ECG Evaluation as Part of the Clinical Pharmacology Strategy in the Development of New Drugs: A Review of Current Practices and Opportunities Based on Five Case Studies.

The International Conference on Harmonization (ICH) E14 document was revised in 2015 to allow concentration-corrected QT interval (C-QTc) analysis to be applied to data from early clinical pharmacology studies to exclude a small drug-induced effect on QTc. Provided sufficiently high concentrations of the drug are obtained in the first-in-human (FIH) study, this approach can be used to obviate the need for a designated thorough QT (TQT) study. The E14 revision has resulted in a steady reduction in the number of TQT studies and an increased use of FIH studies to evaluate electrocardiogram (ECG) effects of drugs in development. In this review, five examples from different sponsors are shared in which C-QTc analysis was performed on data from FIH studies. Case 1 illustrates a clearly negative C-QTc evaluation, despite observations of QTc prolongation at high concentrations in nonclinical studies. In case 2 C-QTc analysis of FIH data was performed prior to full pharmacokinetic characterization in patients, and the role of nonclinical assays in an integrated risk assessment is discussed. Case 3 illustrates a positive clinical C-QTc relationship, despite negative nonclinical assays. Case 4 demonstrates a strategy for characterizing the C-QTc relationship for a nonracemic therapy and formulation optimization, and case 5 highlights an approach to perform a preliminary C-QTc analysis early in development and postpone the definitive analysis until proof of efficacy is demonstrated. The strategy of collecting and storing ECG data from FIH studies to enable an informed decision on whether and when to apply C-QTc analysis to obviate the need for a TQT study is described.

Correction to: Adverse drug reaction causality assessment tools for drug-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: room for improvement.

The correct name of the 9th Author is David J. Margolis. The original article was corrected.

Adverse drug reaction causality assessment tools for drug-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: room for improvement.

PURPOSE: Establishment of causality between drug exposure and adverse drug reactions (ADR) is challenging even for serious ADRs such as Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Several causality assessment tools (CAT) exist, but the reliability and validity of such tools is variable. The objective of this study was to compare the reliability and validity of existing ADR CATs on SJS/TEN cases. METHODS: Seven investigators completed three CAT (ALDEN, Naranjo, Liverpool) for 10 SJS/TEN cases. Each CAT categorized the causality of 30 potential drugs as definite/very probable, probable, possible, or doubtful/unlikely. An additional reviewer provided expert opinion by designating the implicated drug(s) for each case. A Kappa score was generated to compare CAT responses both by method (reliability of all 7 reviewers, by CATs) and by reviewer (reliability of the 3 CAT, by reviewer). A c statistic was calculated to assess validity. RESULTS: Inter-rater reliability by CAT was poor to fair: ALDEN 0.22, Naranjo 0.11, and Liverpool 0.12. Reliability was highest when causality classification was definite/very probable (0.16-0.41). Similarly, intra-rater reliability by reviewer was poor. When comparing the validity of the overall CAT to expert reviewer, area under the curve was highest for ALDEN (c statistic 0.65) as compared to Liverpool (0.55) or Naranjo (0.54). CONCLUSION: Available CAT have poor reliability and validity for drug-induced SJS/TEN. Due to the importance of determining ADR causality for research, industry, and regulatory purposes, development of an enhanced tool that can incorporate data from immunological testing and pharmacogenetic results may strengthen CAT usefulness and applicability for drug-induced SJS/TEN.

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis Standard Reporting and Evaluation Guidelines: Results of a National Institutes of Health Working Group.

