Efavirenz plasma concentrations at 1, 3, and 6 months post-antiretroviral therapy initiation in HIV type 1-infected South African children
Date
2010Author
Viljoen, Michelle
Kruger, Herculina S.
Rheeders, Malie
Gous, Hermien
Riddick, Alison
Metadata
Show full item recordAbstract
The aim of this study was to quantify the plasma efavirenz concentrations over 6 months in black HIV-1-infected
South African children (3–14 years), from resource-limited households, attending an outpatient clinic. The
children were antiretroviral treatment (ART) naive and received efavirenz in combination with two nucleoside
reverse transcriptase inhibitors according to South African national guidelines. Two blood samples were taken
between 12 and 20 h after the last efavirenz dose at 1 (
n
¼
58), 3 (
n
¼
54), and 6 (
n
¼
54) months post-ART
initiation. A total of 328 efavirenz mid-dose plasma samples from 58 patients was determined with a validated
liquid chromatography tandem mass spectrometry method. Viral suppression (
<
25 copies
=
ml) was achieved in
95% of the children after 6 months on ART. The median (range) plasma concentration at time points 1 and 2 were
2.06 (0.10–11.14) and 1.80 (0.14–10.70)
m
g
=
ml with respective mean (
SD) blood sampling times of 15.24 (2.03)
and 16.91 (2.03) h post-evening dose. Efavirenz plasma samples within the therapeutic range of 1–4
m
g
=
ml
accounted for 58%; 17% were
<
1
m
g
=
ml and 25% were
>
4
m
g
=
ml over the 6 months. Efavirenz levels persistently
>
4
m
g
=
ml were recorded for 13 (23%) children and 3 (5%) children had persistent efavirenz levels
<
1
m
g
=
ml.
Possible reasons for efavirenz plasma levels outside the accepted therapeutic range include genetic variation in
drug metabolism, incorrect dosing, drug–drug interactions, and nonadherence. However, these need to be
further explored and the importance of sequential plasma levels has been highlighted in this study
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