Screening for problematic opioid use in the emergency department: Comparison of two screening measures

Study objective

Earlier intervention for opioid use disorder (OUD) may reduce long-term health implications. Emergency departments (EDs) in the United States treat millions with OUD annually who may not seek care elsewhere. Our objectives were (1) to compare two screening measures for OUD characterization in the ED and (2) to determine the proportion of ED patients screening positive for OUD and those who endorse other substance use to guide future screening programs.

Methods

A cross-sectional study of randomly selected adult patients presenting to three Midwestern US EDs were enrolled, with duplicate patients excluded. Surveys were administered via research assistant and documented on tablet devices. Demographics were self-reported, and OUD positivity was assessed by the DSM 5 checklist and the WHO ASSIST 3.1. The primary outcome was the concordance between two screening measures for OUD. Our secondary outcome was the proportion of ED patients meeting OUD criteria and endorsed co-occurring substance use disorder (SUD) criteria.

Results

We enrolled 1305 participants; median age of participants was 46 years (range 18-84), with 639 (49.0%) Non-Hispanic, White, and 693 (53.1%) female. Current OUD positivity was identified in 17% (222 out of 1305) of the participants via either DSM-5 (two or more criteria) or ASSIST (score of 4 or greater). We found moderate agreement between the measures (kappa = 0.56; Phi coefficient = 0.57). Of individuals screening positive for OUD, 182 (82%) endorsed criteria for co-occurring SUD.

Conclusions

OUD is remarkably prevalent in ED populations, with one in six ED patients screening positive. We found a high prevalence of persons identified with OUD and co-occurring SUD, with moderate agreement between measures. Developing and implementing clinically feasible OUD screening in the ED is essential to enable intervention.

Advancing Pharmacogenomics-Based Care Through Interprofessional Education

As genomic medicine becomes increasingly complex, pharmacists need to work collaboratively with other healthcare professionals to provide genomics-based care. The core pharmacist competencies in genomics were recently updated and mapped to the entrustable professional activities (EPAs). The new competency that is mapped to the "Interprofessional Team Member" EPA domain emphasizes the role of pharmacists as the pharmacogenomics experts in an interprofessional healthcare team. Interprofessional education (IPE) activities involving student pharmacists and students from other healthcare disciplines are crucial to prepare student pharmacists for a team-based approach to patient-centered care. This commentary discusses the pharmacogenomics-focused IPE activities implemented by 3 programs, the challenges faced, and the lessons learned. It also discusses strategies to develop pharmacogenomics-focused IPE activities based on existing resources. Developing pharmacogenomics-focused IPE activities will help prepare pharmacy graduates with the knowledge, skills, and attitudes to lead collaborative, interprofessional teams in the provision of pharmacogenomics-based care, consistent with the standards described in the genomics competencies for pharmacists.

Designer benzodiazepine rat pharmacokinetics: A comparison of alprazolam, flualprazolam and flubromazolam

Designer benzodiazepines, including flualprazolam and flubromazolam, are clandestinely produced to circumvent federal regulations. Although flualprazolam and flubromazolam are structurally similar to alprazolam, they do not have an approved medical indication. Flualprazolam differs from alprazolam by the addition of a single fluorine atom. Whereas, flubromazolam differs by the addition of a single fluorine atom and substitution of a bromine for a chlorine atom. The pharmacokinetics of these designer compounds have not been extensively evaluated. In the present study, we evaluated flualprazolam and flubromazolam in a rat model and compared the pharmacokinetics of both compounds to alprazolam. Twelve male, Sprague-Dawley rats were given a 2 mg/kg subcutaneous dose of alprazolam, flualprazolam and flubromazolam and plasma pharmacokinetic parameters were evaluated. Both compounds displayed significant two-fold increases in volume of distribution and clearance. Additionally, flualprazolam displayed a significant increase in half-life leading to a nearly double half-life when compared to alprazolam. The findings of this study demonstrate that fluorination of the alprazolam pharmacophore increases pharmacokinetic parameters including half-life and volume of distribution. The increase in these parameters for flualprazolam and flubromazolam leads to an overall increased exposure in the body and a potential for greater toxicity than alprazolam.

Genetic Variants Associated with Opioid Use Disorder

Genetics are presumed to contribute 30-40% to opioid use disorder (OUD), allowing for the possibility that genetic markers could be used to identify personal risk for developing OUD. We aimed to test the potential association among 180 candidate single nucleotide polymorphisms (SNPs), 120 of which were related to the dopamine reward pathway and 60 related to pharmacokinetics. Participants were randomly recruited in 2020-2021 in a cross-sectional genetic association study. Self-reported health history including Diagnostic and Statistical Manual of Mental Disorders (DSM-5) OUD criteria and buccal swabs were collected. A total of 1,301 participants were included in the analyses for this study. Of included participants, 250 met the DSM-5 criteria for ever having OUD. Logistic regression, adjusting for age and biologic sex, was used to characterize the association between each SNP and DSM-5 criteria consistent with OUD. Six SNPs found in 4 genes were associated with OUD: increased odds with CYP3A5 (rs15524 and rs776746) and DRD3 (rs324029 and rs2654754), and decreased odds with CYP3A4 (rs2740574) and CYP1A2 (rs2069514). Homozygotic CYP3A5 (rs15524 and rs776746) had the highest adjusted odds ratio of 2.812 (95% confidence interval (CI) 1.737, 4.798) and 2.495 (95% CI 1.670, 3.835), respectively. Variants within the dopamine reward and opioid metabolism pathways have significant positive (DRD3 and CYP3A5) and negative (CYP3A4 and CYP1A2) associations with OUD. Identification of these variants provides promising possibilities for genetic prognostic and therapeutic targets for future investigation.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2C19 Genotype and Clopidogrel Therapy: 2022 Update

CYP2C19 catalyzes the bioactivation of the antiplatelet prodrug clopidogrel, and CYP2C19 genotype impacts clopidogrel active metabolite formation. CYP2C19 intermediate and poor metabolizers who receive clopidogrel experience reduced platelet inhibition and increased risk for major adverse cardiovascular and cerebrovascular events. This guideline is an update to the 2013 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for the use of clopidogrel based on CYP2C19 genotype and includes expanded indications for CYP2C19 genotype-guided antiplatelet therapy, increased strength of recommendation for CYP2C19 intermediate metabolizers, updated CYP2C19 genotype to phenotype translation, and evidence from an expanded literature review (updates at www.cpicpgx.org).

