Potential Drug-Drug Interactions among Patients with Schizophrenia Spectrum Disorders: Prevalence, Association with Risk Factors, and Replicate Analysis in 2021.

Background and Objectives: Patients with schizophrenia are often exposed to polypharmacotherapy, which may lead to drug-drug interactions. The aim of the study was to investigate the prevalence of potential drug-drug interactions (pDDIs) in hospitalized patients with schizophrenia spectrum disorders and to identify factors associated with pDDIs and manifested symptoms and signs. Materials and Methods: This cross-sectional observational study included 311 inpatients admitted to a psychiatric hospital. The LexiComp drug interaction program was used to identify pDDIs in 2014. Factors associated with the prevalence of pDDIs and factors related to clinically observed symptoms and signs were assessed using multivariable regression. In addition, replicate analysis of pDDI was performed using 2021 program updates. Results: The prevalence of pDDIs was 88.7%. Our study showed that more than half of the patients received at least one drug combination that should be avoided. The most common pDDIs involved combinations of two antipsychotics or combinations of antipsychotics and benzodiazepines, which can lead to cardio-respiratory depression, sedation, arrhythmias, anticholinergic effects, and neuroleptic malignant syndrome. The number of prescribed drugs was a risk factor for pDDIs (OR 2.85; 95% CI 1.84-5.73). All groups of clinically observed symptoms and signs were associated with the number of drugs. In addition, symptoms and signs characteristic of the nervous system and psychiatric disorders were associated with antipsychotic dosage (IRR 1.33; 95% CI 1.12-1.58), which could contribute to the development of extrapyramidal syndrome, insomnia, anxiety, agitation, and bipolar mania. The 2021 version of the drug interaction program showed a shift in drug interactions toward a lower risk rating, implying less severe patient management and possibly less alert fatigue. Conclusions: Patients with schizophrenia spectrum disorders are at high risk of developing drug-drug interactions. Optimization of drug therapy, patient monitoring, and use of drug interaction programs could help to prevent pDDIs and subsequent adverse drug events.

Downregulation of ABCB1 gene in patients with total hip or knee arthroplasty influences pharmacokinetics of rivaroxaban: a population pharmacokinetic-pharmacodynamic study.

PURPOSE: Rivaroxaban is a substrate for ABCB1 transporter and is commonly used in patients undergoing hip or knee replacement surgery for thromboprophylaxis. The objective of this study was to develop a population pharmacokinetic-pharmacodynamic (PK-PD) model to investigate the influence of ABCB1 gene expression and polymorphism on rivaroxaban exposure and anticoagulation effects. METHODS: Five blood samples per patient were collected during 5 days after the surgery for the determination of rivaroxaban concentration in plasma and for determination of prothrombin time and partial thromboplastin time. Non-linear mixed effects model was used for a population PK-PD analysis and for testing covariate effects. RESULTS: A one-compartment PK model with first-order absorption adequately described the pharmacokinetic data. The typical oral clearance (CL/F) was 6.12 L/h (relative standard error, 15.8%) and was associated with ABCB1 expression. Compared to base line before the surgery, a significant ABCB1 downregulation was observed 5 days after the surgery (p < 0.001). Prothrombin time and partial thromboplastin time were both linearly associated to the logarithm of the rivaroxaban plasma concentration. CONCLUSIONS: We confirmed that variable rivaroxaban CL/F is associated with ABCB1 expression, which is in accordance with previous studies on P-glycoprotein involvement in rivaroxaban PK. Furthermore, we observed the downregulation of ABCB1 expression after the surgery. The cause remains unclear and further research is needed to explain the underlying mechanisms.

Impact of drugs on venous thromboembolism risk in surgical patients.

PURPOSE: This review focuses on the most common drugs administered to surgical patients during the perioperative period that affect the risk of venous thromboembolism (VTE). RESULTS: Among analgesics, the risk of VTE is increased in patients treated with diclofenac, ibuprofen, and rofecoxib, but not naproxen, while metamizole can confer a protective effect. The relationship between sedatives and VTE has not been sufficiently studied. Tricyclic antidepressants, low-potency serotonin reuptake inhibitors, and antipsychotics have been associated with increased risk of VTE. The use of diuretics in the perioperative period is poorly researched; however, hyponatremia is considered a risk factor. Other factors that may influence the risk of VTE include bridging anticoagulation, allogeneic transfusion, and hemostatic management before surgery. Pharmacotherapy for HIV or cancer may also increase VTE risk. CONCLUSION: Increased monitoring for VTE is therefore advisable in surgical patients and those receiving antipsychotics, antidepressants, diuretics, or analgesics.

Population pharmacokinetics of rituximab in patients with diffuse large B-cell lymphoma and association with clinical outcome.

AIMS: Pharmacokinetic (PK) studies suggest that there is a room for improvement in clinical use of rituximab through more individualized treatment. The objective of this study was to characterize rituximab PK in 29 newly diagnosed patients with diffuse large B-cell lymphoma treated with rituximab in combination with cyclophosphamide, doxorubicin, vincristine and methylprednisolone every 3 weeks. We also evaluated the association of rituximab PK with clinical outcome. METHODS: Rituximab serum levels were determined by enzyme-linked immunosorbent assay and evaluated by a population PK analysis applying nonlinear mixed effects modelling. RESULTS: The data were best described by a two-compartment model comprising linear nonspecific clearance of 0.252 [95% confidence interval (CI): 0.227-0.279] l day-1 and time-varying specific clearance of 0.278 (95% CI: 0.181-0.390) l day-1 , corresponding to target-mediated drug disposition of rituximab. Nonspecific clearance was lower in older patients and those with lower body weight. Additionally, volume of the central compartment was higher in males. A clear association of clinical response with rituximab PK has been observed. Rate constant of specific clearance decay was 0.143 day-1 (95% CI: 0.0478-0.418) in patients with no disease progression, while in patients with disease progression it was 82.2% lower (95% CI: 33.4-95.0). CONCLUSIONS: This finding indicates that time-changes in clearance could serve as a predictive marker of response to rituximab. Our report demonstrates the rationale for studies evaluating higher doses of rituximab in selected patients.

Comparative analysis of three drug-drug interaction screening systems against probable clinically relevant drug-drug interactions: a prospective cohort study.

PURPOSE: Drug-drug interaction (DDI) screening systems report potential DDIs. This study aimed to find the prevalence of probable DDI-related adverse drug reactions (ADRs) and compare the clinical usefulness of different DDI screening systems to prevent or warn against these ADRs. METHODS: A prospective cohort study was conducted in patients urgently admitted to medical departments. Potential DDIs were checked using Complete Drug Interaction®, Lexicomp® Online™, and Drug Interaction Checker®. The study team identified the patients with probable clinically relevant DDI-related ADRs on admission, the causality of which was assessed using the Drug Interaction Probability Scale (DIPS). Sensitivity, specificity, and positive and negative predictive values of screening systems to prevent or warn against probable DDI-related ADRs were evaluated. RESULTS: Overall, 50 probable clinically relevant DDI-related ADRs were found in 37 out of 795 included patients taking at least two drugs, most common of them were bleeding, hyperkalemia, digitalis toxicity, and hypotension. Complete Drug Interaction showed the best sensitivity (0.76) for actual DDI-related ADRs, followed by Lexicomp Online (0.50), and Drug Interaction Checker (0.40). Complete Drug Interaction and Drug Interaction Checker had positive predictive values of 0.07; Lexicomp Online had 0.04. We found no difference in specificity and negative predictive values among these systems. CONCLUSION: DDI screening systems differ significantly in their ability to detect probable clinically relevant DDI-related ADRs in terms of sensitivity and positive predictive value.

Prescribing patterns for inpatients with schizophrenia spectrum disorders in a psychiatric hospital in Slovenia: Results of 16-month prospective, non-interventional clinical research.

