The pharmaceutical applications of a biopolymer isolated from Trigonella foenum-graecum seeds: Focus on the freeze-dried matrix forming capacity.

The aim of the present study was to evaluate the funtion of fenugreek seed mucilage (FSM) as potential matrix forming agent for orodispersible pharmaceutical lyophilisates. The FSM was isolated and characterized. FSM colloidal dispersions were prepared and the rheological evaluation was performed. Oral lyophilisates (OLs) with different FSM concentrations, containing meloxicam as model drug were prepared by freeze drying method. The OLs were characterized and compared to gelatin containing tablets, prepared under the same conditions. The FSM dispersions revealed shear thinning flow type. Based on colloidal dispersions' rheological properties, five FSM concentrations were taken forward to the lyophilization step. Completely dry and elegant tablets were obtained. Texture analysis indicated highly porous structures, confirmed by SEM analysis, which explain the fast disintegration properties. All the prepared tablets disintegrated in less than 47 s. The disintegration process was prolonged by the increase in FSM content, due to the high viscosity the polymer creates in aqueous media. FSM tablets presented longer disintegration times, as compared to gelatin tablets, but also higher crushing strength. Considering the fast disintegration and the high crushing strength, FSM is a good candidate as matrix forming agent for fast disintegrating dosage forms or other freeze-dried preparations.

Piecewise function parameters as responses of the design of experiment in the development of a pulsatile release chronopharmaceutical system.

The aim of this work was to develop a pulsatile release system with metoprolol for chronotherapeutical use by coating swellable mini-tablets with Eudragit RS. To study the influence of the formulation factors (amount of coating polymer, plasticizer percentage in film coating and swelling agent percentage in mini-tablets), a Box-Behnken design of experiment (DoE) was used. To evaluate the influence of the studied factors on the sigmoid shape of the dissolution profile, piecewise function parameters were used as the responses of DoE. The results show that higher concentrations of coating polymer and higher concentrations of plasticizer polymer led to a thicker and more elastic polymeric film, which led to a delay in drug release. Using the parameters of the piecewise function as DoE responses, an optimum formulation with a sigmoid shape dissolution profile and a 2.5-h lag time followed by rapid drug release were obtained.

Optimization of the sonication process for meloxicam nanocrystals preparation.

BACKGROUND AND AIMS: Meloxicam, a widely recommended AINS, presents poor water solubility, which limits its bioavailability and effect onset. The objective of this study is the investigation of the most important factors that influence the efficiency of sonication in the preparation of meloxicam nanocrystals. METHODS: The effects of crucial technological sonication parameters (amplitude, time and applied cycle) on the crystal sizes and dissolution were investigated using a central composite experimental design with three factors and three levels. Different mathematical models were applied for the evaluation of the influence of each factor on the measured responses. RESULTS: The amplitude and the time were found as the most important variables. Their increase determined significant size reduction and homogeneity due to cavitation phenomenon, while the applied cycle was less important. The crystal size greatly influenced dissolution; a strong correlation was noted between small crystals and fast dissolution after freeze-drying the nanosuspensions. The optimal formulation was obtained by sonication at 100% amplitude, for 45 minutes and cycle 1, conditions which led to 600 nm crystals with 0.521 polydispersion index. The morphological analysis revealed small, round-shaped crystals with narrow size distribution. CONCLUSIONS: The results provided the optimal sonication conditions needed to obtain meloxicam nanosuspensions with high drug dissolution capacity.

Investigation into the role of Cu/Zn-SOD delivery system on its antioxidant and antiinflammatory activity in rat model of peritonitis.

