Antiviral Therapy 13:675–685 Original article Factors influencing efavirenz and nevirapine plasma concentration: effect of ethnicity, weight and co-medication Wolfgang Stöhr1, David Back 2, David Dunn1, Caroline Sabin3, Alan Winston4, Richard Gilson5, Deenan Pillay 6, Teresa Hill 3, Jonathan Ainsworth7, Anton Pozniak8, Clifford Leen9, Loveleen Bansi3, Martin Fisher10, Chloe Orkin11, Jane Anderson12, Margaret Johnson13, Phillippa Easterbrook14, Sara Gibbons2 and Saye Khoo2* on behalf of the Liverpool TDM Database and the UK CHIC Study 1MRC Clinical Trials Unit, London, UK 2University of Liverpool, Liverpool, UK 3Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London, UK 4St. Mary’s Hospital, London, UK 5Mortimer Market Centre, Royal Free and University College Medical School (RFUCMS), London, UK 6Department of Infection, RFUCMS, Centre for Infection, Health Protection Agency, London, UK 7North Middlesex University Hospital, London, UK 8Chelsea and Westminster NHS Trust, London, UK 9University of Edinburgh, Western General Hospital, Edinburgh, UK 10Brighton and Sussex University Hospitals NHS Trust, Sussex, UK 11Barts and The London NHS Trust, London, UK 12Homerton Hospital, London, UK 13Royal Free NHS Trust and RFUCMS, London, UK 14King’s College Hospital, London, UK *Corresponding author: E-mail:
[email protected] Background: The aim of this study was to examine and zidovudine (25% lower; P=0.010). Notably, without factors influencing plasma concentration of efavirenz and adjustment for other factors, patients on rifampicin had nevirapine. 48% higher efavirenz concentration, as these patients Methods: Data from the Liverpool Therapeutic Drug Mon- were mostly black and on 800 mg/day. For nevirapine the itoring (TDM) registry were linked with the UK Collabora- predictors were black ethnicity (39% higher; P=0.002), tive HIV Cohort (CHIC) Study.