BACKGROUND: In Slovenia, there has been no evidence about the prescribing patterns for inpatients with psychotic disorders. The research aims to analyze drug utilization patterns for inpatients with psychotic disorder that are coded as F20-F29 according to International Classification of Diseases (ICD) 10th revision (schizophrenia spectrum disorders). SUBJECTS AND METHODS: Prospective research was conducted at the Psychiatric Hospital Idrija. The medical records of the inpatients admitted over a 12-month period were collected from the beginning to the end of their hospitalization. RESULTS: A total of 311 inpatients with 446 hospitalizations were included, producing a total of 3954 medication prescriptions. Medications prescribed pro re nata (the use of as needed) were also taken into account. Antipsychotics (N=1149, 43% of prescriptions) were the most often prescribed medications, followed by anxiolytics, antiparkinsonians, antidepressants, mood stabilizers and cardiovascular drugs. A total of 256 (82%) inpatients received at least one pro re nata medication. It was observed that the studied population was treated with one antipsychotic on 27 percent of prescriptions. CONCLUSIONS: Inpatients with schizophrenia spectrum disorders were exposed to a large number of different drugs. They were not received only psychotropic drugs but also other medications. With the knowledge about medications the implementation of clinical pharmacy services to the psychiatrists would significantly improve medication of inpatients with psychotic disorders and polypharmacotherapy.

Drug-drug interaction software in clinical practice: a systematic review.

PURPOSE: Several electronic databases which report the prevalence of drug-drug interactions (DDIs) are used as a tool for evaluation of potentially harmful DDIs. The aim of our review was to evaluate the usability and appropriateness of commercially available electronic databases which assess the prevalence of potential DDIs. METHODS: The systematic electronic literature search was conducted with the following search terms: "database" AND "software," and "drug-drug interactions" AND "database," and the inclusion and exclusion criteria were applied in order to identify the publications of interest. RESULTS: A total of 3766 papers were identified by systematic search. After applying inclusion and exclusion criteria, 38 publications were included in the analysis. The most commonly used software in the included studies was Micromedex® Drug-Reax, for which some authors argue to be the most reliable due to highest sensitivity. It gives information about clinical consequences of DDIs, classifies underlying mechanism and onset of the adverse outcome (either rapid, or delayed) as well as severity (such as minor, moderate, or major), and provides the level of evidence which supports this information. This data is also provided by Drug Interaction Facts®, Lexi-Interact®, and Pharmavista®. A small number of studies which compared assessment of DDIs with electronic database and the clinician's assessment showed large discrepancy in number and relevance of detected DDIs. The overlap was in some cases as low as 11 %. CONCLUSION: The deficiency of clinical relevance of detected DDIs should be addressed in the upcoming research as it would provide more relevant information to the prescribers' in clinical practice.

Febrile neutropenia in chemotherapy treated small-cell lung cancer patients.

BACKGROUND: Chemotherapy with platinum agent and etoposide for small-cell lung cancer (SCLC) is supposed to be associated with intermediate risk (10-20%) of febrile neutropenia. Primary prophylaxis with granulocyte colony-stimulating factors (G-CSFs) is not routinely recommended by the treatment guidelines. However, in clinical practice febrile neutropenia is often observed with standard etoposide/platinum regimen. The aim of this analysis was to evaluate the frequency of neutropenia and febrile neutropenia in advanced SCLC patients in the first cycle of standard chemotherapy. Furthermore, we explored the association between severe neutropenia and etoposide peak plasma levels in the same patients. METHODS: The case series based analysis of 17 patients with advanced SCLC treated with standard platinum/etoposide chemotherapy, already included in the pharmacokinetics study with etoposide, was performed. Grade 3/4 neutropenia and febrile neutropenia, observed after the first cycle are reported. The neutrophil counts were determined on day one of the second cycle unless symptoms potentially related to neutropenia occurred. Adverse events were classified according to Common Toxicity Criteria 4.0. Additionally, association between severe neutropenia and etoposide peak plasma concentrations, which were measured in the scope of pharmacokinetic study, was explored. RESULTS: Two out of 17 patients received primary GCS-F prophylaxis. In 15 patient who did not receive primary prophylaxis the rates of both grade 3/4 neutropenia and febrile neutropenia were high (8/15 (53.3%) and 2/15 (13.3%), respectively), already in the first cycle of chemotherapy. One patient died due to febrile neutropenia related pneumonia. Neutropenic events are assumed to be related to increased etoposide plasma concentrations after a standard etoposide and cisplatin dose. While the mean etoposide peak plasma concentration in the first cycle of chemotherapy was 17.6 mg/l, the highest levels of 27.07 and 27.49 mg/l were determined in two patients with febrile neutropenia. CONCLUSIONS: Our study indicates that there is a need to reduce the risk of neutropenic events in chemotherapy treated advanced SCLC, starting in the first cycle. Mandatory use of primary G-CSF prophylaxis might be considered. Alternatively, use of improved risk models for identification of patients with increased risk for neutropenia and individualization of primary prophylaxis based on not only clinical characteristics but also on etoposide plasma concentration measurement, could be a new, promising options that deserves further evaluation.