Pharmacists Leading the Way to Precision Medicine: Updates to the Core Pharmacist Competencies in Genomics

Genomics is becoming an increasingly important part of health care, and pharmacists are well-positioned to be practice-based leaders in pharmacogenomics and precision medicine. Competencies available through the Genetics/Genomics Competency Center provide a framework for pharmacogenomics instruction in both pharmacy school curricula and continuing education programs. Given the significant advancements in pharmacogenomics over the past decade, the 2019-2020 American Association of Colleges of Pharmacy Pharmacogenomics Special Interest Group updated the pharmacist competencies. The process used a systematic approach which included mapping pharmacogenomics-specific competencies to the entrustable professional activities for pharmacists and seeking consensus from key stakeholders. The result is an expansion to 30 competencies that reflect the contemporary roles pharmacists play in the application of pharmacogenomics in clinical practice. When implemented into curricula, these competencies will ensure that learners are "practice ready" to integrate pharmacogenomics into patient care. Additional postgraduate training is needed for advanced roles in pharmacogenomics implementation, education, and research.

Systematic review of Pharmacogenomics Knowledgebase evidence for pharmacogenomic links to the dopamine reward pathway for heroin dependence

Genetics play an important role in opioid use disorder (OUD); however, few specific gene variants have been identified. Therefore, there is a need to further understand the pharmacogenomics influences on the pharmacodynamics of opioids. The Pharmacogenomics Knowledgebase (PharmGKB), a database that links genetic variation and drug interaction in the body, was queried to identify polymorphisms associated with heroin dependence in the context of opioid related disorders/OUD. Eight genes with 22 variants were identified as linked to increased risk of heroin dependence, with three genes and variants linked to decreased risk, although the level of evidence was moderate to low. Therefore, continued exploration of biomarker influences on OUD, reward pathways and other contributing circuitries is necessary to understand the true impact of genetics on OUD before integration into clinical guidelines.

Defining the role of pharmacists in medication-related genetic counseling

There is little question that precision medicine will eventually be the standard of care in treatment with algorithms designed for therapy selection and is already being used in some specialties such as cystic fibrosis and multiple cancer treatments. Genetic counselors are the heart of the treatment team in relation to counseling regarding genetic risk factors and disease states. A framework for treatment within the interdisciplinary team with more defined roles and areas of specialty will need to be in place as this practice approach expands with new data and treatments. Pharmacists are poised to be of great assistance in this matrix as many of these roles are merely an extension of current tasks and responsibilities of pharmacy practice.

The Expanded Potential Role of Pharmacogenomics

The topic of phenoconversion was chosen for discussion in this editorial to add to the work presented by Cox and Marshall in this issue of The Senior Care Pharmacist. When considering the increased sensitivity that older patients have to medications, the inclusion of pharmacogenomics (PGx) information can be of great importance. Understanding the consequences of phenoconversion can further expand the role of PGx in patient care.

Pharmacogenomics in the United States Community Pharmacy Setting: The Clopidogrel-CYP2C19 Example

Pharmacogenomics (PGx) is expanding across health-care practice settings, including the community pharmacy. In the United States, models of implementation of PGx in the community pharmacy have described independent services and those layered on to medication therapy management. The drug-gene pair of clopidogrel-CYP2C19 has been a focus of implementation of PGx in community pharmacy and serves as an example of the evolution of the application of drug-gene interaction information to help optimize drug therapy. Expanded information related to this drug-gene pair has been provided by the US Food and Drug Administration and clinical PGx guidelines have and continue to be updated to support clinical decision-making. Most recently direct-to-consumer (DTC) PGx has resulted in patient generated sample collection and submission to a genetic testing-related company for analysis, with reporting of genotype and related phenotype information directly to the patient without a health-care professional guiding or even being involved in the process. The DTC testing approach needs to be considered in the development or modification of PGx service models in the community pharmacy setting. The example of clopidogrel-CYP2C19 is discussed and current models of PGx implementation in the community pharmacy in the United States are presented. New approaches to PGx services are offered as implementation continues to evolve and may now include DTC information.

Pharmacogenomics: A Practical Primer for Senior Care Pharmacists

Pharmacogenomics (PGx), the study of how an individual's genetic makeup affects his or her response to drugs, is a fast-growing field that gives health care providers a valuable tool to help safely and effectively manage medication. However, few providers have experience in applying the results of PGx tests to their practices, and this can lead to disregarding the data or unnecessarily modifying medication regimens. Pharmacists are uniquely positioned to become wellversed in the interpretation of PGx data, critically evaluating the "green-yellow-red" result categories that seemingly signal "go, caution, stop" regarding the use of a particular medication. Pharmacists also can evaluate genotype and phenotype information, commonly included in PGx laboratory reports, to optimize therapy. Using a case-based approach, this primer is intended to provide consultant pharmacists with practical direction to aid in PGx interpretation that will provide contextappropriate recommendations that contributes to positive patient outcomes.

A review of the influence of functional group modifications to the core scaffold of synthetic cathinones on drug pharmacokinetics

RATIONALE

The synthetic cathinones are a class of designer drugs of abuse that share a common core scaffold. The pharmacokinetic profiles of the synthetic cathinones vary based on the substitutions to the core scaffold.

OBJECTIVES

To provide a summary of the literature regarding the pharmacokinetic characteristics of the synthetic cathinones, with a focus on the impact of the structural modifications to the pharmacokinetics.

RESULTS

In many, but not all, instances the pharmacokinetic characteristics of the synthetic cathinones can be reasonably predicted based on the substitutions to the core scaffold. Mephedrone and methylone are chemically alike and have similar T_max and t_1/2 in male rats. MDPV, a structurally distinct synthetic cathinone from mephedrone and methylone, has a lower T_max and t_1/2. Increasing the length of the alkyl chain on the α position of methylone, to produce pentylone, results in increased plasma concentrations and longer t_1/2. Metabolism of the synthetic cathinones is reasonably predictable based on the chemical structure, and several phase I metabolites retain pharmacodynamic activity. CYP2D6 is implicated in the metabolism of all of the synthetic cathinones, and other P450s (CYP1A2, CYP2B6, and CYP2C19) are known to contribute variably to the metabolism of specific synthetic cathinones.

CONCLUSIONS

Continued research will lead to a better understanding of the pharmacokinetic changes associated with structural modifications to the cathinone scaffold, and potentially in the long range, enhanced overdose and addiction therapy. Additionally, the areas of polydrug use and pharmacogenetics have been largely overlooked with regard to synthetic cathinones.

Expanding Pharmacist and Student Pharmacist Access to Genetics/Genomics/Pharmacogenomics Competency Education

BACKGROUND

As pharmacogenomics (PGx), a component of genetics/genomics and precision medicine, gains traction in the clinical setting, education of health care providers and health professions students must be made broadly available to improve accessibility of such services to patients. As medication experts with education in pharmacology, pharmacokinetics, and pharmacodynamics, pharmacists must further their education to include pharmacogenomics. Currently, few opportunities exist to gain this type of education, and therefore, these services are not yet broadly available to the public.

OBJECTIVE

The specific goal of this study was to evaluate pharmacists' and student pharmacists' self-assessed perception of competence related to genetics, genomics, and pharmacogenomics as presented via an online "pharmacogenomics certification program" (PGx program).

