Binding of ketoprofen enantiomers in various human albumin preparations

Therapeutic solutions of human albumin - The possible effect of process-induced molecular alterations on clinical efficacy and safety

Human albumin solutions were developed as therapeutic during the Second World War to address blood loss due to battlefield injury. This indication was based on the recognition that albumin provided most of the oncotic capacity of human plasma. For the succeeding sixty years, this formed the basis for the use of albumin in traumatology and emergency medicine. In more recent times, the pharmacological properties arising from albumin's complex structure have become a focus of attention by clinical researchers. In particular, albumin, through anti-inflammatory and anti-oxidant properties, has been proposed as an agent for the treatment of sepsis, cirrhosis and other inflammatory states. Some evidence for these indications has accrued from a number of small clinical trials and observational studies. These studies have not been confirmed in other large trials. Together with other investigators, we have shown that the process of plasma fractionation results in alterations in the structure of albumin, including those parts of the molecule involved in anti-oxidant and anti-inflammatory effects. Albumin products from diverse manufacturers show heterogeneity in their ability to address these effects. In this article, we review the historical development of albumin solutions, pointing out the variations in fractionation chemistries which different manufacturers have adopted. We suggest ways by which the manufacturing processes have contributed to variations in the physico-chemical properties of molecule. We review the outcomes of clinical studies assessing the role of albumin in ameliorating conditions such as sepsis and cirrhosis, and we speculate as to the extent which heterogeneity in the products may have contributed to variable clinical outcomes. Finally, we argue for a change in the perception of the plasma product industry and its regulatory overseers. Historically, albumin has been viewed as a generic commodity, with different preparations being interchangeable in their clinical application. We suggest that this implied biosimilarity is not necessarily applicable for different albumin solutions. The use of albumin, in indications other than its historical role as a plasma expander, can only be validated by clinical investigation of each separate albumin product.

Impact of Dendrimers on Solubility of Hydrophobic Drug Molecules

Adequate aqueous solubility has been one of the desired properties while selecting drug molecules and other bio-actives for product development. Often solubility of a drug determines its pharmaceutical and therapeutic performance. Majority of newly synthesized drug molecules fail or are rejected during the early phases of drug discovery and development due to their limited solubility. Sufficient permeability, aqueous solubility and physicochemical stability of the drug are important for achieving adequate bioavailability and therapeutic outcome. A number of different approaches including co-solvency, micellar solubilization, micronization, pH adjustment, chemical modification, and solid dispersion have been explored toward improving the solubility of various poorly aqueous-soluble drugs. Dendrimers, a new class of polymers, possess great potential for drug solubility improvement, by virtue of their unique properties. These hyper-branched, mono-dispersed molecules have the distinct ability to bind the drug molecules on periphery as well as to encapsulate these molecules within the dendritic structure. There are numerous reported studies which have successfully used dendrimers to enhance the solubilization of poorly soluble drugs. These promising outcomes have encouraged the researchers to design, synthesize, and evaluate various dendritic polymers for their use in drug delivery and product development. This review will discuss the aspects and role of dendrimers in the solubility enhancement of poorly soluble drugs. The review will also highlight the important and relevant properties of dendrimers which contribute toward drug solubilization. Finally, hydrophobic drugs which have been explored for dendrimer assisted solubilization, and the current marketing status of dendrimers will be discussed.

Solubility of aceclofenac in polyamidoamine dendrimer solutions

In the present study we investigated the effect of polyamidoamine (PAMAM) dendrimers on the aqueous solubility of aceclofenac. The aqueous solubility of aceclofenac was measured in the presence of dendrimers in distilled water. The effect of variables, such as pH condition, concentration, temperature and generation (molecule size) of dendrimer, has been investigated. Results showed that the solubility of aceclofenac in the dendrimer solutions was proportional to dendrimer concentration. The order in which the dendrimers increased the solubility at a constant pH condition was G3 > G0. The influence of dendrimer solution pH on the solubility enhancement of aceclofenac suggests that it involves an electrostatic interaction between the carboxyl group of the aceclofenac molecule and the amine groups of the dendrimer molecule. The solubility of aceclofenac was inversely proportional to the temperature of dendrimer solution.Different generation (G0 and G3) PAMAM dendrimers have the potential to significantly enhance the solubility of poor water-soluble drugs.