Routine real-time cost-effectiveness monitoring of a web-based depression intervention: a risk-sharing proposal.

BACKGROUND: A new health care technology must be cost-effective in order to be adopted. If evidence regarding cost-effectiveness is uncertain, then the decision maker faces two choices: (1) adopt the technology and run the risk that it is less effective in actual practice, or (2) reject the technology and risk that potential health is forgone. A new depression eHealth service was found to be cost-effective in a previously published study. The results, however, were unreliable because it was based on a pilot clinical trial. A conservative decision maker would normally require stronger evidence for the intervention to be implemented. OBJECTIVE: Our objective was to evaluate how to facilitate service implementation by shifting the burden of risk due to uncertainty to the service provider and ensure that the intervention remains cost-effective during routine use. METHODS: We propose a risk-sharing scheme, where the service cost depends on the actual effectiveness of the service in real-life setting. Routine efficacy data can be used as the input to the cost-effectiveness model, which employs a mapping function to translate a depression specific score into quality-adjusted life-years. The latter is the denominator in the cost-effectiveness ratio calculation, required by the health care decision maker. The output of the model is a "value graph", showing intervention value as a function of its observed (future) efficacy, using the €30,000 per quality-adjusted life-year (QALY) threshold. RESULTS: We found that the eHealth service should improve the patient's outcome by at least 11.9 points on the Beck Depression Inventory scale in order for the cost-effectiveness ratio to remain below the €30,000/QALY threshold. The value of a single point improvement was found to be between €200 and €700, depending on depression severity at treatment start. Value of the eHealth service, based on the current efficacy estimates, is €1900, which is significantly above its estimated cost (€200). CONCLUSIONS: The eHealth depression service is particularly suited to routine monitoring, since data can be gathered through the Internet within the service communication channels. This enables real-time cost-effectiveness evaluation and allows a value-based price to be established. We propose a novel pricing scheme where the price is set to a point in the interval between cost and value, which provides an economic surplus to both the payer and the provider. Such a business model will assure that a portion of the surplus is retained by the payer and not completely appropriated by the private provider. If the eHealth service were to turn out less effective than originally anticipated, then the price would be lowered in order to achieve the cost-effectiveness threshold and this risk of financial loss would be borne by the provider.

Determination of remifentanil in neonatal dried blood spots by liquid chromatography-tandem mass spectrometry.

Remifentanil is an ultra-short-acting synthetic opioid-class analgesic which might be increasingly used "off-label" as pain management during labour. Side effects in parturients during labour, and in the infant at birth are of particular concern, especially respiratory depression which is concentration-dependent, and can occur at levels as low as 3-5 ng mL-1. The safety of such use, particularly in newborns due to remifentanil placental transfer, has not been fully demonstrated yet, partly due to the lack of a suitable non-invasive analytical method. The aim of our work was to develop a sensitive method to monitor the levels of remifentanil in neonates by a non-invasive sampling of umbi lical cord blood to support efficacy and safety trials. The presented LC-MS method is sensitive enough to reliably quantify remifentanil in just 20 µL of blood at only 0.3 ng mL-1. The dried blood spot sample preparation included solvent extraction with subsequent solid-phase extraction. The method was validated in terms of accuracy, precision, recovery, matrix effect, and stability, and was successfully applied to a small pilot study. The estimated arterial blood concentrations at the time of delivery ranged from 0.2 to 0.3, and up to 0.9 ng mL-1 in neonatal, and maternal samples, respectively.

