Margarida Castel-Branco

Linear regression for calibration lines revisited: weighting schemes for bioanalytical methods

When the assumption of homoscedasticity is not met for analytical data, a simple and effective way to counteract the greater influence of the greater concentrations on the fitted regression line is to use weighted least squares linear regression (WLSLR). The purpose of the present paper is to stress the relevance of weighting schemes for linear regression analysis and to show how this approach can be useful in the bioanalytical field. The steps to be taken in the study of the linear calibration approach are described. The application of weighting schemes was shown by using a high-performance liquid chromatography method for the determination of lamotrigine in biological fluids as a practical example. By using the WLSLR, the accuracy of the analytical method was improved at the lower end of the calibration curve. Bioanalytical methods data analysis was improved by using the WLSLR procedure.

Lamotrigine analysis in blood and brain by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatography assay was developed and validated to determine plasma and brain lamotrigine concentrations allowing pharmacokinetic-pharmacodynamic studies of this new antiepileptic drug in patients and laboratory animals. Lamotrigine and its internal standard were extracted, under alkaline conditions, from plasma and brain homogenate, into ethyl acetate; brain proteins were previously precipitated with trichloroacetic acid. The method was linear between 0.1 and 15.0 mg/l for plasma, with a detection limit of 0.008 mg/l, and between 0.1 and 5.0 mg/l for brain homogenate, with a detection limit of 0.023 mg/l. The method proved to be simple, useful and appropriate, not only for clinical and experimental research, but also for routine monitoring of lamotrigine concentrations in patients.

Disposition of eslicarbazepine acetate in the mouse after oral administration

Eslicarbazepine acetate is a promising antiepileptic drug structurally related to carbamazepine and oxcarbazepine, which is in the final phase of clinical development. The metabolism of eslicarbazepine acetate is clearly species dependent and, in this case, among small laboratory animals, the mouse seems to be the most relevant species to humans. Hence, the aim of this study was to investigate the plasma, brain and liver disposition of eslicarbazepine acetate in mice to better understand its disposition in humans. Adult male CD‐1 mice were treated orally with a single dose of eslicarbazepine acetate 350 mg/kg. Blood samples, brain and liver tissues were taken at 0.25, 0.5, 0.75, 1, 2, 4, 6, 10, 16 and 24 h post‐dose. Plasma and tissue levels of eslicarbazepine acetate and its metabolites (S‐licarbazepine, R‐licarbazepine and oxcarbazepine) were assessed by using high‐performance liquid chromatography‐ultraviolet detection. Both eslicarbazepine acetate and R‐licarbazepine concentrations were below the limit of quantification of the assay in all matrices. Eslicarbazepine acetate was rapidly and extensively metabolized to S‐licarbazepine (major metabolite), which was oxidized to oxcarbazepine to a small extent. The brain/plasma ratios suggest that the brain exposure to S‐licarbazepine and oxcarbazepine was approximately 30% of their total systemic exposure. However, S‐licarbazepine crossed the blood–brain barrier (BBB) less efficiently than oxcarbazepine. On the other hand, the liver/plasma ratios support the notion that S‐licarbazepine undergoes hepatic accumulation, whereas oxcarbazepine appears to leave this compartment twice as fast as S‐licarbazepine. Thus, the diffusion through the BBB is favourable to oxcarbazepine and the liver acts like a deposit of the pharmacologically active metabolite of eslicarbazepine acetate (S‐licarbazepine).