DESIGN

The PGx program was delivered online with the content consisting of 3 background lessons and 8 specific drug-gene lessons presented in the context of pharmacist competency statements. In addition, 11 "video modules" with competency-related PGx content were included to provide a comprehensive program. A pre- and post-course survey instrument was used to evaluate the participants' self-assessed perception of competence related to each of 16 statements.

RESULTS

One hundred thirty-seven (137) individuals enrolled in and completed the pharmacogenomics certification program. Overall, participants reported self-perceived improved competency as evidenced by the pre-course survey as compared with the post-course survey for each of the 16 competency statements related to genetics/genomics, including pharmacogenomics. Similar results were observed for the subgroups of student pharmacists (n = 63) and pharmacists (n = 74).

FUTURE DIRECTION

This study showed that dissemination of genetics/genomics/pharmacogenomics competency statements education can be accomplished via online delivery. This delivery approach can expand genetics/genomics/pharmacogenomics content dissemination. The intent is to reach a broader population of pharmacy students, pharmacists, and other health care providers and health professions students to potentially advance the availability of such services, which can improve the safety and efficacy of medication use for patients.

Pharmacokinetic data of synthetic cathinones in female Sprague-Dawley rats

The synthetic cathinones methylone, butylone, and pentylone differ from each other through the one carbon lengthening of the α-alkyl chain: methylone (-CH3), butylone (-CH2CH3), and pentylone (-CH2CH2CH3) while 3,4-methylenedioxymethamphetamine (MDMA) differs from methylone by a single oxygen atom. Studies with MDMA, suggests that there may be male and female pharmacokinetic and pharmacodynamic differences. In the present study, we present the plasma pharmacokinetic data relative to a 20 mg/kg, subcutaneous doses of methylone, butylone and pentylone in female Sprague-Dawley rats. Briefly, plasma samples were collected via a jugular vein cannula, purified, and analyzed using a HPLC system. While we have previously reported on the consistent relationship between structure and pharmacokinetics of these synthetic cathinones in male, Sprague-Dawley rats (Grecco and Sprague, 2016), this data set suggests that there is no consistent relationship of chemical structure and pharmacokinetics of methylone, butylone and pentylone in female Sprague-Dawley rats. The findings from the present study further emphasize the need for the inclusion of female subjects in the pharmacokinetic studies of synthetic cathinones as it is very possible male-female differences may exist in rodent models.

Systematic evaluation of clinical practice guidelines for pharmacogenomics

Aim: To systematically assess methodological quality of pharmacogenomics clinical practice guidelines. Methods: Guidelines published through 2017 were reviewed by at least three independent reviewers using the AGREE II instrument, which consists of 23 items grouped into 6 domains and 2 items representing an overall assessment. Items were assessed on a seven-point rating scale, and aggregate quality scores were calculated. Results: 31 articles were included. All guidelines were published as peer-reviewed articles and 90% (n = 28) were endorsed by professional organizations. Mean AGREE II domain scores (maximum score 100%) ranged from 46.6 ± 11.5% (‘applicability’) to 78.9 ± 11.4% (‘clarity of presentation’). Median overall quality score was 72.2% (IQR: 61.1–77.8%). Conclusion: Quality of pharmacogenomics guidelines was generally high, but variable, for most AGREE II domains.

Allelic frequencies of 60 pharmacogene variants assessed within a Burmese population residing in northeast Indiana, USA

AIM

The aim of this study was to investigate 60 SNPs pertaining to drug metabolism and pharmacodynamics in the Burmese refugee population in the Fort Wayne, Indiana area to better inform patient care.

MATERIALS & METHODS

Sixty-two self-identified Burmese refugees were genotyped for 60 common SNPs pertaining to pharmacokinetic and pharmacodynamic pharmacogenes. The resulting allelic frequencies were compared with Ensembl's database for surrounding populations to Myanmar and America.

RESULTS

The frequency of OPRM1, CYP2D6, SLCO1B1, MTHFR and VKORC1 were approximately 20% different in the Burmese refugee population as compared with the Ensembl populations.

CONCLUSION

Our study demonstrates that genetic differences are expected to affect drug efficacy in patients with a Burmese background.

Pharmacogenetics and pathophysiology of CACNA1S mutations in malignant hyperthermia

A review of the pharmacogenetics (PGt) and pathophysiology of calcium voltage-gated channel subunit alpha1 S (CACNA1S) mutations in malignant hyperthermia susceptibility type 5 (MHS5; MIM #60188) is presented. Malignant hyperthermia (MH) is a life-threatening hypermetabolic state of skeletal muscle usually induced by volatile, halogenated anesthetics and/or the depolarizing neuromuscular blocker succinylcholine. In addition to ryanodine receptor 1 (RYR1) mutations, several CACNA1S mutations are known to be risk factors for increased susceptibility to MH (MHS). However, the presence of these pathogenic CACNA1S gene variations cannot be used to positively predict MH since the condition is genetically heterogeneous with variable expression and incomplete penetrance. At present, one or at most six CACNA1S mutations display significant linkage or association either to clinically diagnosed MH or to MHS as determined by contracture testing. Additional pathogenic variants in CACNA1S, either alone or in combination with genes affecting Ca²⁺ homeostasis, are likely to be discovered in association to MH as whole exome sequencing becomes more commonplace.

Educational strategies to enable expansion of pharmacogenomics-based care

PURPOSE

The current state of pharmacogenomics education for pharmacy students and practitioners is discussed, and resources and strategies to address persistent challenges in this area are reviewed.

SUMMARY

Consensus-based pharmacist competencies and guidelines have been published to guide pharmacogenomics knowledge attainment and application in clinical practice. Pharmacogenomics education is integrated into various pharmacy school courses and, increasingly, into Pharm.D. curricula in the form of required standalone courses. Continuing-education programs and a limited number of postgraduate training opportunities are available to practicing pharmacists. For colleges and schools of pharmacy, identifying the optimal structure and content of pharmacogenomics education remains a challenge; insufficient numbers of faculty members with pharmacogenomics expertise and the inadequate availability of practice settings for experiential education are other limiting factors. Strategies for overcoming those challenges include providing early exposure to pharmacogenomics through foundational courses and incorporating pharmacogenomics into practice-based therapeutics courses and introductory and advanced pharmacy practice experiences. For practitioner education, online resources, clinical decision support-based tools, and certificate programs can be used to supplement structured postgraduate training in pharmacogenomics. Recently published data indicate successful use of "shared curricula" and participatory education models involving opportunities for learners to undergo personal genomic testing.

CONCLUSION

The pharmacy profession has taken a leadership role in expanding student and practitioner education to meet the demand for increased pharmacist involvement in precision medicine initiatives. Effective approaches to teaching pharmacogenomics knowledge and driving its appropriate application in clinical practice are increasingly available.

