How to transform urban institutional green spaces into Ancillary Botanic Gardens to expand informal botanical learning opportunities in cities

Since many cities lack botanical gardens, we introduced the concept of Ancillary Botanic Gardens (ABG), which builds on the premise that organizations can expand informal botanical learning by adding a secondary function to their institutional green spaces. This study guides the application of the ABG concept in various spatial and functional contexts by offering practical and interpretive tools to organizations who are less used to working with nature but are interested in mitigating urban residents' detachment from nature. Online maps of 220 botanic gardens were reviewed to define types of plant collections and produce an exhaustive list of physical botanic garden elements. The collected information was developed into an ABG field checklist that was tested on three case studies in Lebanon and then used to develop guidelines for ABG establishment. The guidelines and checklist are meant to empower and guide organizations interested in establishing an ABG.

In pursuit of the triple crown: mechanism-based pharmacodynamic modelling for the optimization of three-drug combinations against KPC-producing Klebsiella pneumoniae

OBJECTIVES

Optimal combination therapy for Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp) is unknown. The present study sought to characterize the pharmacodynamics (PD) of polymyxin B (PMB), meropenem (MEM) and rifampin (RIF) alone and in combination using a hollow fibre infection model (HFIM) coupled with mechanism-based modelling (MBM).

METHODS

A 10-day HFIM was utilized to simulate human pharmacokinetics (PK) of various PMB, MEM and RIF dosing regimens against a clinical KPC-Kp isolate, with total and resistant subpopulations quantified to capture PD response. A MBM was developed to characterize bacterial subpopulations and synergy between agents. Simulations using the MBM and published population PK models were employed to forecast the bacterial time course and the extent of its variability in infected patients for three-drug regimens.

RESULTS

In the HFIM, a PMB single-dose ('burst') regimen of 5.53 mg/kg combined with MEM 8 g using a 3-hr prolonged infusion every 8 hr and RIF 600 mg every 24 hr resulted in bacterial counts below the quantitative limit within 24 hr and remained undetectable throughout the 10-day experiment. The final MBM consisted of two bacterial subpopulations of differing PMB and MEM joint susceptibility and the ability to form a non-replicating, tolerant subpopulation. Synergistic interactions between PMB, MEM and RIF were well quantified, with the MBM providing adequate capture of the observed data.

DISCUSSION

An in vitro-in silico approach answers questions related to PD optimization as well as overall feasibility of combination therapy against KPC-Kp, offering crucial insights in the absence of clinical trials.

Population Pharmacokinetics Modeling of Unbound Efavirenz, Atazanavir, and Ritonavir in HIV-Infected Subjects With Aging Biomarkers

Unbound drug is the pharmacodynamically relevant concentration. This study aimed to determine if chronologic age or markers of biologic aging, such as the frailty phenotype and p16INK4a gene expression, altered unbound pharmacokinetics (PKs) of efavirenz (EFV) and atazanavir/ritonavir (ATV/RTV). Sixty human immunodeficiency virus (HIV)-infected participants receiving EFV and 31 receiving ATV/RTV provided 1 to 11 samples to quantify total and unbound plasma concentrations. Population PK models with total and unbound concentrations simultaneously described are developed for each drug. The unbound fractions for EFV, ATV, and RTV are 0.65%, 5.67%, and 0.63%, respectively. Covariate analysis suggests RTV unbound PK is sensitive to body size; unbound fraction of RTV is 34% lower with body mass index (BMI) above 30 kg/m2 . No alterations in drug clearance or unbound fraction with age, frailty, or p16INK4a expression were observed. Assessing functional and physiologic aging markers to inform potential PK changes is necessary to determine if drug/dosing changes are warranted in the aging population.

p16INK4a , a Senescence Marker, Influences Tenofovir/Emtricitabine Metabolite Disposition in HIV-Infected Subjects

The goal of this study was to explore the relationships between tenofovir (TFV) and emtricitabine (FTC) disposition and markers of biologic aging, such as the frailty phenotype and p16^INK4a gene expression. Chronologic age is often explored in population pharmacokinetic (PK) analyses, and can be uninformative in capturing the impact of aging on physiology, particularly in human immunodeficiency virus (HIV)‐infected patients. Ninety‐one HIV‐infected participants provided samples to quantify plasma concentrations of TFV/FTC, as well as peripheral blood mononuclear cell (PBMC) samples for intracellular metabolite concentrations; 12 participants provided 11 samples, and 79 participants provided 4 samples, over a dosing interval. Nonlinear mixed effects modeling of TFV/FTC and their metabolites suggests a relationship between TFV/FTC metabolite clearance (CL) from PBMCs and the expression of p16^INK4a, a marker of cellular senescence. This novel approach to quantifying the influence of aging on PKs provides rationale for further work investigating the relationships between senescence and nucleoside phosphorylation and transport.

Management of obstetric anal sphincter injuries (OASIS) in subsequent pregnancy

Obstetric anal sphincter injuries (OASIS) are common and may greatly affect a patient's quality of life. There is very little information regarding optimum management in future pregnancies. Based upon anecdotal experience, this study describes the recommendations of a cohort of consultant obstetricians in the UK, in this clinical situation. There is limited adherence to the available national guidelines due to the absence of available equipment and expertise to perform endo-anal ultrasound and manometry. Elective episiotomy is still recommended by a small number of obstetricians but the majority of patients are routinely followed-up. Caesarean section is only advised for asymptomatic patients with a previous stage 4 tear, and for any symptomatic patient with a previous stage 3 or 4 tear, irrespective of subgrade. A request for elective caesarean section is likely to be granted, irrespective of OASIS grade. The use of postpartum endo-anal ultrasound would help identify those women in whom a further vaginal delivery is unlikely to exacerbate any symptoms of faecal incontinence.

Age-related changes in maxillary and mandibular cortical bone thickness in relation to temporary anchorage device placement

BACKGROUND

The aim of this study was to investigate the correlation between alveolar bone cortical thickness (ABCT) and age in the maxillae and mandible in humans. This information could then be translated into clinical application with temporary anchorage devices (TADs) in orthdontics.

METHODS

Samples comprised 82 post-mortem CT datasets (41 males and 41 females) aged between 11 to 50 years, and were divided into five different age groups and gender. Alveolar ABCT was measured in the labial/buccal and palatal/lingual sides of the incisor, canine, premolar, molar and tuberosity/retromolar regions of the maxillae and mandible. Correlations between ABCT and age and gender were analysed with linear regression analysis.

RESULTS

Strong correlation between ABCT and age was found for the maxilla on the labial side of the maxillary incisor region (p < 0.001). On the palatal aspect, significant correlations between ABCT and age were found in the maxillary incisor and maxillary premolar regions (p = 0.01 and p = 0.047 respectively). Significant correlation between ABCT and gender was found only at the buccal aspect of the maxillary molar region (p = 0.022). In the mandible, a statistically significant correlation between ABCT and age was found in the cortical bone of the labial side of the mandibular incisor region (p = 0.017). However, statistically significant negative correlation between ABCT and age was found in the mandibular canine region (p = 0.033). The only site to demonstrate a significant difference in change in ABCT with age between males and females was the lingual side of the retromolar region, in which female ABCT increased more than in males (slope = 0.015).