Enantiospecific ketoprofen concentrations in plasma after oral and intramuscular administration in growing pigs

Background

Ketoprofen is a non-steroidal anti-inflammatory drug which has been widely used for domestic animals. Orally administered racemic ketoprofen has been reported to be absorbed well in pigs, and bioavailability was almost complete. The objectives of this study were to analyze R- and S-ketoprofen concentrations in plasma after oral (PO) and intra muscular (IM) routes of administration, and to assess the relative bioavailability of racemic ketoprofen for both enantiomers between those routes of administration in growing pigs.

Methods

Eleven pigs received racemic ketoprofen at dose rates of 4 mg/kg PO and 3 mg/kg IM in a randomized, crossover design with a 6-day washout period. Enantiomers were separated on a chiral column and their concentrations were determined by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated and relative bioavailability (F_rel) was determined for S and R –ketoprofen.

Results

S-ketoprofen was the predominant enantiomer in pig plasma after administration of the racemic mixture via both routes. The mean (± SD) maximum S-ketoprofen concentration in plasma (7.42 mg/L ± 2.35 in PO and 7.32 mg/L ± 0.75 in IM) was more than twice as high as that of R-ketoprofen (2.55 mg/L ± 0.99 in PO and 3.23 mg/L ± 0.70 in IM), and the terminal half-life was three times longer for S-ketoprofen (3.40 h ± 0.91 in PO and 2.89 h ± 0.85 in IM) than R-ketoprofen (1.1 h ± 0.90 in PO and 0.75 h ± 0.48 in IM). The mean (± SD) relative bioavailability (PO compared to IM) was 83 ± 20% and 63 ± 23% for S-ketoprofen and R-ketoprofen, respectively.

Conclusions

Although some minor differences were detected in the ketoprofen enantiomer concentrations in plasma after PO and IM administration, they are probably not relevant in clinical use. Thus, the pharmacological effects of racemic ketoprofen should be comparable after intramuscular and oral routes of administration in growing pigs.

Impaired drug-binding capacities of in vitro and in vivo glycated albumin

Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. One of the main properties of this plasma protein is its strong affinity to bind many therapeutic drugs, including warfarin and ketoprofen. In this study, we investigated whether or not there were any significant changes related to in vitro or in vivo glycation in the structural properties and the binding of human albumin to both therapeutic drugs. Structural parameters, including redox state and ketoamine contents of in vitro and in vivo glycated purified albumins, were investigated in parallel with their affinity for warfarin and ketoprofen. High-performance liquid chromatography was used to determine the free drug concentrations and dissociation constants according to the Scatchard method. An alternative method based on fluorescence spectroscopy was also used to assess drug-binding properties. Oxidation and glycation levels were found to be enhanced in albumin purified from diabetic patients or glycated with glucose or methylglyoxal, after determination of their ketoamine, free thiol, amino group and carbonyl contents. In parallel, significant impairments in the binding affinity of in vitro and in vivo glycated albumin, as indicated by the higher dissociation constant values and confirmed by higher free drug fractions, were observed. To a lesser extent, this alteration also significantly affected diabetic albumin affinity, indicated by a lower static quenching in fluorescence spectroscopy. This work provides useful information supporting in vivo diabetic albumin could be the best model of glycation for monitoring diabetic physiopathology and should be valuable to know if glycation of albumin could contribute to variability in drugs response during diabetes.

