be considered for long-acting opioids. Opioids are best administered in the framework of weighing the good against the bad in each patient, recognizing the potential morbidity and sometimes mortality in untreated patients who have severe and disabling pain daily.

Pharmacokinetics and pharmacodynamics of the direct oral thrombin inhibitor dabigatran in healthy elderly subjects

OBJECTIVES

To investigate the pharmacokinetic and pharmacodynamic profile of dabigatran in healthy elderly subjects; to assess the intra- and interindividual variability of dabigatran pharmacokinetics in order to assess possible gender differences; and to assess the effect of pantoprazole coadministration on the bioavailability of dabigatran.

STUDY DESIGN AND SETTING

Open-label, parallel-group, single-centre study, consisting of a baseline screening visit, 7-day treatment period and post-study examination visit.

SUBJECTS AND INTERVENTION

36 healthy elderly subjects (aged > or =65 years) with a body mass index of 18.5-29.9 kg/m(2). Subjects were randomized to receive dabigatran etexilate either with or without coadministration of pantoprazole. Dabigatran etexilate was administered as capsules at 150 mg twice daily over 6 days and once on the morning of day 7. Pantoprazole was administered at 40 mg twice daily, starting 2 days prior to dabigatran etexilate administration and ending on the morning of day 7.

MAIN OUTCOME MEASURES

The primary pharmacokinetic measurements included the area under the plasma concentration-time curve at steady state (AUC(ss)), maximum (C(max,ss)) and minimum (C(min,ss)) plasma concentrations at steady state, terminal half-life (t((1/2))), time to reach C(max,ss) and renal clearance of dabigatran. The secondary pharmacokinetic parameters included the mean residence time, total oral clearance and volume of distribution. The pharmacodynamic parameters measured were the blood coagulation parameters ecarin clotting time (ECT) and activated partial thromboplastin time (aPTT).

RESULTS

With twice-daily administration of dabigatran etexilate, plasma concentrations of dabigatran reached steady state within 2-3 days, which is consistent with a t((1/2)) of 12-14 hours. The mean (SD) peak plasma concentrations on day 4 of treatment in male and female elderly subjects were 256 ng/mL (21.8) and 255 ng/mL (84.0), respectively. The peak plasma concentrations were reached after a median of 3 hours (range 2.0-4.0 hours). Coadministration with pantoprazole decreased the average bioavailability of dabigatran (the AUC(ss)) by 24% (day 4; 90% CI 7.4, 37.8) and 20% (day 7; 90% CI 5.2, 33.3). Intra- and interindividual pharmacokinetic variability in the overall population was low (<30% coefficient of variation), indicating that dabigatran has a predictable pharmacokinetic profile. Prolongation of the ECT and aPTT correlated with, and paralleled, the plasma concentration-time profile of dabigatran, which demonstrates a rapid onset of action without a time delay, and also illustrates the direct mode of action of the drug on thrombin in plasma. The ECT increased in direct proportion to the plasma concentration, and the aPTT displayed a linear relationship with the square root of the plasma concentration. The mean AUC(ss) was 3-19% higher in female subjects than in male subjects, which was likely due to gender differences in creatinine clearance. The safety profile of dabigatran was good, with and without pantoprazole coadministration.

CONCLUSIONS

Dabigatran demonstrated reproducible and predictable pharmacokinetic and pharmacodynamic characteristics, together with a good safety profile, when administered to healthy elderly subjects. Minor gender differences were not considered clinically relevant. The effects of pantoprazole coadministration on the bioavailability of dabigatran were considered acceptable, and dose adjustment is not considered necessary.

Pharmacodynamics in older adults: a review

BACKGROUND

Older individuals experience physiologic changes in organ function related to aging or to specific disease processes. These changes can affect drug pharmacodynamics in older adults.

OBJECTIVE

The goal of this article was to review age-related changes in pharmacodynamics and their clinical relevance.

METHODS

PubMed and International Pharmaceutical Abstracts were searched (January 1980-June 2006) for the following combination of terms: pharmacodynamic and elderly, geriatric or aged. References cited in other reviews were also evaluated. The current review focused on age-related pharmacodynamic changes in agents affecting the central nervous system (CNS), cardiovascular, and endocrine functions.