CONCLUSIONS

There is minimal clinically significant correlation between ABCT and age at the alveolar bone level. Although investigations show statistically significant correlations, these may not be clinically significant as those regions are not ideal for anchorage reinforcement with TADs in orthodontic practice.

AMGET, an R-Based Postprocessing Tool for ADAPT 5

ADAPT 5 is a powerful modeling software for population pharmacokinetic and pharmacodynamic systems analysis, but provides limited built-in functionality for creating pre- and post-analysis diagnostic plots. ADAPT 5 Model Evaluation Graphical Toolkit (AMGET), an external package written in the open source R programming language, was developed specifically to support efficient postprocessing of ADAPT 5 runs, as well as NONMEM and S-ADAPT runs. Using interactive navigational menus, users of AMGET are able to rapidly create informative diagnostic plots enriched by the display of numerical and graphical elements with a high degree of customization using a simple settings spreadsheet. This article describes each feature of the AMGET package and illustrates how it allows users to utilize the powerful numerical routines of the ADAPT 5 package in a more efficient manner through the use of a simulated dataset and a simple pharmacokinetic model optimized using the maximum likelihood expectation maximization (MLEM) algorithm of ADAPT 5.

Pharmacokinetics of two common antiretroviral regimens in older HIV-infected patients: a pilot study

OBJECTIVES

The pharmacokinetics (PK) of antiretrovirals (ARVs) in older HIV-infected patients are poorly described. Here, the steady-state PK of two common ARV regimens [tenofovir (TFV)/emtricitabine (FTC)/efavirenz (EFV) and TFV/FTC/atazanavir (ATV)/ritonavir (RTV)] in older nonfrail HIV-infected patients are presented.

METHODS

HIV-infected subjects ≥ 55 years old not demonstrating the frailty phenotype were enrolled in an unblinded, intensive-sampling PK study. Blood plasma (for TFV, FTC, EFV, ATV and RTV concentrations) and peripheral blood mononuclear cells [PBMCs; for tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP) concentrations] were collected at 11 time-points over a 24-hour dosing interval. Drug concentrations were analysed using validated liquid chromatography-ultraviolet detection (LC-UV) or liquid chromatography tandem mass spectrometry (LC-MS/MS) methods. Noncompartmental pharmacokinetic analysis was used to estimate PK parameters [area under the concentration-time curve over 24 h (AUC0-24h ) and maximal concentration (Cmax )]. These parameters were compared with historical values from the general HIV-infected population.

RESULTS

Six subjects on each regimen completed the study. Compared with the general population, these elderly subjects had 8-13% decreased TFV AUC0-24h and Cmax , and 19-78% increased FTC and RTV AUC0-24h and Cmax . Decreased ATV AUC0-24h (12%) and increased Cmax (9%) were noted, while EFV exposure was unchanged (5%) with a 16% decrease in Cmax . Intracellular nucleoside/tide metabolite concentrations and AUC are also reported for these subjects.

CONCLUSIONS

This study demonstrates that the PK of these ARVs are altered by 5-78% in an older HIV-infected population. Implications of PK differences for clinical outcomes, particularly with the active nucleoside metabolites, remain to be explored. This study forms the basis for further study of ARV PK, efficacy, and toxicity in older HIV-infected patients.

Statin treatment use in diabetic patients with breast cancer: A potential C-reactive protein mediated benefit

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Background: Statin treatment has not yet been evaluated in relation to breast cancer (BC) prognosis in diabetes mellitus (DM) patients. Reported decreased survival following BC in women with metabolic syndrome, led us to investigate whether specific statin therapy may lead to improved BC survival. Reported associations between elevated C-reactive protein (CRP) levels at the time of diagnosis with worse cancer prognosis, and CRP-lowering properties of statin treatment in non-cancer patients, led us to investigate whether statin use is associated with lower CRP levels at the time of BC diagnosis and with improved BC outcomes.

Methods: All DM patients newly diagnosed with BC between 2003 and 2007 (Roswell Park Cancer Institute) were retrospectively reviewed (n = 225). BC pathology, outcomes, existing comorbidities and drug therapy were documented. Follow up began at BC diagnosis and ended with first confirmed recurrence and/or death, or last date of follow-up. Hazard ratios (HR) and 95% confidence intervals (CI)s representing the association between statins, BC and a defined event were computed with Cox proportional hazards model. CRP plasma levels were determined by enzyme-linked immunosorbent assay in specimens donated at the time of BC diagnosis. A total of 98 study patients, DM+BC, and their matched controls, BC only (n = 196) were analyzed.

Results: After a median follow up of 30 months, patients receiving statins for cholesterol management were found to have better disease-free survival (HR 0.27, 95% CI: 0.10, 0.71, X2 = 7.31, p = 0.06), and lower overall mortality (HR 0.23, 95% CI: 0.08, 0.66, X2 = 7.80, p = 0.05) compared to patients not receiving any cholesterol management medication. CRP levels have ranged between 0.2 and 21 mg/L and clinically relevant levels ( > 3mg/L) were noted in the study group.

Conclusions: This study explored for the first time the association between statin therapy and BC prognosis in DM. We observed improved outcomes in statin-treated patients. While we currently analyze statin therapy in relationship with baseline CRP levels and BC prognosis, our existing findings suggest that statins have the potential to improve BC outcomes potentially through lowering overall inflammation.

Utility of Periurethral Electric Stimulation to Reduce Voiding Frequency in Rats

Urinary continence is maintained through coordination of electrical (nervous) and mechanical (muscles, ligaments and other structures) systems in the body. During micturition, the central nervous system sends a signal to the detrusor and sphincter muscles to coordinate voiding. Pathological problems can undermine either of the two systems and result in urinary incontinence (UI). Thirteen million people in the United States live with UI. Clinical treatments to date are largely mechanical in nature, restoring function through surgical interventions. However, electrically-based treatments, such as electric stimulation, offer a promising alternative. Here we investigate the utility of electrical stimulation of the periurethral neuromusculature to reduce voiding contractions in well-controlled animal experiments. Female Sprague Dawley rats were anesthetized with a ketamine/xylazine/acepromazine cocktail and the bladder was catheterized through a small incision in the bladder dome and was infused with saline. Continuous filling of the bladder triggered related cycles of voiding which was identified through bladder pressure increases and visual urination. The pubic symphysis bone was cut to expose the urethra and a stimulating electrode was placed in the periurethral region. The electrical stimulation parameters were 2.8 mA of current, 200 us pluses, and 20 Hz. The electrical stimulation was done in fifteen minute intervals. Statistically, the rats without electrical stimulation have an average contraction period of 63.1 sec (+/– 31.3 sec) and the rats with electrical stimulation have an average contraction period of 97.2 sec (+/– 43.0 sec). The results showed that the electrical stimulation of the periurethral neuromusculature in the group revealed 54.0% increase in average contraction period and decrease in voiding frequency. Electrical stimulation of the periurethral neuromusculature increases the voiding interval and void volume for the rats. This suggests the existence of an external urinary sphincter to the bladder inhibitory pathway and supports periurethral neuromusculature stimulation as an alternative to spinal nerve stimulation for the treatment of bladder overactivity.

