Determining the Risk of Elevated Digoxin Concentrations Following Loading Dose in Patients With Acute and Chronic Kidney Disease

BACKGROUND

The optimal loading dose of digoxin in patients with reduced kidney function is unknown. Tertiary references recommend reduced loading doses; however, these recommendations are based on immunoassays that are falsely elevated by the presence of digoxin-like immunoreactive substances, a problem that is minimized in modern assays.

OBJECTIVE

To determine whether chronic kidney disease (CKD) or acute kidney injury (AKI) is associated with supratherapeutic digoxin concentrations after a digoxin loading dose.

METHODS

A retrospective analysis on patients who received an intravenous loading dose of digoxin with a digoxin concentration collected 6 to 24 hours after the end of the dose. Patients were stratified into 3 groups: AKI, CKD, and non-AKI/CKD (NKI) based on glomerular filtration rate and serum creatinine. The primary outcome was frequency of supratherapeutic digoxin concentrations (>2 ng/mL) and secondary outcomes included frequency of adverse events.

RESULTS

A total of 146 digoxin concentrations were included (AKI = 59, CKD = 16, NKI = 71). Frequencies of supratherapeutic concentrations were similar between groups (AKI: 10.2%, CKD: 18.8%, NKI: 11.3%; P = 0.61). Pre-planned logistic regression demonstrated no significant relationship between kidney function group and the development of a supratherapeutic concentration (AKI: odds ratio [OR]: 1.3, 95% confidence interval [CI]: 0.4-4.5; CKD: OR 4.3, 95% CI: 0.7-23).

CONCLUSION AND RELEVANCE

This is the first study in routine clinical practice evaluating the relationship between kidney function and digoxin peak concentrations that differentiates AKI from CKD. We did not find a relationship between kidney function and peak concentrations; however, the group with CKD was underpowered.

Productivity, workload, and clinical pharmacists: Definitions matter

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Proposed guidance on cost-avoidance studies in pharmacy practice

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

Cost-avoidance studies of pharmacist interventions are common and often the first type of study conducted by investigators to quantify the economic impact of clinical pharmacy services. The purpose of this primer is to provide guidance for conducting cost-avoidance studies pertaining to clinical pharmacy practice.

SUMMARY

Cost-avoidance studies represent a paradigm conceptually different from traditional pharmacoeconomic analysis. A cost-avoidance study reports on cost savings from a given intervention, where the savings is estimated based on a counterfactual scenario. Investigators need to determine what specifically would have happened to the patient if the intervention did not occur. This assessment can be fundamentally flawed, depending on underlying assumptions regarding the pharmacists' action and the patient trajectory. It requires careful identification of the potential consequence of nonaction, as well as probability and cost assessment. Given the uncertainty of assumptions, sensitivity analyses should be performed. A step-by-step methodology, formula for calculations, and best practice guidance is provided.

CONCLUSIONS

Cost-avoidance studies focused on pharmacist interventions should be considered low-level evidence. These studies are acceptable to provide pilot data for the planning of future clinical trials. The guidance provided in this article should be followed to improve the quality and validity of such investigations.

Methods used to attribute costs avoided from pharmacist interventions in acute care: A scoping review

PURPOSE

Cost-avoidance studies are common in pharmacy practice literature. This scoping review summarizes, critiques, and identifies current limitations of the methods that have been used to determine cost avoidance associated with pharmacists' interventions in acute care settings.

METHODS

An Embase and MEDLINE search was conducted to identify studies that estimated cost avoidance from pharmacist interventions in acute care settings. We included studies with human participants and articles published in English from July 2010 to January 2021, with the intent of summarizing the evidence most relevant to contemporary practice.

RESULTS

The database search retrieved 129 articles, of which 39 were included. Among these publications, less than half (18 of 39) mentioned whether the researchers assigned a probability for the occurrence of a harmful consequence in the absence of an intervention; thus, a 100% probability of a harmful consequence was assumed. Eleven of the 39 articles identified the specific harm that would occur in the absence of intervention. No clear methods of estimating cost avoidance could be identified for 7 studies. Among all 39 included articles, only 1 attributed both a probability to the potential harm and identified the cost specific to that harm.

CONCLUSION

Cost-avoidance studies of pharmacists' interventions in acute care settings over the last decade have common flaws and provide estimates that are likely to be inflated. There is a need for guidance on consistent methodology for such investigations for reporting of results and to confirm the validity of their economic implications.

Development of the Critical Care Pharmacotherapy Trials Network

PURPOSE

The development of the Critical Care Pharmacotherapy Trials Network (CCPTN) as a model for practice-based pharmacotherapy research is described.

SUMMARY

The CCPTN was formed in 2010 as a collaborative research network dedicated to scientific investigation in the field of critical care pharmacotherapy. The CCPTN organizational structure is consistent with many professional pharmacy and interdisciplinary organizations and organized into 3 primary domains: executive committee, working committees, and network membership. The network membership consists of critical care investigators dedicated to the mission and vision of the CCPTN and is open to anyone expressing an interest in contributing to high-level research. Network member sites represent the breadth of U.S. critical care practice environments. In addition, network members include individuals with demonstrated expertise in patient safety, administration, research design, grantsmanship, database management, peer review, and scientific writing. In 2015, there were more than 100 site investigators from around the United States and Canada. Projects to date have yielded numerous abstracts, platform presentations, and peer-reviewed publications in high-impact journals. The CCPTN has expanded to form collaborations with researchers in the United Kingdom, Australia, and New Zealand. The CCPTN has identified new potential partnerships and field-based areas for inquiry. Numerous opportunities for continued growth and scientific inquiry in the field of critical care pharmacotherapy research exist for the CCPTN to foster in the coming years.