Enantioselective Pharmacokinetics of Ibuprofen and Involved Mechanisms

Although dexibuprofen (S-ibuprofen) was marketed in Austria and Switzerland, the racemate at various formulations is still extensively used worldwide, and there are no indications that the racemate will be replaced by the single enantiomer. Thus, elucidation of the characteristics and involved mechanisms of the chiral pharmacokinetics of racemic ibuprofen is of special importance for the understanding of the pharmacological and toxicological consequences, and for prediction of the clinically potential drug interactions and influence of the pathological states. Stereoselective pharmacokinetics and metabolism are common features for chiral nonsteroidal antiinflammatory drugs (NSAIDs) and especially for 2-arylpropionic acid derivatives characterized with a chiral center adjacent to the carboxyl group. Although the enantioselective pharmacokinetic characteristics of different NSAIDs should be treated case by case, they share similar mechanisms underlying the protein binding, metabolism and chiral inversion. Ibuprofen was the most extensively researched drug in terms of chiral characteristics and mechanisms. Therefore, elucidation of the mechanisms derived from research on ibuprofen may provide better understanding and prediction of other chiral drugs. This article attempts to elucidate the chiral pharmacokinetics and involved mechanisms of ibuprofen in comparison with other NSAIDs based on recent developments. Topics on history of ibuprofen, enantioselective analysis method, absorption, protein binding, conventional metabolism, metabolic chiral inversion, gene polymorphism, and biochemical developments were included. It is worth mentioning that some underlying biochemical mechanisms, especially for the metabolic chiral inversion and ethnic differences still remain to be seen. Further research is required to develop human-resourced researching model and to provide more evidence concerning the site of inversion, species variation, CYP450 gene polymorphisms, and biochemical mechanisms.

Sequential injection affinity chromatography utilizing an albumin immobilized monolithic column to study drug–protein interactions

In this study, sequential injection affinity chromatography was used for drug-protein interactions studies. The analytical system used consisted of a sequential injection analysis (SIA) manifold directly connected with convective interaction media (CIM) monolithic epoxy disks modified by ligand-immobilization of protein. A non-steroidal, anti-inflammatory drug, naproxen (NAP) and bovine serum albumin (BSA) were selected as model drug and protein, respectively. The SIA system was used for sampling, introduction and propulsion of drug towards to the monolithic column. Association equilibrium constants, binding capacity at various temperatures and thermodynamic parameters (free energy DeltaG, enthalpy DeltaH) of the binding reaction of naproxen are calculated by using frontal analysis mathematics. The variation of incubation time and its effect in on-line binding mode was also studied. The results indicated that naproxen had an association equilibrium constant of 2.90 x 10(6)M(-1) at pH 7.4 and 39 degrees C for a single binding site. The associated change in enthalpy (DeltaH) was -27.36 kcal mol(-1) and the change in entropy (DeltaS) was -73 cal mol(-1)K(-1) for a single type of binding sites. The location of the binding region was examined by competitive binding experiments using a biphosphonate drug, alendronate (ALD), as a competitor agent. It was found that the two drugs occupy the same class of binding sites on BSA. All measurements were performed with fluorescence (lambda(ext)=230 nm, lambda(em)=350 nm) and spectrophotometric detection (lambda=280 nm).

Stereoselective binding of human serum albumin

Stereoselectivity in binding can have a significant effect on the drug disposition such as first-pass metabolism, metabolic clearance, renal clearance, and protein and tissue binding. Human serum albumin (HSA) is able to stereoselectively bind a great number of various endogenous and exogenous compounds. Various experimental data suggested that the two major drug-binding cavities, namely, site I and site II, do not seem to be the stereoselective binding sites of HSA. Stereoselective binding of HSA under disease conditions such as renal and hepatic diseases was found to be enhanced. In addition, site-to-site displacement of a site II-specific drug by another site II-specific drug was found to be stereoselective, too. Endogenous compounds such as long-chain fatty acids and uremic toxins are likely to cause combined direct and cascade effects that contribute to the preferential binding of a particular drug enantiomer. Taking together the findings of other studies, it is highly possible that the stereoselective binding site exists at the interface of the subdomains.