Biomechanical approach to human bitemark reconstruction

This paper investigates the changes in upper and lower dental bite records that occur when the anterior teeth occlude into a three-dimensional rather than a flat object.

METHODS

anterior bite registrations were obtained from 20 volunteers with full and unrestored dentitions. As a three- dimensional, life-like bite target we cast a silicone replica from the impression of an actual arm, fitted with a rigid bony interior. Each participant was asked to bite into a single layer of softened bite registration wax wrapped around the same location on the fake arm, as well as into a flat wafer of the same material. Upper and lower bite registrations were then scanned in the same location on a flat bed scanner. We analysed the sizes of the different bite marks by means of landmark- and semi-landmark analysis to calculate Procrustes distances between tooth outlines. In order to analyse shape variation between the two types of bite registration we carried out principal components analyses on the partial warp scores. These were derived from partial Procrustes coordinates aligned by means of thin-plate spline decomposition based on a bending energy matrix. Our results show that there are significant differences in the shape of the upper or lower teeth when they occlude into a flat or three- dimensional target. We conclude that the use of a traditional flat bite registration in human bitemark reconstruction and analysis has to be seriously questioned.

Impact of antimicrobial dosing regimen on evolution of drug resistance in vivo: fluconazole and Candida albicans

Numerous factors have been theorized to affect the development of antimicrobial resistance, including those specific to the host, the organism, the environment, the drug, and the drug prescriber. One variable under the control of the prescriber is the drug dosing regimen. Dosing regimens can vary in dose level, dosing interval, and treatment duration. The current studies examined the relationships between antimicrobial dosing regimens and resistance development by use of an in vivo model. A murine model of systemic Candida albicans infection was used to examine resistance emergence during exposure to the triazole antifungal fluconazole. Data from this experimental model demonstrated that the more frequently administered dosing prevented selection of the isogenic resistant cell populations. Conversely, dosing regimens producing prolonged sub-MIC effects appeared to contribute to the outgrowth of isogenic resistant strains. The association between dosing and resistance emergence observed in the current investigation is disparate from that described for antimicrobial compounds with cidal killing characteristics. The inhibitory or static antimicrobial activity of the triazole compounds may explain these differences.

The enhanced spontaneous activity of the diabetic colon is not the consequence of impaired inhibitory control mechanisms

1. Approximately 45% of patients with diabetes mellitus have gastrointestinal complications such as diarrhoea and constipation, but the underlying aetiology is unclear. The present study investigates alterations in spontaneous motility of the colon that may be, in part, responsible for these symptoms using an established animal model of diabetes. 2. Rats were rendered diabetic by a single intraperitoneal injection of streptozotocin and age-matched controls were injected with citrate buffer. Rats were sacrificed after 8-weeks and proximal colonic circular muscle tissue mounted in organ baths. 3. Spontaneous activity was observed in both control and diabetic tissues, but this activity was almost doubled in colonic tissue taken from diabetic rats. It was hypothesized that this increase was due to a deficit in inhibitory control of the colon in the diabetic state. 4. Possible alterations in nitrergic and vasoactive intestinal polypeptide (VIP)ergic control were investigated using a range of pharmacological tools. 5. Sodium nitroprusside, VIP and antioxidants (reduced glutathione, ascorbate and alpha-tocopherol) inhibited the spontaneous activity, but the level of inhibition observed was not different in diabetic tissue compared with control. 6. Arginine, [D-p-Cl-Phe6, Leu17]-VIP and alpha-chymotrypsin had no effect on spontaneous activity in either sets of tissue. 7. N omega-nitro-L-arginine produced a small, but significant, increase in the level of spontaneous activity, but the degree of increase was not different between control and diabetic tissues. 8. Western blots demonstrated that there was no inducible-nitric oxide synthase (iNOS) in control or diabetic tissues and that the levels of endothelial-NOS (eNOS) and neuronal-NOS (nNOS) detected were not statistically significantly different. The [3H]-citrulline assay established that the functionality of the NOS isoforms present were unaltered in the diabetic state. 9. This study demonstrates that there is a marked alteration in motility in the colon taken from diabetic animals. However, the change in motility is unlikely to be due to a change in inhibitory control mechanisms and may be due to an increased excitability.

Safety, efficacy and pharmacokinetics of linezolid for treatment of resistant Gram-positive infections in cancer patients with neutropenia

BACKGROUND

Linezolid is a recently approved oxazalidinone with extended activity against Gram-positive bacteria. We evaluated the results of linezolid therapy in neutropenic cancer patients with Gram-positive bacterial infections from a compassionate-use program.

PATIENTS AND METHODS

This was a prospective, multicenter, open-label, non-comparative, non-randomized compassionate-use treatment program in patients with serious Gram-positive infections. To qualify for enrollment patients were required to have an infection resistant to available antimicrobial agents, or in whom available agents had failed or to which they were intolerant. Patients with absolute neutrophil counts (ANC) <500 cells/mm(3) or <1000 cells/mm(3) and expected to decrease to <500 cells/mm(3), and who received linezolid 600 mg twice daily were included. Plasma samples for population pharmacokinetic analysis were collected. Clinical and microbiological assessments of outcomes were made at the end of therapy and at short-term follow-up.

RESULTS

Of the patients in the compassionate-use trial, 103 were neutropenic. The mean [standard deviation (SD)] age was 50.1 (17.5) years, 47% were female, and 47.6% had a baseline ANC </=100 cells/mm(3). The mean (SD) duration of linezolid therapy was 14.6 (11.4) days. The most common site of infection was the bloodstream (90.3%), and the most commonly identified pathogen was vancomycin-resistant Enterococcus faecium (83%). A total of 83 (80.5%) and 52 (50.4%) patients were evaluable for clinical and microbiological outcomes at the end of therapy, respectively. Clinical and microbiological cure rates in the evaluable patients were 79% and 86%, respectively. Linezolid was well-tolerated in this patient population, with an overall adverse event rate of 17.5%; 5% of patients required discontinuation of the drug due to side-effects. The pharmacokinetics of linezolid in patients with neutropenia did not differ from the overall compassionate-use population.

CONCLUSIONS

Linezolid was safe and effective in treating resistant Gram-positive infections in neutropenic cancer patients. Comparative clinical trials to evaluate further the effectiveness and safety of linezolid in this patient population are warranted.