CONCLUSION

The CCPTN has been a successful model for practice-based pharmacotherapy research and assists its members in expanding critical care pharmacotherapy knowledge.

Hydrochloric Acid Infusion for the Treatment of Metabolic Alkalosis in Surgical Intensive Care Unit Patients

BACKGROUND

Older reports of use of hydrochloric acid (HCl) infusions for treatment of metabolic alkalosis document variable dosing strategies and risk.

OBJECTIVES

This study sought to characterize use of HCl infusions in surgical intensive care unit patients for the treatment of metabolic alkalosis.

METHODS

This retrospective review included patients who received a HCl infusion for >8 hours. The primary end point was to evaluate the utility of common acid-base equations for predicting HCl dose requirements. Secondary end points evaluated adverse effects, efficacy, duration of therapy, and total HCl dose needed to correct metabolic alkalosis. Data on demographics, potential causes of metabolic alkalosis, fluid volume, and duration of diuretics as well as laboratory data were collected.

RESULTS

A total of 30 patients were included, and the average HCl infusion rate was 10.5 ± 3.7 mEq/h for an average of 29 ± 14.6 hours. Metabolic alkalosis was primarily diuretic-induced (n = 26). Efficacy was characterized by reduction in the median total serum CO₂ from 34 to 27 mM/L ( P < 0.001). The change in chloride ion deficit and change in apparent strong ion difference (SIDa) were not correlated with total HCl administered. There were no documented serious adverse effects related to HCl infusions.

CONCLUSION

HCl was effective for treating metabolic alkalosis, and no serious adverse events were seen. In this clinical setting, the baseline chloride ion deficit and SIDa were not useful for prediction of total HCl dose requirement, and serial monitoring of response is recommended.

Mathematical modeling to reduce waste of compounded sterile products in hospital pharmacies

In recent years, many US hospitals embarked on "lean" projects to reduce waste. One advantage of the lean operational improvement methodology is that it relies on process observation by those engaged in the work and requires relatively little data. However, the thoughtful analysis of the data captured by operational systems allows the modeling of many potential process options. Such models permit the evaluation of likely waste reductions and financial savings before actual process changes are made. Thus the most promising options can be identified prospectively, change efforts targeted accordingly, and realistic targets set. This article provides one example of such a datadriven process redesign project focusing on waste reduction in an in-hospital pharmacy. A mathematical model of the medication prepared and delivered by the pharmacy is used to estimate the savings from several potential redesign options (rescheduling the start of production, scheduling multiple batches, or reordering production within a batch) as well as the impact of information system enhancements. The key finding is that mathematical modeling can indeed be a useful tool. In one hospital setting, it estimated that waste could be realistically reduced by around 50% by using several process changes and that the greatest benefit would be gained by rescheduling the start of production (for a single batch) away from the period when most order cancellations are made.

Off-Label Use of Gastrointestinal Medications in the Intensive Care Unit

Purpose:

Determine the level of evidence supporting off-label gastrointestinal (GI) medication use and identify the medication class and indication whereby off-label use was most common.

Materials and Methods:

This prospective, multicentered observational study evaluated all medication orders written in 37 intensive care units (ICUs) in the United States, over a 24-hour period. All medications classified as “GI” according to a national reference were identified. The class and indication whereby off-label use was most prominent were determined and the level of evidence was described.

Results:

There were 774 orders from 363 patients and 63% (489 of 774) were considered off-label. Proton pump inhibitors (PPIs) accounted for most of the off-label usage (55% [271 of 489]), followed by laxatives (16% [77 of 489]) and histamine-2-receptor antagonists (H2RAs; 15% [71 of 489]). When prescribed, 99% (271 of 274) of PPIs, 99% (71 of 72) of H2RAs, and 79% (30 of 38) of promotility agents were off-label. Stress ulcer prophylaxis (100% [309 of 309]), GI bleeding (100% [18 of 18]), and gastric motility (88% [30 of 34]) were the most common off-label indications. The most common strength of recommendation and level of evidence for off-label use was indeterminate (58% [282 of 489]) and none (57% [280 of 489]), respectively.

Conclusion:

The PPIs are the most widely used off-label medications in the ICU. Stress ulcer prophylaxis is the most common indication. The level of evidence supporting off-label GI medication use is poor.

New dosing strategies for an old antibiotic: pharmacodynamics of front-loaded regimens of colistin at simulated pharmacokinetics in patients with kidney or liver disease

Increasing evidence suggests that colistin monotherapy is suboptimal at currently recommended doses. We hypothesized that front-loading provides an improved dosing strategy for polymyxin antibiotics to maximize killing and minimize total exposure. Here, we utilized an in vitro pharmacodynamic model to examine the impact of front-loaded colistin regimens against a high bacterial density (10(8) CFU/ml) of Pseudomonas aeruginosa. The pharmacokinetics were simulated for patients with hepatic (half-life [t1/2] of 3.2 h) or renal (t1/2 of 14.8 h) disease. Front-loaded regimens (n=5) demonstrated improvement in bacterial killing, with reduced overall free drug areas under the concentration-time curve (fAUC) compared to those with traditional dosing regimens (n=14) with various dosing frequencies (every 12 h [q12h] and q24h). In the renal failure simulations, front-loaded regimens at lower exposures (fAUC of 143 mg · h/liter) obtained killing activity similar to that of traditional regimens (fAUC of 268 mg · h/liter), with an ∼97% reduction in the area under the viable count curve over 48 h. In hepatic failure simulations, front-loaded regimens yielded rapid initial killing by up to 7 log10 within 2 h, but considerable regrowth occurred for both front-loaded and traditional regimens. No regimen eradicated the high bacterial inoculum of P. aeruginosa. The current study, which utilizes an in vitro pharmacodynamic infection model, demonstrates the potential benefits of front-loading strategies for polymyxins simulating differential pharmacokinetics in patients with hepatic and renal failure at a range of doses. Our findings may have important clinical implications, as front-loading polymyxins as a part of a combination regimen may be a viable strategy for aggressive treatment of high-bacterial-burden infections.

