Lopinavir protein binding in HIV-1-infected pregnant women.
BACKGROUND
Pregnancy may alter protein binding (PB) of highly bound protease inhibitors due to changes in plasma concentrations of albumin and alpha-1 acid glycoprotein (AAG). Small changes in PB can greatly impact the fraction of drug unbound (FU) exerting pharmacological effect. We report lopinavir (LPV) PB during third trimester (antepartum, AP) compared to > or =1.7 weeks postpartum (PP) to determine if FU changes compensate for reduced total concentrations reported previously.


METHODS
P1026s enrolled women receiving LPV/ritonavir, soft gel capsules 400/100 mg or 533/133 mg twice daily. LPV FU, albumin and AAG were determined AP and PP.


RESULTS
AP/PP samples were available from 29/25 women respectively with all but one woman receiving the same dose AP/PP. LPV FU was increased 18% AP vs. PP (mean 0.96+/-0.16% AP vs. 0.82+/-0.21% PP, P=0.001). Mean protein concentrations were reduced AP (AAG=477 mg/L; albumin=3.28 mg/dL) vs. PP (AAG=1007 mg/L; albumin=3.85 mg/dL) (P<0.0001 for each comparison). AAG concentration correlated with LPV binding. Total LPV concentration did not correlate with LPV FU AP or PP. However, higher LPV concentration PP was associated with reduced PB and higher FU after adjustment for AAG.


CONCLUSIONS
LPV FU was higher and AAG lower AP vs. PP. The 18% increase in LPV FU AP is smaller than the reduction in total LPV concentration reported previously and is not of sufficient magnitude to eliminate the need for an increased dose during pregnancy.
Aweeka
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Drug Research Unit, University of California, San Francisco, CA 94143-0622, USA. faweeka@sfghsom.ucsf.edu
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D000209:Acute-Phase Proteins / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000378:metabolism; D017320:HIV Protease Inhibitors / Q000008:administration & dosage / Q000378:metabolism*; D015497:HIV-1; D006801:Humans; D061466:Lopinavir; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000188:drug therapy* / Q000378:metabolism; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D011485:Protein Binding; D011744:Pyrimidinones / Q000008:administration & dosage / Q000378:metabolism*; D019438:Ritonavir / Q000008:administration & dosage; D055815:Young Adult
D000209:Acute-Phase Proteins; D017320:HIV Protease Inhibitors; D011744:Pyrimidinones; D061466:Lopinavir; D019438:Ritonavir