A simple HPLC-UV method for the determination of lacosamide in human plasma.

Lacosamide (Vimpat®) is an antiepileptic drug approved in the USA, Europe and several other countries as adjunctive therapy for partial-onset seizures. We report a simple HPLC method with UV detection for the quantification of lacosamide in human plasma. The method involves protein precipitation with methanol followed by chromatographic separation using an ACE® C18-AR column (2.1 mm × 150 mm, 3.0 µm) and mobile phases consisting of mixtures of ammonium formate buffer at pH 9 and acetonitrile. Briefly, 25 µl of internal standard and 300 µl of methanol are added to 100 µl of plasma. After vortexing and centrifugation, 70 µl of supernatant is transferred to an autosampler vial and 5.0 µl is injected. Calibration curves are linear in the range of 0.5 to 12.5 µg/ml. A validation was performed that consisted of the evaluation of accuracy and precision, specificity, limit of detection and carryover. Moreover, the possibility of using single-point calibration was evaluated and a crossvalidation between this method and an established LC-MS/MS method using pooled clinical study samples was performed. The method's sensitivity, simplicity and reliance on simpler HPLC equipment should allow for straightforward application in drug monitoring.

Differential effect of dipyridamole upon thymidine incorporation and expression of surface activation antigens by in vitro stimulated lymphocytes.

Dipyridamole inhibits, by 50% at 10(-6) M and 100% at 10(-5) M, the incorporation of tritiated thymidine by lymphocytes stimulated with 1 microgram/ml phytohaemagglutinin A for 72 h. At the latter concentration, a clinically relevant one, dipyridamole fails to inhibit lymphocyte proliferation and expression of the cell surface stimulation markers, CD25 and HLA-DR, or differential regulation of the CD45 -RA and -RO isoforms, as determined by single laser two-colour flow-cytometry. No significant immunodepressant effect of dipyridamole can be demonstrated in vitro.

In vitro stimulation of peripheral blood mononuclear cells by phytohaemagglutinin A induces CD45RA expression on monocytes.

Following phytohaemagglutinin A stimulation, CD45RA positive monocytes increased from 12.2 +/- 8.9% to 63.5 +/- 8.8% (p < 0.001), without a significant change in cell surface antigen density. In contrast, HLA-DQ antigen, also expressed in 76.8 +/- 10.5% of the monocytes after PHA stimulation for 48 h, revealed a marked enhancement in fluorescence intensity (p < 0.001). This up-regulation is already evident in unstimulated cultures. The percentages of CD45RA and HLA-DQ positive monocytes were correlated (r = 0.80, p < 0.001), substantiating a previous clinical observation. CD45RA expression may probe activated mono/macrophages.