BACKGROUND: The current study evaluated the role of delivery system (solution, conventional liposomes and PEG-ylated liposomes) on superoxide dismutase (SOD) antioxidant and antiinflammatory properties in a rat model of lipopolysaccharide (LPS)-induced peritonitis. METHODS: Fifty male albino rats (Wistar-Bratislava) were divided into five groups (n=10). Control group received saline and the other four groups received intraperitoneal injections of LPS (5mg/kg). Among the LPS-injected groups, one was LPS control group and the other three groups received the endotoxin injection 30min after receiving the same dose of SOD (500U/kg, ip) in different delivery systems: saline solution (SOD-S), conventional liposomes (SOD-L) or PEG-ylated liposomes (SOD-PL). The animals were euthanized 6h after LPS injection, blood samples were collected and acute phase response (total and differential leukocytes count; tumor necrosis factor α), antioxidants (total antioxidants; reduced glutathione), oxidative stress (total oxidants; lipid peroxidation) and nitrosative stress (nitric oxide metabolites; nitrotyrosine) were evaluated. RESULTS: Intraperitoneal administration of LPS to rats induced a marked inflammatory and oxidative response in plasma. On the other hand, all SOD formulations had protective effect against endotoxin-induced inflammation and oxidative/nitrosative stress, but PEG-ylated liposomes had the most significant activity. Thus, SOD-PL administration significantly reduced the effects of LPS on bone marrow acute phase response, the oxidative status and production of nitric oxide metabolites, while increasing the markers of antioxidant response in a significant manner. CONCLUSION: SOD supplementation interferes both with inflammatory and oxidative pathways involved in LPS-induced acute inflammation, PEG-ylated liposomal formulation being of choice among the tested delivery systems.

Quantification of ascorbic acid and sodium ascorbate in powder blends for tableting and in vitamin C chewable tablets by NIR-chemometry.

The paper proposes a near infrared method able to directly and simultaneously quantify ascorbic acid and sodium ascorbate in powder blends for tableting and in vitamin C chewable tablets without any sample preparation. In the first step, calibration models for the quantification of ascorbic acid and sodium ascorbate in powder blends for tableting and subsequently in chewable vitamin C tablets (corresponding to 80-120 % active substance) were developed according to an experimental design with 2 variables and 5 levels. Then, using the best calibration models, the methods were fully validated in terms of recovery, precision and accuracy for both powder blends and vitamin C chewable tablets. The validated concentration range was 15.14-18.51 % for ascorbic acid and 12.06-14.49 % for sodium ascorbate in powder blends and 91.85-111.03 mg per tablet for ascorbic acid and 71.01-84.50 mg per tablet for sodium ascorbate in tablets. Validation results showed good precision and accuracy.

Development and in vitro evaluation of multiparticulate sustained release carbamazepine formulation.

The objective of the present study was the development and the in vitro evaluation of extended release multiparticulate dosage forms with carbamazepine, starting from drug crystals of established granulometry as cores and using Eudragit NE aqueous dispersions as coating film polymer in a bottom spray fluid bed coating system. The chosen independent variables, i.e., the quantity of film coating (Eudragit NE) and the % of hydrophilic polymer in film coating that act as pores generating (hydroxypropyl methylcellulose ratio) were optimized with a two-factor, three-level central composite experimental design. The chosen dependent variables were cumulative percentage values of carbamazepine released after 1, 2, 4, 6, 8 and 12 h and Peppas kinetic release equation parameters (k and n). Based on the experimental design, different carbamazepine formulations were proposed and their release profiles were determined. The second-order polynomial model coefficients and response surface plots were used to analyze the relation between the dependent and the independent variables. The optimized formulation prepared according to computer-determined levels provided a release profile which was close to the predicted values. The dissolution profile of carbamazepine from the coated crystals and tablets prepared with them were similar, and were unchanged after storage for 3 months under controlled conditions.

Pharmacokinetic interaction between ivabradine and phenytoin in healthy subjects.