Importance: Toxic epidermal necrolysis (TEN) and Stevens-Johnson Syndrome (SJS) are rare, acute, life-threatening dermatologic disorders involving the skin and mucous membranes. Research into these conditions is hampered by a lack of standardization of case reporting and data collection. Objective: To establish a standardized case report form to facilitate comparisons and maintain data quality based on an international panel of SJS/TEN experts who performed a Delphi consensus-building exercise. Evidence Review: The elements presented for committee scrutiny were adapted from previous case report forms and from PubMed literature searches of highly cited manuscripts pertaining to SJS/TEN. The expert opinions and experience of the members of the consensus group were included in the discussion. Findings: Overall, 21 out of 29 experts who were invited to participate in the online Delphi exercise agreed to participate. Surveys at each stage were administered via an online survery software tool. For the first 2 Delphi rounds, results were analyzed using the Interpercentile Range Adjusted for Symmetry method and statements that passed consensus formulated a new case report form. For the third Delphi round, the case report form was presented to the committee, who agreed that it was "appropriate and useful" for documenting cases of SJS/TEN, making it more reliable and valuable for future research endeavors. Conclusions and Relevance: With the consensus of international experts, a case report form for SJS/TEN has been created to help standardize the collection of patient information in future studies and the documentation of individual cases.

New era in drug interaction evaluation: US Food and Drug Administration update on CYP enzymes, transporters, and the guidance process.

Predicting clinically significant drug interactions during drug development is a challenge for the pharmaceutical industry and regulatory agencies. Since the publication of the US Food and Drug Administration's (FDA's) first in vitro and in vivo drug interaction guidance documents in 1997 and 1999, researchers and clinicians have gained a better understanding of drug interactions. This knowledge has enabled the FDA and the industry to progress and begin to overcome these challenges. The FDA has continued its efforts to evaluate methodologies to study drug interactions and communicate recommendations regarding the conduct of drug interaction studies, particularly for CYP-based and transporter-based drug interactions, to the pharmaceutical industry. A drug interaction Web site was established to document the FDA's current understanding of drug interactions (http://www.fda.gov/cder/drug/drugInteractions/default.htm). This report provides an overview of the evolution of the drug interaction guidances, includes a synopsis of the steps taken by the FDA to revise the original drug interaction guidance documents, and summarizes and highlights updated sections in the current guidance document, Drug Interaction Studies-Study Design, Data Analysis, and Implications for Dosing and Labeling.

Prescription of QT-prolonging drugs in a cohort of about 5 million outpatients.

Many drugs prolong the QT interval and increase the risk of torsade de pointes. Concurrent use of two or more of these drugs can further increase the risk, but the prevalence of concurrent prescription of QT-prolonging drugs is not known. Using the administrative claims database of a national pharmaceutical benefit manager, we conducted a retrospective cohort study in 4,825,345 subjects aged 18 years or older. After identifying 50 drugs with QT-prolonging potential, and an additional 26 drugs that inhibit the metabolic clearance of QT-prolonging drugs, we measured the frequency of overlapping prescriptions for two or more of these drugs in the outpatient setting in 1999. Nearly 1.1 million subjects (22.8%) filled 4.4 million prescriptions for QT-prolonging drugs. Of these, 103,119 subjects (9.4%) filled overlapping prescriptions for two or more of the drugs or for a QT-prolonging drug and another drug that inhibits its clearance; 7249 subjects (0.7%) filled overlapping prescriptions for three or more of these drugs. Twenty-two percent of subjects who filled overlapping prescriptions were aged 65 or older; 74% were women. Antidepressants were involved in nearly 50% of the cases. Concurrent prescription of QT-prolonging drugs is common in the outpatient setting, and antidepressants are involved in half of these cases. Large pharmaceutical claims databases are useful for detecting potentially harmful prescribing behaviors, but better clinical evidence on medication safety is needed before such a system can be implemented fully.

Teaching rational prescribing: a new clinical pharmacology curriculum for medical schools.

