Pharmacokinetics of mycophenolic acid administered 3 times daily after hematopoietic stem cell transplantation with reduced-intensity regimen.

Mycophenolate mofetil (MMF) is an immunosuppressive drug used as a prophylactic agent to prevent acute graft-versus-host disease (aGVHD) after hematopoietic stem cell transplantation (HSCT). After reduced-intensity conditioning (RIC) regimen, administration of MMF orally 3 times a day (tid) seems to be more beneficial than twice a day (bid). However, information regarding the pharmacokinetic (PK) parameters of mycophenolic acid (MPA), the active metabolite of MMF, administered in this regimen are very limited. We performed a prospective study in 15 patients for whom 3 sets of sampling were performed: at the beginning of the treatment, after 1 week, and after 1 month. Two consecutive 8-hour sets of sampling were performed at day 0 (D0) and D7. Plasma concentrations of MPA were quantified and areas under the curve for 8hours (AUC(0-8)), and maximal and through concentrations were calculated. The results show that AUC(0-8) increases between the beginning of treatment and the end of the first week, but remains stable thereafter. Moreover, a trend to lower AUC(0-8) was observed for the patients who experienced GVHD > or =2 compared to those patients who did not. The other PK parameters are not associated with pharmacodynamic events. A limited sampling strategy with Bayesian estimators is currently under investigation to confirm these data and the role of D7 AUC(0-8) as a potential target of therapeutic drug monitoring (TDM).

Validation of a microdialysis-gas chromatographic-mass spectrometric method to assess 8-methoxypsoralen in psoriatic patient dermis.

8-Methoxypsoralen (8-MOP) is currently used in PUVA therapy (psoralen+UVA) to treat dermatological diseases such as psoriasis, vitiligo and atopic dermatitis. The aim of this work was to validate a method for collecting 8-MOP from patient dermis by a non invasive technique, microdialysis, and then to assess this molecule by gas chromatography-mass spectrometry (GC-MS). 5-Methoxypsoralen (5-MOP) was used as an internal standard. The calibration curve demonstrated a linear relationship between the peak areas of 8-MOP and 5-MOP over a wide range of 8-MOP concentrations (0.9-100 ng/ml). Within- and between-run precisions were measured, using four different 8-MOP concentrations, which varied from 98.0 to 102.0% and from 98.5 to 101.8%, respectively. The limits of detection and quantification were 0.29 and 0.52 ng/ml, respectively. The method was validated and then applied to determine the pharmacokinetic of 8-MOP in ten psoriatic patient dermis, after oral intake of this drug. The results demonstrated that the association of microdialysis with the GC-MS method was an efficient procedure to collect and assess 8-MOP in human dermis, in vivo.

An APCI LC-MS/MS method for routine determination of capecitabine and its metabolites in human plasma.

The anticancer drug capecitabine and its metabolites [including the active metabolite 5-fluorouracil (5-FU)] display high pharmacokinetic inter-patient variability. Such variability, which may lead to treatment failure or toxicity, could need drug concentration measurement to individualize dosing regimen. However, usual assay methods are often long and fastidious. A simultaneous and cost-effective method was thus developed for the determination of the concentrations of these compounds in human plasma. Compounds were extracted via a classic liquid-liquid extraction. Chromatographic analysis was performed on a C18 reverse phase column with detection by atmosphere pressure chemical ionization LC-MS/MS. Our method allows a good chromatographic separation of the compounds and was fully validated following Food and Drug Administration (FDA) recommendations (good selectivity, no carry-over, linearity of the calibration curves without weighting, deviations from nominal concentrations of standard samples lower than 15%, intra- and inter-assay precision and accuracy lower than 15%). Recovery and stability were also acceptable following the FDA guidelines. A matrix effect impairing the determination of 5-FU was avoided by using a stable isotopic derivative of 5-FU as internal standard. Interestingly, this method allows detection of TetraHydroUridine, an inhibitor of ex vivo degradation of metabolites, which is essential for the stability, the adequate conditioning of blood samples and for good laboratory practice, essential in routine determination. This method seems usable to routinely determine concentrations of capecitabine and its metabolites in blood and may be helpful in further studies aiming at performing therapeutic drug monitoring.

