A polishing hybrid AER/UF membrane process for the treatment of a high DOC content surface water.

The efficacy of a combined AER/UF (Anion Exchange Resin/Ultrafiltration) process for the polishing treatment of a high DOC (Dissolved Organic Carbon) content (>8 mgC/L) surface water was investigated at lab-scale using a strong base AER. Both resin dose and bead size had a significant impact on the kinetic removal of DOC for short contact times (i.e. <15 min). For resin doses higher than 700 mg/L and median bead sizes below 250 µm DOC removal remained constant after 30 min of contact time with very high removal rates (80%). Optimum AER treatment conditions were applied in combination with UF membrane filtration on water previously treated by coagulation-flocculation (i.e. 3 mgC/L). A more severe fouling was observed for each filtration run in the presence of AER. This fouling was shown to be mainly reversible and caused by the progressive attrition of the AER through the centrifugal pump leading to the production of resin particles below 50 µm in diameter. More important, the presence of AER significantly lowered the irreversible fouling (loss of permeability recorded after backwash) and reduced the DOC content of the clarified water to l.8 mgC/L (40% removal rate), concentration that remained almost constant throughout the experiment.

Virus removal retention challenge tests performed at lab scale and pilot scale during operation of membrane units.

The determination of the virus retention capabilities of UF units during operation is essential for the operators of drinking water treatment facilities in order to guarantee an efficient and stable removal of viruses through time. In previous studies, an effective method (MS2-phage challenge tests) was developed by the Water Research Center of Veolia Environnement for the measurement of the virus retention rates (Log Removal Rate, LRV) of commercially available hollow fiber membranes at lab scale. In the present work, the protocol for monitoring membrane performance was transferred from lab scale to pilot scale. Membrane performances were evaluated during pilot trial and compared to the results obtained at lab scale with fibers taken from the pilot plant modules. PFU culture method was compared to RT-PCR method for the calculation of LRV in both cases. Preliminary tests at lab scale showed that both methods can be used interchangeably. For tests conducted on virgin membrane, a good consistency was observed between lab and pilot scale results with the two analytical methods used. This work intends to show that a reliable determination of the membranes performances based on RT-PCR analytical method can be achieved during the operation of the UF units.

Development of a high throughput 96-well plate sample preparation method for the determination of trileptal (oxcarbazepine) and its metabolites in human plasma.

A high throughput preparation method for the determination of trileptal (oxcarbazepine, OXC) and its mono (MHD) and dihydroxy (DHD) metabolites in human plasma, using 96-well plate technology, has been developed and validated according to international regulatory requirements. Preparation of plasma samples (50 microl) containing the compounds to be analysed involved solid-phase extraction (SPE) on Empore C18 96-well SPE plates. Eluates from the plate were injected onto a reversed-phase column (Hypersil C18,3 microm) with UV detection at 210 nm. Detector response was linear over the ranges 0.2-10, 0.1-200 and 0.1-20 micromol/l, for OXC, MHD and DHD, respectively, with relative standard deviations from 1 to 10% and mean accuracies within 4% of the nominal values (number of standard curves=3 in duplicate). The limits of quantitation were 0.2, 0.1 and 0.1 micromol/l, respectively. The overall mean accuracies ranged from 96 to 106% and precision was in the range 4 to 11%. Cross validation indicated no significant difference between plasma concentrations obtained using the 96-well method and the previous method using a traditional SPE method with a 50 mg C18 cartridge. About a threefold increase in sample throughput and a twofold decrease of plasma volume required for the assays, were the main advantages obtained from the previous method. The method was applied for the determination of 3000 plasma samples from clinical studies.

Determination of a new oral iron chelator, ICL670, and its iron complex in plasma by high-performance liquid chromatography and ultraviolet detection.