Pharmacogenomics competencies in pharmacy practice: A blueprint for change

The emerging use of genomic data to inform medication therapy populates the medical literature and provides evidence for guidelines in the prescribing information for many medications. Despite the availability of pharmacogenomic studies, few pharmacists feel competent to use these new data in patient care. The first pharmacogenomics competency statement for pharmacists was published in 2002. In 2011, the Pharmacogenomics Special Interest Group of the American Association of Colleges of Pharmacy led a process to update this competency statement with the use of a consensus-based method that incorporated input from multiple key professional pharmacy organizations to reflect growth in genomic science as well as the need for pharmacist application of genomic data. Given the rapidly evolving science, educational needs, and practice models in this area, a standardized competency-based approach to pharmacist education and training in pharmacogenomics is needed to equip pharmacists for leadership roles as essential members of health care teams that implement clinical utilization strategies for genomic data.

History repeats itself: the family medication history and pharmacogenomics

Related to many drug gene-product interactions, application of pharmacogenomics can lead to improved medication efficacy while decreasing or avoiding adverse drug reactions. However, utilizing pharmacogenomics without other information does not allow for optimal medication therapy. Currently, there is a lack of documentation of family medication history, in other words, inefficacy and adverse reactions across family members throughout generations. The family medication history can serve as an impetus for pharmacogenomic testing to explain lack of medication efficacy or an adverse drug reaction and pre-emptive testing can drive recognition and documentation of medication response in family members. We propose combining the family medication history via pedigree construction with pharmacogenomics to further optimize medication therapy. We encourage clinicians to combine family medication history with pharmacogenomics.

An Interdisciplinary Experience focused on Pharmacogenetics: Engaging pharmacy and physician assistant students in conversations about antiplatelet therapy with respect to CYP2C19 genotype

Objective: The goals of the interdisciplinary laboratory were to educate and engage pharmacy and physician assistant (PA) students in a discussion focused on the collection, interpretation, and application of pharmacogenetic data. Design: Interdisciplinary teams participated in a one-hour, case-based discussion and provided a therapeutic recommendation using the Clinical Pharmacogenetics Implementation Consortium guidelines. Assessment: All students were surveyed before and after the laboratory on knowledge and application of pharmacogenetics and working in interdisciplinary teams. The interdisciplinary laboratory successfully enhanced the student’s knowledge about sample collection and interpretation of pharmacogenetic information. Additionally, the laboratory improved student confidence in working in interdisciplinary teams to apply pharmacogenetic information to clinical decision making. Furthermore, the majority of students indicated that the interdisciplinary laboratory is valuable and useful in healthcare curriculums. Conclusion: The laboratory highlighted the differences between pharmacy and PA education regarding PGt, and brought to light several important uncertainties: (1) What is the depth of PGt knowledge that healthcare practitioners need? (2) What are best practices for conveying PGt information?   Type: Case Study

Relationship between discriminative stimulus effects and plasma methamphetamine and amphetamine levels of intramuscular methamphetamine in male rhesus monkeys

Methamphetamine is a globally abused drug that is metabolized to amphetamine, which also produces abuse-related behavioral effects. However, the contributing role of methamphetamine metabolism to amphetamine in methamphetamine's abuse-related subjective effects is unknown. This preclinical study was designed to determine 1) the relationship between plasma methamphetamine levels and methamphetamine discriminative stimulus effects and 2) the contribution of the methamphetamine metabolite amphetamine in the discriminative stimulus effects of methamphetamine in rhesus monkeys. Adult male rhesus monkeys (n=3) were trained to discriminate 0.18mg/kg intramuscular (+)-methamphetamine from saline in a two-key food-reinforced discrimination procedure. Time course of saline, (+)-methamphetamine (0.032-0.32mg/kg), and (+)-amphetamine (0.032-0.32mg/kg) discriminative stimulus effects were determined. Parallel pharmacokinetic studies were conducted in the same monkeys to determine plasma methamphetamine and amphetamine levels after methamphetamine administration and amphetamine levels after amphetamine administration for correlation with behavior in the discrimination procedure. Both methamphetamine and amphetamine produced full, ≥90%, methamphetamine-like discriminative stimulus effects. Amphetamine displayed a slightly, but significantly, longer duration of action than methamphetamine in the discrimination procedure. Both methamphetamine and amphetamine behavioral effects were related to methamphetamine and amphetamine plasma levels by a clockwise hysteresis loop indicating acute tolerance had developed to the discriminative stimulus effects. Furthermore, amphetamine levels after methamphetamine administration were absent when methamphetamine stimulus effects were greatest and peaked when methamphetamine discriminative stimulus effects returned to saline-like levels. Overall, these results demonstrate the methamphetamine metabolite amphetamine does not contribute to methamphetamine's abuse-related subjective effects.

Academic and professional pharmacy education: a pharmacogenomics certificate training program

Aim: The aim of this study was to evaluate a pharmacogenomics certificate training program relative to pharmacist competencies in basic genetic concepts, genetics and disease, pharmacogenetics/pharmacogenomics and ethical, legal and social implication. Methods: Participants, including pharmacists, pharmacy students and pharmacy educators completed a survey related to to the competency statements. Following the pre-program survey, participants completed a 6-week home self-study with subject matter including basic science (three chapters) and clinical application of pharmacogenomics (eight chapters). The participants completed a quiz for each of the self-study chapters. Following the self-study, participants completed a day-long, 7-h live program which included a review of the competency statements and counseling sessions with seven different simulated patients (primarily pharmacy students). Participants then completed a post-program survey which included the same items as the pre-program survey. Results: Specifically, for the pharmacist participants, the average score of the self-study quizzes was 91%. For the pharmacists specifically, there was a statistically significant increase in self-assessed perception of competence related to pharmacogenomics. Additionally, it was observed that recommendations related to specific drug–gene interactions for the simulated patients were addressed correctly 95% of the time across all participant–patient encounters. Conclusion: Self-study and a live, interactive component in the certificate training program led to increased self-understanding of defined pharmacogenomics competencies. Additionally, pharmacy students, in the role of simulated patients gained knowledge during the live component of the program. This type of program, especially if made available through electronic-based platforms can serve to educate pharmacists and increase the uptake of pharmacogenomics in various healthcare settings.

Implementation of a pharmacogenetic management service for postmyocardial infarction care in a community pharmacy

AIM

The purpose of this study was to pilot a multisite, proof-of-concept model where community pharmacists could engage patients and physicians to provide pharmacogenetic (PGt) testing and clinical decision support.

PATIENTS & METHODS

Patients with history of acute myocardial infarction and percutaneous coronary intervention with no prior history of CYP2C19 testing.

RESULTS

Four community pharmacies provided pharmacogenetic testing and medication therapy management services to 30 patients, resulting in eight recommendations for antiplatelet therapy adjustment.