Stereoselective Disposition of S- and R-Licarbazepine in Mice

The stereoselective disposition of S-licarbazepine (S-Lic) and R-licarbazepine (R-Lic) was investigated in plasma, brain, liver, and kidney tissues after their individual administration (350 mg/kg) to mice by oral gavage. Plasma, brain, liver, and kidney concentrations of licarbazepine enantiomers and their metabolites were determined over the time by a validated chiral HPLC-UV method. The mean concentration data, attained at each time point, were analyzed using a non-compartmental model. S-Lic and R-Lic were rapidly absorbed from gastrointestinal tract of mouse and immediately distributed to tissues supplied with high blood flow rates. Both licarbazepine enantiomers were metabolized to a small extent, each parent compound being mainly responsible for the systemic and tissue drug exposure. The stereoselectivity in the metabolism and distribution of S- and R-Lic was easily identified. An additional metabolite was detected following R-Lic administration and S-Lic showed a particular predisposition for hepatic and renal accumulation. Stereoselective processes were also identified at the blood-brain barrier, with the brain exposure to S-Lic almost twice that of R-Lic. Another finding, reported here for the first time, was the ability of the mouse to perform the chiral inversion of S- and R-Lic, albeit to a small extent.

Developing an adherence in hypertension questionnaire short version: MUAH-16

The Maastricht Utrecht Adherence in Hypertension (MUAH) questionnaire provides clinicians with information about the causes of a patients poor adherence to antihypertensive drugs. In this study, the authors aimed to develop and validate a short version of the MUAH questionnaire. After an exploratory factor analysis, the number of MUAH items was reduced. The original MUAH questionnaire (model 1) was compared with the 16‐item MUAH short version (model 2). Next, this short version of MUAH (MUAH‐16) with all factors correlated (model 2a) was compared with the short version of MUAH with four subscales that contribute to a global factor of adherence (model 2b). Model 1 had a poor fit to the data (χ2269 = 663.41, P < .001, comparative fit index = 0.695, root mean square error of approximation = 0.06), and model 2 had a very good fit to the data (χ2100 = 171.07, P < .001, comparative fit index = 0.92, root mean square error of approximation = 0.04). When comparing model 2a with model 2b, the chi‐square difference of the model (Δχ22 = 4.06; P = .067) revealed that the fits of both models were not significantly different. These findings suggest that MUAH‐16 better represents a patients adherence to antihypertensive medication than the original MUAH questionnaire.

Identification of inhaler technique errors with a routine procedure in Portuguese community pharmacy

Background: A correct selection of drugs prescribed, but also the choice of the appropriate inhaler device, is crucial for the control of respiratory diseases. Objective: To evaluate the inhaler technique and identify potential errors of patients when treated with inhalers by testing a routinary procedure to be implemented in any community pharmacy. Methods: Adults with asthma/COPD and under inhalation therapy were invited to demonstrate how they use their inhalers. After direct observation it was registered whether all the sequential steps included in the summary of product characteristics (SmPC) were performed. Results: The study involved 67 patients from 4 community pharmacies (Portugal central region): 34 (50.7%) males, 65.4 (SD=18.28) years old, 42 (62.7%) with COPD, and 23 (34.3%) using more than one inhaler. The 67 patients used 95 inhalers, comprising: 57 (60.0%) multiple dose DPI (dry powder inhalers), 18 (18.9%) single dose DPI, 16 (16.8%) pMDI (pressurized metered dose inhalers), 2 (2.1%) pMDI+spacer and 2 (2.1%) SMI (soft mist inhalers). No errors were made only by 9 (13.4%) patients. In the 75 DPIs techniques, the most frequent errors were ‘no previous forced expiration’ (46=61.3%) and ‘no 10s apnea after inhalation’ (51=68.0%); in the 16 pMDIs techniques common errors were ‘lack of hand-lung coordination’ (7=43.8 %), ‘no previous forced exhalation’ (8=50.0%) and ‘no apnea after inhalation’ (10=62.5%). After inhaling from 56 devices containing corticosteroids, 34 (60.7%) of the patients did not wash their mouth. Conclusion: The study demonstrated the possibility of performing this procedure routinely in Portuguese community pharmacies and also its utility, since 58 (87%) of patients had at least one error during the inhalers use.

A case study of polypharmacy management in nine European countries: implications for change management and implementation.

