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Investigations in pharmacology and toxicology range from molecular studies to clinical care. Studies in basic and clinical pharmacology and in preclinical and clinical toxicology are all essential in bringing new knowledge and new drugs into clinical use. The 30 reviews in Volume 63 of the Annual Review of Pharmacology and Toxicology explore topics across this spectrum. Examples include “Zebrafish as a Mainstream Model for In Vivo Systems Pharmacology and Toxicology” and “Artificial Intelligence and Machine Learning for Lead-to-Candidate Decision-Making and Beyond.” Other reviews discuss components important for drug discovery and development and the use of pharmaceuticals in a variety of diseases. Air pollution continues to increase globally; accordingly, “Air Pollution–Related Neurotoxicity Across the Life Span” is a timely and forward-thinking review. Volume 63 also explores the use of contemporary technologies such as electronic health records, pharmacogenetics, and new drug delivery systems that help enhance and improve the utility of new therapies.

Introduction The cytostatic drugs doxorubicin (Dox) and ibrutinib (Ibr) are established in the treatment of various tumor diseases. In (pre-) clinical studies, both chemotherapeutic agents showed cardiotoxic side effects, including atrial fibrillation [1]. In this context, patients with limited cardiac performance or diabetes might be particularly vulnerable, as these pre-existing conditions represent independent risk factors for cardiac complications [2]. Objectives The dose-dependency of acute pro-arrhythmogenic effects of Dox and Ibr on the contractile activity of human atrial muscle tissue was investigated. Patients and methods Atrial samples were taken intraoperatively during cardiac procedures. Functional muscle strips were prepared from the cardiac trabeculae, followed by incubation with different concentrations of Dox or Ibr for 30 minutes. Subsequently, functional measurements were performed. Isometric contraction force and arrhythmogenic occurrences were recorded. The samples were consecutively exposed to external stressors during measurement (Fig. 1). We evaluated the overall occurrence of arrhythmogenic contractions and during which phase of the protocol they occurred. The latter was expressed as degree of arrhythmogenesis (Fig. 1). Following the functional measurements, the muscle strips were conserved at −80°C. Results We isolated 127 muscle strips from 29 patients. Highest rates of overall arrhythmic contractions were observed at 10μM Dox and 0.5μM Ibr (77.8 & 100% vs. 58.4% (control)). Mean degree of arrhythmogenesis increased from 1.63 (control) to 2.17 (10μM Dox) and 3.11 (0.5μM Ibr). Analyzing our data according to the included individuals, treatment with Dox and Ibr enhanced the degree of arrhythmogenesis in the majority of patients. (Fig. 2) Conclusion Our protocol is suitable for investigating drug related acute pro-arrhythmogenic effects on human atrial myocardium. Treatment of isolated atrial myocardium with Dox and Ibr enhanced its susceptibility to arrhythmogenic occurrences. Optimal pro-arrhythmogenic conditions were observed at 10μM Dox and 0.5μM Ibr. The treated samples showed higher overall rates of arrhythmogenic contractions and the arrhythmogenic activity occurred earlier within our protocol. Outlook We will correlate the experimentally obtained data with clinical patient data, such as LVEF, BMI and diabetic status. The conserved muscle strips will be analyzed using standardized assays comparing post-translational modification (e.g. phosphorylation and oxidation) of key regulators of excitation contraction coupling (e.g. PKA, CaMKII, Ca2+ channels). Funding Acknowledgement Type of funding sources: Other. Main funding source(s): DZHK (German Centre for Cardiovascular Research), partner site Berlin

Neuromyelitis optica spectrum disorders (NMOSD) represent rare autoimmune diseases of the central nervous system largely targeting optic nerve(s) and spinal cord. The present analysis used real-world data to identify clinical and epidemiological correlates of treatment change in patients with NMOSD.CIRCLES is a longitudinal, observational study of NMOSD conducted at 15 centers across North America. Patients with ≥ 60 days of follow-up and receiving on-study maintenance treatment were evaluated. The mean annual relapse rate (ARR) was estimated using negative binomial models; the likelihood of treatment change was estimated using Cox proportional hazards models. Relapses were included as time-varying covariates to estimate the relationship to treatment change.Of 542 patients included, 171 (31.5%) experienced ≥ 1 relapse on the study and 133 patients (24.5%) had ≥ 1 change in the treatment regimen. Two categories of variables significantly correlated with the likelihood of treatment change: (1) relapse: any on-study relapse (hazard ratio [HR] = 2.91; p 0.001), relapse phenotypes (HR range = 2.15-5.49; p 0.001), and pre-study ARR 0.75 (HR 2.28; p 0.001); 2) disease phenotype: brain syndrome only vs transverse myelitis involvement at onset (HR 2.44; p = 0.008), disease duration 1 vs 5 years (HR 1.66; p = 0.028), or autoimmune comorbidity (HR 1.55; p = 0.015). A subset of these factors significantly correlated with shorter time to first rituximab discontinuation.In CIRCLES, relapse patterns and disease phenotype significantly correlated with changes in the maintenance treatment regimen. Such findings may facilitate the identification of patients with NMOSD who are likely to benefit from treatment change to reduce relapse risk or disease burden and enhance the quality of life.