CONCLUSION

Pharmacists involved in the study were able to facilitate antiplatelet therapy adjustments based on PGt data regardless of baseline antiplatelet drug selection. Whereas prior literature largely revolved around PGt management in the inpatient setting, this project supports the involvement of the community pharmacist in making PGt-based recommendations.

Pharmacogenetic considerations in the elderly patient

OBJECTIVE

To outline how the inclusion of pharmacogenetic data lends additional information in the overall decision making relative to drug therapy in the elderly patient.

DATA SOURCES

The National Center for Biotechnology's PubMed database was searched for relevant pharmacogenetic-based dosing guidelines, as well as papers discussing drug use, and pharmacogenetics in the elderly. Google Scholar was also searched for the related documents.

STUDY SELECTION

Papers cited were those that presented a rationale for drug therapy in the elderly, presented pharmacogenetic-based dosing guidelines with supporting information, and specifically discussed pharmacogenetics and other therapeutic principles relative to drug therapy in the elderly.

DATA SYNTHESIS

Specific examples were extracted for presentation where data on drug use in the elderly corresponded with pharmacogenetic information. Specific examples were selected to illustrate pharmacogenetic influences on medications of clinical significance in the elderly population including meperidine, tramadol, amitriptyline, nortriptyline, flecainide, and propafenone. These medications were identified as intersecting points in the Beers criteria and pharmacogenetic guidelines provided by the Clinical Pharmacogenetics Implementation Consortium and the Dutch Pharmacogenetics Working Group, or where mechanisms of pharmacogenetic influences were applicable.

CONCLUSIONS

Inclusion of pharmacogenetic data/information in the decision-making process may help the clinician to more appropriately guide therapy in the elderly patient.

Improving the Tenure Committee's Review Efficiency with Embedded Dossier Functionality

Numerous manuscripts have been published addressing perceptions of the promotion and tenure process. Very little has been published on mechanism to improve the efficiency of dossier review or tools to assist the reviewer in understanding the comprehensive scope of the applicant’s experiences. An innovative dossier format was utilized to assess the hyperlinks and pop-up tool tips would enhance the reviewer efficiency when reviewing the applicant’s materials. Super scripted numbers at the end of the narrative’s sentences, in the same manner as a journal article, contained the embedded hyperlinks and pop-up tool tips. A majority of the reviewers found the embedded functionality in the dossier did enhance their efficiency in completing the review.   Type: Case Study

Drug-gene interactions: inherent variability in drug maintenance dose requirements

The influence of genetics on pharmacokinetics can introduce variability among individual patients that may cause treatment failure, toxicity, or both. Such variability, specifically in clearance rates, can influence drug maintenance dosing regimens.

Pharmacogenetics in the Community Pharmacy: Thienopyridine Selection Post-Coronary Artery Stent Placement

INTRODUCTION

Although antiplatelet therapy is a mainstay of post-percutaneous coronary intervention therapy, pharmacogenetic (PGt) considerations of therapy are often ignored despite related Food and Drug Administration warnings. Pharmacists are well situated to provide PGt guidance, and the community pharmacy is one setting where PGt testing, interpretation, and recommendations can take place to ensure optimal therapeutic outcomes.

CASE REPORT

A 65-year-old man who had a myocardial infarction that was treated with PCI and stent placement was determined by a community pharmacist to be a candidate for PGt testing to ensure optimal antiplatelet therapy. The patient was seen in the pharmacy as a part of a medication therapy management encounter and underwent genetic testing. Results of the genetic testing indicated the need for modification of therapy. The community pharmacist interpreted the results and made the appropriate recommendation to the cardiologist who in turn modified antiplatelet therapy appropriately.

CONCLUSION

This case describes the potential for collaboration between pharmacists and physicians to optimize antiplatelet therapy through PGt testing. Points of consideration for others looking to implement related PGt services are also discussed.

Introducing Pharmacogenetics and Personalized Medicine via a Weblog

Objectives: To evaluate a weblog (blog)-based course introducing pharmacogenetics (PGt) and personalized medicine (PM) relative to freshmen pharmacy students' knowledge base. Methods: Incoming freshmen pharmacy students were invited by email to enroll in a one semester-hour, elective, on-line blog-based course entitled "Personal Genome Evaluation". The course was offered during the students' first semester in college. A topic list related to PGt and PM was developed by a group of faculty with topics being presented via the blog once or twice weekly through week 14 of the 15 week semester. A pre-course and post-course survey was sent to the students to compare their knowledge base relative to general information, drug response related to PGt, and PM. Results: Fifty-one freshmen pharmacy students enrolled in the course and completed the pre-course survey and 49 of the 51 students completed the post-course survey. There was an increase in the students' general, PGt and PM knowledge base as evidenced by a statistically significant higher number of correct responses for 17 of 21 questions on the post-course survey as compared to the pre-course survey. Notably, following the course, students had an increased knowledge base relative to "genetic privacy", drug dosing based on metabolizer phenotype, and the breadth of PM, among other specific points. Conclusions: The study indicated that introducing PGt and PM via a blog format was feasible, increasing the students' knowledge of these emerging areas. The blog format is easily transferable and can be adopted by colleges/schools to introduce PGt and PM.   Type: Case Study

Exploring a Laboratory Model of Pharmacogenetics as Applied to Clinical Decision Making

Objective: To evaluate a pilot of a laboratory model for relating pharmacogenetics to clinical decision making. Case Study: This pilot was undertaken and evaluated to help determine if a pharmacogenetics laboratory should be included in the core Doctor of Pharmacy curriculum. The placement of the laboratory exercise in the curriculum was determined by identifying the point in the curriculum where the students had been introduced to the chemistry of deoxyribonucleic acid (DNA) as well as instructed on the chemistry of genetic variation. The laboratory included cytochrome P450 2C19 genotyping relative to the *2 variant. Twenty-four students served as the pilot group. Students provided buccal swabs as the source of DNA. Students stabilized the samples and were then provided instructions related to sample preparation, polymerase chain reaction, and gel electrophoresis. The results were reported as images of gels. Students used a reference gel image to compare their results to. Students then applied a dosing algorithm to make a "clinical decision" relative to clopidogrel use. Students were offered a post laboratory survey regarding attitudes toward the laboratory. Twenty-four students completed the laboratory with genotyping results being provided for 22 students (91.7%). Sixteen students were wild-type (*1/*1), while six students were heterozygous (*1/*2). Twenty-three students (96%) completed the post laboratory survey. All 23 agreed (6, 26.1%) or strongly agreed (17, 73.9%) that the laboratory "had relevance and value in the pharmacy curriculum" Conclusion: The post pilot study survey exploring a laboratory model for pharmacogenetics related to clinical decision making indicated that such a laboratory would be viewed positively by students. This model may be adopted by colleges to expand pharmacogenetics education.   Type: Case Study

Nelarabine in the treatment of refractory T-cell malignancies

Nelarabine is a nucleoside analog indicated for the treatment of adult and pediatric patients with T-cell acute lymphoblastic leukemia (T-ALL) or T-cell lymphoblastic lymphoma (T-LBL) that is refractory or has relapsed after treatment with at least two chemotherapy regimens. After being first synthesized in the late 1970s and receiving FDA approval in 2005, the appropriate use of nelarabine for refractory hematologic malignancies is still being elucidated. Nelarabine is the prodrug of 9-β-D-arabinofuranosylguanine (ara-G) which when phosphorylated intracellularly to ara-G triphosphate (ara-GTP), preferentially accumulates in cancerous T-cells. Dose-dependent toxicities, including neurotoxicity and myelosuppression, have been documented and may, in turn, limit the ability to appropriately treat the diagnosed malignancy. This article will summarize the pharmacologic properties of nelarabine and will address the current place in therapy nelarabine holds based upon the results of the available clinical trials to date.