ICL670 is a representative of a new class of orally active tridentate selective iron chelators. Two molecules of ICL670 are required to form a complete hexacoordinate chelate Fe-[ICL670]2 with one ferric iron. A simple and rapid HPLC-UV method for the separate determination of ICL670 and Fe-[ICL670]2 in the plasma of iron-overloaded patients is described. Plasma samples were prepared as rapidly as possible, the tubes being kept at 4 degrees C. Plasma proteins were precipitated with methanol. The supernatant was diluted with water and placed on the refrigerated sample rack of an autosampler before injection. The chromatographic separations were achieved on an Alltima C18 column using 0.05 M Na2HPO4 and 0.01 M tetrabutylammonium hydrogen sulfate-acetonitrile-methanol (41:9:50, v/v/v) as mobile phase. The analytes were detected at 295 nm. Calibration and quality control samples were prepared in normal human plasma. The mean accuracy (n=6) over the entire investigated concentration range 0.25-20 microg/ml ranged from 91 to 109% with a coefficient of variation (C.V.) from 4 to 8% for ICL670, and from 95 to 105% with a C.V. from 2 to 20% for the iron complex. The dissociation of the complex during analysis was shown to be marginal. The iron removal from plasma of iron-overloaded patients by free ICL670 during analysis was low. The in vitro iron transfer from the iron pools of iron-overloaded plasma onto ICL670 was shown to be a slow process.

Plasma deproteinization by precipitation and filtration in the 96-well format.

The need for fast bioanalytical methods within the pharmaceutical sector is rapidly growing. Sample preparation is often the bottleneck step. A new approach to increasing sample throughput involves precipitated protein removal by filtration in the 96-well format, thereby eliminating the need for centrifugation and manual handling of individual tubes. The potential for such a new technique has been investigated for the determination of an iron chelator, a highly protein-bound compound (> or =99.5%) in plasma. An analog was used as internal standard. Acetonitrile and plasma were sequentially aspirated, separated by an air gap, using a manual electronic pipettor. They were then dispensed into the channel of an Empore filter PPT plate above the filter, and a slight vacuum was applied. The eluate was collected and diluted prior to injection. The compounds were then separated by reversed-phase chromatography and detected by UV at 295 nm. The chromatographic run time was 6 min. The mean recovery following protein precipitation was 78%, which shows that the technique can apply to a highly protein-bound compound. Replicate quality control samples were prepared in drug-free normal human plasma at four different concentrations. The mean accuracy ranged from 87 to 108% with the CV ranging from 3 to 8%. The described procedure is simple, fast and reproducible. It requires minimal equipment. The time required to prepare a plate manually is only about 20 min. The use of 12-channel repeater pipettors reduces the risk of error and improves productivity. Automation should be an aid to further increasing sample throughput when more than one plate a day is to be prepared.

Practice of solid-phase extraction and protein precipitation in the 96-well format combined with high-performance liquid chromatography-ultraviolet detection for the analysis of drugs in plasma and brain.

C18 Empore 96-well extraction disc plates have been employed for the analysis of three drugs with different polarities in plasma in conjunction with HPLC-UV, rufinamide, ICL670 and an anticonvulsant agent (AA1) in an early stage of development. With the most polar compound (AA1), ion-pair extraction at pH 12 was applied. The method developed for the assay of AA1 in plasma was applied to its determination in brain using an Oasis HLB plate following homogenisation in a pH 7.4 buffer and protein precipitation with NaOH-ZnSO4, thereby saving time for method development. Protein precipitation in the 96-well format with filtration of the precipitate was applied to the determination of ICL670, a highly protein-bound compound (>99.5%), with a good recovery (78%). Reversed-phase chromatography was applied using a short 5 cm column packed with 3 microm particles for the determination of ICL670 and AA1 and two parallel columns (15 cm long) for the determination of rufinamide. The methods were used routinely, one plate per analysis day being processed, resulting in increase in sample throughput and saving in solvents.

A pharmacokinetic study of Neoral in childhood steroid-dependent nephrotic syndrome.

Seven children with steroid-dependent nephrotic syndrome who were on stable remission under Sandimmun therapy were switched to Neoral at the same dosage. During the 4-month follow-up period, two patients relapsed, due to poor compliance in one of them. Serum creatinine remained stable in all patients. Pharmacokinetic profiles were performed at day 0 while on Sandimmun and 4 weeks after conversion to Neoral. Following conversion to Neoral, the peak concentration occurred earlier (2+/-1.4 h vs 3.9+/-2.4 h), and the maximum concentration (677+/-386 ng/ml vs 488+/-265 ng/ml) and the area under the curve (3,082+/-1,536 ng/ml/h vs 2,201+/889 ng/ml/h) were higher. We conclude that Neoral results in an increased bioavailability of cyclosporine (CsA) as compared to Sandimmun in patients with steroid-dependent nephrotic syndrome in remission.

