Aprepitant is the first NK 1 receptor antagonist approved for use with corticosteroids and 5HT 3 receptor antagonists to prevent chemotherapy‐induced nausea and vomiting (CINV). The effective dose to prevent CINV is a 125‐mg capsule on day 1 followed by an 80‐mg capsule on days 2 and 3. Study 1 evaluated the bioavailability of the capsules and estimated the effect of food. The mean (95% confidence interval [CI]) bioavailabilities of 125‐mg and 80‐mg final market composition (FMC) capsules, as assessed by simultaneous administration of stable isotope‐labeled intravenous (IV) aprepitant (2 mg) and FMC capsules, were 0.59 (0.53, 0.65) and 0.67 (0.62, 0.73), respectively. The geometric mean (90% CI) area under the plasma concentration time curve (AUC) ratios (fed/fasted) were 1.2 (1.10, 1.30) and 1.09 (1.00, 1.18) for the 125‐mg and 80‐mg capsule, respectively, demonstrating that aprepitant can be administered independently of food. Study 2 defined the pharmacokinetics of aprepitant administered following the 3‐day regimen recommended to prevent CINV (125 mg/80 mg/80 mg). Consistent daily plasma exposures of aprepitant were obtained following this regimen, which was generally well tolerated.

Clinical Pharmacology & Therapeutics (2003) 73, P6–P6; doi:

Background. Aprepitant is a neurokinin, receptor antagonist that enhances prevention of chemotherapy-induced nausea and vomiting when added to conventional therapy with a corticosteroid and a 5-hydroxytryptamine(3) (5-HT3) antagonist. Because aprepitant may be used with a variety of chemotherapeutic agents and ancillary support drugs, which may be substrates of cytochrome P450 (CYP) 3A4, assessment of the potential of this drug to inhibit CYP3A4 activity in vivo is important. The effect of aprepitant on in vivo CYP3A4 activity in humans with oral midazolam used as a sensitive probe of CYP3A4 activity was evaluated in this study.Methods: In this open-label, randomized, single-period study, 16 healthy mate subjects were enrolled. Subjects received one of two oral aprepitant regimens for 5 days (8 subjects per regimen): (1) 125 mg aprepitant on day 1 and then 80 mg/d on days 2 to 5 or (2) 40 ing aprepitant on day 1 and then 25 mg/d on days 2 to 5. All subjects also received a single oral dose of midazolam, 2 mg, at prestudy (3 to 7 days before aprepitant treatment) and on days 1 and 5 (1 hour after aprepitant administration).Results. Coadministration of midazolam and 125/80 mg aprepitant increased the midazolam area under the plasma concentration-time curve by 2.3-fold on day 1 (P < .01) and by 3.3-fold on day 5 (P < .01), as compared with midazolam alone (prestudy). The 125/80-mg regimen of aprepitant also increased the midazolam maximum observed concentration by 1.5-fold on day 1 (P < .05) and by 1.9-fold on day 5 (P < .01). The midazolam half-life values increased from 1.7 hours (prestudy) to 3.3 hours on both day 1 and day 5. Coadministration of 40/25 ing aprepitant and midazolam did not result in significant changes in the midazolam area under the plasma concentration-time curve, maximum observed concentration, and half-life at either day 1 or day 5.Conclusions. The 5-day 125/80-mg regimen of aprepitant produced moderate inhibition of CYP3A4 activity in humans, as measured with the use of midazolam as a probe drug.