Dendrimers as potential drug carriers. Part II. Prolonged delivery of ketoprofen by in vitro and in vivo studies

Ketoprofen, a non-steroidal anti-inflammatory drug with well-known anti-inflammatory, antipyretic and analgesic properties, has low solubility in water and causes local or systemic disturbance in the gastrointestinal tract. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers as drug carriers of ketoprofen by in vitro and in vivo studies. The in vitro release of ketoprofen from the drug-dendrimer complex is significantly slower compared to pure ketoprofen. Anti-nociceptive studies using the acetic acid-induced writhing model in mice showed a prolonged pharmacodynamic behavior for the ketoprofen-PAMAM dendrimer complex. Also, the blood level studies were investigated. We concluded that PAMAM dendrimers might be considered as a potential drug carrier of ketoprofen with a sustained release behavior under suitable conditions.

Polyamidoamine dendrimers used as solubility enhancers of ketoprofen

Ketoprofen is a non-steroidal anti-inflammatory drug which is not freely soluble in water and creates gastrointestinal problems. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers to increase the solubility of ketoprofen. The effect of variables, such as pH condition, concentration and generation of dendrimer, has been investigated. The experimental results showed that the solubility of ketoprofen in the dendrimer solutions was proportional to dendrimer concentration. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of ketoprofen.

Dendrimers as potential drug carriers. Part I. Solubilization of non-steroidal anti-inflammatory drugs in the presence of polyamidoamine dendrimers

The aqueous solubility of non-steroidal anti-inflammatory drugs (NSAIDs) Ketoprofen, Ibuprofen, Diflunisal and Naproxen were measured in the presence of the ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers at 37 degrees C. The effect of concentration and generation of the PAMAM dendrimers has been investigated. Results showed that the solubility of NSAIDs in the PAMAM dendrimer solutions was approximately proportional to dendrimer concentration; the solubility of NSAIDs in higher generation PAMAM solutions was in fact higher that those in lower ones; the order of increased solubility of NSAIDs in PAMAM dendrimers at a constant dendrimer concentration and generation was Naproxen>Ketoprofen>Ibuprofen>Diflunisal. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of NSAIDs.

High performance capillary electrophoresis for determination of the enantiomers of 2-arylpropionic acid derivatives in human serum

A stereospecific capillary zone electrophoresis (CZE) method for determination of the enantiomers of some 2-arylpropionic acid derivatives (2-APA, profens) in human serum has been developed. Racemic-ibuprofen (rac-IBP), racemic-flurbiprofen (rac-FBP), racemic-ketoprofen (rac-KTP) and (+)-S-naproxen ((+)-S-NPX--an internal standard) were chosen for these studies. The 2-APA enantiomers were extracted from acidified serum samples using methylene chloride separated in a fused silica capillary. The capillary was filled with a background electrolyte, which consisted of 0.05 M heptakis 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbetaCD) (chiral selector) in 0.02 M triethanolamine-phosphate buffer of pH 5.0. Separation and resolution of the enantiomer mixture were obtained in one analytical run. The calculated electrophoretic parameters of the analytes were as follows: electrophoretic mobility, micorep(-)-R = -0.75 x 10(-4) to -0.30 x 10(-4) cm2/Vs; micorep(+)-S = -0.83 -(-0.38) cm2/Vs and electroosmotic mobility, microEOF = 2.35 x 10(-4) cm2/Vs, migration times, tmigr R = 12.55 - 16.07 min; tmigr s = 13.08 - 16.9 min, resolution factors, RS = 1.88 - 3.70 and chiral selectivity, alpha = 1.16 - 1.34. The method developed for the enantiomers was validated. The calibration curves were linear in the range of 0.5-50.0 microg/ml for FBP or KTP and of 1.0-50.0 microg/ml for IBP enantiomer concentrations. Recovery of the enantiomers from serum was about 90%. At the limit of quantification (LOQ) precision and accuracy were within 15%. The validated method was successfully applied to pharmacokinetic and bioavailability studies on KTP enantiomers in humans after administration of standard and sustained release tablets of rac-KTP. Significant differences in the pharmacokinetic parameters of both formulations were observed and the studied formulations were not bioequivalent.