New oral formulation of cyclosporin A (Neoral) pharmacokinetics in allogeneic bone marrow transplant recipients.

Cyclosporin A (CsA) absorption is variable in bone marrow transplant (BMT) patients compromising the efficacy of graft-versus-host disease prevention. Neoral, a new microemulsion formulation of CsA which has an improved bioavailability, increases intestinal absorption of the drug with less variable pharmacokinetic parameters in non-BMT patients. In order to predict the best dosage of Neoral when patients are switched from i.v. to oral administration we performed a randomised study comparing two oral doses, either the same or twice the last i.v. dose used after BMT. Fourteen adults were randomised around day 25 after BMT. Whole blood CSA concentrations were measured 2 and 12 h after the oral administration of Neoral on days 0, 7 and 14 to determine residual and maximum concentration, and modified whenever necessary to maintain blood level CsA concentration within therapeutic range (150-250 ng/ml). We found that patients who received twice the last i.v. dose had better concentrations than patients from the other group while toxicity was identical in both groups. We conclude that doubling the last i.v. dose during the switch to oral administration of Neoral gives the best therapeutic range concentration and should be recommended for graft-versus-host prevention.

Pharmacokinetics of dexamethasone and valspodar, a P-glycoprotein (mdr1) modulator: implications for coadministration.

STUDY OBJECTIVE: To assess the potential for a drug-drug interaction between valspodar, a P-glycoprotein (mdrl) modulator used as a chemotherapy adjunct, and dexamethasone, widely included in oncology antiemetic regimens. DESIGN: Randomized, open-label, three-period crossover study. SETTING: Clinical pharmacology research center. SUBJECTS: Eighteen healthy men volunteers (age 25.8+/-3.5 yrs, weight 71.6+/-10.3 kg). INTERVENTIONS: Subjects received single fasting oral doses of valspodar 400 mg, dexamethasone 8 mg, and both drugs concomitantly with 2- to 3-week washout phases between administrations. MEASUREMENTS AND MAIN RESULTS: Lack of a pharmacokinetic drug-drug interaction with respect to valspodar was conclusively demonstrated for both Cmax,b (2.3+/-0.4 vs 2.4+/-0.5 microg/ml) and AUCb (19.8+/-4.8 vs 19.6+/-4.9 microg x hr/ml) inasmuch as bioequivalence criteria were satisfied when comparing administration alone with coadministration, respectively. Although no changes in the rate of dexamethasone absorption were noted on coadministration with valspodar (Cmax 88+/-23 vs 91+/-20 ng/ml), overall exposure was significantly increased by 24% on average (AUC 400+/-87 vs 494+/-90 ng x hr/ml). Regression analysis of valspodar Cmax,b and AUCb during coadministration versus the extent of the interaction (percentage increase in dexamethasone AUC) did not reveal a concentration-effect relationship (p=0.7299 and 0.9718, respectively). CONCLUSION: Given dexamethasone's wide therapeutic index and the short duration of coadministration foreseen for these drugs in a clinical setting (maximum 1 wk/chemotherapy cycle), the 24% increase in dexamethasone's AUC is unlikely to be relevant. Thus no alterations in valspodar or dexamethasone dosages appear warranted when the two drugs are coadministered. Multiple-dose experience in patients would be desirable to confirm these conclusions.

Pharmacokinetics of terbinafine and five known metabolites in children, after oral administration.