Analysis of the mouse transcriptome based on functional annotation of 60,770 full-length cDNAs

Only a small proportion of the mouse genome is transcribed into mature messenger RNA transcripts. There is an international collaborative effort to identify all full-length mRNA transcripts from the mouse, and to ensure that each is represented in a physical collection of clones. Here we report the manual annotation of 60,770 full-length mouse complementary DNA sequences. These are clustered into 33,409 'transcriptional units', contributing 90.1% of a newly established mouse transcriptome database. Of these transcriptional units, 4,258 are new protein-coding and 11,665 are new non-coding messages, indicating that non-coding RNA is a major component of the transcriptome. 41% of all transcriptional units showed evidence of alternative splicing. In protein-coding transcripts, 79% of splice variations altered the protein product. Whole-transcriptome analyses resulted in the identification of 2,431 sense-antisense pairs. The present work, completely supported by physical clones, provides the most comprehensive survey of a mammalian transcriptome so far, and is a valuable resource for functional genomics.

Effects of the concomitant administration of tamsulosin (0.8 mg) on the pharmacokinetic and safety profile of intravenous digoxin (Lanoxin) in normal healthy subjects: a placebo-controlled evaluation

A 20-day, nonrandomized, open-label, placebo-controlled study was performed to investigate whether concomitant administration of tamsulosin (0.8 mg) affects the pharmacokinetic and safety profile of intravenous digoxin (0.5 mg) in healthy subjects. Ten healthy subjects aged 21-39 years received a single oral dose of placebo on study days 1-8 and tamsulosin on days 9-18. Tamsulosin was initiated at 0.4 mg/day and the dose was increased to 0.8 mg/day from day 11. On days 2 and 15, subjects received a single intravenous dose of digoxin (0.5 mg). Safety monitoring was carried out throughout the study. Following digoxin administration, blood was drawn and urine collected over a 96-h period for pharmacokinetic determinations. Plasma tamsulosin concentrations were measured at regular intervals after dosing on day 15. The digoxin pharmacokinetic parameters with and without concomitant tamsulosin were compared. No significant difference was observed, and no irregularity was found in the plasma tamsulosin concentration data. Six subjects experienced adverse events while receiving placebo and seven while on tamsulosin. The most frequent adverse event was mild dizziness reported by four subjects. Moderate chest pain was reported in two subjects, but this was not considered to be related to the administration of the study medications. Some significant changes in vital signs were observed; however, none was accompanied by symptoms of medical concern. These changes were not temporally related to the administration of study drugs. Thus, concurrent administration of digoxin with tamsulosin did not produce any change in the pharmacokinetics of digoxin and the safety profile was acceptable. As reflected in the prescribing information for tamsulosin, no adjustment in tamsulosin dosing is required when it is administered concomitantly with digoxin.

Effects of the concomitant administration of tamsulosin (0.8 mg/day) on the pharmacokinetic and safety profile of theophylline (5 mg/kg): a placebo-controlled evaluation

We performed a single-blind, sequential-design study to investigate the effects of concomitant oral tamsulosin 0.8 mg/day on the pharmacokinetics and safety of intravenous theophylline 5 mg/kg in healthy subjects. Ten healthy volunteers aged 19-39 years received placebo on study days 0, 1, 2 and 10 and tamsulosin on days 3-9. Theophylline was administered intravenously on days 1 and 9. Theophylline and tamsulosin pharmacokinetic data were determined following administration of the drugs on days 1 and 9 and day 9, respectively. No differences were observed in theophylline pharmacokinetic parameters with and without concomitant tamsulosin, and there were no abnormalities in tamsulosin pharmacokinetic data. Some significant changes in vital signs and a number of mild adverse reactions were reported, but the overall safety profile of tamsulosin and theophylline was acceptable. The results of the study suggest that no dose adjustment in tamsulosin is necessary when it is administered concomitantly with theophylline.

Ganciclovir pharmacokinetics and cytokine dynamics in renal transplant recipients with cytomegalovirus infection

Ganciclovir is considered to be the first-line treatment for cytomegalovirus (CMV) in renal transplant recipients. This infection is also associated with elevations of specific plasma cytokines post-transplantation. To investigate daily cytokine response to therapy and ganciclovir pharmacokinetics, 4 transplant recipients (3 males, 1 female) with stable renal allograft function diagnosed with CMV infection were enrolled less than 4 months post-transplant. A creatinine clearance (ClCr) was generated by the Cockroft-Gault (C-G) equation (range: 42.3-68.5 mL/min) to determine ganciclovir dosing. Blood samples were collected for ganciclovir and cytokine [including interleukin (IL)-1beta, IL-2, IL-3, IL-4, IL-6, IL-8, IL-10, TNF-alpha, GM-CSF, and interferon (IFN)-gamma analyses after 7 d of intravenous (i.v.) ganciclovir (dosage range: 165-400 mg daily) therapy and again after 7 d of oral (p.o.) ganciclovir (dosage range: 1000 mg, 2-3 times daily) therapy. Pharmacokinetic ganciclovir was described with a two-compartment model. Total clearance of ganciclovir was consistently greater than ClCr, suggesting tubular secretion. Peak concentrations for i.v. ganciclovir averaged 8.39+/-1.87 microg/mL with minimum concentrations of 0.48+/-0.35 microg/mL. Plasma concentrations were lower but more sustained during a p.o. dosing interval (max=2.12+/-0.58 microg/mL, min=1.15+/-0.34 microg/mL). IL-6, IL-8, IL-10, and TNF-alpha were detectable at multiple times during the study periods while the remainder of the cytokines were only intermittently detectable. Average concentrations (i.v. versus p.o. study period) for TNF-alpha were 40.1+/-17.5 versus 22.1+/-11.2 pg/mL, for IL-8 were 17.1+/-15.6 versus 4.12+/-2.59 pg/mL, and for IL-10 were 7.39+/-5.54 versus 2.64+/-1.06 pg/mL. Concentrations were similar for IL-6 during both studies (9.39+/-5.42 versus 14.7+/-14.8 pg/mL). TNF-alpha, IL-8, and IFN-gamma appeared to correlate with CMV antigenemia. Further investigation of ganciclovir disposition and changes in plasma cytokines in renal transplant recipients during CMV infection may provide insight into variable antiviral responses in renal transplant recipients.

Pharmacokinetics and pharmacodynamics of aztreonam and tobramycin in hospitalized patients

BACKGROUND

Pharmacokinetic/pharmacodynamic (PK/PD) optimization of antibiotic therapy has been shown to improve outcomes in several antibiotic classes. Despite the frequent use of beta-lactams, clinical data in humans remain limited.

OBJECTIVE

This study evaluated the relationship between serum pharmacokinetics, pharmacodynamics, pathogen susceptibility, and clinical outcomes in patients receiving aztreonam or tobramycin monotherapy.

METHODS

The case-report forms of hospitalized patients who received either aztreonam or tobramycin for a bacterial infection in 3 clinical trials conducted between 1982 and 1984 were reviewed for the present study. A pathogen was identified for all included patients, and susceptibility testing was performed to determine the minimum inhibitory concentration (MIC) for each agent. Pharmacokinetic parameters for each antibiotic were determined using population modeling, and variables potentially related to outcomes were evaluated using tree-based modeling, logistic regression, and nonlinear regression methods.