BACKGROUND: Phenytoin is an inductor of the main metabolizing enzyme of ivabradine and it could influence its pharmacokinetics. Changes in ivabradine pharmacokinetics could have clinical significance regarding the safety of the treatment. OBJECTIVE: The study objective was evaluation of the pharmacokinetic interaction between ivabradine and phenytoin in healthy subjects. METHODS: A single dose of ivabradine 10 mg was administered alone or in combination with phenytoin 150 mg to 18 healthy subjects in a two-treatment study design, separated by 5 days in which the phenytoin alone was administered at a dose of 150 mg twice daily. Plasma concentrations of ivabradine were determined during a 12-hour period following drug administration, using a high-throughput liquid chromatography coupled with mass spectrometry analytical method. Pharmacokinetic parameters of ivabradine administered in each treatment were calculated using non-compartmental analysis and compared to determine if the differences were statistically significant. RESULTS: In the two treatment periods, the mean ± SD peak plasma concentrations (C(max)) were 18.6 ± 8.0 ng/mL (ivabradine alone) and 6.5 ± 3.1 ng/mL (ivabradine after pre-treatment with phenytoin). The mean ± SD times taken to reach C(max) (t(max)) were 1.2 ± 0.7 h and 0.8 ± 0.6 h, respectively, and the total areas under the plasma concentration-time curve from time zero to infinity (AUC(∞)) were 62.3 ± 18.7 ng · h/mL and 19.2 ± 17.0 ng · h/mL, respectively. Statistically significant differences were observed for the C(max) and AUC(∞) of ivabradine when administered alone or with phenytoin, whereas for t(max) and the half-life the differences were non-significant. CONCLUSION: This study showed that phenytoin has an important effect on the pharmacokinetics of ivabradine in healthy subjects, reducing its bioavailability by approximately 70%.

Drug delivery systems with modified release for systemic and biophase bioavailability.

This review describes the most important new generations of pharmaceutical systems: medicines with extended release, controlled release pharmaceutical systems, pharmaceutical systems for the targeted delivery of drug substances. The latest advances and approaches for delivering small molecular weight drugs and other biologically active agents such as proteins and nucleic acids require novel delivery technologies, the success of a drug being many times dependent on the delivery method. All these dosage forms are qualitatively superior to medicines with immediate release, in that they ensure optimal drug concentrations depending on specific demands of different disease particularities of the body. Drug delivery of these pharmaceutical formulations has the benefit of improving product efficacy and safety, as well as patient convenience and compliance. This paper describes the biopharmaceutical, pharmacokinetic, pharmacologic and technological principles in the design of drug delivery systems with modified release as well as the formulation criteria of prolonged and controlled release drug delivery systems. The paper presents pharmaceutical prolonged and controlled release dosage forms intended for different routes of administration: oral, ocular, transdermal, parenteral, pulmonary, mucoadhesive, but also orally fast dissolving tablets, gastroretentive drug delivery systems, colon-specific drug delivery systems, pulsatile drug delivery systems and carrier or ligand mediated transport for site specific or receptor drug targeting. Specific technologies are given on the dosage forms with modified release as well as examples of marketed products, and current research in these areas.

Simultaneous quantification of l-α-phosphatidylcholine and cholesterol in liposomes using near infrared spectrometry and chemometry.

This paper describes the development and validation of a multivariate method based on transmittance NIR spectroscopy for simultaneous quantification of l-α-phosphatidylcholine (LPC) and cholesterol (CHO). Method development was based on a D-optimal experimental design consisting of 16 LPC-CHO mixtures. Calibration models were generated by partial least-squares (PLS) and principal component regression (PCR) method followed by leave-one-out cross-validation. Among the spectra pretreatment methods tested, Norris Gap first derivative was the best for both LPC and CHO quantification, combined with PLS multivariate method. The method was validated (trueness, precision, accuracy) for the concentration range 50-150% of the expected concentration in liposomes. This method was successfully applied for the characterization of liposomes prepared using the two excipients.

High-Throughput NIR-Chemometric Method for Meloxicam Assay from Powder Blends for Tableting.

A near infrared (NIR) method able to directly quantify the active content in pharmaceutical powder blends used for manufacturing meloxicam tablets, without any sample preparation, was developed and fully validated. To develop calibration models for the assay of meloxicam in powder blends for tableting, the NIR reflectance spectra of different meloxicam powder blends prepared according to a calibration protocol was analysed using different preprocessing methods by partial last-square regression (PLS) and principal component regression (PCR).The best calibration model was found when partial last-square regression (PLS) was used as regression algorithm in association with Smoothing-Savitsky as pre-processing spectrum method. The trueness, precision (repeatability and intermediate precision), accuracy, linearity and range of application of the developed NIR method were validated according to the International Conference of Harmonization (ICH) and Medicine European Agency (EMA) guidelines and found to be fit for its intended purpose.