Funding Acknowledgements Type of funding sources: None. BACKGROUND/ INTRODUCTION Lead-induced tricuspid regurgitation (TR) in patients with cardiac implantable electronic devices (CIED) is associated with increased morbidity and mortality. Mechanisms proposed to explain CIED-induced TR can be classified as primary (implantation-related, lead-related) and secondary (pacing related). Primary CIED-induced TR results from the direct interaction of the lead with the tricuspid valve (TV). Determination of exact lead position via echocardiography is crucial however often difficult via standard views. Previous research has shown the value of an atypical subcostal 2D en-face view to describe the exact anatomy of the TV (Figure 1) (1-3). PURPOSE In this prospective observational investigation, we aimed to demonstrate the feasibility of the subcostal 2D en-face view of the TV to determine RV lead position at the level of TV passage and thereby to unmask potentially unfavorable lead-positions and interactions with the TV, which might otherwise remain unnoted. METHODS Consecutive patients who underwent implantation of CIED with at least one RV lead were prospectively included. Comprehensive transthoracic echocardiography (TTE) was performed before and after the procedure. An en-face view of the TV by an approximately 90° counter-clockwise rotation of the transducer from a standard subcostal 4-chamber view was attempted in all patients. Exact lead-position (e.g. postero-septal commissural, central, etc., see Figure 1) was described whenever possible. RESULTS A total of 35 patients were included in the final analysis, median age was 62 years, 27/35 (77%) were male. Thirteen patients (37%) already had an RV lead prior to the recent procedure and therefore showed 2 or more leads passing the TV in post-procedural controls. Implanted devices included cardiac contractility modulation (CCM) (7/35 patients, 20%), implantable cardioverter-defibrillator (ICD) (11/35 patients, 31%), cardiac resynchronization therapy (CRT) (7/35 patients 20%) and pacemaker (PM) (7/35 patients, 20%). Three patients (9%) received an additional RV lead due to RV lead dysfunction. The exact position of the RV lead could be determined applying the en-face view in 27/35 patients (77%). In the majority of cases (20/35 patients, 57%), the RV lead passed through the tricuspid plane in a postero-septal commissural position. Central trajectory was observed in 5/35 patients (14%). Anteroseptal and anteroposterior passage were each found in one patient. In the remaining 8/35 patients (23%), lead position could not be determined due to inferior image quality from the subcostal view. CONCLUSIONS RV lead position can be determined from a subcostal en-face view of the TV in a majority of patients after CIED implantation. Hereby, 2D-TTE can add significant value to the management, follow-up, and monitoring and should therefore be included in the standard TTE protocol of every patient with CIED. Abstract Figure 1

“Ion Channels and Neuropharmacology: From the Past to the Future” is the main theme of articles in Volume 60 of the Annual Review of Pharmacology and Toxicology. Reviews in this volume discuss a wide spectrum of therapeutically relevant ion channels and GPCRs with a particular emphasis on structural studies that elucidate drug binding sites and mechanisms of action. The regulation of ion channels by second messengers, including Ca2+ and cyclic AMP, and lipid mediators is also highly relevant to several of the ion channels discussed, including KCNQ channels, HCN channels, L-type Ca2+ channels, and AMPA receptors, as well as the aquaporin channels. Molecular identification of exactly where drugs bind in the structure not only elucidates their mechanism of action but also aids future structure-based drug discovery efforts to focus on relevant pharmacophores. The ion channels discussed here are targets for multiple nervous system diseases, including epilepsy and neuropathic pain. This theme complements several previous themes, including “New Therapeutic Targets,” “New Approaches for Studying Drug and Toxicant Action: Applications to Drug Discovery and Development,” and “New Methods and Novel Therapeutic Approaches in Pharmacology and Toxicology.”

The reviews in Volume 62 of the Annual Review of Pharmacology and Toxicology (ARPT) cover a diverse range of topics. A theme that encompasses many of these reviews is their relevance to common diseases and disorders, including type 2 diabetes, heart failure, cancer, tuberculosis, Alzheimer's disease, neurodegenerative disorders, and Down syndrome. Other reviews highlight important aspects of therapeutics, including placebos and patient-centric approaches to drug formulation. The reviews with this thematic focus, as well as other reviews in this volume, emphasize new mechanistic insights, experimental and therapeutic strategies, and novel insights regarding topics in the disciplines of pharmacology and toxicology. As the editors of ARPT, we believe that these reviews help advance those disciplines and, even more importantly, have the potential to improve the health care of the world's population. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The urgent global public health need presented by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has brought scientists from diverse backgrounds together in an unprecedented international effort to rapidly identify interventions. There is a pressing need to apply clinical pharmacology principles and this has already been recognized by several other groups. However, one area that warrants additional specific consideration relates to plasma and tissue protein binding that broadly influences pharmacokinetics and pharmacodynamics. The principles of free drug theory have been forged and applied across drug development but are not currently being routinely applied for SARS-CoV-2 antiviral drugs. Consideration of protein binding is of critical importance to candidate selection but requires correct interpretation, in a drug-specific manner, to avoid either underinterpretation or overinterpretation of its consequences. This paper represents a consensus from international researchers seeking to apply historical knowledge, which has underpinned highly successful antiviral drug development for other viruses, such as HIV and hepatitis C virus for decades.

Requiring regional or in-country confirmatory clinical trials before approval of drugs already approved elsewhere delays access to medicines in low- and middle-income countries and raises drug costs. Here, we discuss the scientific and technological advances that may reduce the need for in-country or in-region clinical trials for drugs approved in other countries and limitations of these advances that could necessitate in-region clinical studies.

The theme “New Approaches for Studying Drug and Toxicant Action: Applications to Drug Discovery and Development” links 13 articles in this volume of the Annual Review of Pharmacology and Toxicology (ARPT). The engaging prefatory articles by Arthur Cho and Robert Lefkowitz set the stage for this theme and for the reviews that insightfully describe new approaches that advance research and discovery in pharmacology and toxicology. Examples include the progress being made in developing Organs-on-Chips/microphysiological systems and human induced pluripotent stem cell–derived cells to aid in understanding cell and tissue pharmacokinetics, action, and toxicity; the recognition of the importance of circadian rhythm, the microbiome, and epigenetics in drug and toxicant responses; and the application of results from new types of patient-derived information to create personalized/precision medicine, including therapeutics for pain, which may perhaps provide help in dealing with the opioid epidemic in the United States. Such new information energizes discovery efforts in pharmacology and toxicology that seek to improve the efficacy and safety of drugs in patients and to minimize the consequences of exposure to toxins.