Background Multimorbidity and its associated polypharmacy contribute to an increase in adverse drug events, hospitalizations, and healthcare spending. This study aimed to address: what exists regarding polypharmacy management in the European Union (EU); why programs were, or were not, developed; and, how identified initiatives were developed, implemented, and sustained. Methods Change management principles (Kotter) and normalization process theory (NPT) informed data collection and analysis. Nine case studies were conducted in eight EU countries: Germany (Lower Saxony), Greece, Italy (Campania), Poland, Portugal, Spain (Catalonia), Sweden (Uppsala), and the United Kingdom (Northern Ireland and Scotland). The workflow included a review of country/region specific polypharmacy policies, key informant interviews with stakeholders involved in policy development and implementation and, focus groups of clinicians and managers. Data were analyzed using thematic analysis of individual cases and framework analysis across cases. Results Polypharmacy initiatives were identified in five regions (Catalonia, Lower Saxony, Northern Ireland, Scotland, and Uppsala) and included all care settings. There was agreement, even in cases without initiatives, that polypharmacy is a significant issue to address. Common themes regarding the development and implementation of polypharmacy management initiatives were: locally adapted solutions, organizational culture supporting innovation and teamwork, adequate workforce training, multidisciplinary teams, changes in workflow, redefinition of roles and responsibilities of professionals, policies and legislation supporting the initiative, and data management and information and communication systems to assist development and implementation. Depending on the setting, these were considered either facilitators or barriers to implementation. Conclusion Within the studied EU countries, polypharmacy management was not widely addressed. These results highlight the importance of change management and theory-based implementation strategies, and provide examples of polypharmacy management initiatives that can assist managers and policymakers in developing new programs or scaling up existing ones, particularly in places currently lacking such initiatives.

Response to the letter entitled: Developing an adherence in hypertension questionnaire short version, MUAH-16: Statistical and methodological issues

To the Editor: Although we do not agree with their criticism, we would like to thank the interest showed by Salimi and Abdollahpour in our study.1 Several scale reduction techniques to obtain short versions of questionnaires are described,2 being the most prevalent those that maximize the scale’s internal consistency. Important limitations of these approaches exist, because choosing items to maximize internal consistency may lead to highly redundant items, narrowing content, and potentially making it low in validity.3,4 Stanton et al4 suggested that researchers may also need to examine other criteria beyond statistical relations to determine which items should remain in an abbreviated scale (eg, judgmental item qualities). Beaton et al5 evaluated 3 itemreduction techniques to develop a short and reliable version of the 30item DASH (disabilities of the arm, shoulder, and hand) outcome measure, concluding that the conceptretention technique, which allows for the selection of items based on their clinical relevance rather than on statistical testing alone, produced a comparable, if not slightly better, instrument than statistically driven approaches. Other researchers had used this methodology, reinforcing that the short versions obtained are more similar to the original instrument.6 Our development of the short version of MUAH was based on a process that integrates both theoretical and statistical decisions, associating the conceptretention technique to the results of an exploratory factor analysis (EFA). Thus, for each item, we considered not only its loading factor, but also its clinical relevance. Salimi and Abdollahpour’s statement about convergent validity is misleading because they mention only the correlation coefficients between the subscale “active coping with health problems” of MUAH16 with the global scores of MMAS8 and MAT. It is important to note that MMAS8 and MAT are instruments that result in overall adherence scores that positively and significantly correlate with overall MUAH16 scores (0.45 and 0.41, respectively). Neither MMAS8 nor MAT has items that address “active coping with health problems,” so small correlation with this domain is expected. When assessing convergent validity, domain description should be taken into consideration. A simple arithmetic calculation explains why reducing the number of items is always associated with a reduction in internal consistency coefficients.7-9 As we explained in the Study Strengths and Limitations section, measures of unidimensionality, such as factor analysis, are equally important to Cronbach alpha for homogeneity assessment of the instrument in shorter scales. Although with lower Cronbach alpha, confirmatory factor analysis for both models shows that MUAH16 has a better fit to the data than the original MUAH (χ2 [100] = 171.07, P < .001, CFI = 0.92, RMSEA = 0.04, vs χ2 [269] = 663.41, P < .001, CFI = 0.695, RMSEA = 0.06), suggesting that MUAH16 better represents each adherence dimension.