As an extensive study, the pharmacokinetics of terbinafine and five known metabolites have been investigated after single and repeated oral administration to 12 pediatric patients. After single administration of 125 mg terbinafine, four compounds were unconjugated and the hydroxymetabolites appeared in trace amounts as glucuronides. The main metabolites in plasma were unconjugated carboxy compounds. Kinetics of terbinafine and N-desmethylterbinafine metabolite were comparable. The interindividual AUCt variability was similar for terbinafine, N-desmethylterbinafine and carboxyterbinafine. In urine, the major fraction was the hydrophilic unconjugated N-desmethyl-carboxyterbinafine (15%). After repeated administration of 125 mg day(-1), mean trough levels of terbinafine, N-desmethylterbinafine, carboxyterbinafine and N-desmethylhydroxy-terbinafine, and also that of hydroxyterbinafine metabolite were similar, for each compound, on days 21, 42 and 56 denoting that steady state was reached at least on day 21 and no accumulation occurred between days 21 and 56.

[Variability of the bioavailability of cyclosporine: benefit of the Neoral formulation]. / Variabilité de la biodisponibilité de la ciclosporine: avantage de la formulation Néoral.

After oral administration of Sandimmun, the bioavailability of cyclosporin can vary substantially especially in view of its narrow therapeutic index. As a consequence, optimal exposure of patients to the drug is sometimes difficult to ensure. The new formulation of cyclosporin, Neoral, improves the absorption of the drug. This results in an increase in bioavailability, a lower dependency on food, bile or pancreatic enzymes and a markedly reduced intra- and inter-patient variability in pharmacokinetic parameters. This allows an easier adjustment of patient exposure. The clinical efficacy of Neoral is equivalent to, or even better than, that of Sandimmun. The tolerability of the two formulations is comparable.

Human pharmacokinetics of dihydroergotamine administered by nasal spray.

OBJECTIVES: A nasal spray of dihydroergotamine was developed for the treatment of migraine headaches, and pharmacokinetic studies were scheduled to evaluate the bioavailability of dihydroergotamine by this new route of administration. METHODS: Nine studies were performed with dihydroergotamine administered by nasal spray to evaluate the bioavailability of the nasal route versus the intramuscular route, the linearity of the kinetics, the interindividual and intraindividual variations, and the influence of different factors. RESULTS: Nasally administered dihydroergotamine (1 mg) becomes rapidly available to the systemic circulation, with peak plasma levels of 1 ng/ml achieved in 0.9 hour. The relative bioavailability versus intramuscular route is 38.4%. Dihydroergotamine administered by the nasal route exhibits linear dose proportionality (1 to 4 mg). Intraindividual variations of bioavailability evaluated for a 1-year period were higher (29%) than those found for the intramuscular route (20%) but comparable to the oral route. Interindividual variations for bioavailability were greater (25% versus 14% by the intramuscular route) but comparable to the oral route. Caffeine contained in the nasal solution (1%) had no effect on the absorption. Vasomotor phenomena, which could also affect the nasal mucosa during a migraine headache, do not modify the bioavailability. The constriction of the nasal mucosa by fenoxazoline leads to a slight decrease (-15%) in the bioavailability. The presence of acute viral rhinitis did not result in any change in dihydroergotamine nasal absorption compared with the normal state of the nasal mucosa. From a pharmacokinetic point of view, nasally administered dihydroergotamine can be given, without risk of overdose, to patients receiving long-term oral dihydroergotamine medication. CONCLUSION: These results show the reliability and reproducibility of this route of dihydroergotamine administration adapted for the treatment of migraine headaches.

Evaluation of pharmacokinetic studies: is it useful to take into account concentrations below the limit of quantification?

PURPOSE: Based on real data, to evaluate the usefulness of taking into account samples with values below the limit of quantification (LOQ) for the evaluation of pharmacokinetic studies. METHODS: To compare for two drugs, after single dose administration the pharmacokinetic parameters obtained by using a poorly sensitive assay (PSA) and a highly sensitive assay (HSA), acting as reference; To evaluate the results of pharmacokinetic studies in the light of different values for the LOQ. RESULTS: Under certain conditions, such as homogeneous population, sufficient subject number, sufficient sampling times and acceptable accuracy (CV < 20%) for the concentrations, it is possible to get valuable and more reliable kinetic information by using concentrations obtained with a poor precision (CV > 20%). This is especially true for the parameters associated with the terminal phase, such as t1/2 beta and AUC, but also for parameters depending to a lesser extent on the terminal phase, such as t1/2 alpha and AUCm. Moreover, the mean concentration time curve is by far best defined by using all the concentrations. CONCLUSIONS: In some situations, it is preferable to use concentrations with values below the LOQ to evaluate the results of pharmacokinetic studies. However, this should not be the rule, especially when this does not bring any additional information, or when it is possible to increase the sensitivity of the bioanalytical assay.