Assessment of principal parabens used in cosmetics after their passage through human epidermis-dermis layers (ex-vivo study).

Concern is continuously raised about the safety of parabens which are present in most of the cosmetic preparations. In this investigation, methyl-, ethyl-, propyl- and butyl paraben (MP, EP, PP, BP), in a commercial cosmetic lotion, were deposited on human skin fragments, collected after surgical operations. Permeated parabens were determined after their passage through human epidermis-dermis layers, fixed on Franz diffusion cells. Bovine serum albumin (3%) was employed as receptor fluid. Then, parabens were assessed by liquid chromatography. The objective of this research was to determine the permeation of these molecules through human epidermis-dermis layers, and their possible passage to body tissues and/or accumulation in skin layers. Two groups of experiments were performed. In the first experimental group (G1), unique doses of the cosmetic were deposited on skin fragments fixed on Franz cells (n = 6), at time 0 h, followed with different withdrawn times of the receptor fluid at 12, 24 and 36 h. G1 results demonstrated that parabens penetration was influenced by their lipophilicity: more lipophilic the parabens were (BP > PP > EP > MP), less they crossed the skin layers (BP < PP < EP < MP). The second experimental group (G2) was constituted of three equal deposits on each Franz cell (n = 6) at different hour times 0, 12 and 24 h followed with three withdrawn times of the receptor fluid at 12, 24 and 36 h. The G2 results indicated that investigated parabens had significant increasing permeations in skin layers. This situation provokes the accumulation of these molecules which were considered by some authors as the cause of skin toxicities and carcinogenicity.

Comparison of fluorescence polarization immunoassay and high-performance liquid chromatography methods for assay of teicoplanin: can correlation be improved?

Teicoplanin is a glycopeptide indicated in serious infections due to Staphylococcus aureus and requires monitoring and dose adjustment based on measurement of trough concentration. Measurement of teicoplanin can be carried out by the fluorescence polarization immunoassay (FPIA) method or by high-performance liquid chromatography (HPLC) methods. We aimed to compare HPLC method using the sum of the peaks of A2-2, A2-3, A2-4 and A2-5 with FPIA method. Thirty-six serum samples obtained over a 6-month period from patients treated by teicoplanin were first analyzed by a HPLC method by determining both the A2-2 peak and the sum of areas of A2-2 to A2-5 and were then stored at -20 degrees C for FPIA assay. Correlation between FPIA and HPLC A2-2 methods was as: HPLC(A2-2) = 0.694FPIA - 0.892 with r(2) = 0.93. A paired t-test revealed significant differences between the results (P < 0.001). To improve the FPIA and HPLC correlation, we performed a linear regression between FPIA and the sum of A2-2, A2-3, A2-4 and A2-5 obtained in the HPLC method: HPLC(A2-2 to A2-5) = 0.953FPIA - 0.915 with r(2) = 0.96. A paired t-test did not show any significant difference between the results of the two methods (P = 0.94). These results show a better correlation between FPIA and HPLC when the sum of A2-2 to A2-5 was used for calculations. In conclusion, HPLC(A2-2 to A2-5) must be preferred to HPLC(A2-2) for the assay of teicoplanin, even if the HPLC(A2-2 to A2-5) runtime is higher than in the HPLC(A2-2) method.

A neutropenia suggesting an interaction between valacyclovir and mycophenolate mofetil.

Mycophenolate mofetil (MMF) is a drug which decreases the frequency of renal transplantation rejection. However, cytomegalovirus infections are a common feature of this treatment leading the physicians to prescribe antiviral prophylactic drugs like valacyclovir. During this association, neutropenia occur and the cause of this adverse effect is difficult to define. This report presents a case of neutropenia in a woman treated with MMF and valacyclovir. As the duration of the valacyclovir treatment exactly corresponds to the neutropenia duration, and the mycophenolate trough levels increased with the neutrophil count, the responsibility of this neutropenia was ascribed to valacyclovir. However, an examination of the literature for cases of neutropenia led to the suspicion of an interaction between MMF and valacyclovir. Mycophenolate may increase intracellular concentrations of valacyclovir up to haematotoxic levels. This mechanism may explain the interaction and further research is needed to confirm this interaction.