Major advances in scientific discovery and insights can result from the development and use of new techniques, as exemplified by the work of Solomon Snyder, who writes a prefatory article in this volume. The Editors have chosen “New Methods and Novel Therapeutic Approaches in Pharmacology and Toxicology” as the Theme for a number of articles in this volume. These include ones that review the development and use of new experimental tools and approaches (e.g., nanobodies and techniques to explore protein-protein interactions), new types of therapeutics (e.g., aptamers and antisense oligonucleotides), and systems pharmacology, which assembles (big) data derived from omics studies together with information regarding drugs and patients. The application of these new methods and therapeutic approaches has the potential to have a major impact on basic and clinical research in pharmacology and toxicology as well as on patient care.

BackgroundExcellent adherence to tuberculosis (TB) treatment is critical to cure TB and avoid the emergence of resistance. Wirelessly observed therapy (WOT) is a novel patient self-management system consisting of an edible ingestion sensor (IS), external wearable patch, and paired mobile device that can detect and digitally record medication ingestions. Our study determined the accuracy of ingestion detection in clinical and home settings using WOT and subsequently compared, in a randomized control trial (RCT), confirmed daily adherence to medication in persons using WOT or directly observed therapy (DOT) during TB treatment.Methods and findingsWe evaluated WOT in persons with active Mycobacterium tuberculosis complex disease using IS-enabled combination isoniazid 150 mg/rifampin 300 mg (IS-Rifamate). Seventy-seven participants with drug-susceptible TB in the continuation phase of treatment, prescribed daily isoniazid 300 mg and rifampin 600 mg, used IS-Rifamate. The primary endpoints of the trial were determination of the positive detection accuracy (PDA) of WOT, defined as the percentage of ingestions detected by WOT administered under direct observation, and subsequently the proportion of prescribed doses confirmed by WOT compared to DOT. Initially participants received DOT and WOT simultaneously for 2-3 weeks to allow calculation of WOT PDA, and the 95% confidence interval (CI) was estimated using the bootstrap method with 10,000 samples. Sixty-one participants subsequently participated in an RCT to compare the proportion of prescribed doses confirmed by WOT and DOT. Participants were randomized 2:1 to receive WOT or maximal in-person DOT. In the WOT arm, if ingestions were not remotely confirmed, the participant was contacted within 24 hours by text or cell phone to provide support. The number of doses confirmed was collected, and nonparametric methods were used for group and individual comparisons to estimate the proportions of confirmed doses in each randomized arm with 95% CIs. Sensitivity analyses, not prespecified in the trial registration, were also performed, removing all nonworking (weekend and public holiday) and held-dose days. Participants, recruited from San Diego (SD) and Orange County (OC) Divisions of TB Control and Refugee Health, were 43.1 (range 18-80) years old, 57% male, 42% Asian, and 39% white with 49% Hispanic ethnicity. The PDA of WOT was 99.3% (CI 98.1; 100). Intent-to-treat (ITT) analysis within the RCT showed WOT confirmed 93% versus 63% DOT (p < 0.001) of daily doses prescribed. Secondary analysis removing all nonworking days (weekends and public holidays) and held doses from each arm showed WOT confirmed 95.6% versus 92.7% (p = 0.31); WOT was non-inferior to DOT (difference 2.8% CI [-1.8%, 9.1%]). One hundred percent of participants preferred using WOT. WOT associated adverse events were ConclusionsIn terms of accuracy, WOT was equivalent to DOT. WOT was superior to DOT in supporting confirmed daily adherence to TB medications during the continuation phase of TB treatment and was overwhelmingly preferred by participants. WOT should be tested in high-burden TB settings, where it may substantially support low- and middle-income country (LMIC) TB programs.Trial registrationClinicalTrials.gov NCT01960257.

Objective to develop a resource of systematically collected, longitudinal clinical data and biospecimens for assisting in the investigation into neuromyelitis optica spectrum disorder (NMOSD) epidemiology, pathogenesis, and treatment. Methods to illustrate its research-enabling purpose, epidemiologic patterns and disease phenotypes were assessed among enrolled subjects, including age at disease onset, annualized relapse rate (ARR), and time between the first and second attacks. Results as of December 2017, the Collaborative International Research in Clinical and Longitudinal Experience Study (CIRCLES) had enrolled more than 1,000 participants, of whom 77.5% of the NMOSD cases and 71.7% of the controls continue in active follow-up. Consanguineous relatives of patients with NMOSD represented 43.6% of the control cohort. Of the 599 active cases with complete data, 84% were female, and 76% were anti-AQP4 seropositive. The majority were white/Caucasian (52.6%), whereas blacks/African Americans accounted for 23.5%, Hispanics/Latinos 12.4%, and Asians accounted for 9.0%. The median age at disease onset was 38.4 years, with a median ARR of 0.5. Seropositive cases were older at disease onset, more likely to be black/African American or Hispanic/Latino, and more likely to be female. Conclusions collectively, the CIRCLES experience to date demonstrates this study to be a useful and readily accessible resource to facilitate accelerating solutions for patients with NMOSD., The Guthy-Jackson Charitable Foundation, The CIRCLES Project

The objective of our study was to evaluate the effect of adherence patterns on the sample size and power of a clinical trial. Simulations from a population pharmacokinetic/pharmacodynamic (PK/PD) model linked to an adherence model were used. Four types of drug characteristics, such as long (~35 hours) and short (~12 hours) half-life in combination with earlier or delayed time to reach steady-state PD end points were studied. Adherence patterns were simulated using Markov chains. Our results clearly demonstrate the significant impact of varying levels and patterns of nonadherence on the sample size and power of a study. For drugs with short half-lives the evidence to support efficacy could be diluted by various patterns of nonadherence that would make its efficacy indistinguishable from the response to placebo. Prospectively utilizing clinical trial simulations with thorough incorporation of various adherence patterns would provide valuable information when designing a trial.