Profile of nelarabine: use in the treatment of T-cell acute lymphoblastic leukemia

Nelarabine is the prodrug of 9-beta-arabinofuranosylguanine (ara-G) and is therapeutically classified as a purine nucleoside analog. Nelarabine is converted to ara-G by adenosine deaminase and transported into cells by a nucleoside transporter. Ara-G is subsequently phosphorylated to ara-G triphosphate (ara-GTP), thereby initiating the therapeutic effect by inhibiting DNA synthesis. Nelarabine has been extensively studied in regards to its pharmacokinetics, and the data have demonstrated that ara-GTP preferentially accumulates in malignant T-cells. Clinical responses to nelarabine have been demonstrated in various T-cell malignancies and appear to correlate with a relatively high intracellular concentration of ara-GTP compared to nonresponders. Therefore, this unique drug feature of nelarabine accounts for clinical utilization in treating adult and pediatric patients with relapsed or refractory T-cell acute lymphoblastic leukemia or T-cell lymphoblastic lymphoma. Neuropathy is the most predominant adverse effect associated with nelarabine and the incidence correlates with the dose administered. Myelosuppression has been observed, with thrombocytopenia and neutropenia as the most common hematologic complications. This article reviews the pharmacology, mechanism of action, and pharmacokinetic properties of nelarabine, as well as nelarabine's clinical efficacy in T-ALL, T-LBL, and other hematologic malignancies. The toxicity profile, dosage, and administration, and areas of ongoing and future research, are also presented.

Ambient Temperature Effects on 3,4-Methylenedioxymethamphetamine-Induced Thermodysregulation and Pharmacokinetics in Male Monkeys

Changes in ambient temperature are known to alter both the hyperthermic and the serotonergic consequences of 3,4-methylenedioxymethamphetamine (MDMA). Metabolism of MDMA has been suggested to be a requisite for these neurotoxic effects, whereas the hyperthermic response is an important contributing variable. The aim of the present study was to investigate the interaction between ambient temperature, MDMA-induced thermodysregulation, and its metabolic disposition in monkeys. MDMA (1.5 mg/kg i.v.) was administered noncontingently at cool (18 degrees C; n = 5), room (24 degrees C; n = 7), and warm (31 degrees C; n = 7) ambient temperatures. For 240 min following MDMA administration, core temperature was recorded and blood samples were collected for analysis of MDMA and its metabolites 3,4-dihydroxymethamphetamine (HHMA), 3,4-dihydroxyamphetamine, and 3,4-methylenedioxyamphetamine (MDA). A dose of 1.5 mg/kg MDMA induced a hypothermic response at 18 degrees C, a hyperthermic response at 31 degrees C, and did not significantly change core temperature at 24 degrees C. Regardless of ambient temperature, plasma MDMA concentrations reached maximum within 5 min, and HHMA was a major metabolite. Curiously, the approximate elimination half-life (t(1/2)) of MDMA at 18 degrees C (136 min) and 31 degrees C (144 min) was increased compared with 24 degrees C (90 min) and is most likely because of volume of distribution changes induced by core temperature alterations. At 18 degrees C, there was a significantly higher MDA area under the concentration-time curve (AUC) and a trend for a lower HHMA AUC compared with 24 degrees C and 31 degrees C, suggesting that MDMA disposition was altered. Overall, induction of hypothermia in a cool environment by MDMA may alter its disposition. These results could have implications for MDMA-induced serotonergic consequences.

Nelarabine: efficacy in the treatment of clinical malignancies

Nelarabine is a nucleoside analog prodrug of 9-β-D-arabinofuranosylguanine. Nelarabine is indicated for the treatment of adult and pediatric patients with T-cell acute lymphoblastic leukemia or T-cell lymphoblastic lymphoma whose disease has not responded to, or has relapsed after treatment with, at least two chemotherapy regimens. Nelarabine was granted Orphan Medical Product Status in Europe in June 2005, and accelerated approval by the US FDA in October 2005. The most common adverse events associated with nelarabine are neurotoxic in nature and have been dose-limiting.

Nelarabine use in leukemias

Drug discovery and development over the past 60 years has played a central role in the continuous improvement in survival rates of patients undergoing treatment for acute lymphoblastic leukemia. It has recently been suggested that in children and adolescents diagnosed with acute lymphoblastic leukemia, an overall cure rate of 90% may be achieved (1, 2). Cure rates in adults, typically less than 40%, are considerably lower than in the younger populations, even in the face of currently prescribed optimal drug therapy and supportive care (3-5). The search for more effective and safer anti-leukemia therapy continues to identify agents and combinations of agents that have activity against specific types of acute lymphoblastic leukemia (1). This review presents a new compound, nelarabine, that has shown efficacy in treating patients with T-cell acute lymphoblastic leukemia or T-cell lymphoblastic lymphoma.

Phase I study of 506U78 administered on a consecutive 5-day schedule in children and adults with refractory hematologic malignancies

PURPOSE

A phase I study was conducted to determine the maximum-tolerated dose (MTD), toxicity profile, and pharmacokinetics of a novel purine nucleoside, nelarabine, a soluble prodrug of 9-beta-D-arabinosylguanine (araG; Nelarabine), in pediatric and adult patients with refractory hematologic malignancies.

PATIENTS AND METHODS

Between April 1994 and April 1997, 93 patients with refractory hematologic malignancies were treated with one to 16 cycles of study drug. Nelarabine was administered daily, as a 1-hour intravenous infusion for 5 consecutive days, every 21 to 28 days. First-cycle pharmacokinetic data, including plasma nelarabine and araG levels, were obtained on all patients treated. Intracellular phosphorylation of araG was studied in samples of leukemic blasts from selected patients.