High prevalence of potential drug interactions affecting mycophenolic acid pharmacokinetics in nonmyeloablative hematopoietic stem cell transplant recipients.

OBJECTIVE: Mycophenolic acid (MPA) exposure is associated with clinical outcomes in hematopoietic cell transplant (HCT) recipients. Various drug interaction studies, predominantly in healthy volunteers or solid organ transplant recipients, have identified medications which impact MPA pharmacokinetics. Recipients of nonmyeloablative HCT, however, have an increased burden of comorbidities, potentially increasing the number of concomitant medications and potential drug interactions (PDI) affecting MPA exposure. Thus, we sought to be the first to characterize these PDI in nonmyeloablative HCT recipients. MATERIALS AND METHODS: We compiled PDI affecting MPA pharmacokinetics and characterized the prevalence of PDI in nonmyeloablative HCT recipients. A comprehensive literature evaluation of four databases and PubMed was conducted to identify medications with PDI affecting MPA pharmacokinetics. Subsequently, a retrospective medication review was conducted to characterize the cumulative PDI burden, defined as the number of PDI for an individual patient over the first 21 days after allogeneic graft infusion, in 84 nonmyeloablative HCT recipients. RESULTS: Of the 187 concomitant medications, 11 (5.9%) had a PDI affecting MPA pharmacokinetics. 87% of 84 patients had one PDI, with a median cumulative PDI burden of 2 (range 0 - 4). The most common PDI, in descending order, were cyclosporine, omeprazole and pantoprazole. CONCLUSION: Only a minority of medications (5.9%) have a PDI affecting MPA pharmacokinetics. However, the majority of nonmyeloablative HCT recipients had a PDI, with cyclosporine and the proton pump inhibitors being the most common. A better understanding of PDI and their management should lead to safer medication regimens for nonmyeloablative HCT recipients.

Cost-effectiveness of a novel e-health depression service.

OBJECTIVES: A recent trial assessed feasibility of an e-health service (" Improvehealth.eu ") to support depression care and reported positive outcomes. Our objective was to examine cost-effectiveness of the Improvehealth.eu service. A baseline model was used to evaluate cost and effects of the intervention. Given the high uncertainty in the input space, a series of alternative scenarios were evaluated to challenge the result. The aim was to find if conservative or even pessimistic estimates and assumptions could result in a change of the cost-effectiveness from the baseline model. MATERIALS AND METHODS: A probabilistic depression model combined with bootstrapping was built and populated with data from the literature and from the pilot efficacy trial of the e-health service. The core of the model was a stochastic mapping function that translated depression-specific outcomes to quality-adjusted life years. Correlated sampling was used to obtain unbiased and consistent piecewise linear transformation of Beck Depression Inventory scores to utilities. The results are shown as cost-effectiveness acceptability curves with value of information data. An extreme scenario analysis was then performed to deal with parameter, structural, and modeling uncertainty. RESULTS: Cost-effectiveness of the e-health service was favorable because of low cost and high efficacy of the intervention. Apart from the most pessimistic one, none of the 13 alternative scenarios changed the preferred alternative. CONCLUSIONS: Improvehealth.eu is cost-effective relative to usual care, given the available efficacy data. Results of the health economic evaluation were robust to alternative assumptions, despite considerable uncertainty in input data.

Oral treatment with etoposide in small cell lung cancer - dilemmas and solutions.