Pharmacist-managed antimicrobial stewardship program for patients discharged from the emergency department

Positive outcomes of antimicrobial stewardship programs in the inpatient setting are well documented, but the benefits for patients not admitted to the hospital remain less clear. This report describes a retrospective case-control study of patients discharged from the emergency department (ED) with subsequent positive cultures conducted to determine whether integrating antimicrobial stewardship responsibilities into practice of the emergency medicine clinical pharmacist (EPh) decreased times to positive culture follow-up, patient or primary care provider (PCP) notification, and appropriateness of antimicrobial therapy. Pre- and post-implementation groups of an EPh-managed antimicrobial stewardship program were compared. Positive cultures were identified in 177 patients, 104 and 73 in pre- and post-implementation groups, respectively. Median time to culture review in the pre-implementation group was 3 days (range 1-15) and 2 days (range 0-4) in the post-implementation group (P = .0001). There were 74 (71.2%) and 36 (49.3%) positive cultures that required notification in the pre- and post-implementation groups, respectively, and the median time to patient or PCP notification was 3 days (range 1-9) and 2 days (range 0-4) in the 2 groups (P = .01). No difference was seen in the appropriateness of therapy. In conclusion, EPh involvement reduced time to positive culture review and time to patient or PCP notification when indicated.

Interdisciplinary patient care in the intensive care unit: focus on the pharmacist

The field of critical care medicine began to flourish only within the last 40 years, yet it provides some of the best examples of collaborative pharmacy practice models and evidence for the value of pharmacist involvement in interdisciplinary practice. This collaborative approach is fostered by critical care organizations that have elected pharmacists into leadership positions and recognized pharmacists through various honors. There is substantial literature to support the value of the critical care pharmacist as a member of an interdisciplinary intensive care unit (ICU) team, particularly in terms of patient safety. Furthermore, a number of economic investigations have demonstrated cost savings or cost avoidance with pharmacist involvement. As the published evidence supporting pharmacist involvement in patient care activities in the ICU setting has increased, surveys have demonstrated an increase in the percentage of pharmacists performing clinical activities. In addition, substantial support of pharmacists has been provided by other clinicians, safety officers, and administrative personnel who have been involved with the initiation and expansion of critical care pharmacy services in their own institutions. Although there is still room for improvement in the range of pharmacist involvement, particularly with respect to interdisciplinary activities related to education and scholarship, pharmacists have become essential members of interdisciplinary care teams in ICU settings.

The outcomes of emergency pharmacist participation during acute myocardial infarction

BACKGROUND

Current guidelines recommend door-to-balloon times of 90 min or less for patients presenting to the emergency department (ED) with ST-segment elevation myocardial infarction (STEMI).

OBJECTIVES

To determine if a clinical pharmacist for the ED (EPh) is associated with decreased door/diagnosis-to-cardiac catheterization laboratory (CCL) time and decreased door-to-balloon time.

METHODS

A retrospective observational cohort study of ED patients with STEMI requiring urgent cardiac catheterization was conducted. Blinded data collection included timing of ED and CCL arrival, diagnostic electrocardiogram (ECG), and balloon angioplasty. For cases diagnosed after ED arrival, diagnosis time was substituted for door time. Diagnosis was the time ST elevations were evident on serial ECG. EPh present and not-present groups were compared. During the study period there were two EPhs and presence was determined by their scheduled time in the ED. Univariate and multivariate analyses was used to detect differences.

RESULTS

Multivariate analysis of 120 patients, controlled for CCL staff presence and arrival by pre-hospital services, determined that EPh presence is associated with a mean 13.1-min (95% confidence interval [CI] 6.5-21.9) and 11.5-min (95% CI 3.9-21.5) decrease in door/diagnosis-to-CCL and door-to-balloon times, respectively. Patients were more likely to achieve a door/diagnosis-to-CCL time≤ 30 min (odds ratio [OR] 3.1, 95% CI 1.3-7.8) and≤ 45 min (OR 2.9, 95% CI-1.0, 8.5) and a door-to-balloon time≤ 90 min (OR 1.9, 95% CI 0.7-5.5) more likely when the EPh was present.

CONCLUSIONS

EPh presence during STEMI presentation to the ED is independently associated with a decrease in door/diagnosis-to-CCL and door-to-balloon times.

Key articles and guidelines relative to intensive care unit pharmacotherapy: 2009 update

Compilations of key articles and guidelines in a particular clinical practice area are useful not only to clinicians who practice in that area, but also to all clinicians. We compiled pertinent articles and guidelines pertaining to drug therapy in the intensive care setting from the perspective of experienced critical care pharmacists. A broad assembly of practitioners with expertise in various areas of intensive care unit pharmacology were involved in the compilation of this update.