Effect of fluoxetine on the pharmacokinetics of lansoprazole: a two-treatment period study in healthy male subjects.

BACKGROUND: Fluoxetine is an inhibitor of the main metabolizing enzymes of lansoprazole and could influence the pharmacokinetics of lansoprazole. The changes in lansoprazole pharmacokinetics could have clinical significance concerning the safety of the therapy. OBJECTIVE: The aim of this study was to evaluate the pharmacokinetic interaction between fluoxetine and lansoprazole in healthy subjects. METHODS: A dose of lansoprazole 30 mg, alone or in combination with fluoxetine 60 mg, was administered to 18 healthy male subjects in a two-treatment study design, separated by an 8-day period in which fluoxetine alone was administered as a single oral daily dose. Plasma concentrations of lansoprazole were determined during a 12-hour period following drug administration. Lansoprazole plasma concentrations were determined by a validated liquid chromatography-mass spectrometry method. The pharmacokinetic parameters of lansoprazole were calculated using non-compartmental analysis. RESULTS: In the two periods of treatment, the mean maximum plasma concentration (C(max)) values were 817 ng/mL (lansoprazole alone) and 1370 ng/mL (lansoprazole in combination with fluoxetine after pre-treatment with fluoxetine for 8 days) [p < 0.0001]. The observed area under the plasma concentration-time curve (AUC) from time zero to time of last measurable concentration values were 2400 and 6220 ng · h/mL (p < 0.0001), respectively, and the AUC from time zero to infinity values were 2480 and 7290 ng · h/mL (p < 0.0001), respectively. The time to reach C(max) values were 2.72 and 2.64 hours, respectively. The elimination rate constant from the central compartment values were 0.50 and 0.21 h-1, respectively (p < 0.0001). The elimination half-life values were 1.47 and 3.56 hours (p < 0.0001), respectively, and the mean residence times were 4.0 and 6.9 hours (p < 0.0001), respectively. CONCLUSION: The data demonstrate a pharmacokinetic interaction between fluoxetine and lansoprazole and suggest that the observed interaction may be clinically significant, although its clinical relevance has yet to be confirmed.

Pharmacokinetic interaction between zolpidem and ciprofloxacin in healthy volunteers.

Our objective was to evaluate a possible pharmacokinetic interaction between zolpidem and ciprofloxacin in healthy volunteers. The study consisted of two periods: Period 1 (reference), when each volunteer received a single dose of 5 mg zolpidem and Period 2 (test), when each volunteer received a single dose of 5 mg zolpidem and 500 mg ciprofloxacin. Between the two periods, the subjects were treated for 5 days with a single daily dose of 500 mg ciprofloxacin. Plasma concentrations of zolpidem were determined during a 12-hour period following drug administration. Pharmacokinetic parameters of zolpidem administered in each treatment period were calculated using non-compartmental analysis and the data from two periods were compared to determine statistically significant differences. In the two periods of treatments, the mean peak plasma concentrations (Cmax) were 75.73±28.34 ng/ml (zolpidem alone) and 80.58±22.40 ng/ml (zolpidem after pre-treatment with ciprofloxacin). The tmax, times taken to reach Cmax, were 0.91±0.42 and 1.44±0.61 h, respectively, and the total areas under the curve (AUC0-∞) were 300.2±115.5 and 438.1±142.6 ng h/ml, respectively. The half-life of zolpidem was 2.39±0.53 h when administered alone and 3.34±0.87 h after pre-treatment with ciprofloxacin. These differences were statistically significant for Cmax, tmax, AUC0-∞, half-life and mean residence time. Ciprofloxacin interacts with zolpidem in healthy volunteers, raising its bioavailability by about 46%. This magnitude of effect is likely to be clinically significant.