High-resolution measurement of medication adherence is essential to personalized drug therapy. A US Food and Drug Administration (FDA)-cleared device, using an edible ingestion sensor (IS), external wearable patch, and paired mobile device can detect and record ingestion events. Oral medications must be combined with an IS to generate precise "digitized-medication" ingestion records. We developed a Good Manufacturing Practice protocol to repackage oral medications with the IS within certified Capsugel capsules, termed co-encapsulation (CoE). A randomized bioequivalence study of CoE-IS-Rifamate (Isoniazid/Rifampin 150/300 mg) vs. native-Rifamate was conducted in 12 patients with active Mycobacterium tuberculosis and demonstrated bioequivalence using the population method ratio test (95% confidence interval). Subsequently, CoE-IS-medications across all biopharmaceutical classes underwent in vitro dissolution testing utilizing USP and FDA guidelines. CoE-IS medications tested met USP dissolution specifications and were equivalent to their native formulations. CoE combines oral medications with the IS without altering the quality of the native formulation, generating "digitized" medications for remote capture of dosing histories.

ObjectiveTo gain insights into NMOSD disease impact, which may negatively affect QoL of patients, their families, and social network.MethodsThe current study used validated instruments to assess physical, emotional, and socioeconomic burden of NMOSD on QoL among 193 patients.ResultsA majority of patients reported an initial diagnosis of a disease other than NMOSD. Overall, two-thirds of patients reported NMOSD as having a strong negative impact on physical health (Short Form-36 [SF-36] score 27.1 ± 39.1), whereas emotional well-being was relatively unimpaired on average (SF-36 score 54.0 ± 44.9). A subset of patients reported having the highest category of emotional health despite worse physical health or financial burden, suggesting psychological resilience. Pain (r = 0.61) and bowel/bladder dysfunction (r = 0.41) imposed the greatest negative physical impact on overall QoL. In turn, ability to work correlated inversely with worsened health (r = −0.68). Increased pain, reduced sexual function, inability to work, and reduced QoL had greatest negative impacts on emotional well-being. Dissatisfaction with treatment options and economic burden correlated inversely with QoL.ConclusionsCollectively, the current findings advance the understanding of physical, emotional, social, and financial tolls imposed by NMOSD. These insights offer potential ways to enhance QoL by managing pain, enhancing family and social networks, and facilitating active employment.

Satisfactory adherence to aptly prescribed medications is essential for good outcomes of patient care and reliable evaluation of competing modes of drug treatment. The measure of satisfactory adherence is a dosing history that includes timely initiation of dosing plus punctual and persistent execution of the dosing regimen throughout the specified duration of treatment. Standardized terminology for initiation, execution, and persistence of drug dosing is essential for clarity of communication and scientific progress. Electronic methods for compiling drug dosing histories are now the recognized standard for quantifying adherence, the parameters of which support model-based, continuous projections of drug actions and concentrations in plasma that are confirmable by intermittent, direct measurements at single time points. The frequency of inadequate adherence is usually underestimated by pre-electronic methods and thus is clinically unrecognized as a frequent cause of failed treatment or underestimated effectiveness. Intermittent lapses in dosing are potential sources of toxicity through hazardous rebound effects or recurrent first-dose effects.

Autoimmune diseases are chronic, life threatening, and of burgeoning public health concern. They rank among the 10 most common causes of death in women, and some have incidence rates surpassing those of heart disease and cancer. Emerging information regarding molecular and cellular mechanisms affords opportunities for the discovery of novel therapeutic strategies or the repurposing of FDA-approved pharmacologic agents. Yet, obstacles to drug development amplify as an inverse function of the incidence of rare autoimmune disease; challenges include heterogeneous clinical presentation, paucity of definitive biomarkers, and poorly validated measures of therapeutic response. An integrative continuum model to address these challenges is being applied to neuromyelitis optica (NMO)—a potentially devastating neurodegenerative process that has had limited therapeutic options. This model links target discovery with pharmacologic application to accelerate improved clinical efficacy. The application of such innovative strategies may help researchers overcome barriers to therapeutic advances in NMO and other rare autoimmune diseases.

Poor adherence to medicines in clinical trials can undermine the value of the trials; for example, by compromising estimates of the benefits and risks of a medicine. In this article, we highlight such consequences and also discuss approaches to tackle this problem.

It is generally accepted that a high degree of adherence to the dosing regimens of protease inhibitors is essential to avoid virological failure. It is also believed that once-daily dosing of protease inhibitors, by improving adherence, will lead to better outcomes. This review will discuss the patterns of adherence for once-daily and twice-daily regimens and illustrate how differences in these patterns might favor twice-daily regimens in some settings.Using electronic monitoring of more than 1800 patients enrolled in HIV clinical trials, the fraction of doses taken by patients on a once-daily regimen was about 10% higher than that taken by patients on a twice-daily regimen. However, patients on the twice-daily regimen were less likely to have their trough concentrations fall below a minimum effective concentration. In an outcome study that compared once-daily with twice-daily lopinavir/ritonavir, there was no difference in virological failure through 48 weeks, but patients with a viral load of more than 100 000 copies/ml had a greater probability of a sustained viral response on a twice-daily regimen.Although patients and providers strongly favor once-daily regimens, recent clinical and model-based studies suggest that twice-daily protease inhibitor containing regimens may yield better outcomes in some settings. Continued reinforcement of adherence is necessary to improve both the execution of the drug regimen as well as continuation (persistence) with antiretroviral therapy.

