An alternative method for population pharmacokinetic data analysis under noncompliance

Noncompliance presents a persistent problem while analyzing PK data from outpatient clinical studies. Ignoring dose omission or making uninformed assumptions about patient drug intake history can prove detrimental to the objectives of the analysis (e.g. determining the PK model parameters or identifying covariates) and ultimately compromise the interpretation of the data. In order to overcome this problem, an alternative method of handling noncompliant data is evaluated in this report. The proposed approach is based on the principle of superposition and works by separating the estimation of the elimination rate from the model based steady-state PK concentration. Simulations implementing this method under different scenarios of noncompliance demonstrate that it performs better than the conventional method of analyzing population PK data when compared on the basis of bias and imprecision in parameter estimation and power (and type I error) for covariate detection. Overall, the new method exhibits great potential to address the issue of uncertain/unreliable dosing histories frequently encountered in clinical trials.     

Simultaneous versus sequential pharmacokinetic-pharmacodynamic population analysis using an iterative two-stage Bayesian technique

A method for simultaneous pharmacokinetic-pharmacodynamic (PK-PD) population analysis using an Iterative Two-Stage Bayesian (ITSB) algorithm was developed. The method was evaluated using clinical data and Monte Carlo simulations.Data from a clinical study with rocuronium in nine anesthetized patients and data generated by Monte Carlo simulation using a similar study design were analysed by sequential PK-PD analysis, PD analysis with nonparametric PK data and simultaneous PK-PD analysis. Both PK and PD data sets were 'rich' with respect to the number of measurements per individual. The accuracy and precision of the estimated population parameters were evaluated by comparing their mean error (ME) and root mean squared error (RMSE), respectively. The influence of PD model misspecification on the results was also investigated.The simultaneous PK-PD analysis resulted in slightly more precise population parameter estimates than the sequential PK-PD analysis and the nonparametric PK method. In the presence of PD model misspecification, however, simultaneous analysis resulted in poor PK parameter estimates, while sequential PK-PD analysis performed well.In conclusion, ITSB is a valuable technique for PK-PD population analysis of rich data sets. The sequential PK-PD method is better suited for the analysis of rich data than the simultaneous analysis.     

Evaluation of dried blood spots as an alternative sample matrix for equine antidoping analysis

Controlling the abuse of prohibited substances such as anabolic steroids, selective androgen receptor modulators, β-adrenoceptor agonists, and blood doping agents is of great interest to racing authorities. The use of dried blood spots (DBS) as an alternative sampling approach may be a feasible approach for controlling the use of these agents. To assess the feasibility of using DBS in equine blood, an 11-min liquid chromatography–mass spectrometry method was developed on a triple quadrupole mass spectrometer following extraction from Whatman 903 DBS cards. A total of 50 compounds across multiple compound classes were detectable with reproducible results. The stability was assessed with good results after almost 3 months of storage at ambient temperatures. These results suggest that the use of DBS may be a feasible alternative sampling approach in equine drug testing.     

Rapid inexpensive assay method for verapamil by spectrophotometric sequential injection analysis

Sequential injection analysis (SIA) technique with a miniaturized fibre optic spectrophotometry was exploited to optimize and validate a new method for the assay of verapamil in pharmaceutical formulations. The reduction of acidified permanganate by verapamil was spectrophotometrically detected at 546 nm. The 2(3) full-factorial design was adopted for screening the effect of conditions controlling the proposed method, and accordingly for the purpose of optimization. The remarkable advantages of the method are high rapidity (sample frequency was 10.6 samples/h), saving in reagents and sample (total consumed volume was 190 μl) and better safety for the environment (total waste production volume was 2140 μl). Additionally, the method was selective in the presence of excipients usually found in tablet and injection formulations. The average of recovery in synthetic samples as well as dosage forms was 98.8-103.0%. The obtained results were realized by the British Pharmacopoeia method and comparable results were obtained.     

Development of an in vitro alternative assay method for vaginal irritation

The vaginal mucosa is commonly exposed to chemicals and therapeutic agents that may result in irritation and/or inflammation. In addition to acute effects, vaginal irritation and inflammation can make women more susceptible to infections such as HIV-1 and herpes simplex virus 2 (HSV-2). Hence, the vaginal irritation potential of feminine care formulations and vaginally administered therapeutic agents is a significant public health concern. Traditionally, testing of such materials has been performed using the rabbit vaginal irritation (RVI) assay. In the current study, we investigated whether the organotypic, highly differentiated EpiVaginal? tissue could be used as a non-animal alternative to the RVI test. The EpiVaginal tissue was exposed to a single application of ingredients commonly found in feminine hygiene products and the effects on tissue viability (MTT assay), barrier disruption (measured by transepithelial electrical resistance, TEER and sodium fluorescein (NaFl) leakage), and inflammatory cytokine release (interleukin (IL)-1α, IL-1β, IL-6, and IL-8) patterns were examined. When compared to untreated controls, two irritating ingredients, nonoxynol 9 and benzalkonium chloride, reduced tissue viability to <40% and TEER to <60% while increasing NaFl leakage by 11–24% and IL-1α and IL-1β release by >100%. Four other non-irritating materials had minimal effects on these parameters. Assay reproducibility was confirmed by testing the chemicals using three different tissue production lots and by using tissues reconstructed from cells obtained from three different donors. Coefficients of variation between tissue lots reconstructed with cells obtained from the same donor or lots reconstructed with cells obtained from different donors were less than 10% and 12%, respectively. In conclusion, decreases in tissue viability and barrier function and increases in IL-1α and IL-1β release appear to be useful endpoints for preclinical screening of topically applied chemicals and formulations for their vaginal irritation potential.     