A sensitive and selective assay for the determination of N-[1(R)-[(1,2-dihydro-1-methylsulfonylspiro[3H-indole-3,4'-piperidin]-1'-yl)carbonyl]-2-(phenylmethoxy)-ethyl]-2-hydroxyamino-2-methylpropanamide (I), a hydroxyl amine metabolite of a novel growth hormone secretagouge (II) has been developed utilizing high-performance liquid chromatography with ion spray tandem mass spectrometric detection (HPLC-MS-MS). The analyte and an internal standard (III) were isolated from the basified biological matrix using a liquid-liquid extraction with methyl tert.-butyl ether (MTBE). The organic extract was evaporated to dryness at room temperature. The residue was reconstituted in the mobile phase and injected into the HPLC-MS-MS system. Multiple reaction monitoring using the precursor-->product ion combinations of m/z 545-->267 and 543-->267 was used to quantify I and III, respectively, after chromatographic separation under isocratic conditions. The assay was validated in the concentration range of 0.5 to 500 ng/0.1 ml in both human and dog plasma. The precision of the assay, expressed as relative standard deviation, was less than 10% over the entire concentration range with the exception of the low concentration of 0.5 ng/0.1 ml which was 14.0% for human plasma. The HPLC-MS-MS method provided sufficient sensitivity to completely map the pharmacokinetic time course of I following a single 5 mg dose of II to human subjects and a 0.5 mg/kg dose to beagle dogs.

Clinical Pharmacology & Therapeutics (1996) 59, 166–166; doi: 10.1038/sj.clpt.1996.165

High-performance liquid chromatography (HPLC) assays using ultraviolet (UV) and fluorescence (FL) detection were developed and compared with a liquid chromatography/tandem mass spectrometry (LC/MS-MS) method for determination of the glycine receptor antagonist 7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(1H)-quinolone (L-701, 324, I) in human plasma and urine. The drug and internal standard (II) were isolated from the biological matrix through liquid-liquid extraction. In the HPLC-UV and HPLC-FL methods, the samples were initially injected onto a Cyano BDS Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 BDS Hypersil column via a column-switching device. The analyte was quantified by monitoring either absorbance at 226 nm or fluorescence at 385 nm following 230 nm excitation. The limit of quantitation for I extracted from 1 ml of plasma or urine was 5 ng ml−1, and the assays were validated in the concentration range of 5–200 ng ml−1. The LC/MS-MS method also utilized a column-switching protocol and was validated in the concentration range of 1–200 ng ml−1. Both assays provided data with precision and accuracy within less than 10% for all points in the standard curve range.

Sensitive assays for the determination of cyclobenzaprine (I) in human plasma and urine were developed utilizing high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) and ultraviolet (UV) absorbance detections. These two analytical techniques were evaluated for reliability and sensitivity, and applied to support pharmacokinetic studies. Both methods employed a liquid-liquid extraction of the compound from basified biological sample. The organic extract was evaporated to dryness, the residue was reconstituted in the mobile phase and injected onto the HPLC system. The HPLC assay with MS-MS detection was performed on a PE Sciex API III tandem mass spectrometer using the heated nebulizer interface. Multiple reaction monitoring using the parent-->daughter ion combinations of m/z 276 --> 215 and 296 --> 208 was used to quantitate I an internal standard (II), respectively. The HPLC-MS-MS and HPLC-UV assays were validated in human plasma in the concentration range 0.1-50 ng/ml and 0.5-50 ng/ml, respectively. In urine, both methods were validated in the concentration range 10-1000 ng/ml. The precision of the assays, as expressed as coefficients of variation (C.V.) was less than 10% over the entire concentration range, with adequate assay specificity and accuracy. In addition to better sensitivity, the HPLC-MS-MS assay was more efficient and allowed analysis of more biological fluid samples in a single working day than the HPLC-UV method.

A method for the simultaneous determination of a topical carbonic anhydrase inhibitor, L-693,612, and two of its potential metabolites in human whole blood is described. The analytes are isolated from the matrix via liquid-liquid extraction with a mixture of toluene, ethyl acetate and isopropanol (49:50:1, v/v/v). The analytes are then back extracted into dilute phosphoric acid prior to injection into the HPLC system. A cyano column (Zorbax SB-CN, 150 x 4.6 mm) with a mobile phase of phosphoric acid(0.085%)-acetonitrile (73.5:26.5) containing 10 mM sodium decane sulfonate and adjusted to pH 3 is used for the analysis. Detection is based on UV absorbance at 252 nm. The assay was found to be linear in the concentration range of 5-500 ng/ml for each analyte when 1-ml aliquots of whole blood were extracted.