Pharmacokinetics of terbinafine and of its five main metabolites in plasma and urine, following a single oral dose in healthy subjects.

The plasma pharmacokinetics, and the urinary excretion, of terbinafine and its five main metabolites have been investigated after a single oral dose administration of 125 mg to 16 healthy subjects. In plasma, the highest concentrations are observed for the two carboxybutyl metabolites, with a predominance for the carboxybutylterbinafine. For this metabolite, as compared to terbinafine, the Cmax and AUC are 2.4 and 13 times higher respectively. The demethylterbinafine presents a plasma profile close to that of terbinafine. The two hydroxy metabolites are only found as glucuronide and are of minor importance. The apparent terminal half-lives of terbinafine, demethylterbinafine, and the two carboxy metabolites appear to be similar (approximately 25 h). As compared to the plasma concentration of total radioactivity observed after a single oral administration of the same dose of 14C-terbinafine, the parent drug and these five metabolites, account for more than 80% of the total radioactivity in plasma over the 0-48 h interval following administration. In urine, the major metabolite is demethylcarboxybutylterbinafine, which amounted to about 10% of the administered dose. Terbinafine and demethylterbinafine are only excreted as trace amounts in urine. Carboxybutylterbinafine and the two hydroxy metabolites are excreted in the range of 0.5-2% either as glucuronides or free. Urinary excretion over the 0-48 h interval of terbinafine and of the five metabolites amounted to about 14% of the administered dose. This is far below the level of total radioactivity measured in urine over the same interval (approximately 57%), after administration of 14C-terbinafine. This shows in contrast to plasma, that numerous other metabolites are present in urine.

Pilot study of terbinafine in children suffering from tinea capitis: evaluation of efficacy, safety and pharmacokinetics.

In an open pilot study, 12 children with tinea capitis were treated for 6 weeks with oral terbinafine (125 mg/day), and followed up 2 weeks later. The study was conducted to evaluate the efficacy, safety and pharmacokinetics of terbinafine. All patients were completely cured at the end of the treatment period, and there was no evidence of relapse at follow-up. Seven had a negative culture after 3 weeks of treatment. The time to obtain culture conversion from positive to negative did not appear to be related to body weight, but to clinical severity at baseline. Terbinafine is well tolerated and safe over a 56-day period. The kinetic data show a higher clearance of terbinafine in children compared with adults, with shorter alpha- and beta-phase elimination half-lives. However, a longer terminal gamma-phase (at least 6 days) is observed, as in adults, after multiple dose administration, and this is related to elimination from the tissues. The plasma concentrations are comparable between children and adults at a steady state (125 mg/day).

Determination of terbinafine and its desmethyl metabolite in human plasma by high-performance liquid chromatography.

A reliable reversed-phase high-performance liquid chromatographic method has been developed for the determination of terbinafine (Terb) and its desmethyl metabolite (DMT) in human plasma. The analytes and the internal standard (I.S.) are extracted by a liquid-liquid technique followed by an aqueous back-extraction, allowing injection of an aqueous solvent in the HPLC system. The mobile phase is acetonitrile + 0.012 M triethylamine -0.020 M orthophosphoric acid (50:50, v/v) and the UV detection is at 224 nm. The inter-assay precision over the concentration range 2-1000 ng/ml is between 2.9 and 9.8% for both compounds. The limit of quantification, 2 ng/ml for both compounds, is sufficient for investigating the pharmacokinetics of Lamisil in human studies. With an additional preparation step, this method can be used for assaying Terb in tissues such as nail, sebum and stratum corneum.

In vitro-in vivo correlation of a modified-release oral form of ketotifen: in vitro dissolution rate specification.