Evaluation of an International Pharmacopoeia method for the analysis of ritonavir by liquid chromatography

A gradient LC method for the determination of related substances in ritonavir (RTV) has been recently published in the International Pharmacopoeia. The method uses a base-deactivated reversed-phase C18 column kept at a temperature of 35 degrees C. The mobile phases consist of acetonitrile, phosphate buffer pH 4.0 and water. UV detection is performed at 240 nm. A system suitability test (SST) is described to govern the quality of the separation. Since no brand names of columns are mentioned in pharmacopoeial texts, analysts often have problems to select a suitable stationary phase which is only described in general terms. So, the separation towards RTV components was investigated on 18 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was further evaluated using a Hypersil BDS C18 column (25 cm x 4.6mm i.d.), 5 microm, which was also used for the development of the method. A central composite design was applied to examine the robustness of the method. The method shows good precision, linearity, sensitivity and robustness. Four commercial samples were examined using this method.     

Development and applications of a chemical method for sequential analysis of reducing oligosaccharides

A new method based on the chemical reaction has been devised for the sequential analysis of reducing oligosaccharides using 8-amino-2-naphthalenesulfonic acid (ANS), a fluorescent precolumn derivatization reagent for reducing saccharides. The procedure established includes 1) the derivatization of a reducing oligosaccharide to produce a Schiff base, 2) the reduction of the base with sodium cyanoborohydride (NaBH₃CN), 3) the methoxycarbonylation of the resultant secondary amino group, 4) the cleavage of the glycoside bond next to the reducing end, based on the intramolecular acid hydrolysis by the action of a sulfonic acid group of the ANS derivative, 5) the identification of the liberated reducing end by high-per-formance liquid chromatography (HPLC), and finally 6) the recovery of the resultant oligosaccharide fragment from the cleavage reaction mixture. The extensive examination of the conditions for the sequential analysis of reducing oligosaccharides resulted in the procedure of simplicity, high selectivity and high recovery. This procedure was found to be useful for the sequential analysis of di-, tri- and tetrasaccharides.     

Evaluation of an antibiotic intravenous to oral sequential therapy program

AIM: This study was designed to analyse the drug consumption difference and economic impact of an antibiotic sequential therapy focused on quinolones. METHOD: We studied the consumption of quinolones (ofloxacin/levofloxacin and ciprofloxacin) 6 months before and after the implementation of a sequential therapy program in hospitalised patients. It was calculated for each antibiotic, in its oral and intravenous forms, in defined daily dose (DDD/100 stays per day) and economical terms (drug acquisition cost). At the beginning of the program ofloxacin was replaced by levofloxacin and, since their clinical uses are similar, the consumption of both drugs was compared during the period. RESULTS: In economic terms, the consumption of intravenous quinolones decreased 60% whereas the consumption of oral quinolones increased 66%. In DDD/100 stays per day, intravenous forms consumption decreased 53% and oral forms consumption increased 36%. CONCLUSIONS: Focusing on quinolones, the implementation of a sequential therapy program based on promoting an early switch from intravenous to oral regimen has proved its capacity to alter the utilisation profile of these antibiotics. The program has permitted the hospital a global saving of 41420 dollars for these drugs during the period of time considered.     

Evaluation of an alternative mucosal irritation test using slugs

The objective of this study was to evaluate an alternative mucosal irritation test using the slug Arion lusitanicus as test organism. The effect of 28 reference substances on the mucosal tissue of the slugs was determined by the amount of mucus produced, the reduction in body weight, and the release of proteins from the body wall. The data of the mucosal irritation test were compared with the available in vivo Draize scores for eye irritation (MMAS). The amount of mucus produced and the reduction in body weight caused by a 60-min contact period were significantly correlated (r = 0.73) with the MMAS score for eye irritation. However, the mucus production was the best endpoint to classify the chemicals into the three categories corresponding the EU classification (NI, R36, and R41). Since irritating alcohols did not induce an increased mucus production and therefore the irritation potential of these molecules was underestimated, two prediction models were developed. For nonalcohols a 60-min contact period with the chemicals was sufficient and the molecules were classified according to the amount of mucus produced. A concordance, specificity, and sensitivity of 65, 100 and 83%, respectively, was obtained. For the alcohols a second 60-min contact period was necessary and the molecules were classified using the protein release as endpoint. Ninety-one percent of the alcohols were correctly classified with a sensitivity and specificity of 100%. We can conclude that the mucosal irritation test using slugs seems to be a reliable and promising method for the evaluation of the irritation potential of drugs instead of diverse tests using different animal models to estimate the irritation on human mucosal tissues.     