A prospective evaluation of propylene glycol clearance and accumulation during continuous-infusion lorazepam in critically ill patients

Propylene glycol is a commonly used diluent in several pharmaceutical preparations, including the sedative lorazepam. Fifty critically ill patients receiving continuous-infusion lorazepam for a minimum of 36 hours were prospectively evaluated to determine the extent of propylene glycol accumulation over time, characterize propylene glycol clearance in the presence of critical illness, and develop a pharmacokinetic model that would predict clearance based on patient-specific clinical, laboratory, and demographic factors. In this cohort, the median lorazepam infusion rate was 2.1 mg/h (0.5-18). Propylene glycol concentration correlated poorly with osmolality, osmol gap, and lactate. In all, 8 patients (16%) had significant propylene glycol accumulation (>25mg/dL). When propylene glycol concentrations were >25 mg/dL, the median lorazepam infusion rate before sample collection was higher, 6.4 (1.9-11.3) versus 2.0 (0.5-7.4) mg/h (P =.0003). A linear first-order model with interoccasion variability on clearance adjusted for total body weight and Acute Physiology and Chronic Health Evaluation II score predicted propylene glycol concentration.

Predictive Value of Sputum Gram Stain for the Determination of Appropriate Antibiotic Therapy in Ventilator-Associated Pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is diagnosed in about 30% to 50% of critically ill postsurgical and trauma patients. Early appropriate antibiotic therapy has been associated with improved survival rates. The diagnosis, however, continues to be a challenge. We routinely employ clinical pulmonary infection scores to warrant a bronchoalveolar lavage (BAL) quantitative culture to subsequently diagnose VAP. Presumptive antibiotic therapy for the first 48 to 72 hours is based on the sputum Gram stain, obtained at the time of BAL. This study was conducted to analyze the predictive value of sputum Gram stain for selecting appropriate early antibiotic therapy for VAP as confirmed by a BAL quantitative culture (>10 CFU/mL considered diagnostic).

METHODS

The retrospective analysis included 124 consecutive intensive care unit patients with 186 identified episodes of presumed VAP from December 2002 to June 2006. VAP episodes were identified by a clinical pulmonary infection score > or =6, availability of a sputum Gram stain, and a corresponding quantitative culture result from a BAL sample.

RESULTS

The overall correlation between Gram stain and subsequent organism identified on the BAL quantitative culture was only fair with a kappa score of 0.314. The best predictive value calculated was for the category of negative Gram stain. However, in 10 of 45 episodes where the sputum Gram stain did not identify a predominant organism, the BAL culture isolated pathogenic strains. Pseudomonas sp. was the most common bacteria isolated from the BAL samples.

CONCLUSIONS

Irrespective of sputum Gram stain, presumptive triple antibiotic coverage should be instituted to provide dual antibiotic coverage for gram-negative bacilli, and vancomycin for gram-positive cocci. Additionally, identification of no organisms in the sputum Gram stain should still prompt broad-spectrum antibiotic coverage until the final results of the BAL quantitative culture are available.

Pharmacokinetics and Pharmacodynamics of Enoxaparin in Multiple Trauma Patients

BACKGROUND

Enoxaparin is the only low molecular-weight heparin (LMWH) with documented efficacy for the prevention of venous thromboemobolism (VTE) following trauma, and it is currently considered the treatment of choice. Recent reports have suggested that the pharmacokinetics (PK) and pharmacodynamics of LMWH products may be altered in critically ill patients.

METHODS

Two cohorts of critically ill multiple trauma patients were enrolled in this study: A (nonedematous) and B (edematous, defined as the presence of peripheral edema and an increase in body weight of > or =10 kg). All patients received at least four doses of enoxaparin 30 mg subcutaneously every 12 hours before the study dose. Blood samples were collected before and 0.5, 1, 2, 3, 4, 6, 8, and 12 hours following a morning dose. Plasma anti-Xa and antithrombin (AT) activities were determined using chromogenic assays. A compartmental PK analysis model was defined for the data. PK parameters for the two cohorts were compared using a Mann-Whitney Rank Sum test.

RESULTS

The area under the curve (AUC)0-12 hour, maximal plasma anti-activated Factor Xa (anti-Xa) activity (Amax), and AT activity were significantly lower in the edematous trauma patients (p < 0.05). The AUC0-12 hour for plasma anti-Xa activity was highly variable in both study cohorts. Seven of the 10 edematous patients had barely quantifiable anti-Xa results. Activity levels were too low to reliably estimate the PK parameters for most patients in cohort B.

CONCLUSION

The standard dose of enoxaparin recommended for the prevention of VTE following multiple trauma provides unreliable and highly variable anti-Xa activity in critically ill trauma patients, and is strongly affected by the presence of significant peripheral edema.

Analysis of omeprazole, midazolam and hydroxy-metabolites in plasma using liquid chromatography coupled to tandem mass spectrometry

A method has been developed and validated for the quantitation of midazolam, alphahydroxy-midazolam, omeprazole, and hydroxyomeprazole from one 250 microL sample of human plasma using high performance liquid chromatography coupled to tandem mass spectrometry. The method was validated for a daily working range of 0.400-100 ng/mL, with limits of detection between 2 and 15 pg/mL. The inter-assay variation was less than 15% for all analytes at four control concentrations and the samples were stable for three freeze-thaw cycles under the analysis conditions and 24 h in the post-preparative analysis matrix. This method was used to analyze samples in support of clinical studies probing the activity of the cytochrome P-450 enzyme system.

