Pascal Odou

LC determination of oxcarbazepine and its active metabolite in human serum.

Twenty-five percent of epileptic patients present refractory seizures to current frontline antiepileptic drugs, needing new treatments and leading to the introduction of several new AEDs, among which is oxcarbazepine (Trileptal). This 10-ketoanalogue of carbamazepine seems to be a weaker inducer of cytochrome P450 3A4. However, pharmacokinetic interactions with clinical significance have already been reported, before the marketing of Trileptal in France. The aim of this study was to develop and validate a HPLC method allowing simultaneous dosage of oxcarbazepine, 10-hydroxycarbamazepine, epoxycarbamazepine, carbamazepine, phenobarbital and phenytoïn. After plasma defecation by acetonitrile, dosage was obtained by analysis of the supernatants on a C(18) reversed-phase column coupled with UV detection (240 nm). The statistical validation was performed according to the recommendations of a European technical commission. This method seems to provide a quite good selectivity from the psychotropic therapeutics, which is commonly coprescribed with AEDs. Linearity was established for the whole concentration range, whatever the compound. Quantization limits of oxcarbazepine, 10-hydroxycarbamazepine, epoxycarbamazepine, carbamazepine, phenobarbital and phenytoïn are 0.58, 3.5, 2.35, 0.66, 1.02 and 3.13 microg/ml, respectively, and absolute recoveries are 105.15, 84.76, 94.45, 96.52, 98.62 and 95.08%, respectively.

Impact of multiaccess infusion devices on in vitro drug delivery during multi-infusion therapy.

BACKGROUND: Multiaccess infusion sets allow multiple simultaneous infusions but may induce interference in drug delivery resulting from large variations in the delivery rate of potent drugs. In this study, we sought to understand the influence of multiaccess infusion device properties (dead space volume and antireflux valve [ARV]) on drug delivery during multi-infusion therapy. METHODS: Infusion sets differing in length, dead space volume, and presence of an ARV were assessed. Three drugs were infused simultaneously through different access points, and their concentrations were obtained using UV spectrophotometric analysis of the effluent. Different infusion configurations were compared by assessing (1) the amount of drug delivered to the patient per unit of time, (2) the mean amount of drug delivered to the patient per unit of time during the steady-state infusion (mass flow rate plateau), and (3) flow change efficiency calculated from the ratio of the area under the experimental instant mass flow rate curve to the area corresponding to theoretical instant mass flow rate curve. RESULTS: Infusion sets with lower dead space volumes offered significantly higher flow change efficiency (53.0% ± 15.4% with a dead space volume equal to 0.046 mL 5 min after the start of infusion) than infusion sets with higher dead space volume (5.6% ± 8.2% with a dead space volume equal to 6.16 mL), whatever the flow rate changes. Even in case of large dead space volumes, the presence of an ARV significantly increased the mass flow rate plateau (from 92.4% to 99.3% of the theoretical plateau without and with the presence of an ARV, respectively). CONCLUSIONS: Multi-infusion therapy induces perturbation in drug delivery. These perturbations (lag time, backflow, and bolus) could be reduced by using infusion sets including very low dead space volume and an ARV.

Study of the complexation of risperidone and 9-hydroxyrisperidone with cyclodextrin hosts using affinity capillary electrophoresis and 1H NMR spectroscopy

The complexation of risperidone (Risp) and 9-hydroxyrisperidone (9-OH-Risp), atypical antipsychotics, with seven cyclodextrins (CDs) of pharmaceutical interest (native and hydroxypropylated (HP) alpha-, beta-, gamma-CDs and methyl (Me)-beta-CD) was studied by affinity capillary electrophoresis (ACE) and nuclear magnetic resonance spectroscopy (NMR) for acidic pH 2.5 and physiological pH 7.4. The 1:1 stoichiometry of the complexes was established by (1)H NMR spectroscopy using the continuous variation method developed by Job. The apparent binding constants of the 14 complexes at both pH were determined by ACE through the linear Scotts plots. The NMR spectroscopy investigation of the binding constants was achieved for the two CDs allowing the highest complexation: the beta-CD and Me-beta-CD. Both ACE and NMR spectroscopy studies provide similar conclusions by considering the influence of the 9-hydroxylation, the influence of the CD substitution and the influence of the pH. Moreover, the NMR spectroscopy results have allowed to suppose a pH-dependent inclusion mechanism. A thermodynamic study was then performed by ACE at both pH for the Risp.Me-beta-CD and 9-OH-Risp.Me-beta-CD complexes: the opposite signs of the entropic change (DeltaS degrees <0 at pH 2.5 and DeltaS degrees >0 at pH 7.4) confirms the influence of the pH on the complexation mechanism and the possible difference in the depth of the analyte inclusion in the hydrophobic cavity of the CD. Last, the two-dimensional ROESY (rotating-frame Overhauser spectroscopy) ((1)H-(1)H) and HOESY (heteronuclear Overhauser effect spectroscopy) ((19)F-(1)H) experiments have proved the inclusion of the aromatic part of the Risp and 9-OH-Risp in the hydrophobic CD cavity and lead us to propose a model of complexation.