Evaluation of an International Pharmacopoeia method for the analysis of indinavir sulfate by liquid chromatography

A gradient LC method for the determination of indinavir sulfate (IDV) and its impurities has been recently published in a consultation document of the International Pharmacopoeia, WHO Drug Information. The method uses a base-deactivated reversed-phase C18 column (25 cm x 4.6 mm i.d.), 5 microm kept at a temperature of 40 degrees C. The mobile phases consist of acetonitrile, phosphate buffer pH 7.5 and water. The flow rate is 1.0 ml/min. UV detection is performed at 220 nm. A system suitability test (SST) is described to govern the quality of the separation. The separation towards IDV components was investigated on 16 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was evaluated using a Hypersil BDS C18 column (25 cm x 4.6 mm i.d.), 5 microm. A central composite design was applied to examine the robustness of the method. The method shows good precision, linearity, sensitivity and robustness. Six commercial samples were examined using this method.     

Evaluation of an alternative program for MMTP drop-outs: impact on treatment re-entry

INTRODUCTION: Retention in a Methadone Maintenance Treatment Program (MMTP) is predictive of abstaining from heroin and has other benefits. Many individuals leave treatment before they experience these positive outcomes. OBJECTIVE: This research project targeted MMTP drop-outs with an intervention designed to assist them in returning to drug treatment. METHODS: Subjects who had left MMTP within the prior 12 months were randomly assigned to intervention or comparison groups. The 3-month long intervention consisted of street outreach, cognitive behavioral groups, and individual counseling. Data were analyzed for 175 subjects who were out of treatment at baseline and who returned for a 6-month follow-up interview (Intervention group, N=111; Comparison group, N=64). RESULTS: A total of 87% of subjects assigned to the intervention condition participated in at least one component. Intervention subjects who attended two or more cognitive behavioral group sessions were more likely than those who attended 0-1 sessions or those in the comparison group to have returned to treatment during the 6 month follow up time period (72 vs. 53 vs. 50%, respectively, P<0.05, chi square test). CONCLUSION: MMTP drop-outs need not be lost to the drug treatment system if special efforts are made to engage them in interventions developed to encourage treatment re-entry.     

Evaluation of an alternative methodology for investigating leadership and binge drinking among sorority members

Recent research suggests that leaders in Greek organizations use alcohol more frequently and more heavily than non-leaders in Greek organizations. These results carry considerable implications for the majority of existing alcohol education programs that rely heavily on peer modeling. The purpose of the present study was to determine whether a more complex and realistic assessment of leadership involvement produced different results than the previous study. Results from 327 women in five randomly selected sororities provide evidence that binge drinking is related to some negative academic outcomes, but that a significant relationship between binge drinking and leadership involvement in Greek organizations does not exist. Furthermore, the results provide evidence that leadership styles do not influence the leadership involvement-binge drinking relationship.     

Development of an extraction method for mycobacterial metabolome analysis

As a prerequisite for studying the intracellular metabolome of mycobacteria, several methods were evaluated for efficient breakage of the cell using Mycobacterium bovis (BCG) as a model microorganism. Several pulping methods, treating with an Ultra-Turax, deep-freezing in liquid nitrogen followed by mechanical grinding, sonicating with probe head or cup horn and bead beating prior to solvent extraction were applied and compared. Gravimetry, electron microscopy, and nuclear magnetic resonance spectrometry were used to analyze the extracts. All analytical methods prove that sonicating is superior to mechanical grinding of deep-frozen cells. Two methods indicated that sonicating with a probe head enhances the efficiency of cell disruption compared to sonicating with a cup horn. The highest extract yield and chemical diversity were achieved by a combination of mechanical grinding and sonicating. Within the scope of a metabolomic analysis, the method of choice to treat mycobacterial cells is a combination of deep-freezing in liquid nitrogen and mechanical grinding followed by sonicating with a probe head.     

Adaptive group sequential test for clinical trials with changing patient population

In clinical trials, a standard group sequential test with a fixed number of planned interim analyses is usually considered to assess the effect of a test treatment under study. The standard group sequential test is statistically valid under the assumption that the patient population remains unchanged from one interim analysis to another. In practice, however, this assumption is often not met because the trial may be modified after the review of the clinical data at interim. As a result, the original patient population may have changed to a similar but different patient population. In this paper, we consider changes in patient population related to some covariates of an on-going trial through a linear regression model. Under this model, we can make inference on the original target population based on additional data from the changed populations. A new group sequential test procedure that accounts for the effect of population changes is proposed. A simulation was performed to evaluate the performance of the proposed method. The results indicate that the type I error rate of the proposed test procedure is well preserved, while the type I error rate of the standard group sequential test is inflated as the population changes. Statistical powers of the proposed group sequential test are also presented.