Determination of unbound platinum concentrations in human plasma using ultrafiltration and precipitation methods.

Quantification of the unbound portion of platinum (Pt) in human plasma is important for assessing the pharmacokinetics of the chemotherapeutic drug cisplatin. In this study, we sought to compare the recovery of unbound Pt using Nanosep® filters to 1) traditional filters (Centrifree®, Centrisart®, Amicon®) or trichloroacetic acid (TCA) protein precipitation, and 2) unbound, bound, and total Pt concentrations in clinical specimens. For the tested filters, the impact of 1) molecular weight cut-offs, 2) centrifugation force, and 3) total Pt concentration on Pt binding in human plasma was evaluated. Pt was quantified using inductively coupled-plasma mass spectrometry. In human plasma spiked with 0.9 µg/mL Pt, the percent of unbound Pt increased at higher centrifugation speeds. By comparison, the percent of unbound Pt was highest (42.1%) following TCA protein precipitation. When total Pt was ≤0.9 µg/mL, unbound Pt (∼20-30%) was consistent across filters. Conversely, when plasma was spiked with Pt exceeding 0.9 µg/mL, the percent of unbound Pt increased from 36.5 to 48% using ultrafiltration, compared to 63.4% to 79% with TCA precipitation. In patients receiving cisplatin-containing chemotherapy, the fraction of unbound Pt at concentrations exceeding 0.9 µg/mL ranged between 35 and 90%. Moreover, the unbound fraction of Pt in plasma correlated with the concentration of unbound (R2 = 0.738) and total Pt (R2 = 0.335). In summary, this study demonstrates that 1) the percent of unbound Pt is influenced by total and unbound Pt levels in vitro and in clinical specimens, and 2) ultrafiltration with Nanosep® filters is a feasible method for quantifying unbound Pt concentrations in human plasma.

Evaluation of Cisplatin-Induced Acute Kidney Injury in Patients Co-Prescribed Serotonin Receptor Antagonists: A Retrospective Analysis.

BACKGROUND: Cisplatin is an effective first line therapy for a variety of cancers. Cisplatin is highly emetogenic and resulting volume depletion can contribute to acute kidney injury (AKI). Anti-emetic drugs such as 5-hydroxytryptamine type 3 receptor antagonists (5-HT3RAs) are commonly prescribed to prevent this complication. Preclinical studies suggest first generation 5-HT3RAs may alter the renal clearance and increase cisplatin toxicity. This retrospective study evaluated whether different 5-HT3RAs modify the risk of AKI in patients receiving cisplatin. METHODS: Patients with cancer who received cisplatin between January 1, 2010 and December 31, 2016 were included. Patients over 18 years old with available data for baseline and post-treatment serum creatinine, cisplatin cumulative dose, and administration of 5-HT3RAs including first generation (ondansetron, granisetron, and ramosetron) and second generation (palonosetron) were analyzed. AKI defined as 1.5x increase in serum creatinine. Fisher's exact and Wilcoxon rank-sum tests were used to assess univariable associations between baseline covariates and AKI, and logistic regression for multivariable associations with AKI. RESULTS: Of 8703 patients identified with cisplatin exposure, 6889 were included. A total of 3881 (56.3%) patients received at least one 5-HT3RA, including palonosetron (3750, 54.4%), ondansetron (1399, 20.3%) and granisetron (11, 0.2%). AKI developed in 1666 (24.2%) patients following cisplatin. Patients who received any 5-HT3RAs were less likely to experience AKI as compared to patients that did not (22.6% vs 26.2%, p=0.001). Older age, male gender, African ethnicity, and cumulative cisplatin dose were univariately associated with higher risk for AKI (P<0.001). After adjusting for these variables, use of any of these antiemetic drugs was protective for AKI (OR 0.84, 95% CI: 0.75, 0.94; P= 0.003) with no difference detected between type of 5-HT3RA. CONCLUSION: Nephrotoxicity continues to be a concern following cisplatin therapy. Given its emetogenic nature, use of antiemetic drugs such as 5-HT3RAs can lessen emesis and lower risk of kidney injury. This retrospective analysis supports use of any 5-HT3RAs to lower risk of AKI.

Development and validation of an UPLC-MS/MS method for the simultaneous determination of fexofenadine and olmesartan in human serum: Application to in vivo pharmacokinetic studies.

A sensitive, reproducible, robust, high-throughput ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantification of fexofenadine and olmesartan in human serum. Samples (50 µL) undergo protein precipitation prior to UPLC-MS/MS analysis. The analytes were separated using an Acquity BEH C18 column (2.1 mm × 50 mm, 1.7 µm) at a flow rate of 0.5 mL/min using a gradient elution with a total run time of 4 min. The analytes were detected in positive ion mode and selected reaction monitoring (SRM) was used for quantitation. The standard curve concentration range was 1.0-500.0 ng/mL for both analytes and each analyte showed excellent linearity with correlation coefficients (R2 > 0.99). The intra- and inter-day accuracy and precision were ±15% for each analyte, and excellent recovery was demonstrated (93-98%) for both analytes. The method is well suited for high-throughput quantitative determination of fexofenadine and olmesartan simultaneously and was successfully applied to an in vivo pharmacokinetic and transporter phenotyping study in humans.