Comparative study of the complex forming ability and enantioselectivity of cyclodextrin polymers by CE and 1H NMR.

The interactions between nine drugs (baclofen, bupivacaine, chlorpheniramine, ketoconazole, paliperidone, promethazine, propranolol, risperidone and verapamil) and six cyclodextrins (α-CD, β-CD, γ-CD, HP-β-CD, HP-γ-CD and Me-β-CD) or six polymers of cyclodextrins (polyα-CD, polyβ-CD, polyγ-CD, polyHP-β-CD, polyHP-γ-CD and polyMe-β-CD) were studied by affinity capillary electrophoresis and/or (1)H NMR at pH 2.5. An exhaustive qualitative study was performed through the determination of the retardation factor. Then, four compounds and both β-CD and polyβ-CD were selected for the quantitative study of the interactions at pH 2.5 and 7.0. By comparing the results obtained with the β-CD and polyβ-CD, it appears that the apparent binding constants are up to five times higher with the polymer. The 2D-NMR results seem to indicate that the structure of the polymeric network favours the inclusion of the guest in the hydrophobic cavity of the CD units. Moreover, the poly-CDs have shown very high enantioselective abilities at both pH.

Infusion set characteristics such as antireflux valve and dead-space volume affect drug delivery: an experimental study designed to enhance infusion sets.

BACKGROUND: The ability of an infusion set to deliver a specific amount of drug to the patient can be directly related to the presence of an antireflux valve and dead-space volume. In this study we quantified separately the impact of these 2 components on drug delivery. METHODS: Various infusion sets were assessed differing in length, in dead-space volume, and with or without an antireflux valve. Noradrenalin was infused with a syringe pump simultaneously with a carrier flow. Effluent drug concentration was measured using ultraviolet spectrophotometry. Flow change efficiency (FCE) was calculated from the ratio of the area under the experimental mass flow rate curve to the area under the theoretical instantaneous mass flow rate curve. RESULTS: The FCE for infusion sets with or without antireflux valves were significantly different 10 to 15 minutes after the start of an infusion at flow rates of 7 mL/h for noradrenalin and 35 mL/h to 70 mL/h for the carrier fluid. They were not different with a carrier flow of 115 mL/h. DISCUSSION: These findings suggest that antireflux valves have a significant impact on FCE when the ratio of drug flow rate to carrier fluid flow rate is high. Infusion sets with very low dead-space volume connectors yield better FCE. There is a nonlinear relationship between dead-space volume and FCE 5 to 10 minutes after the onset of drug infusion. CONCLUSION: Care providers must consider dead-space volume and the presence of an antireflux valve when choosing their infusion sets.

Experimental study on infusion devices containing polyvinyl chloride: To what extent are they di(2-ethylhexyl)phthalate-free?

The use of medical devices containing highly criticized phthalates including di(2-ethylhexyl) phthalate (DEHP) has been challenged by European directive 2007/47/CE, put into effect in March 2010. New plasticizers are now being used to soften PVC in medical devices: trioctyltrimellitate (TOTM), di-isononyl-cyclohexan-1,2-dicarboxilate (DINCH) and di(2-ethylhexyl) terephthalate (DEHT). To quantify DEHP in nine DEHP-free medical devices made of PVC softened by alternative plasticizers, high performance liquid chromatography analysis with ultraviolet detection at 220 nm wavelength was achieved. An NMR spectroscopy was performed to confirm DEHP presence. Only two medical devices out of the nine tested were truly without DEHP. One of them showed traces of DEHP exceeding the threshold contamination of 0.1% in plastic mass set by REACH regulations. TOTM plasticizer is still incriminated when polyvinyl-chloride (PVC) is contaminated with DEHP. Manufacturers must verify the purity of their raw material, not only on PVC, but also on other soft plastics entering into the composition of medical infusion devices. The clinical consequences of exposure to certain levels of DEHP have not been evaluated. A solution could be to use alternative PVC-free materials.

Risperidone Drug Monitoring

AbstractBackground: Risperidone is an atypical antipsychotic drug that has been marketed in France since 1996. Therapeutic failures have been observed with risperidone. Objective: To investigate whether interactions with the cytochrome P450 (CYP) isoenzymes implicated in risperidone metabolism could explain these treatment failures. Design and Setting: This was a retrospective study of clinical and drug monitoring data from 50 patients treated by five psychiatrists in northern France. Methods: The concentration of active drug (risperidone + 9-hydroxy-risperidone) in serum was evaluated by high performance liquid chromatography and radio receptor assay. Clinical efficacy was assessed by the global improvement (CGI2) item of the Clinical Global Impression rating scale. Results: Statistical analysis revealed a significant increase in efficacy when the serum concentration of active drug was between 25 and 150 μg/L compared with when it was out of this range. Carbamazepine, a CYP3A4 inducer, dramatically decreased the concentration of the active moiety of risperidone; on the contrary, CYP3A4 inhibitors (alprazolam and valproic acid) increased the concentration of active drug. The metabolism of risperidone by CYP3A4 did not lead to the formation of metabolite(s) with anti-D2 dopaminergic activity. Drugs interacting with CYP2D6 altered the risperidone/9-hydroxy-risperidone ratio but did not change the total amount of active drug. Conclusions: We have established a therapeutic range for risperidone. CYP3A4 is a major pathway for risperidone metabolism. Consideration of these factors in clinical practice should lead to improved outcomes for patients treated with risperidone.

