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.

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.

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.

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.