15th Annual Conference of the British HIV Association 1-3 April 2009, Liverpool, UK

SWITCHING FROM EFAVIRENZ (EFV) TO NEVIRAPINE (NVP): A NOVEL PHARMACOLOGICAL STRATEGY

HIV Med 2009 Apr 1-3 (Suppl 1);15:11 (abstract no. O21)

NE Dufty, S Barrett and S Taylor
Birmingham Heartlands Hospital, Birmingham, UK

BACKGROUND: Switching from EFV to NVP is often required in clinical situations but the optimal switch strategy is unknown. Current strategies include switching directly from EFV to NVP 200 mg BD or using a traditional 2 week NVP 200 mg OD lead-in period after stopping EFV. In our unit, typical side effects of rash and hepatitis have been observed in patients despite a low nadir CD4 count. This prompted us to re-evaluate both strategies. We hypothesised that a 2 week cross-over period of EFV with NVP 200 mg OD would provide therapeutic concentrations of EFV during possible sub therapeutic NVP concentrations [NVP] whilst minimising the risk of rash or hepatotoxicity.

METHODS: Thirteen HIV positive patients (7 male) switching from EFV to NVP were followed prospectively following a standard protocol. Plasma [EFV] were measured at 0, 2 and 4 weeks. EFV was stopped at week 2. NVP was dose escalated from 200 mg OD to 200 mg BD at week 2 and plasma [NVP] were measured at weeks 2 and 4. Viral load (VL) and serum transaminases were measured at weeks 0, 2 and 4.

RESULTS: The median time on EFV was 17 months (2–116). The median CD4 count at switch was 395 cells/mm³ (17–807). The median plasma [EFV] at week 0 was 1618 ng/mL (957–4341) and at week 2 was 1564 [(699–6356); P=0.46] with eight patients having plasma [EFV] above the MEC (1000 ng/mL). After 2 weeks of co-dosing EFV and NVP 200 mg OD, the median 24 h predicted trough [NVP] was 1542 ng/mL (573–2919). As predicted, no patients had [NVP] above the MEC (3000 ng/mL). In contrast by week 4 (2 weeks after stopping EFV), 10 patients had trough NVP in excess of the MEC with median [NVP] of 4357 ng/mL (2235–9678). By week 4, 2 patients still had detectable [EFV] at 940 and 201 ng/mL. Virological control was maintained in all patients. There were no significant elevations in LFTs or rash from weeks 0 to 4.

CONCLUSIONS: Our data supports the rationale for using a 2 week cross over strategy when changing patients from EFV to NVP.

2009-04-01
O21

Copyright © 2009 - 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