In contrast to the widespread practice in life-threatening emergencies, delegation of medical pain therapy to paramedics by the medical director of Emergency Medical Services, EMS, are still the exception in Germany. This is due to the fact that in non-life-threatening situations, the expected benefit and potential side effects of drug therapy have to be carefully weighed. In addition, in Germany federal law generally restricts the administration of opiates to physicians.In 2011 the medical directors of EMS in the German state of Rhineland- Palatinate (4 million inhabitants) developed and implemented a standard operating procedure (SOP) for paramedics related to the prehospital parenteral administration of paracetamol for patients with isolated limb trauma. After a 2 h training session and examination, paramedics were authorized to administer 1 g of paracetamol to patients with a pain score 5 points on an 11-point numerical rating scale (NRS). For purposes of quality management, every administration of paracetamol had to be prospectively documented on a specific electronic mission form.A total of 416 mission forms could be analyzed. After administration of paracetamol the median NRS score decreased from 8 points (interquartile range: 6; 8) to 4 points (interquartile range: 3; 7). In 51.2 % of the patients the pain intensity was reduced by at least 3 NRS points and in 50.5 % of the patients the NRS was less than 5 points after treatment. The extent of pain reduction was positively correlated with the initial NRS value (r = 0.31, p 0.0001). No serious side effects were noted. The percentage of patients with an initial heart rate 100/min declined from 14.6 % to 5.2 % after the administration of paracetamol (p 0.0001), 18.7 % of the patients received paracetamol for trauma not related to the extremities and 7 % of the patients for nontraumatic pain. An emergency physician was involved in 50 % of the EMS missions and 98.6 % of the patients were transported to a hospital for further diagnostics and treatment.The prehospital intravenous administration of paracetamol by paramedics to patients with limb trauma is simple, safe and in 50 % of the patients effective in achieving a NRS value 5; however, further improvements in prehospital pain therapy initiated by paramedics are desirable, especially in patients with an initial NRS value 7.

Data from clinical trials present numerous problems for the data analyst. These include non-compliance with the prescribed dosing regimen and inaccurate recollection of dosing history by patients as well as mistakes in recording data. Several methods have been proposed to address these issues. One such technique by Lu et al. (Selecting reliable pharmacokinetic data for explanatory analyses of clinical trials in the presence of possible noncompliance. J. Pharmacokinet. Pharmacodyn. 28:343-362 (2001)) identifies occasions in pharmacokinetic (PK) data where the preceding dosing history is likely to be unreliable. We used this method, implemented in the software program NONMEM (beta) VI, to clean a dataset containing indinavir (IDV) plasma concentrations from HIV-1 infected patients. The data was also cleaned by inspection in Microsoft Excel using clinical PK criteria. A one-compartment model with first order absorption and elimination was fit to both sets of cleaned data. IDV population PK parameters obtained from these analyses were similar to those reported previously. It is established that IDV nephrotoxicity is related to high IDV exposure. However, no relationships were found between any PK parameters and nephrotoxicity in the "compliance cleaned" dataset. In the "PK cleaned" dataset, the oral clearance and apparent volume were lower by 9.1% and 6.6%, respectively in patients with any type of nephrotoxicity and the maximum IDV concentration (C(max)) was 12.1% higher. In patients suffering from nephrolithiasis in particular, C(max) was 15.5% higher. Accordingly, the use of the non-compliance detection method did not improve the reliability of our dataset over the usual method of applying clinical criteria. In fact, analyses on the compliance-cleaned dataset missed some exposure-toxicity relationships. Thus, automated methods must be tested rigorously with 'real life' datasets, used with caution, and always in conjunction with clinical reasoning to avoid overlooking a signal in noisy data.

Objectives To determine the characteristics of the binding of nelfinavir and active M8 to α1-acid glycoprotein (AAG) and human serum albumin (HSA), and to examine the displacement effects of drugs binding extensively to AAG (ritonavir and saquinavir) or to HSA (salicylic acid and valproic acid). Methods Free drugs were separated by equilibrium dialysis after incubation with human plasma or purified plasma proteins and after co-incubation with potential displacers. Association constants were estimated from double-reciprocal plots of the data. Results Nelfinavir and M8 free fractions [fractions of unbound drug (fus)] were 0.42±0.08% (mean±standard deviation) and 0.64±0.07%, respectively. For the two analytes, respectively, association constants were 7.25 × 107/m and 3.33 × 107/m for AAG and 1.11 × 106/m and 7.92 × 105/m for HSA. Nelfinavir fu in an AAG solution was significantly (P

The full benefit of many effective medications will be achieved only if patients adhere to prescribed treatment regimens. Unfortunately, applying terms such as “noncompliant” and “nonadherent” to patients who do not consume every pill at the desired time can stigmatize them in their future relationships with health care providers. This article on medication adherence (or compliance) reviews strategies to assess and enhance this important aspect of patient care.

Peroxisome proliferator-activated receptor {gamma} (PPARgamma), the nuclear receptor that binds the insulin-sensitizing thiazolidinediones (TZDs), is prominently upregulated in intimal vascular smooth muscle cells (VSMC) after mechanical injury to the vessel wall. Several TZD PPARgamma ligands have been shown to inhibit neointima formation in both normal and insulin-resistant vasculature. The suppression of intimal hyperplasia by TZD PPARgamma ligands probably results from their activity to inhibit VSMC growth and promote apoptosis. TZDs prevent VSMC proliferation by blocking the activity of regulatory proteins, such as phosphorylation of the retinoblastoma protein (Rb). Rb functions as a G(1) gatekeeper by controlling S phase gene expression mediated by the E2F transcription factor. Consistent with their effect on Rb phosphorylation, PPARgamma ligands inhibit the mitogenic induction of minichromosome maintenance (MCM) proteins 6 and 7, two E2F-regulated S phase genes essential for DNA replication. PPARgamma ligands also induced apoptosis in VSMC, which correlated with a potent induction of GADD45, a gene implicated in controlling cell growth and survival. A constitutively active form of PPARgamma targeted the same cell cycle regulators as did PPARgamma ligands, consistent with a nuclear-receptor-dependent mechanism of action. This review will summarize mechanisms through which PPARgamma modulates VSMC proliferation and apoptosis suggesting that PPARgamma itself is a novel important regulator of cell cycle and apoptosis and may provide a new therapeutic approach to prevent restenosis.