RESULTS

Data from 91 patients were analyzed, 68 treated with aztreonam monotherapy and 23 treated with tobramycin monotherapy. Of the types of infections treated, 39 were intra-abdominal, 42 involved the lower respiratory tract, and 10 involved the skin and skin structures. The pharmacodynamic ratio of the 24-hour area under the curve (AUC24) to the MIC was associated with clinical outcome for both antibiotics: aztreonam and to-bramycin patients with ratios meeting or exceeding the respective 24-hour inverse serum inhibitory titer breakpoints of 184 and 110 were significantly more likely to achieve a successful outcome than were those with ratios not meeting these values (P < 0.01). The probabilities of clinical success in patients at or above and below the AUC24/MIC breakpoints were a respective 85% and 53% for aztreonam and 80% and 47% for tobramycin (both, P < 0.01). When all patients were considered, the likelihood of achieving cure was 5.1 times greater in patients exceeding the target ratios (P < 0.01).

CONCLUSION

PK/PD optimization of both aztreonam and tobramycin is associated with improved patient outcomes.

Cdc25B activity is regulated by 14-3-3

In the G2 phase cell cycle checkpoint arrest, the cdc25-dependent activation of cyclin B/cdc2, a critical step in regulating entry into mitosis, is blocked. Studies in yeast have demonstrated that the inhibition of cdc25 function involves 14-3-3 binding to cdc25. In humans, two cdc25 isoforms have roles in G2/M progression, cdc25B and cdc25C, both bind 14-3-3. Abrogating 14-3-3 binding to cdc25C attenuates the G2 checkpoint arrest, but the contribution of 14-3-3 binding to the regulation of cdc25B function is unknown. Here we demonstrate that high level over-expression of cdc25B in G2 checkpoint arrested cells can activate cyclin B/cdc2 and overcome the checkpoint arrest. Mutation of the major 14-3-3 binding site, S323, or removal of the N-terminal regulatory domain are strong activating mutations, increasing the efficiency with which the mutant forms of cdc25B not only overcome the arrest, but also initiate aberrant mitosis. We also demonstrate that 14-3-3 binding to the S323 site on cdc25B blocks access of the substrate cyclin/cdks to the catalytic site of the enzyme, thereby directly inhibiting the activity of cdc25B. This provides direct mechanistic evidence that 14-3-3 binding to cdc25B can regulate its activity, thereby controlling progression into mitosis.

Factors associated with postoperative infection

OBJECTIVE

We have developed and analyzed a large surgical prophylaxis database and now report the factors significantly associated with early infection, readmission due to infection, and death within 28 days of surgery. This study is intended to be a stepping-stone for further studies using our clinical database.

DESIGN AND SETTING

A computerized database of 9,016 surgical patients from a 400-bed community hospital was examined. Multivariate logistic regression and tree-based modeling were used to identify factors associated with the outcomes. Factors considered included surgical procedure, prophylactic antibiotic, age, gender, serum creatinine, and albumin.

RESULTS

12.6% had an early infection, 2.5% were readmitted due to infection, and 2.5% died within 28 days. Most combination prophylactic antibiotics were associated with an increased probability of an early infection. Decreased albumin and increased age were associated with an increased probability of an early infection. Tracheostomy and amputations were associated with an increased probability of an early infection, whereas gallbladder and orthopedic procedures involving the arm were associated with a decreased probability. Factors associated with readmission due to infection included dialysis shunt, vascular repair, and an early infection. Factors associated with increased probability of death within 28 days included age, albumin, serum creatinine, and an early infection. Gallbladder procedures and obstetric-gynecologic procedures were associated with a decreased probability of death within 28 days.

DISCUSSION

Older patients and those with a decreased albumin were most likely to have an early infection. To the extent that an early infection was a significant risk factor for readmission due to infection, the impact of age and albumin on the probability of readmission due to infection is demonstrated by their effects on early infections. Interestingly, albumin and age were significantly associated with death within 28 days, in addition to early infection, showing the predictive association between these factors and early death.

Normalization of hypertensive responses during ambulatory surgical stress by perioperative music

OBJECTIVE

The purpose of this study was to determine whether cognitive appraisals of stress level and hypertensive responses to ambulatory ophthalmic surgery can be ameliorated by patient-selected music.

METHODS

We studied 40 elderly individuals requiring ophthalmic surgery, 20 in an experimental group (mean age, 74 years) and 20 in a control group (mean age, 77 years). All patients had an established resting blood pressure <140/90 mm Hg. In the experimental group self-selected music was provided by headphones throughout the preoperative, surgical, and postoperative periods. In the control group patients had neither headphones nor music. All patients received similar (weight-determined) doses of alfentanil and midazolam during surgery. Heart rate, blood pressure, and patient-reported stress and coping levels were the dependent variables.

RESULTS

In both groups, blood pressure values were normal (approximately 129/82 mm Hg) during screening examinations 1 week before surgery. On the day of surgery both groups displayed increased preoperative blood pressures (approximately 159/92 mm Hg) associated with increases in heart rate (by approximately 17 beats/min). Intraoperative blood pressures in the experimental group returned quickly to screening baseline values, whereas the control group experienced persistent elevations in intraoperative blood pressure similar to preoperative levels. Over the course of the surgical experience, patients with music reported significant reductions in perceived stress and increases in coping abilities (p < .001), whereas those without music did not.

CONCLUSIONS

The perceived stress of ambulatory surgery in geriatric patients is associated with a clinical hypertensive response that is ameliorated by self-selected perioperative music, which also decreases perceived stress and increases patients' sense of personal control and well-being.

Cdc25-dependent activation of cyclin A/cdk2 is blocked in G2 phase arrested cells independently of ATM/ATR

Cyclin A/cdk2 is active during S and G2 phases of the cell cycle, but its regulation and function during G2 phase is poorly understood. In this study we have examined the regulation of cyclin A/cdk2 activity during normal G2 phase progression and in genotoxin-induced G2 arrest. We show that cyclin A/cdk2 is activated in early G2 phase by a cdc25 activity. In the G2 phase checkpoint arrest initiated in response to various forms of DNA damage, the cdc25-dependent activation of both cyclin A/cdk2 and cyclin B1/cdc2 is blocked. Ectopic expression of cdc25B, but not cdc25C, in G2 phase arrested cells efficiently activated both cyclin A/cdk2 and cyclin B1/cdc2. Finally, we demonstrate that the block in cyclin A/cdk2 activation in the G2 checkpoint arrest is independent of ATM/ATR. We speculate that the ATM/ATR-independent block in G2 phase cyclin A/cdk2 activation may act as a further layer of checkpoint control, and that blocking G2 phase cyclin A/cdk2 activation contributes to the G2 phase checkpoint arrest.