Pharmacokinetic interaction between zolpidem and carbamazepine in healthy volunteers.

The objective of this study was to evaluate the pharmacokinetic interaction between zolpidem and carbamazepine in healthy volunteers. The study consisted of 2 periods: period 1 (reference), when each volunteer received a single dose of 5 mg zolpidem, and period 2 (test), when each volunteer received a single dose of 5 mg zolpidem and 400 mg carbamazepine. Between the 2 periods, the participants were treated for 15 days with a single daily dose of 400 mg carbamazepine. Pharmacokinetic parameters of zolpidem administered in each treatment period were calculated using noncompartmental analysis. In the 2 periods of treatments, the mean peak plasma concentrations (C(max)) were 59 ng/mL (zolpidem alone) and 35 ng/mL (zolpidem after pretreatment with carbamazepine). The t(max), times taken to reach C(max), were 0.9 hours and 1.0 hour, respectively, and the total areas under the curve (AUC(0-∞)) were 234.9 ng·h/mL and 101.5 ng·h/mL, respectively. The half-life of zolpidem was 2.3 and 1.6 hours, respectively. Carbamazepine interacts with zolpidem in healthy volunteers and lowers its bioavailability by about 57%. The experimental data demonstrate the pharmacokinetic interaction between zolpidem and carbamazepine and suggest that the observed interaction may be clinically significant, but its relevance has to be confirmed.

Pharmacokinetics and comparative bioavailability of two fenofibrate capsule formulations in healthy volunteers.

The objective of this study was to evaluate the pharmacokinetics of fenofibric acid, the main metabolite of fenofibrate (CAS 49562-28-9), and to assess the average bioequivalence of two immediate release formulations of 200 mg fenofibrate capsules in 24 healthy volunteers. The relative bioavailability of the test (generic) product Lipivim with respect to the reference product was determined in a single dose, randomized, crossover study. Only the concentrations of fenofibric acid could be used for bioequivalence determination, because the concentrations of the parent drug were too low to be accurately measured in the biological matrix. The mean values for the Cmax were 3.08 (+/- 1.69) microg/ml for the test and 3.05 (+/- 1.79) microg/ml for the reference product. The mean values for the AUC(0-infinity) were 94.5 (+/- 41.5) microg/ml h for the test and 88.2 (+/- 41.4) microg/ml h for thereference, respectively. The 90% confidence intervals for test/reference mean ratios of the plasma pharmacokinetic variables Cmax, AUC(0-t) and AUC(0-infinity) lie within the conventional bioequivalence range of 80-125% (Schuirman test). The difference between Tmax of the test and reference products was statistically non-significant (Friedman test). The test product is therefore bioequivalent to the reference product with respect to the rate and extent of fenofibric acid pharmacokinetics.

Rapid high-performance liquid chromatography-tandem mass spectrometry method for determination of pentoxifylline and its active metabolites M1 and M5 in human plasma and its application in bioavailability study.

A new rapid, sensitive and selective liquid chromatography coupled with mass spectrometry method was developed and validated for the simultaneous quantification of pentoxifylline (PTX) and two major active metabolites in human plasma (M1 and M5). After a deproteinization step, chromatographic separation of the selected analytes was performed on a RP-C18 column. The detection of target compounds was in multiple reaction monitoring mode using an ion trap mass spectrometer equipped with an electrospray ion source. The method was validated and proved to be linear, accurate and precise over the range 5.08-406.14, 10.08-806.40 and 20.15-1611.60 ng/mL in case of PTX, M1 and M5, respectively. The major advantages of this method are the small sample volume, simple sample processing technique, the high sensitivity and the very good selectivity guaranteed by the MS/MS (in case of PTX) or MS/MS/MS (in case of M1 and M5) detection. The validated method has been successfully applied to a bioequivalence study.

Pharmacokinetic interaction between fluoxetine and omeprazole in healthy male volunteers: a prospective pilot study.

