Significant decrease in nelfinavir systemic exposure after omeprazole coadministration in healthy subjects.
OBJECTIVE
To assess the effect of omeprazole on the multiple-dose (steady-state) pharmacokinetics and safety of nelfinavir, and to evaluate the safety and tolerability of nelfinavir when administered alone and with omeprazole.


METHODS
Open-label, two-period, single-fixed-sequence study.


METHODS
Clinical research unit of a large, teaching hospital.


METHODS
Twenty healthy volunteers (mean age 26 +/- 9 yrs, range 18-48 yrs). Intervention. Subjects received nelfinavir 1250 mg every 12 hours for 4 days (period 1). After a 7-day washout period, subjects were coadministered nelfinavir 1250 mg every 12 hours and omeprazole 40 mg every 24 hours for 4 days (period 2).


RESULTS
The pharmacokinetics of nelfinavir and its active metabolite M8 were determined on day 4 of both periods. Plasma samples were assayed by a high-performance liquid chromatography-ultraviolet method for nelfinavir and M8 concentrations, and noncompartmental pharmacokinetic analysis was performed by using analytical software. In the presence of omeprazole, nelfinavir area under the concentration-time curve over the dosing interval (AUC(tau)), maximum observed plasma concentration (C(max)), and minimum observed plasma concentration (C(min)) were reduced by an average of 36%, 37%, and 39%, respectively, relative to administration of nelfinavir alone. The AUC(tau), C(max), and C(min) of M8 were reduced by an average of 92%, 89%, and 75%, respectively. The slopes of the terminal elimination phase of nelfinavir and M8 plasma concentration-time curves were similar between treatments. Nelfinavir was well tolerated when administered alone and when coadministered with omeprazole.


CONCLUSIONS
The observed reduction in the systemic exposure to both nelfinavir and its active metabolite M8 after coadministration with omeprazole could result in loss of virologic control and potential emergence of drug resistance. Hence, omeprazole should not be coadministered to patients taking nelfinavir.
D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors; D002851:Chromatography, High Pressure Liquid; D065731:Cytochrome P-450 CYP2C19; D051544:Cytochrome P-450 CYP3A; D065692:Cytochrome P-450 CYP3A Inhibitors; D003967:Diarrhea / Q000139:chemically induced; D004244:Dizziness / Q000139:chemically induced; D004347:Drug Interactions; D005260:Female; D005750:Gastric Juice / Q000187:drug effects; D017320:HIV Protease Inhibitors / Q000009:adverse effects / Q000493:pharmacokinetics; D006261:Headache / Q000139:chemically induced; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors; D019888:Nelfinavir / Q000009:adverse effects / Q000378:metabolism / Q000493:pharmacokinetics*; D009853:Omeprazole / Q000009:adverse effects / Q000493:pharmacokinetics*; D054328:Proton Pump Inhibitors / Q000009:adverse effects / Q000493:pharmacokinetics; D013575:Syncope / Q000139:chemically induced; D013607:Tablets
D065692:Cytochrome P-450 CYP3A Inhibitors; D017320:HIV Protease Inhibitors; D054328:Proton Pump Inhibitors; D013607:Tablets; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D019888:Nelfinavir; D009853:Omeprazole