BACKGROUND: Etoposide is a chemotherapeutic agent, widely used for the treatment of various malignancies, including small cell lung cancer (SCLC), an aggressive disease with poor prognosis. Oral etoposide administration exhibits advantages for the quality of life of the patient as well as economic benefits. However, widespread use of oral etoposide is limited by incomplete and variable bioavailability. Variability in bioavailability was observed both within and between patients. This suggests that some patients may experience suboptimal tumor cytotoxicity, whereas other patients may be at risk for excess toxicity. CONCLUSIONS: The article highlights dilemmas as well as solutions regarding oral treatment with etoposide by presenting and analyzing relevant literature data. Numerous studies have shown that bioavailability of etoposide is influenced by genetic, physiological and environmental factors. Several strategies were explored to improve bioavailability and to reduce pharmacokinetic variability of oral etoposide, including desired and undesired drug interactions (e.g. with ketoconazole), development of suitable drug delivery systems, use of more water-soluble prodrug of etoposide, and influence on gastric emptying. In addition to genotype-based dose administration, etoposide is suitable for pharmacokinetically guided dosing, which enables dose adjustments in individual patient. Further, it is established that oral and intravenous schedules of etoposide in SCLC patients do not result in significant differences in treatment outcome, while results of toxicity are inconclusive. To conclude, the main message of the article is that better prediction of the pharmacokinetics of oral etoposide may encourage its wider use in routine clinical practice.

Organic anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants influence the pharmacokinetics and pharmacodynamics of raloxifene.

BACKGROUND: Raloxifene, a selective estrogen receptor modulator, exhibits quite large and unexplained interindividual variability in pharmacokinetics and pharmacodynamics. The aim of this study was to determine the role of organic-anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants in the pharmacokinetics and pharmacodynamics of raloxifene. METHODS: To test the role of OATP1B1 and OATP1B3 transporters on hepatic uptake of raloxifene and its metabolites an in vitro model of Chinese Hamster Ovary cells expressing OATP1B1 or OATP1B3 was employed. The influence of OATP1B1 and OATP1B3 genetic variants on in vivo pharmacokinetics and pharmacodynamics was evaluated in 53 osteoporotic postmenopausal women treated with raloxifene. RESULTS: Our in vitro results showed that raloxifene and two of the three metabolites, raloxifene-4'-ß-glucuronide (M2) and raloxifene-6,4'-diglucuronide (M3), interact with OATP1B1 and OATP1B3. Higher M3 and total raloxifene serum concentrations in patients correlated with lower serum levels of bone resorption marker, serum C-terminal telopeptide fragments of type I collagen, indicating a higher antiresorptive effect of raloxifene. Higher concentrations of M2 correlated with higher increase of lumbar spine bone mineral density supporting the raloxifene vertebral fracture specific protection effect. Finally, raloxifene, M3 and total raloxifene serum concentrations were significantly higher in patients with SLCO1B1 c.388A > G polymorphism and *1b haplotype implicating a considerable genetic effect on pharmacokinetics and pharmacodynamics of raloxifene. CONCLUSIONS: These findings indicate that SLCO1B1 c.388A > G polymorphism could play an important role in pharmacokinetics and pharmacodynamics of raloxifene.

Adverse drug events during transitions of care : Randomized clinical trial of medication reconciliation at hospital admission.

BACKGROUND: During transitions of care, patient's medications are prone to medication errors. This study evaluated the impact of pharmacist-led medication reconciliation at hospital admission on unintentional medication discrepancies and adverse drug events. METHODS: A randomized controlled clinical trial was conducted in 120 adult medical patients hospitalized in a tertiary hospital in Slovenia. In the intervention group, a pharmacist-led medication reconciliation was performed on admission, while the control group received usual care. Patient's drug treatment before admission was compared with their admission and inpatient treatment to identify discrepancies. The intention of discrepancies and related adverse drug events were assessed as a consensus of an expert panel. RESULTS: Included patients were elderly (median 72 years) and treated with polypharmacy (median 7 medications). Upon admission, discrepancies and unintentional discrepancies, representing a medication error, were identified in 61.2% (825/1347) and 18.3% (247/1347) of medications, respectively. In the intervention group, only 29.1% (37/127) of unintentional discrepancies were reported to the physicians in person. The majority of admission discrepancies (88%) persisted through hospitalization. Unintentional discrepancies resulted in 51 adverse drug events even during hospitalization. There were no differences between the intervention and control group in the occurrence of unintentional discrepancies (p = 0.481) or adverse drug events (p = 0.801). CONCLUSIONS: Medication reconciliation at hospital admission failed to reduce unintentional discrepancies and adverse drug events, possibly due to its poor integration into clinical practice. Discrepancies resulted in patient harm even during the short period of hospitalization, which warrants the implementation of medication reconciliation at hospital admission.

