9th Annual Conference Of The British HIV Association [BHIVA] 24 – 26 April 2003, University of Manchester Institute of Science & Technology (UMIST) Manchester

[AUTHOR(S):] A Winston, A Pozniak, N Smith, C Fletcher, S Mandalia, D Parmar, S Gibbons, D Back, BG Gazzard and MR Nelson
Chelsea and Westminster Hospital, London, UK

BHIVA Conf 2003 Apr 24-26;9:O11

BACKGROUND: The NNRTIs nevirapine (NVP) and efavirenz (EFV) are both capable of inducing the metabolism of co-administered drugs. Not uncommonly, it is necessary to switch from one drug to another. When switching from EFV to NVP it is not known whether to dose-escalate or switch to full dose.

METHODS: This is a pharmacokinetic observational study, powered to 80% for detection of average trough drug levels. Patients established on EFV, changing to NVP, were randomised to dose escalation [200 mg once daily for 2 weeks then 200 mg twice daily (bd)] or full dose (200 mg bd). Trough drug levels were checked on days 2, 8, 15, 22 and 29 as were liver function tests, CD4 and viral load (VL).

RESULTS: Seven patients were randomised to dose escalation (group 1) and six to full-dose NVP (group 2). Average trough NVP levels to day 15 in group 1 were below the recommended level for virological success of 3000 ng/ml (Table 1). Average trough NVP levels in group 2 were above this threshold except for day 2 but were significantly higher than group 1 on this day. There was no increased incidence of raised alanine aminotransferase between either groups or VL changes.

CONCLUSIONS: When changing from EFV to NVP, patients should start on 200 mg bd initially, for therapeutic plasma drug levels without increased toxicity. Although virological failure was seen in those given lowerdose NVP, subtherapeutic plasma levels occurred for 3 weeks, which has potential for the development of drug-resistant virus.

Table 1: Average nevirapine plasma levels (ng/ml); *P<0.025.

PRESENTING AUTHOR: A Winston

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Copyright © 2003 - British HIV Association (BHIVA) Reproduction of this abstract (other than one copy for personal reference) must be cleared through the BHIVA Organising Secretariat 1 Mountview Court, 310 Friern Barnet Lane, London N20 0LD