Pharmacokinetic/pharmacodynamic predictors of time to clinical resolution in patients with acute bacterial exacerbations of chronic bronchitis treated with a fluoroquinolone

Forty nine subjects with acute bacterial exacerbations of chronic bronchitis (ABECB) treated with grepafloxacin were evaluated for parameters predictive of clinical outcome. Signs and symptoms associated with ABECB were serially collected and evaluated for changes. Coughs per day, sputum volume and the percentage of sputum neutrophils were associated with clinical outcome. A by groups analysis, based on clinical success was performed using Cox regression analysis to determine factors associated with time to clinical success and time to reduction in sputum volume, coughs per day and sputum neutrophil percent. Factors evaluated included AUIC (AUC/MIC), isolate species, years and type of underlying lung disease, alcohol use, smoking history and number of ABECB within the previous 12 months. AUIC<276 (mg h/l)/mg/l (P<0.03) and or the presence of mild bronchiectasis (P<0.01) were associated with longer time to clinical success. In addition a relationship was found between AUIC>212 (mg h/l)/mg/l (P<0.01) and AUIC>576 (mg h/l)/mg/l (P<0.02) and decreasing days to sputum volume reduction and coughs per day, respectively. A diagnosis of mild bronchiectasis prolonged the time to reduce coughs per day (P<0.03) and neutrophil percentage (P<0.01). Patients with mild bronchiectasis were found to have an increase in the time to clinical success, coughs per day improvement and sputum neutrophil percent improvement. AUIC is an important PK/PD parameter predictive of successful outcome in ABECB, even in subjects with mild bronchiectasis. Grepafloxicin has been withdrawn from sale since these studies were carried out. This work is published to illustrate the relationship between pharmacodynamics and clinical efficacy and the use of AUIC as a valuable predictive parameter for fluoroquinolones.

Area under the inhibitory curve and a pneumonia scoring system for predicting outcomes of vancomycin therapy for respiratory infections by Staphylococcus aureus

Treatment factors predictive of clinical and microbiological outcomes and the relationship between a pneumonia scoring system and clinical outcomes in vancomycin-treated patients with a Staphylococcus aureus-associated lower-respiratory-tract infection (LRTI) were studied. A computer database review identified patients for whom S. aureus was isolated from a respiratory-tract specimen between January 1 and December 31, 1998, and who had antimicrobials ordered within 72 hours of isolation of that organism. Through further review of individual patient charts, this group was restricted to those treated with vancomycin for a documented S. aureus-associated LRTI. Classification-and-regression-tree (CART) modeling was performed to determine which clinical variables were correlated with clinical outcomes and microbiological outcomes. Median changes in clinical pneumonia scores from baseline in two patient groups (those with clinical success and those with clinical failure) were compared. Seventy patients met the study criteria. CART modeling found that both outcomes were associated with area under the inhibitory curve (AUIC). The pneumonia scoring system was predictive of eventual clinical success as early as day 3 of treatment; having at least a 4-point decrease in the pneumonia score by day 3 was correlated with an 87% clinical success rate. Both AUIC and a pneumonia scoring system were useful for predicting clinical and microbiological outcomes of vancomycin therapy in patients with LRTIs caused by S. aureus.

Safety, tolerability, and pharmacokinetics of single oral doses of BCH-10652 in healthy adult males

Racemic dOTC (BCH-10652) is a novel nucleoside reverse transcriptase inhibitor consisting of two enantiomers of 2'-deoxy-3'-oxa-4'-thiocytidine, (-)dOTC and (+)dOTC, that have both shown activity against human immunodeficiency virus type 1. The objectives of this study were to characterize the safety, tolerability, and stereospecific pharmacokinetics of single oral doses of racemic dOTC in healthy, nonsmoking adult male volunteers. Subjects received single oral doses of 100, 200, 400, 800, and 1,600 mg of racemic dOTC in a placebo-controlled, dose-rising, incomplete crossover study design, and the pharmacokinetics of both (+)dOTC and (-)dOTC were determined. At least six subjects were studied at each dose level, with each subject studied in three of five periods, receiving two different doses of racemic dOTC and one placebo dose. Plasma and urine drug concentrations were measured for 24 to 48 h after each dose. Pharmacokinetic models were fitted to the plasma concentrations of (+)dOTC and (-)dOTC using maximum likelihood and maximum a posteriori Bayesian procedures. Statistical hypothesis testing was by nonparametric analysis of variance (where possible) and, when tests with dose as a covariate were performed, by linear mixed-effects modeling. The mean terminal elimination half-lives for (+)dOTC and (-)dOTC were 15.3 h (coefficient of variation [CV], 28%) and 11.3 h (CV, 43%), respectively (P<0.05). The mean CV for total oral clearance (liter/h/65 kg) was 17.5 (25%) for (+)dOTC and 21.5 (24%) for (-)dOTC; for oral steady-state volume of distribution (liter/65 kg), values were 61.8 (24%) for (+)dOTC and 34.1 (33%) for (-)dOTC (P<0.05). The mean CV for renal clearance (liter/h/65 kg) of (+)dOTC was 10.4 (19%) and for (-)dOTC was 13.6 (20%) (P<0.05). There was no significant effect of dose size on the pharmacokinetics of racemic dOTC. All doses were well tolerated, and no serious adverse events or laboratory abnormalities were observed.

Cost effectiveness of cephalosporin monotherapy and aminoglycoside/ureidopenicillin combination therapy. For the treatment of febrile episodes in neutropenic patients

OBJECTIVE

To assess the relative cost effectiveness of cephalosporin monotherapy options and aminoglycoside/ureidopenicillin combination therapy for the treatment of febrile episodes in adult patients with neutropenia.

DESIGN AND SETTING

This was a retrospective cost-effectiveness analysis conducted from the institutional perspective.

METHODS

The analysis was based on 741 febrile episodes in adult patients with neutropenia enrolled in 5 randomised trials: 3 comparing monotherapy with ceftazidime or cefepime, and 2 comparing cefepime monotherapy versus aminoglycoside/ureidopenicillin combination therapy. Resource utilisation included costs for study antibacterials, treatment of adverse effects and failures, and hospitalisation. The primary end-point was the overall cost of treatment per patient. Cost-effectiveness ratios were also analysed.

RESULTS

No significant differences in clinical success rates were detected. Median per-patient costs in the monotherapy comparisons were $US7849 for cefepime and $US7788 for ceftazidime [1997 values; not significantly different (NS)]. Corresponding costs for the monotherapy versus combination therapy comparisons were $US9780 for cefepime and $US10 159 for gentamicin/ureidopenicillin (NS). Despite a higher acquisition cost for cefepime, there were no statistically significant differences in cost effectiveness compared with either ceftazidime monotherapy or gentamicin/ureidopenicillin combination therapy. Sensitivity analyses revealed that monotherapy can be cost effective compared with combination therapy in many situations.

CONCLUSION

There were no economic differences between the 3 regimens tested. Therefore drug cost should not be a deciding factor when choosing antibacterial therapy for the treatment of febrile episodes in adult patients with neutropenia.