Raloxifene glucuronidation in human intestine, kidney, and liver microsomes and in human liver microsomes genotyped for the UGT1A1*28 polymorphism.

Raloxifene, a selective estrogen receptor modulator, exhibits quite large interindividual variability in pharmacokinetics and pharmacodynamics. In women, raloxifene is metabolized extensively by different isoforms of UDP-glucuronosyltransferase (UGT) to its glucuronides. To gain an insight into intestine, kidney, liver, and lung glucuronidation of raloxifene, human microsomes of all tested organs were used. Raloxifene-6-ß-glucuronide (M1) formation followed the Michaelis-Menten kinetics in intestinal, kidney, and liver microsomes; meanwhile, raloxifene-4'-ß-glucuronide (M2) formation followed the substrate inhibition kinetics. Human lung microsomes did not show any glucuronidation activity. The tissue intrinsic clearances for kidney, intestine, and liver were 3.4, 28.1, and 39.6 ml · min(-1) · kg(-1), respectively. The aim of our in vitro study was to explain the mechanism behind the observed influence of UGT1A1*28 polymorphism on raloxifene pharmacokinetics in a small-sized in vivo study (Br J Clin Pharmacol 67:437-444, 2009). Incubation of raloxifene with human liver microsomes genotyped for UGT1A1*28 showed a significantly reduced metabolic clearance toward M1 in microsomes from donors with *28 allele. On the contrary, no significant genotype influence was observed on the formation of M2 because of the high variability in estimated apparent kinetic parameters, although a clear trend toward lower glucuronidation activities was observed when UGT1A1*28 polymorphism was present. The liver intrinsic clearances of both homozygotes differed significantly, whereas the clearance of heterozygotes did not differ from the wild-type and the mutated homozygotes. In conclusion, our results show the high importance of the liver and intestine in raloxifene glucuronidation. Moreover, the significant influence of UGT1A1*28 polymorphism on metabolism of raloxifene was confirmed.

Basophil responsiveness and clinical picture of acetylsalicylic acid intolerance.

BACKGROUND: Exposure to acetylsalicylic acid (ASA) may exacerbate respiratory or skin diseases or induce anaphylactoid reactions in apparently healthy individuals. We wanted to evaluate specific responsiveness of basophils to ASA in correlation with the clinical picture. METHODS: We performed a prospective single-blind study of 59 subjects involved in clinical evaluation and/or ASA provocation testing. Whole blood basophils were stained with anti-CD63/CD123/HLA-DR mAbs after stimulation with 0.25 or 1 mg/ml ASA. RESULTS: We found that 40 subjects were ASA tolerant and 19 were ASA intolerant. Both groups had comparable manifestations of asthma and/or rhinitis (13 in the tolerant and 9 in the intolerant group). Intolerant subjects showed significantly higher basophil responsiveness to ASA in comparison to tolerant subjects, which was concentration-dependent in both groups. The ratio between responses at 1 mg/ml of ASA and at baseline (activation index) was analyzed according to the clinical picture. We demonstrate that the activation index was higher only in the intolerant subjects with anaphylactoid reactions, but not in a subgroup of subjects with asthma/rhinitis. The ROC calculations show that the optimal threshold activation index was more than 2.18. The sensitivity was 80% and the specificity was 83% in the subgroup with anaphylactoid reactions. In the asthma/rhinitis subgroup, the sensitivity was 78% and the specificity was 50%. CONCLUSIONS: Our study demonstrates that there is a significantly higher in vitro basophil response to ASA in intolerant as compared to tolerant subjects. ROC analyses suggest that this measurement might only have a diagnostic value in subjects without asthma and/or rhinitis.

A nonlinear mixed effects modelling analysis of topiramate pharmacokinetics in patients with epilepsy.

