Lopinavir, an HIV protease inhibitor, is coformulated with ritonavir to enhance the bioavailability and pharmacokinetics of lopinavir. The original solid oral formulation of lopinavir/ritonavir, a soft-gelatin capsule (SGC), requires refrigerated storage, is taken as 6 capsules daily at the recommended adult dose, and is administered with food to maximize the bioavailability of lopinavir. Melt extrusion technology was used to produce a tablet formulation reducing the number of dosage units administered per day and simplifying storage requirements. Three studies assessed the bioavailability of tablet doses of lopinavir/ritonavir at 800/200 mg or 400/100 mg under different meal conditions compared with equal doses of the SGC after a moderate-fat meal. The tablet was bioequivalent to the SGC after a moderate-fat meal with respect to lopinavir and ritonavir areas under the concentration-time curve. Compared with the SGC formulation, the tablet formulation resulted in more consistent lopinavir and ritonavir exposures within and across studies and across meal conditions. The diminished food effect and decreased variability of the tablet are likely to result in more consistent lopinavir and ritonavir exposures, minimizing the likelihood of extreme high or low values compared with the SGC.

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A total of 71 HIV-negative healthy adults were randomized to 1 of 6 regimens to receive lopinavir/ritonavir tablets 400/100 mg twice daily (bid) or 800/200 mg once daily (qd) or atazanavir 300 mg + ritonavir 100 mg qd from study days 1 to 15 with a moderate-fat meal. One hour before breakfast, either omeprazole 40 mg qd was administered on study days 11 through 15, or a single dose of ranitidine 150 mg was administered on study day 11. Lopinavir, atazanavir, and ritonavir pharmacokinetics were determined on study days 10, 11, and 15 and compared using point estimates and 90% confidence intervals (CIs). The point estimates for lopinavir Cmax and AUCtau were in the range of 0.92 to 1.08, with 90% CI contained within the range of 0.80 to 1.25 after coadministration of omeprazole or ranitidine. The point estimates for atazanavir Cmax and AUCtau were decreased by 48% to 62% with the upper bound of the 90% CI

The effect of rifampin, a cytochrome P450 3A4 inducer, on the pharmacokinetics of atrasentan was assessed in 12 healthy male subjects in an open-label study. Single doses of atrasentan 10 mg were administered orally on days 1 and 12. Rifampin 600 mg was given once daily from days 4 through 14. On day 12, atrasentan and rifampin were administered simultaneously. Blood samples were collected before and during 72 hours after each atrasentan dose. On average, rifampin increased atrasentan peak plasma concentrations by 150% and reduced its terminal half-life by 77% (P<.05), without affecting the AUC or peak time of atrasentan. Rifampin may affect atrasentan pharmacokinetics by acting as both an inhibitor of organic anion transporting polypeptide-mediated hepatic uptake of atrasentan and an inducer of atrasentan metabolism. The effect of rifampin on atrasentan pharmacokinetics may depend on the time of rifampin administration relative to that of atrasentan.

We describe a new clinical laboratory instrument, the IMx, used to automate immunoassay testing in the clinical laboratory. The IMx incorporates a novel technology called Microparticle capture Enzyme ImmunoAssay (MEIA) for assays of high-molecular-mass analytes, and fluorescence polarization immunoassay (FPIA) for hapten assays. A front-surface fluorometer is used to quantify the enzymatic generation of fluorescent product at a rate proportional to the concentration of the analyte in an MEIA, and a fluorescence polarization optical system is used to quantify results in an FPIA. The microprocessor-based instrument uses a robotic arm with two degrees of freedom and a rotating carousel to process the samples for assay. One assay can be done on each of 24 patients' specimens in 30 to 40 min with "walk-away" automation. Calibration curves are stable for at least two weeks. Instrument control involves software-labeled "command keys," a numeric keypad, and an interactive display. Results are output to a thermal printer or computer interface.