Pharmacokinetic interaction between efavirenz and dual protease inhibitors in healthy volunteers.
The combination of efavirenz with HIV-1 protease inhibitors (PI) results in complex interactions secondary to mixed induction and inhibition of oxidative metabolism. ACTG A5043 was a prospective, open-label, controlled, two-period, multiple-dose study with 55 healthy volunteers. The objective of the present study was to evaluate the potential pharmacokinetic interaction between efavirenz and dual PIs. The subjects received a daily dose of 600 mg efavirenz for 10 days with amprenavir 600 mg twice daily added at day 11 and were randomized to receive nelfinavir, indinavir, ritonavir, saquinavir, or no second PI on days 15-21. Intensive pharmacokinetic studies were conducted on day 14 and 21. Efavirenz plasma concentrations were fit to candidate models using weighted non-linear regression. The disposition of efavirenz was described by a linear two-compartment model with first order absorption following a fitted lag time. Apparent clearance (CLt/F), volume of distribution at steady state (Vss/F), inter-compartmental clearance, and the central and peripheral volume of distribution were estimated. The mean CLt/F and Vss/F of efavirenz were 0.126 l/h/kg and 4.412 l/kg, respectively. Both AUC and CLt/F of efavirenz remained unchanged after 7 days of dual PI dosing. The mean Vss/F of efavirenz increased an average of 89% across arms, ranging from 52% (nelfinavir) to 115% (indinavir) relative to efavirenz with amprenavir alone. Increases were also observed in Vp/F after the addition of nelfinavir, indinavir, ritonavir and saquinavir by 85%, 170%, 162% and 111%, respectively. In conclusion, concomitant administration of dual PIs is unlikely to have any clinically significant effect on the pharmacokinetics of CYP2B6 substrates in general or oral efavirenz specifically.
Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, Buffalo, NY 14260, USA. qingma@buffalo.edu
Qing
Q
Ma
Alan
A
Forrest
Susan L
SL
Rosenkranz
Michael F
MF
Para
Kevin E
KE
Yarasheski
Richard C
RC
Reichman
Gene D
GD
Morse
D000328:Adult; D000480:Alkynes; D001189:Aryl Hydrocarbon Hydroxylases / Q000502:physiology; D048588:Benzoxazines / Q000009:adverse effects / Q000493:pharmacokinetics*; D003521:Cyclopropanes; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A / Q000502:physiology; D004347:Drug Interactions; D005260:Female; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010089:Oxidoreductases, N-Demethylating / Q000502:physiology; D011446:Prospective Studies; D018894:Reverse Transcriptase Inhibitors / Q000493:pharmacokinetics*
D000480:Alkynes; D048588:Benzoxazines; D003521:Cyclopropanes; D017320:HIV Protease Inhibitors; D018894:Reverse Transcriptase Inhibitors; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating; C098320:efavirenz