Investigation of the impact of urine handling procedures on interpretation of urinalysis findings and product safety in subjects treated with ezogabine

Neil Brickel,1 Sarah DeRossett,2 Mauro Buraglio,3 Christopher Evans,4 Si&ocirc;n Jones51Neurosciences Therapy Area Unit, GlaxoSmithKline, Uxbridge, Middlesex, UK; 2Neurosciences Therapy Area Unit, GlaxoSmithKline, Research Triangle Park, NC, USA; 3Neurosciences Therapy Area Unit, GlaxoSmithKline, Stevenage, Hertfordshire, UK; 4Bioanalytical Science and Toxicokinetics, PTS-DMPK, GlaxoSmithKline, King of Prussia, PA, USA; 5Global Clinical Safety and Pharmacovigilance, GlaxoSmithKline, Uxbridge, Middlesex, UKBackground: Ezogabine (also known by the international nonproprietary name of retigabine) is an antiepileptic drug codeveloped and comarketed by Valeant Pharmaceuticals North America and GlaxoSmithKline, which reduces neuronal excitability by enhancing the activity of potassium channels and has the potential to have effects on the urinary system through a pharmacologic action on bladder smooth muscle. In a single post-herpetic neuralgia trial, but not in an extensive epilepsy development program, proteinuria was unexpectedly reported in patients receiving ezogabine. Consequently, investigations were conducted to determine whether the reported proteinuria represented a true or false-positive finding.Methods: Patients receiving ezogabine 900&ndash;1200 mg/day in an open-label extension (Study 303) of a Phase III epilepsy trial voluntarily provided urine samples. Fresh samples were analyzed immediately at the study site, and stabilized aliquots were analyzed 1&ndash;3 days after collection at two central laboratories. In an open-label study in healthy volunteers receiving ezogabine 600&ndash;900 mg/day (Study RTG114137), urine samples were analyzed fresh (<2 hours after collection) and, using two different stabilizers and storage at room temperature, after 24 and 72 hours. Fluid intake was restricted prior to one sample point. Albumin:creatinine ratios were assessed in both studies.Results: In Study 303, there was notable variation in clarity, color, and proteinuria between fresh and stored urine samples, and between samples analyzed at different laboratories. In RTG114137, reporting rates of proteinuria were elevated following storage using one stabilizer, and the frequency of color change from fresh to stored samples differed between the stabilizers and between 24 and 72 hours with one stabilizer. Following fluid restriction, proteinuria rates were elevated with both stabilizers. Poor tolerability of ezogabine 750&ndash;900 mg/day resulted in limited titration beyond 750 mg/day and early termination of RTG114137.Conclusion: Hydration status, interval between urine collection and analysis, and the type of stabilizer used are all factors that may lead to false-positive proteinuria findings in patients receiving ezogabine and should be borne in mind if abnormalities are reported.Keywords: antiepileptic drugs, ezogabine, retigabine, urinary safety, urinalysi

Collaboration in pharmacovigilance: lamotrigine and fatal severe cutaneous adverse reactions &ndash; a review of spontaneous reports

Neil Brickel,1 Haris Shaikh,1 Andrew Kirkham,2 Greg Davies,1 Michelle Chalker,1 Pascal Yoshida3 1Global Clinical Safety and Pharmacovigilance, GlaxoSmithKline, Uxbridge, Middlesex, UK; 2Classic and Established Products, GlaxoSmithKline, Brentford, Middlesex, UK; 3Clinical Safety and Post-marketing Surveillance, GlaxoSmithKline KK, Tokyo, Japan Abstract: Pharmacovigilance presents many challenges, particularly when managing unpredictable, rare conditions, eg, severe cutaneous adverse reactions (SCARs). Such rare events are often only detected from spontaneous reports, which present their own limitations, particularly during a prolonged global launch schedule. GlaxoSmithKline&rsquo;s routine pharmacovigilance includes regular reviews of global adverse event (AE) reports and aggregate data from a central safety database. Lamotrigine is one of the several antiepileptic drugs associated with SCARs. After identification of increased rates of fatal SCAR cases with lamotrigine in Japan between September and December 2014, this analysis investigated the global incidence of fatal SCARs with lamotrigine and explored whether known risk factors may have contributed to these cases. Global fatal SCAR cases reported with lamotrigine administration from launch until January 2015 were reviewed for evidence of temporal association with dosing and the presence of risk factors, including comorbidities, concomitant medications, and noncompliance with the prescribing information (PI). Worldwide, the estimated cumulative exposure to lamotrigine was &gt;8.4 million patient-years. Globally, there were 54,513 AE reports for lamotrigine, of which 3,454 (6.3%) concerned SCARs. Of these, 122 (3.5%) had a fatal outcome (attributable and nonattributable to lamotrigine), equating to 0.01 fatal SCARs per 1,000 patient-years. In Japan (estimated cumulative exposure 141,000 patient-years), 17 fatal SCARs were reported (attributable and nonattributable), equating to 0.12 per 1,000 patient-years. Seventy-one percent of fatal SCAR cases in Japan showed evidence of noncompliance with the recommended dosing regimen; in 65% of the cases, a delay in discontinuation of lamotrigine after early signs of hypersensitivity was reported. Despite a number of limitations inherent in comparing spontaneous report data, this analysis highlights the need for adherence to the lamotrigine PI and emphasizes the importance of collaboration between global and local pharmacovigilance departments, to promptly identify and reduce the risk of rare and serious events, such as SCARs. Keywords: antiepileptic drug, pharmacovigilance, Stevens&ndash;Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptom