Biomedical subjects

Cecilia F Lastra

Publications and source records attributed to Cecilia F Lastra.

4 recordsLinked to original sources

PubMed2004

Determination of saquinavir and ritonavir in human plasma by reversed-phase high-performance liquid chromatography and the analytical error function.

Two simple and reproducible high-performance liquid chromatography methods with ultraviolet detection were developed and validated for the quantitation of two protease inhibitors, saquinavir and ritonavir, in human plasma. The same single liquid-liquid extraction procedure with ethyl acetate-hexane (50:50, v/v), reversed-phase column and mobile phase were used. The analyses were accomplished using a Luna C(18) column (150 mm x 4.6mm i.d.) with a C(18) guard column and, the mobile phase consisted of acetonitrile and 70 mM KH(2)PO(4) adjusted to pH 5 with 80 mM Na(2)HPO(4) (46:54, v/v). The wavelength was set at 240 nm for saquinavir and at 210 nm for ritonavir. The retention times were 6.4 min for saquinavir and 8.3 min for ritonavir. The methods were linear over the range of 100-2500 ng/ml for saquinavir and 200-2500 ng/ml for ritonavir. Intra and inter-day precision and accuracy were less than 10.2% for both drugs. Recovery were 90 and 87% for saquinavir and ritonavir, respectively. The drugs were stable at different relevant storage and working conditions. After the validation, their analytical error functions were established as standard deviation (S.D., ng/ml) = 4.84 + 7.14 x 10(-2)C (C is the theoretical concentration value) for saquinavir and S.D. (ng/ml) = 39.98 + 2.40 x 10(-5)C(2) for ritonavir.

Chromatography, High Pressure Liquid↗

PubMed2004

Determination of abacavir in human plasma by high-performance liquid chromatography with ultraviolet detection and the analytical error function.

A rapid and simple high-performance liquid chromatography method has been developed for the determination of the HIV-1 reverse transcriptase inhibitor abacavir in human plasma. It included a single liquid-liquid extraction procedure with a mixture of ethyl acetate-diethyl ether prior to reversed-phase chromatography on a C18 column and C18 precolumn insert. Ultraviolet detection was set at 285 nm. The mobile phase consisted of water-acetonitrile (83:17, v/v) and the flow rate was kept at 1 mL/min. The total run time for a single analysis was 10 min. The method has been validated over the range 50-2500 ng/mL. The assay was linear over the entire concentration range (r2 = 0.9993). Intra- and inter-day precision and accuracy were less than 8.1 and -5.2%, respectively. The extraction recovery was greater than 94.3%. Abacavir was stable under the relevant storage conditions tested. After the validation, the analytical error function was established as standard deviation (SD; ng/mL) = -1.072 + 0.037C (C = theoretical concentration value). The method developed and its associated analytical error function will be suitable for pharmacokinetic studies and monitoring of HIV-1 patients.

Acetonitriles↗

PubMed2003

Self-assembly of drug-polymer complexes: a spontaneous nanoencapsulation process monitored by atomic force microscopy.

Since hydrophilic matrices were proposed for controlled drug delivery, many polymeric excipients have been studied to make drug release fit the desired profiles. It has been pointed out that lambda-carrageenan, a sulfated polymer from algae, can suitably control the release rate of basic drugs from hydrophilic matrices. Furthermore, the relevance of hydrophobic interactions in drug-polymer aqueous systems has already been demonstrated, although no references to morphological features as well as to the kinetics of the interaction complexes formation have been published to date. In this work, we propose a method to monitor the topographical evolution of the interaction between lambda-carrageenan and dexchlorpheniramine maleate, in order to determine how the release profiles can be so easily controlled. For this purpose, solutions of both polymer and drug were prepared at very low concentration. Solutions were mixed and small volumes were taken every hour for over a period of 24 h and subsequently analyzed. The characterization technique used, atomic force microscopy, provides a high resolution, allowing plotting of three-dimensional images of the sample morphology within the nanometric scale. The results demonstrate that lambda-carrageenan is able to nanoencapsulate spontaneously dexchlorpheniramine maleate molecules, which offers the possibility of controlling the release rate of the drug with no need of complex technological processes. Moreover, this work demonstrates the suitability of atomic force microscopy for the specific case of the on-time monitoring of interaction processes that occur in pharmaceutical systems.

Carrageenan↗

PubMed2002

Development, validation and analytical error function of two chromatographic methods with fluorimetric detection for the determination of bisoprolol and metoprolol in human plasma.

This work describes two high-performance liquid chromatographic methods for the individual determination of bisoprolol and metoprolol in human plasma. Analytical methods involve two different liquid-liquid extractions of human plasma, with diethyl ether for bisoprolol and with dichloromethane for metoprolol, coupled with a similar Nucleosil C(18) reversed-phase HPLC column. Fluorimetric detection was used to identify both beta-blockers. Retention times for bisoprolol and metoprolol were 8.7 and 3.2 min, respectively. Linear regressions for the calibration curves were linear at a concentration range of 6.25-200 ng/mL. Intra- and inter-day precision coefficients of variations and accuracy bias were acceptable (within 15%) over the entire range for both drugs. Average recovery was 89% for metoprolol and 98% for bisoprolol. Once the methods had been validated, analytical error functions were established as standard deviation (SD; ng/mL) = 2.216 + 3.608 x 10(-4)C(2) (C = theoretical concentration value) and SD-(ng/mL) = 0.408 + 0.378 x 10(-1)C for bisoprolol and metoprolol, respectively. The methods developed and their associated analytical error functions will be suitable for pharmacokinetic studies and for determination of plasma concentration if posology individualization of these drugs is needed.

Adrenergic beta-Antagonists↗