RESULTS

The MTDs were defined at 60 mg/kg/dose and 40 mg/kg/dose daily x 5 days in children and adults, respectively. Dose-limiting toxicity (DLT) was neurologic in both children and adults. Myelosuppression and other significant organ toxicities did not occur. Pharmacokinetic parameters were similar in children and adults. Accumulation of araGTP in leukemic blasts was correlated with cytotoxic activity. The overall response rate was 31%. Major responses were seen in patients with T-cell malignancies, with 54% of patients with T-lineage acute lymphoblastic leukemia achieving a complete or partial response after one to two courses of drug.

CONCLUSION

Nelarabine is a novel nucleoside with significant cytotoxic activity against malignant T cells. DLT is neurologic. Phase II and III trials in patients with T-cell malignancies are encouraged.

Nelarabine: a nucleoside analog with efficacy in T-cell and other leukemias

OBJECTIVE

To present the pharmacology and pharmacokinetics of nelarabine, 9-beta-D-arabinofuranosylguanine (ara-G) and intraleukemic cellular pharmacokinetics of 9-beta-D-arabinofuranosylguanine triphosphate (ara-GTP) generated from the administration of nelarabine, and clinical and safety information relative to nelarabine use in the treatment of hematologic malignancies.

DATA SOURCES

MEDLINE (1966-December 2004) was searched using the English-language key terms 2-amino-6-methoxypurine arabinoside, 506U78, and nelarabine. Data were also obtained from published abstracts.

STUDY SELECTION AND DATA EXTRACTION

Clinical studies evaluating the pharmacokinetics of nelarabine, ara-G, and cellular ara-GTP and use of nelarabine, alone or in combination with other agents for the treatment of hematologic malignancies, were included in this review.

DATA SYNTHESIS

Nelarabine is the water-soluble, 6-methoxy analog of 9-beta-D-ara-G. Nelarabine is readily converted to ara-G by endogenous adenosine deaminase. The half-life of nelarabine is approximately 15 minutes compared with 2-4 hours for ara-G. The clearance of ara-G is higher in children than in adults (0.312 vs 0.213 L x h(-1) x kg(-1)). Intracellular ara-GTP elimination is slow relative to nelarabine and ara-G. In pediatric and adult patients, neurologic toxicity is dose limiting. Severe myelosuppression was not consistently observed. Major responses were seen in patients with T-cell malignancies. Patients who responded had significantly higher intracellular ara-GTP concentrations compared with those who did not respond.

CONCLUSIONS

Nelarabine is an effective ara-G prodrug. Nelarabine has significant activity against malignant T-cells and appears to be an important addition to treatments of various leukemias.

Pharmacokinetics of nelarabine and 9-beta-D-arabinofuranosyl guanine in pediatric and adult patients during a phase I study of nelarabine for the treatment of refractory hematologic malignancies

PURPOSE

To characterize the pharmacokinetics of nelarabine (506U78), the water-soluble prodrug of 9-beta-D-arabinofuranosyl guanine (ara-G), and ara-G in pediatric and adult patients with refractory hematologic malignancies. Ara-G is phosphorylated within leukemic cells to form ara-G triphosphate (ara-GTP), which acts to terminate DNA chain elongation, resulting in cell death.

PATIENTS AND METHODS

The pharmacokinetics of nelarabine and/or ara-G were evaluated in 71 patients (25 pediatric and 46 adult patients) on the first day of therapy. Blood was collected at specified times for the determination of plasma nelarabine and ara-G concentrations.

RESULTS

There were no statistically significant differences in the pharmacokinetics of nelarabine between any of the groups of patients. The harmonic mean half-life (t1/2) of nelarabine in pediatric and adult patients was 14.1 minutes and 16.5 minutes, respectively. The maximum concentrations (C(max)) of ara-G occurred at or near the end of the nelarabine infusion. The C(max) of ara-G ranged from 11.6 micromol/L to 308.7 micromol/L at nelarabine doses of 5 to 75 mg/kg and was linearly related to the nelarabine dose. No statistically significant differences were noted for the pharmacokinetic parameter estimates of ara-G between adult male and female patients. In children versus adults, the dose-normalized C(max), time of the C(max), and the steady-state volume of distribution of ara-G were similar. However, the clearance of ara-G was higher in pediatric patients (0.312 L.h(-1).kg(-1)) as compared with adult patients (0. 213 L.h(-1).kg(-1)) (P <.001). The t1/2 of ara-G was shorter in pediatric patients as compared with adult patients (2.1 hours v 3.0 hours; P <.01).

CONCLUSION

Nelarabine is an effective prodrug of ara-G, allowing systemic concentrations of ara-G that result in clinical activity.

Clinical pharmacokinetics of cisatracurium besilate

Cisatracurium besilate, one of the 10 stereoisomers that comprise atracurium besilate, is a nondepolarising neuromuscular blocking agent with an intermediate duration of action. Following a 5- to 10-sec intravenous bolus dose of cisatracurium besilate to healthy young adult surgical patients, elderly patients and patients with renal or hepatic failure, the concentration versus time profile of cisatracurium besilate is best characterised by a 2-compartment model. The volume of distribution (Vd) of cisatracurium besilate is small because of its relatively large molecular weight and high polarity. Cisatracurium besilate undergoes Hofmann elimination, a process dependent on pH and temperature. Unlike atracurium besilate, cisatracurium besilate does not appear to be degraded directly by ester hydrolysis. Hofmann elimination, an organ independent elimination pathway, occurs in plasma and tissue, and is responsible for approximately 77% of the overall elimination of cisatracurium besilate. The total body clearance (CL), steady-state Vd and elimination half-life of cisatracurium besilate in patients with normal organ function are approximately 0.28 L/h/kg (4.7 ml/min/kg), 0.145 L/kg and 25 minutes, respectively. The magnitude of interpatient variability in the CL of cisatracurium besilate is low (16%), a finding consistent with the strict physiological control of the factors that effect the Hofmann elimination of cisatracurium besilate (i.e. temperature and pH). There is a unique relationship between plasma clearance and Vd because the primary elimination pathway for cisatracurium besilate is not dependent on organ function. There are minor differences in the pharmacokinetics of cisatracurium besilate in various patient populations. These differences are not associated with clinically significant differences in the recovery profile of cisatracurium besilate, but may be associated with differences in the time to onset of neuromuscular block.

Compound GW506U78 in refractory hematologic malignancies: relationship between cellular pharmacokinetics and clinical response

PURPOSE

In vitro investigations with arabinosylguanine (ara-G) demonstrated potent cytotoxicity to T-lymphoblastoid cell lines. The goals of the present study were to evaluate GW506U78, a prodrug of ara-G, against human hematologic malignancies and to determine its pharmacokinetics in plasma and cells.

PATIENTS AND METHODS

During a phase I multicenter trial of GW506U78, 26 patients were treated at M.D. Anderson Cancer Center (MDACC). Daily doses between 20 and 60 mg/kg were administered for 5 days. Parallel plasma and cellular pharmacokinetic studies were conducted.