RESULTS

Older adults frequently demonstrate an exaggerated response to CNS-active drugs. This is in part due to an underlying age-related decline in CNS function and in part due to increased pharmacodynamic sensitivity for some benzodiazepines, anesthetics, and opioids. The most important pharmacodynamic differences with age for cardiovascular agents are the decrease in effect for beta-adrenergic agents. This decline in response in vascular, cardiac, and pulmonary tissue may be due to a decrease in Gs protein interactions. Most studies indicate there is no decrease in cx-receptor sensitivity with age. Angiotensin-converting enzyme inhibitors do not show age-related differences in elderly patients. With the dihydropyridine calcium channel blockers, there was a slight increase in effect for older adults, but this was only for treatment-naive patients and was transient. Nondihydropyridines did not show an age- associated change in pharmacodynamic effect; however, in the elderly, there appeared to be a decrease in the PR interval prolongation normally seen with these agents. Studies of diuretics indicated that the changes in diuretic and natriuretic effects seen in the elderly were associated with pharmacokinetic changes and were not pharmacodynamic in nature. There was a lack of consistent evidence regarding whether sulfonylureas show age-related changes in pharmacodynamic effect.

CONCLUSIONS

There is a general trend of greater pharmacodynamic sensitivity in the elderly; however, this is not universal, and these age-related changes must be investigated agent-by-agent until further research yields greater understanding of the molecular mechanisms underlying the aging process.

Integrated pharmacokinetics and pharmacodynamics in drug development

Drug development is a complex, lengthy and expensive process. Pharmaceutical companies and regulatory authorities have recognised that the drug development process needs optimisation for efficiency in view of the return on investments. Pharmacokinetics and pharmacodynamics are the two main principles determining the relationship between dose and response. This article provides an update on integrated approaches towards drug development by linking pharmacokinetics, pharmacodynamics and disease aspects into mathematical models. Gradually, a transition is taking place from a rather empirical approach towards a modelling- and simulation-based approach to drug development. The main learning phases should be phases 0, I and II, whereas phase III studies should merely have a confirmatory purpose. In model-based drug development, mechanism-based mathematical models, which are iteratively refined along the path of development, incorporate the accumulating knowledge of the investigational drug, the disease and their mutual interference in different subsets of the target population. These models facilitate the design of the next study and improve the probability of achieving the projected efficacy and safety endpoints. In this article, several theoretical and practical aspects of an integrated approach towards drug development are discussed, together with some case studies from different therapeutic areas illustrating the application of pharmacokinetic/pharmacodynamic disease models at different stages of drug development.

Detection and prevention of prescriptions with excessive doses in electronic prescribing systems

INTRODUCTION

Dose dependent adverse drug reactions are often caused by prescribing errors ignoring upper dose limits. Thus, computerised physician order entry incorporating maximum recommended therapeutic doses (MRTDs) might reduce prescriptions of excessive doses. We evaluated the suitability of MRTD information as published in the Summary of Product Characteristics (SPC) (MRTD(SPC)) or by the US Food and Drug Administration (MRTD(FDA)) and the value of Defined Daily Doses (DDD, World Health Organisation) as knowledge bases for an alerting system.

METHODS

In a large set of critical-dose drugs (N = 140) we compared MRTD(FDA) and DDD values with the corresponding German MRTD(SPC). We then retrospectively assessed a set of 633 electronically prescribed drugs (EPDs) issued at a university hospital and calculated prescription rates of excessive doses.

RESULTS

MRTD(FDA) was similar to MRTD(SPC) in 37% (N = 140), higher in 32%, and lower in 31% of drugs. On average, available DDD values (N = 129) were 1.6 times lower than MRTD(SPC), with 64% being lower, 33% similar, and 3% larger than MRTD(SPC). Prescription rates of excessive doses according to MRTD(FDA) were 2.5-fold higher (6.1%) than according to MRTD(SPC) (2.5%) (p < 0.01). However, only one in four EPDs categorised as overdosed according to MRTD(FDA) exceeded MRTD(SPC), and MRTD(FDA) values were available only for 67% of all assessed EPDs.

CONCLUSION

Our study revealed a remarkable number of prescriptions with doses exceeding approved limits. Their prevention appears feasible but the choice of an appropriate database for MRTDs is essential, and differences between available information sources are large.