The dissolution rate profile of a new modified-release (MR) oral tablet of ketotifen (Zaditen SRO tablet, Sandoz Ltd.) was determined under different conditions (pH, rpm, paddle or basket) with the U.S.P. apparatus. Three different variants of MR tablets were tested. In addition, the in vivo bioavailabilities of these MR tablets were evaluated after a single-dose administration under different conditions (fasting state, with food in morning and/or evening). Several possibilities were evaluated to obtain a correlation between in vitro and in vivo data of the three MR tablets. An excellent linear correlation (r = 0.997) was obtained between the cumulative dissolved percent in vitro and the cumulative absorbed percent in vivo at each time under certain conditions. This was obtained in vitro with the dissolution rate performed in distilled water (37 degrees C) with the U.S.P. apparatus 2 (rotating paddle) and in vivo after a single-dose administration in the morning, fasting state. On the basis of this correlation, of the in vitro dissolution rate for a given variant, and of a simple method of calculation, a reliable prediction of the plasma concentrations obtained following a single dose or at steady state was found. The reliability of this prediction was validated from variants of MR tablet presenting different in vitro dissolution rate profiles and with an upscaled batch which was tested in vivo. This result allows the specifications (upper and lower limits) of the dissolution rate for the MR tablet to be defined and ensures good in vivo characteristics for the different batches of Zaditen SRO tablets during manufacture.

Dose-proportional pharmacokinetics of terbinafine and its N-demethylated metabolite in healthy volunteers.

The dose-dependency of the pharmacokinetic parameters of terbinafine and its N-demethyl derivative was investigated in a randomized four-way crossover study in healthy volunteers following single oral administrations of 125, 250, 500 and 750 mg of terbinafine. Plasma concentrations of terbinafine and its metabolite were measured by a validated high-performance liquid chromatography (HPLC) method using ultraviolet detection. Concentration data were fitted to a two-compartment model. The relationship between Cmax or the area under the concentration curve (AUC) and the terbinafine dose was analysed by classical linear regression. Terbinafine disposition parameters were dose-independent, with the exception of Tmax and t1/2 alpha, which were prolonged with the 500- and 750-mg doses. The terbinafine Cmax and AUC, however, were linear and dose-proportional over the entire dose range. The N-demethylated metabolite appeared in plasma at the same time as terbinafine and showed similar prolongations in Tmax and t1/2 alpha with the 500- and 750-mg doses. In addition, the Cmax deviated from proportionality at these doses, giving values 22% lower than projected, while the AUC was linear and dose-proportional over the whole range of doses. The slight disproportionality in the dispositions of terbinafine and its N-demethyl metabolite at 500 and 750 mg are not expected to be clinically significant.

Ocular distribution of cyclosporin A (Sandimmun) following systemic and topical administration to rabbits.

The purpose of this study was to determine the distribution of cyclosporin A (CsA) in various ocular fluids and tissues in the rabbit by two routes of administration. CsA was administered to two groups of two rabbits either by intramuscular route at a dose of 25 mg/kg/day or by local route using eyedrops, at a dose of 10 mg/day (-2.8 mg/kg/day) for eight days. An extra animal was treated with a placebo solution in each group in order to obtain control values. Samples of blood and tears were collected throughout the 8-day treatment period. On day 9, the six animals were sacrificed and additional samples were collected from the vitreous body, the aqueous humor, the cornea and the globe. The concentrations of CsA were determined by RIA using the specific monoclonal antibody contained in the Sandimmun-kit. After administration by intramuscular route, high concentrations of CsA were detected in the blood. Within the eye, this compound was clearly detected in the tears, the cornea and the globe, and was suspected in the vitreous body and the aqueous humor. After administration by local route, using eyedrops, no CsA was detected in the blood, the vitreous body or the aqueous humor. However, despite doses ten times lower than those administered by the intramuscular route, this compound was clearly detected in the tears, the cornea and the globe of the treated eye. Moreover, similar concentrations were obtained in the untreated eye. These data reveal a real passage of CsA from the left treated eye to the right untreated eye.(ABSTRACT TRUNCATED AT 250 WORDS)