The importance of reviewing and studying sex-based differences in pharmacologic parameters is demonstrated by the increasing data on gender variation in drug efficacy and toxicity profiles. Sex-based differences in the four major factors that contribute to interindividual pharmacokinetic variability—bioavailability, distribution, metabolism, and elimination—are theorized to stem from variations between men and women in factors such as body weight, plasma volume, gastric emptying time, plasma protein levels, cytochrome P450 activity, drug transporter function, and excretion activity. Sex-determined variations in pharmacodynamics have traditionally been more difficult to study, but a number of recent studies have explored these differences. This review examines the biologic basis of differences in pharmacokinetics and pharmacodynamics between the sexes and summarizes studies that have addressed these differences. As an example, sex-based variation in the efficacy and toxicity of antiretroviral therapy in human immunodeficiency virus (HIV)-infected patients is explored more thoroughly to illustrate some of the factors underlying sex-based differences in drug therapy.

There is marked variability in the extent to which the three classes of antiretroviral (ARV) drugs bind to plasma proteins (5 to99%). Protease inhibitors (PIs), with the exception of indinavir, are more than 90% protein bound, mainly to alpha1-acid glycoprotein (AAG). Efavirenz, a nonnucleoside reverse transcriptase inhibitor (NNRTI), is more than 99% bound, mainly to albumin. Nucleoside reverse transcriptase inhibitors (NRTIs) are not highly protein bound. The pharmacological activity of ARV drugs is dependent on unbound drug entering cells that harbor the human immunodeficiency virus (HIV). There has been concern that changes in protein binding could impact on antiviral activity and management. However, for PIs and NNRTIs, and for many drugs given orally, altered plasma binding would not be expected to influence the average exposure to unbound (active) drug after chronic oral dosing. Nevertheless, there will be a change in the relationship between total and unbound concentrations that will be important if, as part of therapeutic drug monitoring, the total rather than the unbound drug is measured. Measuring drug concentrations that are needed to inhibit different HIV strains (wild type and drug resistant) in vitro could also cause confusion because most methods employ bovine serum in the assay medium, and unbound concentrations are not directly measured. Estimating unbound drug concentrations in human plasma and in incubation media can be highly method dependent and thus may affect the calculated IC50 (the concentration of drug that results in 50% inhibition of viral replication). Because inhibitory quotients (IQs = C(trough)/IC50) are becoming part of pharmacokinetic/pharmacodynamic (PK/PD) analyses of clinical trial data, the strengths and weaknesses of the methods used for the determination of unbound drug concentration in plasma and in vitro systems--ultracentrifugation, ultrafiltration, and equilibrium dialysis--need to be understood. Consensus on standard procedures must be reached. In June 2002, a panel of experts assembled by the Forum for Collaborative HIV Research met in Washington, DC, to review the basic principles of protein binding of ARV drugs, and to discuss the impact that changes in plasma protein binding may have on the PKs and activity of ARV drugs as well as on therapeutic drug monitoring. The purpose of the meeting was to discuss the following topics: (1) basic principles of protein binding and how changes in binding can impact on drug PKs and drug exposure in vivo, (2) variability in plasma protein binding among patients taking ARV drugs, (3) the impact of HIV infection and concomitant diseases on the extent of plasma protein binding, (4) the likelihood of clinically relevant drug interactions at the level of plasma protein binding, (5) the evidence that measuring unbound concentrations of ARV drugs in the plasma of patients gives more meaningful information than total drug concentration and, therefore, should be considered in routine therapeutic drug monitoring of ARV agents, (6) optimal method(s) for measuring the unbound concentration of drugs in vitro (for IC50 determination) and in vivo, and (7) future studies that need to be considered to fully understand the importance of plasma protein binding in therapeutic drug monitoring. This report summarizes the topics discussed at this meeting. It guides the reader through the discussions that allowed the panel to formulate a series of statements regarding the significance of plasma protein binding of ARV drugs when studied in vitro and in vivo. The roundtable participants also identified research priorities that are important for understanding the sources of inter- and intraindividual variability in protein binding in patients. These include obtaining data on unbound as well as on total concentrations in PK studies; looking at variants of AAG and whether they differ in binding affinity; and emphasizing the importance of developing a standard procedure for drug susceptibility assays used to determine IC50 values.

Eighteen healthy human immunodeficiency virus-negative subjects participated in an open-label, six-period, incomplete Latin-square crossover pharmacokinetic study. Each subject received two of the three possible pair-wise combinations of single-dose oral ritonavir (R) (400 mg), nelfinavir (N) (750 mg), and saquinavir (S) (800 mg), each pair on three occasions (simultaneous or staggered administration), each occasion at least 2 days after the last. A model-based analysis reveals the following major drug interactions under the conditions of this study: 1). R given simultaneously with S decreases S hepatic intrinsic clearance almost 50-fold relative to that predicted for S given alone and increases its gut bioavailability 90% (but decreases its rate of absorption 40%) relative to when N is given simultaneously; 2). N given simultaneously with S decreases S hepatic intrinsic clearance 10-fold relative to that predicted for S given alone; and 3) R inhibits S hepatic intrinsic clearance even after R plasma levels have become undetectable (48 h after dosing), implying that R, when used as a pharmacokinetic enhancer, can be dosed less frequently than might be predicted from the duration of detectable systemic concentrations.

Background: There are insufficient data on pediatric antiretroviral therapy (ART) pharmacokinetics (PK), particularly for children in low- and middle-income countries. Methods: We conducted a prospective nevirapine (NVP) PK study among HIV-infected Kenyan children aged 3-13 years initiating an NVP-based ART regimen. NVP dose timing was measured through medication event monitors. Participants underwent 2 inpatient assessments: 1 at 4-8 weeks after ART initiation and 1 at 3-4 months after ART initiation. Allometric scaling of oral clearance (CL)/bioavailability (F) and volume of distribution (Vd)/F values were computed. Nonlinear mixed-effects modeling using the first-order conditional estimation with interaction method was performed with covariates. The impact of adherence on time below minimum effective concentration was assessed in the final PK model using medication event monitors data and model-estimated individual parameters. Results: Among 21 children enrolled, mean age was 5.4 years and 57% were female. CL/F was 1.67 L/h and Vd/F was 3.8 L for a median child weighing 15 kg. Participants' age had a significant impact on CL/F (P < 0.05), with an estimated decrease in CL of 6.2% for each 1-year increase in age. Total body water percentage was significantly associated with Vd/F (P < 0.001). No children had >10% of time below minimum effective concentration when the PK model assumed perfect adherence compared with 10 children when adherence data were used. Conclusions: Age and body composition were significantly associated with children's NVP PK parameters. ART adherence significantly impacted drug exposure over time, revealing subtherapeutic windows that may lead to viral resistance.

