Effect of omeprazole on the plasma concentrations of indinavir when administered alone and in combination with ritonavir.
OBJECTIVE
The effects of omeprazole on indinavir when administered alone or in combination with ritonavir were evaluated.


METHODS
Fourteen men and women age 18-55 years not infected with human immunodeficiency virus who met study qualifications were randomized to receive placebo, 20 mg of omeprazole, or 40 mg of omeprazole daily. After seven days, the single-dose pharmacokinetic profile of an 800-mg dose of indinavir alone or in combination with 200 mg of ritonavir was evaluated. Study participants received each of four study regimens in one of four randomly assigned orders. Blood samples were collected, and plasma indinavir and ritonavir concentrations were analyzed using high-performance liquid chromatography.


RESULTS
The coadministration of 20 or 40 mg of omeprazole with indinavir significantly reduced the mean indinavir area under the concentration-versus-time curve (AUC) from 30.0 mg x hr/L (95% confidence interval [CI], 21.9-41.1 mg x hr/L) to 19.7 mg x hr/L (95% CI, 14.6-26.8 mg x hr/L) or 16.0 mg x hr/L (95% CI, 11.8-21.7 mg x hr/L), respectively (p < 0.002). The addition of 200 mg of ritonavir to 800 mg of indinavir in combination with 40 mg of omeprazole significantly increased the mean indinavir AUC from 30.0 mg x hr/L (95% CI, 21.9-41.1 mg x hr/L) to 46.6 mg x hr/L (95% CI, 34.0-63.8 mg x hr/L), but it did not significantly affect mean omeprazole concentrations (p < or = 0.02).


CONCLUSIONS
The AUC of indinavir was substantially decreased in healthy volunteers who received omeprazole 20 or 40 mg daily for seven days before the administration of a single 800-mg dose of indinavir. Concomitant administration of ritonavir 200 mg with indinavir in participants receiving omeprazole led to a significant increase in the AUC of indinavir.
Tappouni
Hiba L
HL
Division of Pharmacotherapy and Experimental Therapeutics, School of Pharmacy, University of North Carolina, Chapel Hill 27599-7360, USA.
Rublein
John C
JC
Donovan
Brian J
BJ
Hollowell
Stephanie B
SB
Tien
Hsiao-Chuan
HC
Min
Sherene S
SS
Theodore
Dickens
D
Rezk
Naser L
NL
Smith
Philip C
PC
Tallman
Melanie N
MN
Raasch
Ralph H
RH
Kashuba
Angela D M
AD
D000293:Adolescent; D000328:Adult; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000494:pharmacology*; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D017320:HIV Protease Inhibitors / Q000493:pharmacokinetics* / Q000494:pharmacology; D006801:Humans; D019469:Indinavir / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D009853:Omeprazole / Q000008:administration & dosage / Q000494:pharmacology*; D019438:Ritonavir / Q000494:pharmacology*
D000897:Anti-Ulcer Agents; D017320:HIV Protease Inhibitors; D019469:Indinavir; D009853:Omeprazole; D019438:Ritonavir