BACKGROUND: Fluoxetine is an inhibitor of the main metabolizing enzymes (cytochrome P450 [CYP] 2C19 and CYP3A4) of omeprazole and thus might influence that drug's pharmacokinetics. The changes in omeprazole's pharmacokinetics may have clinical significance concerning efficacy and tolerability of the treatment. OBJECTIVE: The aim of this study was to assess the pharmacokinetic interaction of fluoxetine with omeprazole in healthy volunteers. METHODS: The study enrolled healthy adult men and consisted of 2 periods. In the first period, all subjects received a single 40-mg dose of omeprazole. This was followed by an 8-day period during which fluoxetine monotherapy (60 mg/d) was administered as a single oral daily dose. At the end of those 8 days, the subjects were administered a 40-mg dose of omeprazole with a 60-mg dose of fluoxetine. Plasma concentrations of omeprazole were determined at 0.5, 1, 1.33, 1.66, 2, 2.5, 3, 4, 5, 6, 7, 8, 10, and 12 hour(s) after study drug administration. Omeprazole plasma concentrations were determined by a validated HPLC method. Pharmacokinetic parameters of omep-razole were calculated using noncompartmental analysis. Adverse events were assessed throughout the study duration. RESULTS: Eighteen healthy male volunteers (mean [SD] age, 22.11 [2.52] years [range, 18-26 years]; body mass index, 23.34 [2.31] kg/m(2) [range, 19.1-27.1 kg/m(2)]) were enrolled and completed the study. In the 2 periods of treatment, the mean Cmax of omeprazole was 730.8 ng/mL (omeprazole monotherapy) and 1725.5 ng/mL (combination treatment with fluoxetine). The observed AUC0-∞ was 1453.3 and 5072.5 ng/mL/h and AUC0-t was 1465.0 and 5185.3 ng/mL/h, respectively. The Tmax was 1.30 and 1.63 hours and the elimination rate constant was 0.753 and 0.482 hr(-1). The t½ was 0.96 and 1.47 hours, whereas the mean residence time was 2.33 and 3.35 hours, respectively. Statistically significant differences were observed for all parameters between periods 1 and 2 (all, P < 0.001). CONCLUSION: The data found in this prospective pilot study suggest a pharmacokinetic interaction between fluoxetine and omeprazole in these healthy volunteers, but its relevance has to be confirmed.

Influence of dextran on the bioadhesive properties of poly(anhydride) nanoparticles.

This work describes the bioadhesive properties of poly(methyl vinyl ether-co-maleic anhydride) (Gantrez AN) nanoparticles (NP) associated with various types of dextran (two hydroxyl-functionalized dextrans and one amino-derivative of dextran). The association of dextran to the polymer was performed either prior NP formation or by the attachment of dextran to the surface of the just formed NP. The amount of dextran associated to the nanoparticles was quantified by a HPLC/ELSD method and dextran presence in the nanoparticles was confirmed by IR spectroscopy, (1)H NMR and in vitro agglutination assay. The in vivo bioadhesion study has demonstrated significantly higher adhesive interactions with the gastrointestinal tract of rats for all types of dextran associated nanoparticles compared with control nanoparticles. For nanoparticles associated with the aminated-dextran, the curves of bioadhesion were characterized by a maximum of adhesion just after administration followed by a rapid and constant decline with time. On the contrary, nanoparticles associated to conventional dextrans displayed a maximum bioadhesion between 1 and 3h post-administration. These results encourage us for further use of these systems for oral delivery of drugs.

High-throughput LC/MS/MS analysis of ruscogenin and neoruscogenin in Ruscus aculeatus L.

A new, sensitive LC/MS/MS method was developed for the quantification of ruscogenin and neoruscogenin in hydrolyzed extracts from Ruscus aculeatus L. (Liliaceae). The two sapogenins were separated on a Zorbax SB-C18 column under isocratic conditions. The detection was performed in the multiple reaction monitoring mode using an ion trap mass spectrometer with an electrospray ionization source operated in positive ionization mode. For the quantification of the ruscogenin and neoruscogenin, calibration curves were constructed over the range of 2-1000 ng/mL. This is the first reported LC/MS/MS method for the simultaneous analysis of ruscogenin and neoruscogenin, and it showed superior sensitivity when compared with other assays described in the literature. The method has been successfully applied to quantify the two sapogenins in aerial (phylloclades) and underground parts (rhizomes, roots) of Ruscus aculeatus L.