Evaluation of lacrimal fluid as an alternative for monitoring glucose in critically ill patients

OBJECTIVE

This study evaluated the use of lacrimal fluid glucose concentrations as a minimally invasive, alternative sampling strategy for monitoring glucose concentrations in surgical/trauma ICU patients.

DESIGN AND SETTING

Prospective, paired sample study in an adult surgical/trauma ICU.

PATIENTS

Patients receiving subcutaneous or intravenous insulin requiring routine capillary blood glucose measurements. Patients receiving ocular lubricants, artificial tears, or routinely administered ophthalmic medications and patients with facial injuries were excluded.

INTERVENTIONS

Lacrimal fluid was collected using glass capillary tube placed near the cul-de-sac of the eye. Capillary blood glucose was determined using a bedside glucose meter as per routine ICU care.

MEASUREMENTS AND RESULTS

Lacrimal fluid glucose concentration was analyzed using high-performance liquid chromatography with pulse amperometric detection. Forty-four paired samples from five patients were analyzed. Pearson correlation between lacrimal fluid (microM) and blood glucose (mM) concentrations and the proportional change from baseline revealed no significant associations. Due to the very poor association, enrollment was discontinued after five patients.

CONCLUSIONS

Lacrimal fluid and blood glucose concentrations were poorly correlated, suggesting that the former is not a reliable alternative to blood glucose monitoring in surgical/trauma ICU patients requiring insulin therapy.

Cytochrome P450 mRNA expression in peripheral blood lymphocytes as a predictor of enzyme induction

OBJECTIVE

Previous reports have supported the concept that messenger ribonucleic acid (mRNA) concentrations for cytochrome P450 (CYP) enzymes in peripheral blood mononuclear cells may be predictive of systemic enzyme activity. We investigated whether changes in mRNA expression for CYP1A2,CYP2C19, CYP2D6 and CYP3A4 in peripheral blood lymphocytes (PBLs) may serve as surrogate markers for changes in CYP enzyme activity following the administration of rifampin.

METHODS

On day 1 and day 9 of the study, 12 healthy volunteers were administered caffeine 100 mg, debrisoquine 10 mg and omeprazole 40 mg orally, along with midazolam 0.025 mg/kg intravenously. Blood samples and urine were collected for 8 h after drug administration. The subjects took rifampin 300 mg (n = 6) or 600 mg (n = 6) daily on days 2-8. Total RNA was isolated from PBLs on day 1 and day 9, and mRNA expression for the CYP enzymes and hGAPDH were determined by means of quantitative, real-time, reverse-transcriptase polymerase chain reaction. CYP1A2 activity was estimated by calculating the plasma paraxanthine to caffeine AUC ratio (caffeine metabolic ratio; CMR), CYP2C19 activity by the 2-h omeprazole hydroxylation index (HI), CYP2D6 activity by the urinary debrisoquine recovery ratio (DBRR) and CYP3A4 activity by midazolam clearance.

RESULTS

Median midazolam clearance (0.362 to 0.740 l/kg/h), omeprazole HI (0.752 to 0.214), CMR (0.365 to 0.450) and DBRR (0.406 to 0.479) all changed significantly following rifampin, consistent with the expected enzyme induction. CYP1A2,CYP2D6 and CYP3A4 mRNA content were measurable in all samples. CYP2C19 mRNA was inconsistently detectable. There were no significant correlations between changes in enzyme activity and mRNA expression by Spearman's rank order correlation.

CONCLUSION

The results do not support the use of mRNA expression assays for CYP1A2, CYP2C19, CYP2D6 and CYP3A4 enzymes in PBLs as surrogates for quantifying changes in systemic enzyme activity in the setting of enzyme induction.

Key articles and guidelines relative to intensive care unit pharmacology--2004

Compilations of key articles and guidelines in a particular clinical practice area are useful not only to clinicians who practice in that area, but to all clinicians. We compiled pertinent articles and guidelines pertaining to drug therapy in the intensive care setting from the perspective of actively practicing critical care pharmacists. This document differs from the original 2002 version in that a broader assembly of intensive care practitioners was involved in the compilation.

Omeprazole Absorption from a Compounded Transdermal Formulation in Healthy Volunteers

OBJECTIVE

To evaluate the plasma concentration versus time profile of omeprazole following the administration of a compounded transdermal gel formulation in healthy volunteers.

DESIGN

Single-dose transdermal pharmacokinetic (PK) study including a comparison with historical data from an oral PK study.

SETTING

Academic clinical research center.

PARTICIPANTS

Eight healthy volunteers between 18 and 50 years of age.

INTERVENTIONS

Omeprazole gel 40 mg (0.8 mL) was applied to the ventral surface of the forearm covering an area of 7 x 15 cm without an occlusive dressing. Blood samples were collected just before application and then at 1, 2, 3, 4, 6, and 8 hours. Plasma concentrations of omeprazole were determined using a validated liquid chromatography tandem mass spectrometry method.

MAIN OUTCOME MEASURES

PK parameters (maximal plasma concentration [C(max)], the time of C(max), [T(max)], the area under the omeprazole concentration versus time curve from 0 to 8 hours, the elimination rate constant, and the half-life of the elimination phase) following transdermal administration, compared with historical controls who had received an oral omeprazole 40 mg dose during a previous study.

