Uncertainty evaluation in the chloroquine phosphate potentiometric titration: application of three different approaches.

A measurement result cannot be properly interpreted if not accompanied by its uncertainty. Several methods to estimate uncertainty have been developed. From those methods three in particular were chosen in this work to estimate the uncertainty of the Eu. Ph. chloroquine phosphate assay, a potentiometric titration commonly used in medicinal control laboratories. The famous error-budget approach (also called bottom-up or step-by-step) described by the ISO Guide to the expression of Uncertainty in Measurement (GUM) was the first method chosen. It is based on the combination of uncertainty contributions that have to be directly derived from the measurement process. The second method employed was the Analytical Method Committee top-down which estimates uncertainty through reproducibility obtained during inter-laboratory studies. Data for its application were collected in a proficiency testing study carried out by over 50 laboratories throughout Europe. The last method chosen was the one proposed by Barwick and Ellison. It uses a combination of precision, trueness and ruggedness data to estimate uncertainty. These data were collected from a validation process specifically designed for uncertainty estimation. All the three approaches presented a distinctive set of advantages and drawbacks in their implementation. An expanded uncertainty of about 1% was assessed for the assay investigated.

LC-MS Determination of remifentanil in maternal and neonatal plasma.

An HPLC-MS with electrospray ionization method for the determination of remifentanil in human plasma samples, pre-treated with SPE cartridge, has been developed and validated. Ionisation was performed by positive-ion electrospray and quadrupole filter mass spectrometer operated in the single ion-recording mode. Pre-treatment was performed using Waters Oasis((R)) SPE cartridges. Chromatographic separation was achieved in isocratic elution using a X-Terra C8 5 microm, 150 mm x 2.1 mm i.d. column. The mobile phase consisted of a mixture of water, methanol and acetonitrile (86:10:4, v/v/v) containing 0.1% of formic acid. The method showed to be linear in the range between 0.5 and 48.0 ng/ml, the estimated LOD is 0.18 ng/ml and the LOQ is 0.5 ng/ml. The method can be used to quantify remifentanil in plasma samples taken from adult and newborn patients in a range suitable for clinical studies.

LC-MS determination of MPTP at sub-ppm level in pethidine hydrochloride.

An HPLC-MS with electrospray ionisation method for the determination of MPTP at sub-ppm level in pethidine hydrochloride has been developed and validated. Ionisation is performed by positive-ion electrospray and the quadrupole filter mass spectrometer is operated in the single ion recording mode. Chromatographic separation was achieved in gradient elution using a symmetry C18, 5 microm, 150 mm x 2.1 mm i.d. The mobile phase comprised water containing 0.1% formic acid (v/v) and acetonitrile containing 0.1% formic acid (v/v). The method showed to be linear in the range between 0.2 and 2.2 ng/ml, the estimated LOD was lower than 0.1 ng/ml and the LOQ was lower than 0.2 ng/ml.

Effect of proton pump inhibitor pretreatment on resistance of solid tumors to cytotoxic drugs.

BACKGROUND: Resistance to antitumor agents is a major cause of treatment failure in patients with cancer. Some mechanisms of tumor resistance to cytotoxic drugs may involve increased acidification of extracellular compartments. We investigated whether proton pump inhibitors (PPIs), currently used in the anti-acid treatment of peptic disease, could inhibit the acidification of the tumor microenvironment and increase the sensitivity of tumor cells to cytotoxic agents. METHODS: We pretreated cell lines derived from human melanomas, adenocarcinomas, and lymphomas with the PPIs omeprazole, esomeprazole, or pantoprazole and tested their response to cytotoxic drugs in cell death assays. We also evaluated extracellular and intracellular pH and vacuolar-H+-ATPase (V-H+-ATPase) expression, distribution, and activity in PPI-pretreated cells by using western blot analyses, immunocytochemistry, laser scanning confocal analysis, and bioluminescence assays. Finally, we evaluated human melanoma growth and cisplatin sensitivity with or without omeprazole pretreatment in xenografted SCID/SCID mice. RESULTS: PPI pretreatment sensitized tumor cell lines to the effects of cisplatin, 5-fluorouracil, and vinblastine, with an IC50 value reduction up to 2 logs. PPI pretreatment was associated with the inhibition of V-H+-ATPase activity and increases in both extracellular pH and the pH of lysosomal organelles. PPI pretreatment induced a marked increase in the cytoplasmic retention of the cytotoxic drugs, with clear targeting to the nucleus in the case of doxorubicin. In in vivo experiments, oral pretreatment with omeprazole was able to induce sensitivity of human solid tumors to cisplatin. CONCLUSION: Our results open new possibilities for the treatment of drug-resistant tumors through combination strategies based on the use of well-tolerated pH modulators such as PPIs.