Containment of heart failure hospitalizations and cost by angiotensin-converting enzyme inhibitor dosage optimization

Using our model relating angiotensin-converting enzyme (ACE) inhibitor dosing and outcomes in heart failure (HF), we designed a prospective intervention trial for patients with systolic dysfunction. A clinical pharmacist initiated or titrated ACE inhibitor therapy or adjusted other medications within an HF management program based on Agency for Healthcare Policy and Research guidelines. Entry into the protocol required the approval of the attending physician. All patients received dietary, nursing, rehabilitation, social service, and clinical pharmacy consultations. Treatment conformed to Agency for Healthcare Policy and Research guidelines in 25% of patients (group A). Suboptimal therapy (75% of patients) was usually due to failure to administer an ACE inhibitor (48%) or inadequate dosing of an ACE inhibitor (46%). In 62% of suboptimal cases, the attending physician agreed to follow the clinical pharmacist's recommendations (group B). Patients of physicians who declined pharmacist intervention served as a negative control (group C). On admission, mean enalapril-equivalent daily doses in groups A, B, and C were 30, 4, and 6 mg, respectively, and at discharge, 36, 18, and 6 mg, respectively. At 180 days, rehospitalization frequency and total charges were lower in groups A (31% and $5,600) and B (35% and $3,800) than in group C (63% [p <0.004] and $9,800 [p <0.04]). Thus, optimization of ACE inhibitor doses by a clinical pharmacist can greatly improve rehospitalization rates and significantly lower cost of care in an HF management program.

Absolute bioavailability and disposition of (-) and (+) 2'-deoxy- 3'-oxa-4'-thiocytidine (dOTC) following single intravenous and oral doses of racemic dOTC in humans

The purpose of this study was to characterize the pharmacokinetics and determine the absolute bioavailability of 2'-deoxy-3'-oxa-4'-thiocytidine (dOTC) (BCH-10652), a novel nucleoside analogue reverse transcriptase inhibitor, in humans. dOTC belongs to the 4'-thio heterosubstituted class of compounds and is a 1:1 mixture of its two enantiomers, (-) and (+) dOTC. Twelve healthy adult male volunteers each received oral (800-mg) and intravenous (100-mg) doses of dOTC in two study periods separated by at least 7 days. Sixteen plasma samples were obtained over 72 h and assayed for (-) and (+) dOTC, and the resultant data fit by candidate pharmacokinetic models. Data were weighted by the fitted inverse of the observation variance; model discrimination was by AIC. The pharmacokinetic model was a linear, three compartment model, with absorption occurring during one to three first-order input phases, each following a fitted lag time. The model goodness-of-fit was excellent; r(2) ranged from 0.995 to 1.0. The mean absolute bioavailabilities of (+) and (-) dOTC were 77.2% (coefficient of variation [given as a percentage] [CV%], 14) and 80.7% (CV%, 15), respectively. The median steady-state volume of distribution for (+) dOTC, 74.7 (CV%, 19.2) liters/65 kg, was greater than that for (-) dOTC, 51.7 (CV%, 16.7) liters/65 kg (P<0.05). The median total clearance of (+) dOTC was less than that of (-) dOTC, 11.7 (CV%, 17.3) versus 15.4 (CV%, 18.6) liters/h/65 kg, respectively (P< 0.05). The intersubject variability of these parameters was very low. The median terminal half-life of (+) dOTC was 18.0 (CV%, 31.5) h, significantly longer than the 6.8 (CV%, 69.9) h observed for (-) dOTC (P<0.01). No serious adverse events were reported during the study. These results suggest that dOTC is well absorbed, widely distributed, and well tolerated. The terminal half-lives indicate that dosing intervals of 12 to 24 h would be reasonable.

Regulation of CDC25B phosphatases subcellular localization

The CDC25B dual specificity phosphatase is involved in the control of the G2/M transition of the cell cycle. Subcellular localization might represent an important aspect of the regulation of its activity. We have examined in transiently transfected asynchronous HeLa cells the localization of HA-tagged CDC25B proteins and found that they are nuclear or cytoplasmic suggesting the existence of an active shuttling. Accordingly, localization analysis of deletion and truncation proteins indicates that CDC25B contains a putative nuclear localization signal located between residues 335 and 354. We also demonstrated that a short 58 residues deletion of the amino-terminus end of CDC25B is sufficient to retain it to the nucleus. Mutational analysis indicates that a nuclear export sequence is located between residues 28 and 40. In addition, treatment of the cells with the exportin inhibitor, Leptomycin B, has the same effect. The mutation of Ser-323, a residue that is essential for the interaction with 14-3-3 proteins, also abolishes cytoplasmic staining. The subcellular localization of CDC25B is therefore dependent on the combined effects of a nuclear localization signal, a nuclear export signal and on the interaction with 14-3-3 proteins.

Comparison of the abilities of grepafloxacin and clarithromycin to eradicate potential bacterial pathogens from the sputa of patients with chronic bronchitis: influence of pharmacokinetic and pharmacodynamic variables

A randomized open-label study was conducted to compare the pharmacokinetics and pharmacodynamics of grepafloxacin with those of clarithromycin in patients with chronic bronchitis whose sputa were colonized with potential bacterial pathogens. Patients received oral grepafloxacin 400 mg od for 10 days (n = 15) or oral clarithromycin 500 mg bd for 10 days (n = 10). Sputum samples were collected before the first dose, 1, 4 and 8 h after a dose on day 1 and then before a dose on days 2, 3, 5, 7 and 10 to determine the time to eradication (T(erad)) of the potential bacterial pathogens. Blood samples for measurement of grepafloxacin or clarithromycin and 14-hydroxyclarithromycin concentrations were obtained before a dose and 1, 2, 4, 8 and 12 h after doses on days 1 and 5. The area under the inhibitory serum concentration-time curve over 24 h (AUIC(24)), peak serum concentration:MIC ratio (C(max):MIC) and the percentage of the dosing interval during which the serum concentration exceeded the MIC (%tau >MIC) were calculated and serum inhibitory titres (SITs) were determined. Haemophilus spp. were the predominant potential bacterial pathogens and were recovered from the sputa of 24 patients. Strains of Streptococcus pneumoniae were isolated from two patients in the grepafloxacin group and a strain of Moraxella catarrhalis was isolated from one patient in the clarithromycin group. Haemophilus spp. isolates were eradicated from the sputa of 13 of 14 (93%) patients given grepafloxacin, but from only two of 10 (20%) patients given clarithromycin (P < 0.05). In the other eight (80%) patients who received clarithromycin, the sputum cultures remained positive throughout the 10 day course. Grepafloxacin eliminated potential bacterial pathogens more quickly than clarithromycin (median T(erad) 4 h versus 76 h). The S. pneumoniae strains were eradicated by grepafloxacin within 4 h and the single M. catarrhalis strain was eradicated by clarithromycin within 1 h. The greater efficacy of grepafloxacin, compared with that of clarithromycin, in terms of the incidence and speed of eradication of the Haemophilus spp. isolates, was associated with higher median values of AUIC(24) (169 SIT(-1)*h versus 8.1 SIT(-1)*h), C(max):MIC ratio (23.6 versus 0.7) and %tau >MIC (100% versus 0%). A Hill-type model adequately described the relationship between the percentage probability of eradicating potential bacterial pathogens from sputa and the plasma grepafloxacin concentration.