RESULTS

Of the eight volunteers, five had undetectable plasma omeprazole concentrations throughout the 8-hour study, precluding a complete PK analysis. For the three volunteers with detectable plasma omeprazole concentrations, the values ranged from 0.204 to 0.552 ng/mL. Including values of 0 for the patients with undetectable levels, the mean (+/- SD) C(max) was 0.153 +/- 0.241 ng/mL, and the T(max) in patients with detectable levels occurred at approximately 6 hours. The plasma concentrations following transdermal administration were approximately 1,000-fold lower than those observed with oral dosing.

CONCLUSION

Transdermal absorption from a single dose of the omeprazole gel formulation used in this study was poor. This transdermal gel formulation is clearly not bioequivalent to the oral capsule.

The Influence of St. John’s Wort on the Pharmacokinetics and Protein Binding of Imatinib Mesylate

STUDY OBJECTIVE

To determine the effect of St. John's wort on the pharmacokinetics of imatinib mesylate.

DESIGN

Open-label, complete crossover, fixed-sequence, pharmacokinetic study.

SETTING

Clinical research center.

SUBJECTS

Ten healthy adult volunteers.

INTERVENTION

Single 400-mg oral doses of imatinib were administered before and after 2 weeks of treatment with St. John's wort 300 mg 3 times/day.

MEASUREMENTS AND MAIN RESULTS

The pharmacokinetics of imatinib were significantly altered by St. John's wort, with reductions of 32% in the median area under the concentration-time curve from time zero to infinity (p=0.0001), 29% in maximum observed concentration (p=0.005), and 21% in half-life (p=0.0001). Protein binding ranged from 97.7-90.3% (mean 94.9%), was concentration independent, and was not altered by St. John's wort. Therapeutic outcomes of imatinib have been shown to correlate with both dose and drug concentrations.

CONCLUSION

Coadministration of imatinib with St. John's wort may compromise imatinib's clinical efficacy.

Acute postoperative hypertension: a review of therapeutic options

PURPOSE

The pathophysiology and treatment of acute postoperative hypertension (APH) are discussed.

SUMMARY

APH is a significant elevation in arterial blood pressure (BP) during the immediate postoperative period. The predominant underlying mechanism appears to be sympathetic activation. APH may lead to serious neurologic, cardiovascular, or surgical-site complications and often requires intervention and management. Postoperative hypertension lasts less than six hours in most patients. Reversible or treatable causes of hypertension, including pain, anxiety, hypothermia, and hypoxemia, should be considered and treated before the implementation of antihypertensive therapy. The ideal agent for treating APH is intravenously administered, is fast acting, and has a short duration of action, allowing the rapid and safe adjustment of therapy to achieve a targeted BP range. Sodium nitroprusside has long been considered the standard therapy and has many of the ideal characteristics. However, because of the need for invasive hemodynamic monitoring and concerns about toxicity in patients given sodium nitroprusside, several newer agents may be preferable in routine clinical practice. Labetalol, nicardipine, and nitroglycerin have been widely studied or used. Hydralazine, esmolol, fenoldopam, angiotensin-converting-enzyme inhibitors, and clonidine may also be useful treatment options.

CONCLUSION

When treatment of APH is necessary, therapy should be individualized for the patient. No one agent is preferred, but effective options include sodium nitroprusside, nitroglycerin, labetalol, and nicardipine.

Effect of Tenofovir Disoproxil Fumarate on the Pharmacokinetics and Pharmacodynamics of Total, R-, and S-Methadone

STUDY OBJECTIVE

To evaluate the potential effect of tenofovir disoproxil fumarate (DF) on the pharmacokinetics of methadone.

DESIGN

Phase I, open-label, fixed-sequence, pharmacokinetic drug-drug interaction study.

SETTING

Clinical research center.

SUBJECTS

Fourteen volunteers receiving stable methadone maintenance therapy who were not infected with the human immunodeficiency virus.

INTERVENTION

Tenofovir DF was added to the subjects' methadone regimens.

MEASUREMENTS AND MAIN RESULTS

The pharmacokinetics of total, R-, and S-methadone were evaluated at baseline and after 2 weeks of daily tenofovir DF coadministration with a light meal. Steady-state tenofovir DF pharmacokinetics were evaluated at day 15. Bioequivalence testing was conducted of total, R-, and S-methadone area under the serum or plasma concentration-time curve during the 24-hour dosing interval at steady state (AUCss) and maximum concentration in serum or plasma (Cmax). Subjects were evaluated for changes in methadone pharmacodynamics by the Short Opiate Withdrawal Scale (SOWS) and pupillary diameter measurements at frequent intervals. Coadministration with tenofovir DF did not affect the pharmacokinetics of methadone. Geometric mean R-methadone systemic exposures, AUCss and Cmax, differed by 5% or less when methadone was dosed with tenofovir DF. Similar results were observed for S-methadone and for total methadone. Both AUCss and Cmax met the strict criteria for bioequivalence between the two study periods for total, R-, and S-methadone, indicating a lack of drug interaction when tenofovir DF was coadministered with methadone. No significant changes in SOWS scores or pupillary diameter measurements occurred, and no notable clinical adverse events were reported.

CONCLUSION

Tenofovir DF pharmacokinetics were comparable to previously reported values of tenofovir DF in HIV-infected patients. Coadministration of methadone with tenofovir DF did not alter the pharmacokinetics or pharmacodynamics of total, R-, or S-methadone. Tenofovir DF may be given as part of a once-daily antiretroviral regimen in patients receiving methadone maintenance therapy.