In most U.S. and Canadian medical schools, pharmacology is taught during the preclinical year 2 of the 4-year-long curriculum. This is despite the fact that medical school graduates and residency directors have identified teaching rational therapeutics as a priority. Hence, we have developed a core curriculum in clinical pharmacology for 4th-year medical students that builds on the core principles of rational therapeutics described by Nierenberg 10 years ago (Nierenberg, DW. Clin Pharmacol Ther 1990; 48:606-610). Here we report on our 3-year experience teaching this course, which addresses the following teaching objectives: to teach medical students on how to (1) critically evaluate medications; (2) obtain a complete medication history including herbal and over-the-counter medications; (3) apply pharmacokinetic principles to clinical practice; (4) recognize and report adverse drug events and interactions; (5) optimize pain management; (6) recognize and treat substance abuse and poisoning; and (7) prescribe rationally regardless of prescribing environment. Student assessment was in the form of multiple-choice and formative oral examinations, which were validated against the clinical part of the U.S. medical licensing examination. The course significantly increased the student rating of clinical pharmacology teaching measured by a national survey of U.S. medical school graduates. We conclude that this course may be useful for teaching rational prescribing to medical students. With the guidance and educational material provided by this article, a successful implementation of such a course should be possible in most medical schools.

The roles of CYP2D6 and stereoselectivity in the clinical pharmacokinetics of chlorpheniramine.

AIMS: To examine the stereoselective disposition of chlorpheniramine and to evaluate the role of CYP2D6 in chlorpheniramine pharmacokinetics in humans. METHODS: Eight healthy volunteers (six extensive metabolizers with respect to CYP2D6 and two poor metabolizers) received a single 8 mg oral dose of rac-chlorpheniramine either given alone or following administration of quinidine 50 mg every 6 h for 2 days prior to the study day and every 6 h thereafter until the end of the study. Plasma concentrations of (S)-(+)- and (R)-(-)-enantiomers of chlorpheniramine were determined using liquid chromatography/mass spectrometry. RESULTS: In extensive metabolizers, mean Cmax was greater (12.55+/-1.51 ng ml-1vs 5.38+/-0.44 ng ml-1) and CLoral was lower (0.49+/-0.08 l h-1 kg-1vs 1.07+/-0.15 l h-1 kg-1) for (S)-(+)- than for (R)-(-)-chlorpheniramine (P<0.005). For (S)-(+)-chlorpheniramine, administration of quinidine, an inhibitor of CYP2D6, resulted in an increase in Cmax to 13.94+/-1.51 (P<0.01), a reduction in CLoral to 0.22+/-0.03 l h-1 kg-1 (P<0.01), and a prolongation of elimination half-life from 18.0+/-2.0 h to 29.3+/-2.0 h (P<0.001). Administration of quinidine decreased CLoral for (R)-(-)-chlorpheniramine to 0.60+/-0.10 l h-1 kg-1 (P<0.005). In CYP2D6 poor metabolizers, systemic exposure was greater after chlorpheniramine alone than in extensive metabolizers, and administration of quinidine resulted in a slight increase in CLoral. CONCLUSIONS: Stereoselective elimination of chlorpheniramine occurs in humans, with the most pharmacologically active (S)-(+)-enantiomer cleared more slowly than the (R)-(-)-enantiomer. CYP2D6 plays a role in the metabolism of chlorpheniramine in humans.

The enantioselective determination of chlorpheniramine and its major metabolites in human plasma using chiral chromatography on a beta-cyclodextrin chiral stationary phase and mass spectrometric detection.

A sensitive enantioselective high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of plasma concentrations of (-)(R)- and (+)(S)-chlorpheniramine (CP) and their metabolites, desmethyl-chlorpheniramine (DCP), didesmethyl-chorpheniramine (DDCP) and chlorpheniramine N-oxide (CPNO). Enantioselective separations were achieved on a beta-cyclodextrin chiral stationary phase (CYCLOBOND I 2000) with a mobile phase consisting of diethylamine acetate (0.25%, pH 4.4):methanol:acetonitrile [85:7.5:7.5, (v/v/v)]and a flow-rate of 0.5 ml/min. For CP, the enantioselectivity (alpha) of the separation was 1.12 with a resolution factor (R(s)) of 1.17. The method was validated for CP by using mass spectroscopy detection (MSD). Concentrations of each enantiomer could be measured down to 125 pg/ml from a 1-ml plasma sample. Extracted calibration curves were linear from 0.13 to 50.00 ng/ml for each enantiomer. The method was applied to samples from two clinical studies.