Topiramate pharmacokinetics is influenced by individual factors such as patient age, renal function and co-treatment. The aim of this study was to develop a population pharmacokinetic model of topiramate to assist dosage adjustments in individual patients. Steady-state topiramate plasma concentrations in patients with epilepsy were determined by HPLC using fluorescent labelling. Demographic, biochemical data and dosing history including concomitant drug therapy were collected from patients' charts. Nonlinear mixed effects modelling was used to fit a one-compartment pharmacokinetic model. The influence of patient weight and gender, body surface area, age, creatinine clearance, serum transaminases, topiramate daily dose and co-treatment with carbamazepine, valproic acid, benzodiazepines, and risperidone on topiramate pharmacokinetics was evaluated. Additionally, the relationship between topiramate plasma concentration and clinical response was investigated. Volume of distribution of topiramate was 0.518 l/kg. For a typical patient oral clearance was estimated at 1.47 l/h, with interindividual variability of 39.2%. Clearance was 70% higher in patients co-treated with carbamazepine and was found to increase with patient age. Somnolence was the most frequently observed adverse event. Incidence of headache was associated with topiramate plasma concentration. Somnolence, ataxia, tremor, speech disorders and fatigue were associated with adjunctive therapy with carbamazepine, valproic acid, benzodiazepines, risperidone, and clozapine. No association of topiramate plasma concentration with frequency of seizures or patient quality of life was observed. The developed model can be used for Bayesian estimation of pharmacokinetic parameters based on sparse plasma samples and for selection of optimum dosing in routine patient care.

Cost-effectiveness analysis of HPV vaccination alongside cervical cancer screening programme in Slovenia.

BACKGROUND: The objective of the present study is to evaluate the cost-effectiveness of human papillomavirus (HPV) vaccination alongside cervical cancer screening programme in Slovenia. METHODS: A previously published Markov model representing natural history of HPV infection was adapted to Slovenian context. The model followed a cohort of 12-year-old girls to 85-year-old women. Two strategies were compared: HPV vaccination alongside conventional cytological screening versus screening alone. Analysis was performed from the health care payer perspective. RESULTS: Vaccination with screening compared with screening alone was associated with an incremental cost-effectiveness ratio (ICER) of 23,178 EUR per quality adjusted life-year (QALY) gained and 54,536 EUR per life-year gained (LYG) at the discounting rate of 5%. Sensitivity analyses demonstrated that the ICER was most sensitive to the need for booster dose and to different values of discount rates. In case the booster dose was assumed 10 years after initial vaccination, the ICER value was increased to 58,690 EUR per QALY. On the other hand, using lower values of discount rates than the base case 5% significantly reduced the ICER value. CONCLUSION: According to the cost-effectiveness thresholds of 30,000 EUR per QALY which was adopted by the Health Council in Slovenia, HPV vaccination alongside screening programme can be regarded as cost-effective. However, cost-effectiveness of HPV vaccination would become questionable in case a booster dose was needed to provide lifetime protection.

Rapid high-performance liquid chromatography method for determination of pregabalin in a pharmaceutical dosage form following derivatization with fluorescamine.

A simple, fast, and sensitive HPLC method was developed and validated for the evaluation of pregabalin in a pharmaceutical dosage form using fluorescamine as a derivatization agent for the first time. After a precolumn derivatization (5 min, room temperature), the reaction mixture was chromatographed on a C18 column with isocratic elution using 0.2% of triethylamine in a mixture of methanol and water (10 + 90, v/v). 3-Aminopentanoic acid was used as the internal standard. Using fluorescent detection (lamdaex 395 nm, lamdaem 476 nm), a low detection limit of 0.02 microg/mL was reached. The method was linear (r > 0.999) over the lower (0.125-25 microg/mL) and higher (1.25-250 microg/mL) concentration range. The intraday and interday precision of the QC samples was < 4.3%, and the accuracy was 94.2-102.5%. The samples were stable for 24 h at 4 degrees C. The robustness study showed that the derivatization is more robust than the chromatography method. The method was applied for the analysis of pregabalin content in 25, 75, and 300 mg capsules, and a good agreement was found with the declared amount of pregabalin (the relative error did not exceed 3.2%). Finally, the method was successfully used for dissolution studies of pregabalin capsules.