RESULTS

Complete (n=5) or partial remission (n=5) was achieved in T-cell acute lymphoblastic leukemia (T-ALL), T-lymphoid blast crisis, T-lymphoma, and B-cell chronic lymphocytic leukemia (B-CLL) (n=13). In contrast, patients with B-ALL, B-lymphoma, acute myelogenous leukemia (AMI), or T-CLL did not respond. Peak plasma concentrations of GW506U78 and ara-G were dose-dependent. The elimination of GW506U78 (half-life [t1/2]=17 minutes) was faster than the elimination of ara-G (t1/2=3.7 hours). Median peak concentrations of ara-GTP were 23, 42, 85, and 93 micromol/L at 20, 30, 40, and 60 mg/kg, respectively. T-lymphoblasts accumulated significantly (P=.0008) higher peak arabinsylguanosine triphosphate (ara-GTP) (median, 140 micromol/L; n=7) compared with other diagnoses (median, 50 micromol/L; n=9) and normal mononuclear cells (n=3). The ara-GTP elimination was slow in all diagnoses (median, > 24 hours). Responders accumulated significantly (P=.0005) higher levels of ara-GTP (median, 157 micromol/L) compared with patients who failed to respond (median, 44 micromol/L).

CONCLUSION

GW506U78 is an effective prodrug and a potent agent for hematologic malignancies with major efficacy in T-cell diseases. The pharmacokinetics of ara-GTP in leukemia cells are strongly correlated with clinical responses to GW506U78.

Pharmacokinetics of RheothRx injection in healthy male volunteers

The objectives of this study were to evaluate the safety and tolerability of RheothRx (poloxamer 188) injection administered as an intravenous (i.v.) infusion to healthy male volunteers and to determine the pharmacokinetic profile of poloxamer 188. Thirty-six healthy male volunteers were enrolled in a randomized, double-blind, placebo-controlled, dose-escalation trial for RheothRx injection. The volunteers were randomized to three treatment groups (12 per treatment group, with eight receiving active therapy and four receiving placebo). In each treatment group, volunteers received RheothRx injection or placebo as an i.v. infusion on two occasions at least 3 weeks apart to make a total of six doses being studied (10, 30, and 45 mg/kg/h for 72 h, 60 mg/kg/h for 43.3 to 72 h, 60 and 90 mg/kg/h for 24 h). Serial plasma samples were collected during and up to 36 h after the end of the infusions; urine was collected over intervals from the start of the infusion until 36 h after the infusions were terminated. Plasma and urine samples were assayed for poloxamer 188 by gel-permeation chromatography. Pharmacokinetic parameter values were calculated by noncompartmental and compartmental methods. Poloxamer 188 was eliminated primarily by renal excretion. Estimates of clearance, elimination rate constant, and apparent volume of distribution at steady state values were independent of infusion rate. Poloxamer 188 displayed no apparent infusion rate dependence in its pharmacokinetics.

Importance of the organ-independent elimination of cisatracurium

Cisatracurium, one of 10 isomers of atracurium, undergoes pH and temperature-dependent Hofmann elimination in plasma and tissues. The clearance of cisatracurium due to Hofmann elimination and organ elimination was estimated by applying a nontraditional two-compartment pharmacokinetic model with elimination occurring from both compartments to plasma cisatracurium concentration-time data from 31 healthy adult surgical patients with normal renal and hepatic function. The elimination rate constant from the central compartment, intercompartmental rate constants, and the volume of the central compartment were obtained from the model fit. The elimination rate constant from the peripheral compartment could not be independently estimated in vivo and was therefore fixed to the rate of degradation of cisatracurium in human plasma (pH 7.4 and 37 degrees C) and held constant in the model. Total body clearance, Hofmann clearance, organ clearance, and the volume of distribution at steady-state were derived from the model parameter estimates. Renal clearance was calculated from cisatracurium urinary excretion data from 12 of the 31 patients. Clearance values (mean +/- SD) were 5.20 +/- 0.86, 4.00 +/- 1.04, 1.20 +/- 0.71, and 0.85 +/- 0.32 mL.min-1.kg-1 for total body clearance, Hofmann clearance, organ clearance, and renal clearance, respectively. Hofmann clearance accounted for 77% of total body clearance. Organ clearance was 23% of total body clearance. Renal clearance, a component of organ clearance, was 16% of total body clearance. The organ-independent nature of the elimination of cisatracurium was characterized by a relationship between steady-state volume of distribution and total body clearance. The half-life is an independent variable and is not dependent on the total body clearance nor the steady-state volume of distribution. Hofmann elimination is the predominant pathway for cisatracurium elimination in humans.

Pharmacokinetics and pharmacodynamics of cisatracurium in patients with end-stage liver disease undergoing liver transplantation

We determined the pharmacokinetics and pharmacodynamics of cisatracurium, one of the 10 isomers of atracurium, in 14 patients with end-stage liver disease undergoing liver transplantation and in 11 control patients with normal hepatic and renal function undergoing elective surgery. Blood samples were collected for 8 h after i.v. bolus administration of cisatracurium 0.1 mg kg-1 (2 x ED95). Plasma concentrations of cisatracurium and its metabolites were determined using an HPLC method with fluorescence detection. Pharmacokinetic variables were determined using non-compartmental methods. Neuromuscular block was assessed by measuring the electromyographic evoked response of the adductor pollicis muscle to train-of-four stimulation of the ulnar nerve using a Puritan-Bennett Datex (Helsinki, Finland) monitor. Pharmacodynamic modelling was completed using semi-parametric effect-compartment analysis. Volume of distribution at steady state was 195 (SD 38) ml kg-1 in liver transplant patients and 161 (23) ml kg-1 in control patients (P < 0.05), plasma clearance was 6.6 (1.1) ml kg-1 min-1 in liver transplant patients and 5.7 (0.8) ml kg-1 min-1 in control patients (P < 0.05), but elimination half-lives were similar: 24.4 (2.9) min in liver transplant patients vs 23.5 (3.5) min in control patients (ns). The time to maximum block was 2.4 (0.8) min in liver transplant patients compared with 3.3 (1.0) min in control patients (P < 0.05), but the clinical effective duration of action (time to 25% recovery) was similar: 53.5 (11.9) min in liver transplant patients compared with 46.9 (6.9) min in control patients (ns). The recovery index (25-75% recovery) was also similar in both groups: 15.4 (4.2) min in liver transplant patients and 12.8 (1.9) min in control patients (ns). After cisatracurium, peak laudanosine concentrations were 16 (5) and 21 (5) ng ml-1 in liver transplant and control patients, respectively. In summary, minor differences in the pharmacokinetics and pharmacodynamics of cisatracurium in liver transplant and control patients were not associated with any clinically significant differences in recovery profiles after a single dose of cisatracurium.