Effect of valproic acid, its unsaturated metabolites and some structurally related fatty acids on the binding of warfarin and dansylsarcosine to human albumin

Pharmacokinetics and tissue distribution of N-(2-hydroxyphenyl)-2-propylpentanamide in Wistar Rats and its binding properties to human serum albumin

N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) is a novel valproic acid derivative that has shown anti-proliferative activity against epitheloid cervix carcinoma (HeLa), rhabdomyosarcoma (A204), and several breast cancer cell lines. The aim of this research was to evaluate the pharmacokinetic profile and tissue distribution of HO-AAVPA in Wistar rats, as well as its human serum albumin binding potential by experimental and in silico methods. A single dose of HO-AAVPA was given to male rats by intravenous, intragastric or intraperitoneal routes at doses of 25, 100, and 100 mg/kg, respectively. Then, blood samples were drawn at predetermined intervals of time, and the HO-AAVPA concentration in the plasma was quantified with a validated HPLC method. The elimination half-life (t1/2) was approximately 222 min, and the systemic clearance (CL) and apparent volume of distribution (Vd) were 2.20 mL/min/kg and 0.70 L/kg, respectively. The absolute oral bioavailability of HO-AAVPA was 33.8%, and the binding rate of HO-AAVPA with rat plasma proteins was between 66.2% and 83.0%. Additionally, in silico, UV and Raman spectroscopy data showed weak interactions between the test compound and human serum albumin. Thus, the results that were obtained demonstrated that despite its low oral bioavailability, the potential anticancer agent HO-AAVPA exhibits acceptable pharmacokinetic properties that would allow it to reach its site of action and exert its pharmacological effect in Wistar Rats, and it has a convenient profile for future assays to evaluate its human applications.

Cross-linked human serum albumin dimer has the potential for use as a plasma-retaining agent for the fatty acid-conjugated antidiabetic drugs

Objectives

The half-life of fatty acid-conjugated antidiabetic drugs are prolonged through binding to albumin, but this may not occur in diabetic patients with nephropathy complicated with hypoalbuminemia. We previously showed that human serum albumin (HSA) dimerized at the protein's Cys34 by 1,6-bis(maleimido)hexane has longer half-life than the monomer under high permeability conditions. The aim of this study was to investigate the superior ability of this HSA dimer as a plasma-retaining agent for fatty acid conjugated antidiabetic drugs.

Methods

The diabetic nephropathy rat model was prepared by administering a single injection of streptozotocin (STZ) intravenously, and the pharmacokinetic properties of HSA monomer and dimer were evaluated. Site-specific fluorescent probe displacement experiments were performed using warfarin and dansylsarcosine as site I and site II specific fluorescent probes, respectively.

Key findings

The half-life of the HSA dimer in STZ-induced diabetic nephropathy model rats was 1.5 times longer than the HSA monomer. The fluorescent probe displacement experiment results for HSA monomer and dimer were similar, where fatty acid-conjugated antidiabetic drugs displaced dansylsarcosine but not warfarin in a concentration-dependent manner.

Conclusions

The HSA dimer shows potential for use as a plasma-retaining agent for antidiabetic drugs due to its favourable pharmacokinetic properties.

Differential effects of methoxy group on the interaction of curcuminoids with two major ligand binding sites of human serum albumin

Curcuminoids are a group of compounds with a similar chemical backbone structure but containing different numbers of methoxy groups that have therapeutic potential due to their anti-inflammatory and anti-oxidant properties. They mainly bind to albumin in plasma. These findings influence their body disposition and biological activities. Spectroscopic analysis using site specific probes on human serum albumin (HSA) clearly indicated that curcumin (Cur), demethylcurcumin (Dmc) and bisdemethoxycurcumin (Bdmc) bind to both Site I (sub-site Ia and Ib) and Site II on HSA. At pH 7.4, the binding constants for Site I were relatively comparable between curcuminoids, while the binding constants for Site II at pH 7.4 were increased in order Cur < Dmc < Bdmc. Binding experiments using HSA mutants showed that Trp214 and Arg218 at Site I, and Tyr411 and Arg410 at Site II are involved in the binding of curcuminoids. The molecular docking of all curcuminoids to the Site I pocket showed that curcuminoids stacked with Phe211 and Trp214, and interacted with hydrophobic and aromatic amino acid residues. In contrast, each curcuminoid interacted with Site II in a different manner depending whether a methoxy group was present or absent. A detailed analysis of curcuminoids-albumin interactions would provide valuable information in terms of understanding the pharmacokinetics and the biological activities of this class of compounds.

Pharmacokinetics of Aripiprazole and Concomitant Lithium and Valproate

The objective of this study was to assess the pharmacokinetics of the antipsychotic aripiprazole when coadministered with lithium or valproate. Two open-label, sequential treatment design studies were conducted in chronically institutionalized patients with schizophrenia or schizoaffective disorder requiring treatment with lithium (n = 12) or valproate (divalproex sodium) (n = 10). Patients received aripiprazole 30 mg/day on days 1 to 14 and aripiprazole with concomitant therapy on days 15 to 36. Lithium was titrated from 900 mg until serum concentrations reached 1.0 to 1.4 mEq/L for at least 5 days. Valproate was titrated to 50 to 125 mg/L. Coadministration with lithium increased mean Cmax and AUC values of aripiprazole by about 19% and 15%, respectively, whereas the apparent oral clearance decreased by 15%. There was no effect on the steady-state pharmacokinetics of the active metabolite of aripiprazole. Coadministration with valproate decreased the AUC and Cmax of aripiprazole by 24% and 26%, respectively, with minimal effects on the active metabolite. Therapeutic doses of lithium and divalproex had no clinically significant effects on the pharmacokinetics of aripiprazole in patients with schizophrenia or schizoaffective disorder.

