LC-MS/MS bioanalysis of loratadine (Claritin) in dried blood spot (DBS) samples collected by subjects in a clinical research study

A high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the quantitative analysis of loratadine, an H1 histamine antagonist, in human dried blood spot (DBS) samples following a single self-administered 20 mg oral dose. The samples were produced by spotting approximately 30 μl of whole blood onto PE-226 cards. Two 3 mm discs were cut from the DBS samples and extracted using aqueous methanol containing the internal standard. After transfer and drying of the sample extract, the reconstituted residues were chromatographed using a Waters XSelect C18 column and isocratic elution for MS/MS detection. The possible impacts due to hematocrit, volume of blood sample, storage temperature, and humidity, on the accuracy of measured DBS results were investigated. The results showed that only the spotted blood volume had a significant impact; a small volume (10 µl) tended to give more negative bias in the measured value. The current method was fully validated over the range of 0.200 to 20.0 ng/ml with correlation coefficients (r2) for three validation batches equal to or better than 0.991. The intraday accuracy and precision at the LLOQs were -11.5 to 0.0 % bias and 6.4 to 8.9 % CV, respectively. For the other QC samples (0.600, 3.00, 10.0 and 15.0 ng/mL), the precision ranged from 4.2 to 9.8% CV and from 6.3 to 8.1% CV, respectively, in the intra-day and interday evaluations; the accuracy ranged from -1.7 to 10.0% and 2.7 to 5.3% bias, respectively, in the intra-day and inter-day batches. Loratadine is stable in the DBS samples for at least 271 days at ambient temperature in a desiccator and for at least 24 hrs at 60C or under 80% relative humidity, followed by re-conditioning at ambient temperature in a desiccator. The current methodology has been applied to determine the loratadine levels in DBS samples collected by subjects in a clinical study to evaluate pharmacokinetic sampling in point-of-care setting