Cytochrome P450 3A4 activity after surgical stress

OBJECTIVE

To evaluate the relationship between the acute inflammatory response after surgical trauma and changes in hepatic cytochrome P450 3A4 activity, compare changes in cytochrome P450 3A4 activity after procedures with varying degrees of surgical stress, and to explore the time course of any potential drug-cytokine interaction after surgery.

DESIGN

Prospective, open-label study with each patient serving as his or her own control.

SETTING

University-affiliated, acute care, general hospital.

PATIENTS

A total of 16 patients scheduled for elective repair of an abdominal aortic aneurysm (n = 5), complete or partial colectomy (n = 6), or peripheral vascular surgery with graft (n = 5).

INTERVENTIONS

Cytochrome P450 3A4 activity was estimated using the carbon-14 [14C]erythromycin breath test (ERMBT) before surgery and 24, 48, and 72 hrs after surgery. Abdominal aortic aneurysm and colectomy patients also had an ERMBT performed at discharge. Blood samples were obtained before surgery, immediately after surgery, and 6, 24, 32, 48, and 72 hrs after surgery for determination of plasma concentrations of interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha. Clinical markers of surgical stress that were collected included duration of surgery, estimated blood loss, and volume of fluids administered in the operating room.

MEASUREMENTS AND MAIN RESULTS

ERMBT results significantly declined in all three surgical groups, with the lowest value at the time of the 72-hr study in all three groups. There was a trend toward differences in ERMBT results among groups that did not reach statistical significance (p =.06). The nadir ERMBT result was significantly and negatively correlated with both peak interleukin-6 concentration (r(s) = -.541, p =.03) and log interleukin-6 area under the curve from 0 to 72 hrs (r(s) = -.597, p =.014). Subjects with a peak interleukin-6 of >100 pg/mL had a significantly lower nadir ERMBT compared with subjects with a peak interleukin-6 of <100 pg/mL (35.5% +/- 5.2% vs. 74.7% +/- 5.1%, p <.001).

CONCLUSIONS

Acute inflammation after elective surgery was associated with a significant decline in cytochrome P450 3A4 activity, which is predictive of clinically important changes in the metabolism of commonly used drugs that are substrates for this enzyme.

Rhabdomyolysis and acute renal failure following an ethanol and diphenhydramine overdose

OBJECTIVE

To report a case of nontraumatic rhabdomyolysis complicated by oliguric, acute renal failure following an intentional overdose of ethanol and diphenhydramine.

CASE SUMMARY

A 21-year-old white man was admitted through the emergency department following an intentional overdose of ethanol and diphenhydramine. The patient subsequently developed acute renal failure, and a diagnosis of nontraumatic rhabdomyolysis was made. With the absence of other common causes in this case, the rhabdomyolysis was believed to be due to the combined ethanol and diphenhydramine overdose.

DISCUSSION

Rhabdomyolysis is a severe and life-threatening syndrome caused by various insults to skeletal muscle, including drug-induced injury. Early detection and institution of effective treatments are essential to minimizing the complications of this syndrome. A delay in establishing the diagnosis in this case likely contributed to the severity of the renal failure.

CONCLUSIONS

Nontraumatic rhabdomyolysis is an uncommon adverse outcome of drug and toxin ingestion. Due to the potential severity of the complications of this syndrome and the importance of early recognition and treatment to prevent renal failure, clinicians should have a high index of suspicion for rhabdomyolysis following overdoses that involve alcohol or antihistamines.

Point-of-care versus laboratory monitoring of patients receiving different anticoagulant therapies

STUDY OBJECTIVE

To compare point-of-care and standard hospital laboratory assays for monitoring patients receiving single or combination anticoagulant regimens.

DESIGN

Prospective analysis.

SETTING

Nursing units and clinics at a large, community hospital.

PATIENTS

One hundred fifty patients receiving anticoagulants for cardiac, vascular, orthopedic, or cancer indications. Thirty patients were enrolled into each treatment group: warfarin, enoxaparin, heparin, warfarin plus enoxaparin, and warfarin plus heparin.

INTERVENTION

Capillary and venous blood samples were collected once in each patient for simultaneous measurement of international normalized ratio (INR) and activated partial thromboplastin time (aPTT) by both assays.

MEASUREMENTS AND MAIN RESULTS

Mean differences in paired INR and paired aPTT by point-of-care and standard assays were small, but 95% confidence intervals were wide. The INR differences were greater for the warfarin plus heparin group than for the warfarin group or warfarin plus enoxaparin group; clinical decision agreement was 47% for warfarin plus heparin, 73% for warfarin, and 93% for warfarin plus enoxaparin. The aPTT difference was greater for the warfarin plus heparin than for the heparin group; however, clinical decision agreement, 67% and 70%, respectively, was similar.

CONCLUSIONS

Point-of-care methods showed limited agreement with standard hospital laboratory assays of coagulation for all treatment groups. For INR values, significantly greater disagreement was noted between the assay methods for the warfarin plus heparin group compared with the warfarin group, but the agreement was similar for the warfarin and warfarin plus enoxaparin groups. Our data indicate that the point-of-care assays should not be considered interchangeable with standard laboratory assays.

Effects of metronidazole on hepatic CYP3A4 activity

STUDY OBJECTIVE

To evaluate the effect of a short course of oral metronidazole, commonly used for bowel-preparation regimens, on hepatic cytochrome P450 (CYP) 3A4 activity, as measured by the [14C N-methyl]-erythromycin breath test (ERMBT) in healthy volunteers.

DESIGN

Prospective, nonrandomized, interventional study

SETTING

University-affiliated, community, teaching hospital.

