Quantitative analysis of erythromycylamine in human plasma by liquid chromatography-tandem mass spectrometry and its application in a bioequivalence study of dirithromycin enteric-coated tablets with a special focus on the fragmentation pattern and carryover effect

A Human Oral Fluid Assay for D- and L- Isomer Detection of Amphetamine and Methamphetamine Using Liquid-Liquid Extraction

Medical providers are increasingly confronted with clinical decision-making that involves (meth)amphetamines. And clinical laboratories need a sensitive, efficient assay for routine assessment of D- and L-isomers to determine the probable source of these potentially illicit analytes. This paper presents a validated method of D- and L-isomer detection in human oral fluid from an extract used for determination of a large oral fluid assay (63 analytes) on an older AB SCIEX 4000 instrument. Taken from the positive extract, D- and L-analytes were added. The method for extraction included addition of internal standard and a 2-step liquid-liquid extraction and dry-down step to concentrate and clean the samples. The samples were suspended in 50% MeOH in water, diluted with mobile phase, with separation and detection accomplished using LC-MS/MS to determine analyte concentration. Once samples were confirmed positive for (meth)amphetamine from the large oral fluid assay, they were further examined for the enantiomeric forms with 50 μl aliquots of the standards and samples of interest combined with 450 μl of D- and L-assay mobile phase, then analyzed using chiral column separation, and LC-MS/MS detection with standard curve spanning the range from 2.5 to 1000 ng/mL. The result is a sensitive and accurate detection of D- and L-isomers of amphetamine and methamphetamine in human oral fluid performed on an older model mass spectrometer (AB SCIEX 4000). The novelty of this assay is twofold (a) the 2-step liquid-liquid extraction and dry-down step to concentrate and clean the samples, and (b) its adoption characteristics as a reflex test from a large ODT panel without the need to invest in newer or expensive LC-MS/MS instruments. Finally, this assay also has potential to add a valuable option to high-throughput laboratories seeking a D- and L-testing alternative to urine drug testing methods.

Ocular Application of Dirithromycin Incorporated Polymeric Nanoparticles: an In Vitro Evaluation

Objectives

Ocular drug delivery is a difficult challenge especially with topical intillation which results in rapid drainage and non-productive drug absorption. For the improvement of the pre-corneal retention time and enhancing the corneal permeability, colloidal drug delivery systems play an important role in enhancement of the ocular bioavailability. In this study, dirithromycin incorporated Kollidon^® SR-based polymeric nanoparticles, an antibacterial agent, were formulated for the efficient treatment of severe ocular bacterial infections.

Materials and Methods

In this study, dirithromycin was incorporated into the Kollidon^® SR-based nanoparticles by spray drying method. In vitro characteristic properties were evaluated in detail during the storage period of three months at three different conditions.

Results

The results of in vitro analyses revealed that characteristic properties of the particles were remained unchanged during the storage period of three months.

Conclusion

Kollidon^® SR-based polymeric nanoparticles are good candidates for drug delivery systems in the treatment of severe ocular bacterial infections with dirithromycin.