Clinical and pharmacokinetics study of oxaliplatin in colon cancer patients.

AIM: to evaluate the therapeutic efficacy of oxaliplatin and to analyze the pharmacokinetics of both ultrafiltrable (free) and protein-bound platinum in patients with metastatic colon cancer. METHOD: 60 patients with stage IV colon carcinoma received 4-6 (mean 4.5) cycles of oxaliplatin based combination chemotherapy. Response rate, progression-free survival (PFS) and toxicity were evaluated. The pharmacokinetics of oxaliplatin was evaluated in 8 patients who were given 85 mg/sqm or 130 mg/sqm using an infusion time of 2-4 h. Pharmacokinetic analysis was performed on blood, plasma and plasma ultrafiltrable by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). RESULTS: Overall response rate (complete and partial) occurred in 33 (55%) patients. The median time of progression was 9.3 months. Cumulative neurotoxicity, vomiting and diarrhea, myelosuppression appeared in 32.3%, 21.3%, and 39.4% patients, respectively. The mean Cmax and AUC 0-24 of oxaliplatin increased in a dose-related manner. The pharmacokinetics of platinum after oxaliplatin administration was triphasic characterized by a short initial distribution phase and a long terminal elimination phase.The clearance of ultrafiltrable platinum was relatively high and the clearance of platinum from plasma and blood cells was relatively low, which is probably a reflection of the covalent binding of platinum to these matrices. CONCLUSION: Oxaliplatin is active and well tolerated in patients with advanced colon cancer. With a relatively low interpatient variability, it is eliminated triphasically and the mean Cmax and AUC 0-24 increases in a dose-related manner. These results provide a scientific basis for the safe and effective use of oxaliplatin in the clinic.

Determination of tramadol and O-desmethyltramadol in human plasma by high-performance liquid chromatography with mass spectrometry detection.

A new simple, sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS) method for quantification of tramadol and its active metabolite O-desmethyltramadol in human plasma was validated. The tramadol and its metabolite were separated on a reversed phase column (Zorbax SB-C18, 100 mm x 3.0 mm I.D., 3.5 microm) under isocratic conditions using a mobile phase of a 10:90 (v/v) mixture of acetonitrile and 0.2% (v/v) trifluoroacetic acid in water. The flow rate was 1 ml/min at the column temperature 45 degrees C. In these chromatographic conditions, the retention times were 2.3 min for O-desmethyltramadol and 3.5 min for tramadol, respectively. The detection of both analytes was in SIM mode using an ion trap mass spectrometer with electrospray positive ionisation. The monitored ions were m/z 264 for tramadol and m/z 250 for its metabolite. The sample preparation was very simple and rapid and consisted in plasma protein precipitation from 0.2 ml plasma using 0.2 ml solution of perchloric acid 7%. Calibration curves were generated over the range of 2-300 ng/ml for both analytes with values for coefficient of correlation greater than 0.998 and by using a weighted (1/y) quadratic regression. The values of precision and accuracy for tramadol at quantification limit were less than 10.9% and 5.1, respectively, both for within- and between-run. For O-desmethyltramadol, precision and accuracy at quantification limit were 10.1% and -9.9% for within-run determinations and 6.7% and 10.4% for between-run determinations, respectively. The mean recovery for both analytes was 96%. Both tramadol and its metabolite demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. This is the first reported method for analysis of tramadol and O-desmethyltramadol in human plasma that uses protein precipitation as sample processing procedure. The method is very simple and allows obtaining a very good recovery of both analytes. The validated LC/MS method has been applied to a pharmacokinetic study of 50 mg tramadol tablets on healthy volunteers.