The impact on drug mass flow rate of interrupting and resuming carrier fluid flow: an in vitro study on a very low dead-space volume infusion set.

BACKGROUND: Stopping and resuming carrier fluid flow can lead to potentially dangerous transient disturbances in drug mass flow rate. We compared the impact of 2 infusion sets, one with very low dead-space volume and the other with greater dead-space volume, on the amount of drug delivered during stop-and-go carrier fluid flows. METHODS: Two infusion sets, both with antireflux, connected to an angiocatheter and with dead-space volumes of 6.185 mL and 0.071 mL, respectively, were assessed. Two protocols were studied: carrier fluid flow of 90 mL/h associated with noradrenaline infused at 7 mL/h and carrier fluid flow of 350 mL/h with a noradrenaline infusion flow of 65 mL/h. During both protocols, the carrier fluid was stopped and resumed at the same rate 30 minutes later. Effluent noradrenaline concentration was measured using UV spectrophotometry. Flow change efficiency was calculated from the ratio of the area under the experimental mass flow rate curve to the area under the theoretical instantaneous mass flow rate curve. RESULTS: For both flow rate conditions, flow change efficiency was significantly different for the 2 infusion sets during the 10-minute period after stopping carrier fluid flow and the 10-minute period after restarting it. The major phenomena were sudden decreases in drug delivery after stopping carrier flow and sudden, temporary increases when it was resumed. The very low dead-space volume infusion set resulted in significant reduction in changes in drug delivery compared with the standard set, even at high flow rates. CONCLUSION: The use of a very low dead-space volume set attenuates disturbances in drug delivery caused by interrupting and resuming carrier fluid flow.

Influence of crystal hydration on the mechanical properties of sodium naproxen.

The aim of this work is to establish a correlation between water uptake by anhydrous sodium naproxen (ASN) at two different relative humidities and modifications in tableting and densification behaviour under hydration. Water uptake was evaluated at different relative humidities. Models for the hydration kinetics of ASN at 55% and 86%, corresponding to the formation of the dihydrated and tetrahydrated forms, respectively, were evaluated assuming Eyrings dependence on temperature. Tabletability, compressibility, compactibility, and densification behaviour were determined using an instrumented single punch tablet machine. Kinetic data are consistent with a model where water molecules enter the crystal preferentially along hydrophilic tunnels existing in the crystal structure and corresponding to the propionate side chain. Water inclusion perturbs the crystallographic structure, causing slight structural changes according to the amount and associated to an increase in entropy. The interposition of water molecules between sodium naproxen molecules weakens intermolecular bonds, and these sites can behave like sliding planes under compression. Such structural changes may explain the improved compression behaviour and modified densification propensity mechanism. Kinetic data describing the water hydration mechanism of ASN explain in an original way the improved tableting and densification properties under hydration.

P-glycoprotein and cytochrome P450 3A4 involvement in risperidone transport using an in vitro Caco-2/TC7 model and an in vivo model.

The possible involvement of P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 in risperidone transport was investigated using in vitro and in vivo models. Firstly, uptake studies were performed on a Caco-2/TC7 cell monolayer; the effects of 1 microg ml(-1) risperidone on apparent permeability were determined for secretory and absorptive directions, in the presence or absence of various P-gp and CYP3A4 inhibitors (verapamil, ketoconazole, erythromycin), and of an associated multidrug-resistant protein inhibitor (indomethacin). Secondly, on a conscious rat model, risperidone pharmacokinetic parameters, notably absorption parameters, were determined using compartmental and deconvolution methods. Three groups of seven rats received respectively an IV risperidone dose, an oral risperidone dose (PO group) and the same oral risperidone dose after verapamil administration (POV group). No formation of 9-hydroxyrisperidone was observed on Caco-2 cells after risperidone administration; there was no evidence that intestinal CYP3A4 is involved in risperidone metabolising. Risperidone secretory permeation was higher than absorptive permeation. Verapamil increased risperidone absorption permeation and decreased its secretory permeation. Indomethacin did not modify these permeation values. In rats, verapamil led to an increase in both risperidone and 9-hydroxyrisperidone plasmatic concentrations. The fraction absorbed in the verapamil group was 3.18 times higher than in the oral group (65.9% and 20.7% for POV group and PO group). The absorption rate constant was lower in the verapamil group. Our results indicate that P-gp decreases the intestinal absorption of risperidone and that intestinal CYP3A4 is not involved in risperidone metabolism.