Many narrow therapeutic index drugs are eliminated primarily by hepatic metabolism. Selecting the proper dosing regimen for such drugs in the presence of liver disease is an important therapeutic problem. However, the effect of liver diseases on drug disposition is complex, and depends on the pathophysiology of the disease and the pharmacokinetic characteristics of the drug itself. Hepatic clearance concepts provide a general framework for understanding and predicting the changes in pharmacokinetics of drugs with high and low intrinsic clearances, but this approach is not sufficiently robust for clinical use due to difficulties in measuring patient-specific hepatocellular function and hepatic blood flow. Further complicating the ability to predict hepatic clearance in the presence of liver disease is that hepatic enzymes may be differentially affected by the presence of liver disease-glucuronidation is well-preserved even in advanced liver disease, and mild to moderate liver disease has selective effects on the catalytic activity of specific cytochrome P 450 metabolizing enzymes, with CYP2C19 more sensitive to liver disease than CYP2D6. Despite considerable efforts to develop non-invasive probes of hepatic metabolic activity, there are still none that are useful clinically. Therapeutic drug monitoring may have some value, but is limited by changes in plasma protein binding that are common in liver disease. More studies are needed to develop better probes, and, in the drug development process, to provide better information on metabolic pathways and laboratory and clinical covariates that can be used to individualize dosing regimens in the presence of coexisting diseases and concurrent drug therapy.

Two international meetings were convened in 1998 to review the current science of drug development and the potential opportunities to optimize the evaluation of new drugs in humans. This report represents a synopsis of these meetings, and focuses on the current state of knowledge pertaining to drug development, future scientific and technical needs, and the relative merits of various strategies intended to accelerate the clinical development of drugs.

Objective To investigate whether heparin produces vasodilation in human veins and to explore the underlying mechanisms. Methods Eleven healthy volunteers were studied with the dorsal hand vein compliance technique. Dose-response curves to heparin and enoxaparin were generated. Dose-response curves to heparin were also constructed before and after heparin was infused with the nitric oxide synthase inhibitor NG-monomethyl-l-arginine (L-NMMA) or combined histamine H1- and H2-receptor blockade. Results Heparin but not enoxaparin caused significant dose-dependent relaxation with an average apparent maximal response (at an infusion rate of 20 IU/min) of 47% ± 23%. L-NMMA attenuated heparin-induced relaxation (P < .001). The combination of H1- and H2-receptor antagonists attenuated heparin-induced relaxation to a lesser extent (P < .05). Heparin-induced relaxation decreased by 52%, 73%, and 35% in the presence of L-NMMA, indomethacin (INN, indometacin) plus L-NMMA, and combined H1- and H2-receptor blockade, respectively. Conclusion Heparin is an endothelium-dependent venodilator in humans. The mechanism of heparin-induced relaxation involves an increased availability of nitric oxide, possibly partially related to local release of histamine. Clinical Pharmacology & Therapeutics (1999) 66, 232–238; doi

The amino acid l-arginine is the precursor of nitric oxide (NO), a powerful vasodilator with antiplatelet properties. The availability of l-arginine has been suggested to be a rate-limiting factor in the production of NO in conditions such as hypercholesterolemia. It was speculated that fluctuations in plasma concentrations of l-arginine during the day may be dependent upon dietary intake of the amino acid, or other variables, and might modify the elaboration of endogenous NO. Over a 24-h period, the plasma concentrations of l-arginine and NO-related compounds (NOx) were measured during an l-arginine and nitrate/nitrite-free diet (diet A) or a nitrate/nitrite-free diet with a fixed amount of l-arginine intake (3.8 g/d) (diet B) in eight healthy volunteers during a 2-day crossover study. Subjects were randomly selected to begin with diet A or diet B and consumed the other diet on the second day. During diet A, plasma l-arginine decreased significantly from 09.00 to 16.00 (21.4 ± 2.0 to 11.9 ± 1.1 mg/ml), rose slightly in the evening (to 16.6 ± 1.7mg/ml) and gradually increased during the night. During diet B, plasma larginine showed a peak after each meal (approximately 23 mg/ml). Plasma NOx concentrations measured by chemiluminescence did not show any circadian variation on either diet. Plasma l-arginine concentrations change during the day and are influenced by dietary intake. Importantly, plasma NOx do not seem to vary with this pattern in healthy individuals.

Conversion of angiotensin I to angiotensin II likely occurs in human veins, supporting the existence of endothelial angiotensin-converting enzyme (ACE) activity in these vessels. Using the dorsal hand vein technique, we investigated the effects of 2 ACE inhibitors, captopril (single oral dose of 6.25 mg) and enalaprilat (local infusion of 1 μg/min), on venous responsiveness in healthy subjects. Orally administered captopril induced a marked decrease in angiotensin I– but not angiotensin II–induced venoconstriction. This blunted response persisted for at least 4 hours. Enalaprilat and captopril increased the sensitivity to bradykinin, decreasing the dose producing half-maximal response (ED50) of bradykinin 18-fold and 5-fold, respectively, without changing the maximal venodilatory response. These results confirm that there is substantial rapid metabolism of angiotensin I in human veins and suggest that a single dose of locally infused angiotensin I can be used with the dorsal hand vein technique to assess the time-course effect of vascular ACE inhibition after oral administration. Our findings also extend previous in vitro observations in human veins by showing that these agents potentiate the venodilatory effects of bradykinin in vivo. Clinical Pharmacology & Therapeutics (1999) 65, 58–65; doi