Pharmaceutical-grade albumin: impaired drug-binding capacity in vitro

Background

Albumin is the most abundant protein in blood plasma, and due to its ligand binding properties, serves as a circulating depot for endogenous and exogenous (e.g. drugs) compounds. Hence, the unbound drug is the pharmacologically active drug. Commercial human albumin preparations are frequently used during surgery and in critically ill patients. Recent studies have indicated that the use of pharmaceutical-grade albumin is controversial in critically ill patients. In this in vitro study we investigated the drug binding properties of pharmaceutical-grade albumins (Baxter/Immuno, Octapharma, and Pharmacia & Upjohn), native human serum, and commercially available human serum albumin from Sigma Chemical Company.

Methods

The binding properties of the various albumin solutions were tested in vitro by means of ultrafiltration. Naproxen, warfarin, and digitoxin were used as ligands. HPLC was used to quantitate the total and free drug concentrations. The data were fitted to a model of two classes of binding sites for naproxen and warfarin and one class for digitoxin, using Microsoft Excel and Graphpad Prism.

Results

The drugs were highly bound to albumin (95–99.5%). The highest affinity (lowest K₁) was found with naproxen. Pharmaceutical-grade albumin solutions displayed significantly lower drug-binding capacity compared to native human serum and Sigma albumin. Thus, the free fraction was considerably higher, approximately 40 times for naproxen and 5 and 2 times for warfarin and digitoxin, respectively. The stabilisers caprylic acid and N-acetyl-DL-tryptophan used in the manufacturing procedure seem to be of importance. Adding the stabilisers to human serum and Sigma albumin reduced the binding affinity whereas charcoal treatment of the pharmaceutical-grade albumin from Octapharma almost restored the specific binding capacity.

Conclusion

This in vitro study demonstrates that the specific binding for warfarin and digitoxin is significantly reduced and for naproxen no longer detectable in pharmaceutical-grade albumin. It further shows that the addition of stabilisers may be of major importance for this effect.

Determination of ketoprofen enantiomers in human serum by capillary zone electrophoresis: man pharmacokinetic studies after administration of rac-ketoprofen tablets

A rapid and stereospecific capillary zone electrophoresis (CZE) method to quantify ketoprofen (KTP) enantiomers was developed. The KTP enantiomers and (+)-S-naproxen [(+)-S-NPX] as an internal standard (IS) were extracted with methylene chloride from serum acidified. Recovery of both enantiomers was in the range of 85-91%. The enantiomers were determined using a background electrolyte (BGE), consisting of 0.05 M heptakis 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbetaCD) in a phosphate-triethanolamine buffer, which filled a fused silica capillary of 75 micrometer i.d. The linear range of calibration curves was between 0.25 and 50 mg l(-1), with detection limit of 0.1 mg l(-1) (signal-to-noise baseline ratio (S/N) >4). Intra- and interday precision and accuracy of the calibration curves, expressed by the coefficient of variation (CV), did not exceed 15.0%. The validated method has been successfully applied for pharmacokinetic studies of KTP enantiomers from tablets with rac-KTP in man.

Influence of a polymeric formulation of ketoprofen on its diffusion into cerebrospinal fluid in rats

Poly(D,L)lactide nanocapsules (NCs) have been proposed as an alternative carrier for many drugs. We investigated the influence of this formulation on the pharmacokinetics of ketoprofen in the plasma and cerebrospinal fluid (CSF). Male Wistar rats were given intraperitoneal dose of ketoprofen (5 mg/kg) in a suspension of NCs or in a carboxymethylcellulose (CMC) solution (reference preparation). Blood and CSF samples were collected at different times up to 24 h after dosing. The unbound fraction of ketoprofen in plasma (f(u)) was determined using ultrafiltration. The total (C(T)) and free (C(F)) concentrations of ketoprofen in plasma and the simultaneous CSF concentrations (C(CSF)) were measured by a HPLC method and the areas under the curve (AUC(T), AUC(F), AUC(CSF)) were calculated. AUC(T) of ketoprofen-loaded NCs in plasma was similar to that of the reference solution, while AUC(F) of the former (5.41 mg/l x h) was higher than that produced by the latter (4.03 mg/l x h). Accordingly, the unbound fraction (f(u)) was higher after administration of NCs than that of the solution (2.5 and 1.8%, respectively). Finally, AUC(CSF) were identical for both formulations. These findings suggest that the binding of ketoprofen to plasma proteins is not the major factor that governs its blood-to-CSF exchanges.