SUBJECTS

Five healthy male volunteers.

INTERVENTION

Subjects underwent a baseline ERMBT in the morning before receiving three oral doses of metronidazole 500 mg administered at 3 P.M., 7 P.M., and 11 P.M. Repeat ERMBTs were performed at 24, 72, and 96 hours after the initial ERMBT. Changes in ERMBT values were compared with baseline results using Freidman's repeated-measures analysis of variance on ranks.

MEASUREMENTS AND MAIN RESULTS

The ERMBT values did not change significantly compared with baseline (p=0.82). Median (range) ERMBT values expressed as a percentage of baseline at 24, 72, and 96 hours were 110.3 (96.2-136.9), 101.3 (99.3-115.0), and 101.8 (95.5-116.3), respectively

CONCLUSION

A short course of oral metronidazole does not result in a significant change in hepatic CYP3A4 activity as measured by the ERMBT.

Antibiotic susceptibility in the surgical intensive care unit compared with the hospital-wide antibiogram

OBJECTIVE

To compare the antibiotic susceptibility of bacterial isolates from patients in the surgical intensive care unit (SICU) with hospital-wide bacterial susceptibility.

DESIGN

Retrospective cohort analytic study.

SETTING

Eight-bed SICU in a university-affiliated teaching hospital.

PATIENTS

All hospitalized patients with culture results positive for microorganisms.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Antibiotic susceptibility data were collected retrospectively for all bacterial isolates from SICU patients during July 1, 1994, to June 30, 1995. All duplicate and surveillance cultures were eliminated from the data set. Susceptibility testing was conducted using our standard laboratory methods. Results were compared with the hospital-wide antibiogram (HWA) for the same time period. Comparisons were made using the chi(2) test with Yates correction or the Fisher exact test, as appropriate. Staphylococcus aureus (HWA, n=494; SICU, n=71) was significantly less susceptible to oxacillin (51% vs 28%; P<.001), ciprofloxacin (50% vs 25%; P<.001), erythromycin (46% vs 23%; P<.001), and clindamycin (51% vs 27%; P<.001) in the SICU. Coagulase-negative staphylococci (HWA, n=339; SICU, n=37) were significantly less susceptible to oxacillin (33% vs 16%; P=.04) and clindamycin (57% vs 34%; P=.02). Pseudomonas aeruginosa (HWA, n=513; SICU, n=96) was less susceptible to imipenem (85% vs 74%, P=.01) and more susceptible to ticarcillin-clavulanic acid (88% vs 100%, P<.001) in the SICU. Escherichia coli (HWA, n=474; SICU, n=36) was more susceptible to most penicillin-derivative antibiotics in the SICU (ampicillin [68% vs 83%, P=.06], ticarcillin [65% vs 86%, P=.01], mezlocillin [76% vs 95%, P=.01], and ticarcillin-clavulanic acid [88% vs 100%, P=.02]).

CONCLUSIONS

The 2 most commonly isolated bacterial pathogens in the SICU (S aureus and P aeruginosa) had significantly different susceptibility patterns compared with the HWA. Surprisingly, E coli isolated in the SICU tended to be more susceptible to penicillin-derivative antibiotics. These data indicate that empiric antibiotic choices in the SICU may be better guided by unit-specific antibiograms.

Bioavailability of phenytoin acid and phenytoin sodium with enteral feedings

STUDY OBJECTIVE

To compare the absolute bioavailability of phenytoin (PHT) sodium solution and PHT acid suspension in healthy volunteers receiving continuously infused enteral feedings.

DESIGN

Randomized, open-label, single-dose, three-period crossover study.

SETTING

University clinical research center.

SUBJECTS

Ten healthy volunteers age 23-43 years.

INTERVENTIONS

The three phases of the study were separated by at least 7 days. During phase A, subjects received PHT sodium 435 mg intravenously over 30 minutes. During phases B and C, subjects had a nasogastric feeding tube placed through which PHT acid suspension 400 mg and PHT sodium solution 435 mg were administered, respectively. For phases B and C, continuous enteral feedings were given by feeding tube for 14 hours before and after the PHT dose. Blood samples were collected over 72 hours after each PHT dose, and the serum was analyzed for PHT.

MEASUREMENTS AND MAIN RESULTS

The rate and extent of PHT absorption and PHT pharmacokinetics were determined using an empirical quadratic function of time method. Bioavailability, rate of absorption, maximum concentration (Cmax), and time to maximum concentration (Tmax) were compared for the two enteral doses by paired Student's t test. There were no significant differences in bioavailability for PHT acid suspension and PHT sodium solution (0.88 +/- 0.15 vs 0.91 +/- 0.7, p=0.57, 90% CI -0.14-0.071). The Cmax was greater (7.4 +/- 0.9 mg/L vs 5.5 +/- 1.7 mg/L, p=0.019) and Tmax was less (2.5 +/- 3.8 vs.14.8 +/- 11.2 hrs, p=0.004) for the sodium solution. The time to 50% fractional absorption (0.33 +/- 0.08 vs 3.2 +/- 2.4 hrs, p=0.004) and 90% fractional absorption (7.9 +/- 6.2 vs 22.3 +/- 17.2 hrs, p=0.021) was also significantly shorter for the sodium solution.

CONCLUSION

The absolute bioavailability of the two dosage forms of PHT administered with concomitant enteral feedings were not significantly different, however, the absorption patterns were significantly different, with the sodium solution being more rapidly absorbed.