Free and total plasma levels of lopinavir during pregnancy, at delivery and postpartum: implications for dosage adjustments in pregnant women.
BACKGROUND
Physiological changes associated with pregnancy may alter antiretroviral plasma concentrations and might jeopardize prevention of mother-to-child HIV transmission. Lopinavir is one of the protease inhibitors more frequently prescribed during pregnancy in Europe. We described the free and total pharmacokinetics of lopinavir in HIV-infected pregnant and non-pregnant women, and evaluated whether significant alterations in its disposition and protein binding warrant systematic dosage adjustment.


METHODS
Plasma samples were collected at first, second and third trimester of pregnancy, at delivery, in umbilical cord and postpartum. Lopinavir free and total plasma concentrations were measured by HPLC-MS/MS. Bayesian calculations were used to extrapolate total concentrations to trough (Cmin).


RESULTS
A total of 42 HIV-positive pregnant women and 37 non-pregnant women on lopinavir/ritonavir were included in the study. Compared to postpartum and control values, total lopinavir Cmin was decreased moderately (31-39%) during pregnancy, and free Cmin minimally, showing significant alteration only at delivery (-35%). However, total and free Cmin remained in all patients above the target concentrations for wild-type virus of 1,000 ng/ml, and above the unbound IC50(WT) of 0.64-0.77 ng/ml of lopinavir, respectively. Lopinavir free fractions remained higher during pregnancy compared to postpartum and controls, and were influenced by α-1-acid-glycoprotein and albumin decrease. Free cord-to-mother ratio (0.43) was 2.7-fold higher than total cord-to-mother ratio (0.16), suggesting higher fetal exposure.


CONCLUSIONS
The moderate decrease of total lopinavir concentrations during pregnancy is not associated with proportional decrease in free concentrations. Both reach a nadir at delivery, albeit not to an extent that would put treatment-naive women at risk of insufficient exposure to the free, pharmacologically active concentrations of lopinavir. No dosage adjustment is therefore needed during pregnancy as it is unlikely to further enhance treatment efficacy but could potentially increase the risk of maternal and fetal toxicity. Nonetheless, in case of viral resistance in treatment-experienced pregnant women, loss of virological control or questionable adherence, it is justified to consider lopinavir dosage adjustment based on total plasma concentration measurement.
Division of Clinical Pharmacology, University Hospital Lausanne, Lausanne, Switzerland.
Aurélie
A
Fayet-Mello
Thierry
T
Buclin
Nicole
N
Guignard
Sandra
S
Cruchon
Matthias
M
Cavassini
Claudia
C
Grawe
Erika
E
Gremlich
Karoline Aebi
KA
Popp
Flavia
F
Schmid
Chin B
CB
Eap
Amalio
A
Telenti
Jérôme
J
Biollaz
Laurent A
LA
Decosterd
Begoña
B
Martinez de Tejada
D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001798:Blood Proteins / Q000378:metabolism; D036861:Delivery, Obstetric; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy* / Q000635:transmission; D006801:Humans; D061466:Lopinavir / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008431:Maternal-Fetal Exchange; D008875:Middle Aged; D009961:Orosomucoid / Q000378:metabolism; D049590:Postpartum Period / Q000097:blood; D011247:Pregnancy; D011446:Prospective Studies; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D055815:Young Adult
D019380:Anti-HIV Agents; D001798:Blood Proteins; D009961:Orosomucoid; D012709:Serum Albumin; D061466:Lopinavir