In vitro distribution of ketoprofen enantiomers in articular tissues of osteoarthritic patients

The distribution of ketoprofen enantiomers in joint tissues was studied as a function of their relative tissular affinities using the multi-chamber distribution dialysis system described by Bickel et al. Selected off-cuts of synovial membrane, joint capsule, cartilage and ligament were obtained from ten patients suffering from osteoarthritis of the knee (n=3) or hip (n=7). Sörensen solution (4 ml) spiked with racemic ketoprofen (2 microg ml(-1)) was dialysed against 1 ml of the four solutions of tissue homogenates (0.4 g ml(-1)). Ketoprofen enantiomers were quantified in buffer and tissue solutions by high-performance liquid chromatography. The distribution of ketoprofen enantiomers in the Bickel's multi-compartment model indicated that there was a non-stereoselective affinity of ketoprofen enantiomers for their potential target tissues. Despite the interindividual variability in articular tissues, the concentrations (+/-S.D.) of R- and S-ketoprofen were significantly higher in synovial membrane (8.69 (4.76) microg g(-1) for S, 9.14 (5.57) microg g(-1) for R), joint capsule (5.71 (2.49) microg g(-1) for S, 5.49 (2.62) microg g(-1) for R) and ligament (6.28 (3.61) microg g(-1) for S, 6.40 (3.64) microg g(-1) for R) than in articular cartilage (3.67 (1.75) microg g(-1) for S, 3.70 (1.67) microg g(-1) for R). There were no significant differences in the distribution of R- and S-ketoprofen between the solutions of joint capsule, synovium and ligament tissues. These data may be related to differences in ketoprofen affinity for the different constituents of joints. This in vitro distribution profile is similar to that reported in vivo for other non-steroidal anti-inflammatory drugs.

Binding constant determination of drugs toward subdomain IIIA of human serum albumin by near-infrared dye-displacement capillary electrophoresis

Drug binding to serum albumin influences several important pharmacological properties such as toxicity, solubility, activity, distribution, and excretion. It is therefore of interest to have methodologies that allow for the determination of drug-albumin affinity constants while simultaneously providing information on the location of the drug binding site. In the present work we describe a method for the determination of binding constants of drugs known to bind to subdomain IIIA of serum albumin. Drugs used in the study were ketoprofen, ibuprofen, quinidine, naproxen, imipramine, and clofibrate. Binding constants of the drugs were determined by near-infrared dye-displacement capillary electrophoresis. The dye-displacement technique uses a competitive-type interaction between the drug of interest and a dye probe to arrive at a binding constant. A heptamethine cyanine dye was used as a probe for drug binding at subdomain IIIA of serum albumin. The utility of the dye as a noncovalent label for serum albumin was investigated. Additionally, the ability of the method to illustrate enantioselective binding is shown. The dye displacement technique has advantages over current electrophoresis-based techniques in that it is faster and uses less reagent.

Use of non-covalent labeling in illustrating ligand binding to human serum albumin via affinity capillary electrophoresis with near-infrared laser induced fluorescence detection

This paper demonstrates the use of a near-infrared (NIR) dye as a non-covalent label for human serum albumin (HSA). The dye is a water soluble, heptamethine cyanine dye. The utility of the dye as a tracer illustrating the binding of various drugs to HSA is demonstrated via affinity capillary electrophoresis with near-infrared laser-induced fluorescence detection (ACE-NIR-LIF). Additionally, the factors affecting the separation of relevant species were investigated. The change in quantum yield of the dye upon complexation with HSA was calculated. Spectrophotometric measurements were conducted to study the stoichiometry of the dye albumin complex.