Aims Recent reports, largely in animal models, have suggested that either inhibition of nitric oxide (NO) synthase or endothelium removal in arteries inhibits the response to isoprenaline, a β-adrenoceptor agonist, and also enhances the response to sodium nitroprusside, a nitrovasodilator. This in vivo study was designed to determine whether NG-monomethyl-l-arginine (l-NMMA), an inhibitor of NO synthesis, influences relaxation of human hand veins mediated by isoprenaline or by sodium nitroprusside. Methods Using the dorsal hand vein technique, full dose-response curves to bradykinin (0.27–278 ng min−1, n=6), isoprenaline (2.12–271 ng min−1, n=8) and sodium nitroprusside (0.01–634 ng min−1, n=7) were generated on separate occasions before and after l-NMMA co-infusion (50 μg min−1 ). Results In veins preconstricted with the α1-adrenoceptor-selective agonist phenylephrine, the three vasodilators induced maximal responses (Emax ) of 119±35, 72±18 and 103±17%, respectively. l-NMMA inhibited relaxation to bradykinin by 64% (P=0.014) but did not influence relaxation induced by isoprenaline. The sensitivity to sodium nitroprusside was significantly enhanced by l-NMMA co-infusion (concentration shift of 2.3, P=0.031). Conclusions We conclude that in human veins, spontaneously released NO does not play a major role in isoprenaline-induced relaxation. Our results also suggest that the effects of sodium nitroprusside in this vascular bed may be attenuated by endothelium-derived NO.

Patient compliance (adherence) with prescribed medication is often erratic, while clinical outcomes are causally linked to actual, rather than nominal medication dosage. We propose here a hierarchical Markov model for patient compliance. At the first stage, conditional upon individual random effects and a set of individual-specific nominal daily dose times, we assume that (i) the subject-specific probability of taking zero, one, or more than one dose associated with a given nominal dose time depends on the value of certain covariates, and on the number of doses associated with the immediate previous time, but is independent of any other previous or future dosing events (the Markov hypothesis); and (ii) the set of 'errors' between actual dose times associated with each nominal time is multivariate normally distributed, conditional on covariates and the number of such actual dose times, as in (i). At the second stage, a multivariate normal distribution is assumed for the individual random effects. We fit this model by maximum likelihood to data collected over three months using an electronic system for recording actual dose times in HIV-positive patients assigned to a regimen of zidovudine thrice daily. Beyond its value for describing and quantifying compliance behaviour, as illustrated here, the model may prove useful for explanatory analyses of clinical trials.

We investigated the pharmacokinetics of zidovudine, zalcitabine, and saquinavir in AIDS Clinical Trial Group protocol 229. Patients received either saquinavir, zalcitabine, or a combination of both, together with zidovudine three times a day. Approximately 100 patients were enrolled in each treatment arm, and intensive pharmacokinetic studies were performed on about 25 patients per arm at weeks 1 and 12. We estimated the pharmacokinetic parameters of all three drugs by using parametric and nonparametric methods. The mean values of the pharmacokinetic parameters of zidovudine (clearance [CL]/bioavailability [F], 168 liters/h; volume of distribution [V]/F, 185 liters; half-life, 0.76 h) and zalcitabine (CL/F, 25 liters/h; V/F, 92.2 liters; half-life, 2.7 h) were similar to those reported previously. For saquinavir, the mean pharmacokinetic parameter estimates using parametric methods were as follows: maximum concentration of drug in serum [Cmax], 70.8 ng/ml; time to Cmax, 3.11 h; area under the curve, 809 ng x h/ml; CL/F, 989 liters/h; V/F, 1,503 liters; half-life, 1.38 h. For all three drugs, clearance decreased with age. Weight did not influence the clearance of zidovudine, but the clearance of zalcitabine and saquinavir increased with weight. There were no differences in pharmacokinetic parameters between study weeks and arms, suggesting that there is no change in kinetics with chronic administration and that there are no significant pharmacokinetic interactions among these three drugs.

We propose a semiparametric method to estimate model-independent pharmacokinetic (PK) measures such as area under concentration–time, peak concentration and time to peak concentration (Tpeak ), for noisy population PK data from a sparsely sampled prospectively designed trial. The method is developed within the mixed-effect model framework, for the single-dose and steady-state case. We describe individual concentration vs. time using a longitudinal spline, consisting of a template spline, common to all individuals, and an individual-specific distortion spline accounting for individual differences. We impose a number of constraints on the longitudinal spline, including (i) it has a decreasing tail, (ii) its typical Tpeak is near the modal Tpeak observed in the population data, and (iii) its value is zero at time zero (single dose), or the same nonzero value at the beginning and end of a dosing interval (steady state). We test our method using simulated data and compare its performance to that of a parametric and a nonparametric method. An actual data example is also shown. The performance of the method is as good or better than that of a standard nonparametric method, and when the analysis model is misspecified, the method is superior to a standard parametric one. Since it is often not apparent that an analysis model is correct, we propose this approach as a general method for analysis.

Morphine has been extensively used in the treatment of pulmonary edema, and its action is believed to be mediated in part by its ability to produce peripheral venodilation. This study investigated whether opiates produce venodilation in human hand veins and explored the underlying mechanism(s). Fifteen healthy volunteers (11 men and four women) were studied with use of the dorsal hand vein compliance technique. After preconstriction with the selective alpha 1-adrenergic receptor agonist phenylephrine, dose-response curves were constructed to (1) opiate receptor agonists morphine (1 to 30 micrograms/min) or fentanyl (0.07 to 1 microgram/min), (2) a combination of morphine and the mu-opiate receptor antagonist naloxone, and (3) morphine and a combination of histamine (H1 and H2) receptor antagonists. Infusion of morphine caused venodilation in a dose-dependent manner, whereas fentanyl did not produce venodilation. Coinfusion of naloxone and morphine impaired the venodilation only slightly. Coinfusion of the H1- and H2-antagonists completely abolished the venodilatory effect of morphine. These results suggest that the venodilatory effect of morphine is mediated through histamine release and that mu-opiate receptors have little or no involvement in this process.