A nationwide, multicenter, case-control study comparing risk factors, treatment, and outcome for vancomycin-resistant and -susceptible enterococcal bacteremia

National Nosocomial Resistance Surveillance Group participants from 22 hospitals across the United States reviewed medical records for hospitalized patients with vancomycin-resistant enterococcal (VRE) or vancomycin-susceptible enterococcal (VSE) bacteremia to identify risk factors associated with the acquisition of VRE bacteremia, describe genetic traits of VRE strains, and identify factors predictive of clinical outcome. VRE cases were matched to VSE controls within each institution. Multiple logistic regression (LR) and classification and regression tree (CART) analysis were used to probe for factors associated with VRE bacteremia and clinical outcome. A total of 150 matched-pairs of VRE cases and VSE controls were collected from 1995 to 1997. Using LR, the following were found to be highly associated with VRE bacteremia: history of AIDS, positive HIV status, or drug abuse (OR 9.58); prior exposure with parenteral vancomycin (OR 8.37); and liver transplant history (OR 6. 75). CART analysis revealed that isolation of Enterococcus faecium, prior vancomycin exposure, and serum creatinine values > or = 1.1 mg/dl were predictors of VRE bacteremia. Greater proportions of clinical failure (60% versus 40%, P < 0.001) and all-cause mortality (52% versus 27%, P < 0.001) were seen in patients with VRE versus VSE bacteremia. Results from both LR and CART indicated that patients with persisting enterococcal bacteremia, intubation at baseline, higher APACHE II scores, and VRE bacteremia were at greater risk for poor outcome.

Gender-related effects on metoprolol pharmacokinetics and pharmacodynamics in healthy volunteers

OBJECTIVE

To determine whether there are gender-specific differences in the pharmacokinetics and pharmacodynamics of metoprolol enantiomers.

METHODS

Twenty normal volunteers (10 men and 10 women) received 100 mg oral metoprolol tartrate twice daily for a total of nine doses. Pharmacokinetics and pharmacodynamics were studied after the last dose. Subjects also completed a control pharmacodynamic study; the order of drug and control studies was randomized. Measurements of heart rate and systolic blood pressure were obtained during peak submaximal bicycle exercise testing. (R)-Metoprolol and (S)-metoprolol concentrations were determined by stereospecific HPLC. The percentage difference in exercise heart rate and systolic blood pressure (metoprolol versus control), and (R)- and (S)-metoprolol plasma concentrations were comodeled.

RESULTS

Men and women showed stereoselective pharmacokinetics; (S)-metoprolol concentrations were significantly greater than those for (R)-metoprolol for both groups. Women had greater drug exposure than men (higher maximum concentration and area under the plasma concentration-time curve). No differences were observed between genders with respect to elimination half-life. Females had a greater reduction in exercise heart rate and systolic blood pressure; however, the area under the effect curve was significantly greater for heart rate only. Pharmacodynamic data were best fitted by the Hill equation with the effect site in the central compartment. The fitted maximum effect and the concentration at one-half of the maximum effect for heart rate and systolic blood pressure did not differ between men and women (P > .20).

CONCLUSIONS

Gender-related differences exist in the pharmacokinetics of metoprolol enantiomers, resulting in greater drug exposure in female subjects. However, concentration-effect relationships did not differ between men and women. Therefore the observed differences in drug effects were the result of gender-specific differences in metoprolol pharmacokinetics.

The population pharmacokinetics of amphotericin B colloidal dispersion in patients receiving bone marrow transplants

The purpose of this study was to identify the pharmacokinetics of Amphotericin B Colloidal Dispersion in patients undergoing bone marrow transplantations with systemic fungal infections and to assess the influence of ABCD on renal function. Seventy-five patients (42 females, 33 males) with a median age of 34.5 years and median weight of 70.0 kg were enrolled in the study. The plasma concentration data was available in 51/75 patients and was best described by a two-compartment model; both plasma clearance and volume of distribution increased with escalating doses; the overall average terminal elimination half-life was 29 h. Serum creatinine values over the duration of therapy were available in 59/75 patients. Overall, there was no net change in renal function over the duration of therapy.

Patterns of prescribing ACE inhibitors after myocardial infarction

We attempted to determine physician prescribing patterns of angiotensin-converting enzyme (ACE) inhibitors in patients who experienced a myocardial infarction, stratified by left ventricular function. We retrospectively reviewed drug therapy at discharge in 534 patients to assess prescription of ACE inhibitor therapy, including dosage. Thirty-four percent of patients were discharged taking an ACE inhibitor, of whom only 11% received recommended dosages. The drugs were prescribed more often for patients who had an ejection fraction below 40% than for those with an ejection fraction of 40% or above (54% vs 28%, p<0.05). We conclude that ACE inhibitors are underprescribed for patients who experienced a myocardial infarction, illustrating the gap between clinical research and clinical practice, and the need for programs to ensure optimal medical management.

Antibiotic dosing issues in lower respiratory tract infection: population-derived area under inhibitory curve is predictive of efficacy

Several lower respiratory tract infection (LRTI) trials have documented a correlation between clinical response and area under the inhibitory curve (24 h AUC/MIC; AUIC). The AUIC values in these studies were based on measured MICs and measured serum concentrations. This study evaluates AUIC estimates made using population pharmacokinetic parameters, and MICs from an automated microbiological susceptibility testing system. A computer database review over 2 years yielded 81 patients at Millard Fillmore Hospital with a culture-documented gram-negative LRTI who had been treated with piperacillin and an aminoglycoside, ceftazidime, ciprofloxacin or imipenem. Their AUIC values were estimated using renal function, drug dosages and MIC values. Outcome groups (clinical and microbiological cures and failures) were related to the AUIC values using Kruskal-Wallis ANOVA, linear regression and classification and regression tree (CART) analysis. A significant breakpoint for clinical cures was an AUIC value at least 72 SIT(-1) x 24 h (inverse serum inhibitory titre integrated over time). All antibiotics performed significantly better above this value than below it. Clinical cure was well described by a Hill-type equation. Within the piperacillin/aminoglycoside regimen, most of the activity came from the piperacillin, which had a higher overall AUIC value than the aminoglycoside. AUIC estimations based upon MIC values derived from the automated susceptibility testing method differed from NCCLS breakpoint data and from tube dilution derived values in this hospital by as much as three tube dilutions. These automated methods probably overestimated the MIC values of extremely susceptible organisms. The lack of precise MIC estimates in automated clinical microbiology methods impairs the use of AUIC to prospectively optimize microbiological outcome. Even ignoring this limitation and using the values as they are reported, the results of this analysis suggest that AUIC targets between 72 and 275 SIT(-1) x 24 h are useful in predicting clinical outcome.