Treatments for late-life bipolar disorder

BACKGROUND

Bipolar affective disorder is not uncommon in the elderly; prevalence rates in the United States range from 0.1% to 0.4%. However, it accounts for 10% to 25% of all geriatric patients with mood disorders and 5% of patients admitted to geropsychiatric inpatient units. These patients often present a tremendous treatment challenge to clinicians. They frequently have differing treatment needs compared with their younger counterparts because of substantial medical comorbidity and age-related variations in response to therapy. Unfortunately, the management of geriatric bipolar disorder has been relatively neglected compared with the younger population. There continues to be a scarcity of published, controlled trials in the elderly, and no treatment algorithms specific to bipolar disorder in the elderly have been devised.

OBJECTIVE

The goal of this article was to review the current literature on both the pharmacologic and nonpharmacologic management of late-life bipolar disorder.

METHODS

English-language articles written on the treatment of bipolar disorder in the elderly were identified. The first step in data collection involved a search for evidence-based clinical practice guidelines in the Cochrane Database of Systematic Reviews (up until the third quarter of 2006). Systematic reviews were then located in the following databases: MEDLINE (1966-September 2006), EMBASE (1980-2006 [week 36]), and PsycINFO (1967-September 2006 [week 1]). Additional use was made of these 3 databases in searching for single randomized controlled trials, meta-analyses, cohort studies, case-control studies, case series, and case reports. "Elderly," used synonymously with "geriatric," was defined as individuals aged > or =60 years. However, to take into account ambiguity in the nomenclature, the key words aged, geriatric, elderly, and older were combined with words indicating pharmacologic treatments such as pharmacotherapy; classes of medications (eg, lithium, antidepressants, antipsychotics, anticonvulsants, benzodiazepines); and names of selected individual medications (eg, lithium, valproic acid, lamotrigine, carbamazepine, oxcarbazepine, topiramate, gabapentin, zonisamide, clozapine, risperidone, olanzapine, quetiapine, ziprasidone, aripiprazole). These terms were then combined with the diagnostic terms bipolar disorder, mania, hypomania, depression, or bipolar depression. Finally, the terms ECT and psychotherapy were also queried in combination with indicators for age and diagnosis. A few articles on "older adults," usually defined as individuals aged 50 to 55 years, were also included. They may allow for possible extrapolation of data to the geriatric population. Additionally, several mixed-age studies were included for similar considerations. Case reports and case series were described for their potential heuristic value.

RESULTS

Unfortunately, there is a considerable dearth of literature involving evidence-based clinical practice guidelines and even randomized controlled trials in elderly individuals with bipolar disorder. Available options for the treatment of bipolar disorder (including those for mania, hypomania, depression, or maintenance) in the elderly include lithium, antiepileptics, antipsychotics, benzodiazepines, antidepressants, electroconvulsive therapy (ECT), and psychotherapy.

CONCLUSIONS

The data for the treatment of late-life bipolar disorder are limited, but the available evidence shows efficacy for some commonly used treatments. Lithium, divalproex sodium, carbamazepine, lamotrigine, atypical antipsychotics, and antidepressants have all been found to be beneficial in the treatment of elderly patients with bipolar disorder. Although there are no specific guidelines for the treatment of these patients, monotherapy followed by combination therapy of the various classes of drugs may help with the resolution of symptoms. ECT and psychotherapy may be useful in the treatment of refractory disease. There is a need for more controlled studies in this age group before definitive treatment strategies can be enumerated.

Plasma protein binding of an antisense oligonucleotide targeting human ICAM-1 (ISIS 2302)

In vitro ultrafiltration was used to determine the plasma protein-binding characteristics of phosphorothioate oligonucleotides (PS ODNs). Although there are binding data on multiple PS ODNs presented here, the focus of this research is on the protein-binding characteristics of ISIS 2302, a PS ODN targeting human intercellular adhesion molecule-1 (ICAM-1) mRNA, which is currently in clinical trials for the treatment of ulcerative colitis. ISIS 2302 was shown to be highly bound (> 97%) across species (mouse, rat, monkey, human), with the mouse having the least degree of binding. ISIS 2302 was highly bound to albumin and, to a lesser, extent alpha2-macroglobulin and had negligible binding to alpha1-acid glycoprotein. Ten shortened ODN metabolites (8, 10, and 12-19 nucleotides [nt] in length, truncated from the 3' end) were evaluated in human plasma. The degree of binding was reduced as the ODN metabolite length decreased. Three additional 20-nt (20-mer) PS ODNs (ISIS 3521, ISIS 2503, and ISIS 5132) of varying sequence but similar chemistry were evaluated. Although the tested PS ODNs were highly bound to plasma proteins, suggesting a commonality within the chemical class, these results suggested that the protein-binding characteristics in human plasma may be sequence dependent. Lastly, drug displacement studies with ISIS 2302 and other concomitant drugs with known protein-binding properties were conducted to provide information on potential drug interactions. Coadministered ISIS 2302 and other high-binding drugs evaluated in this study did not displace one another at supraclinical plasma concentrations and, thus, are not anticipated to cause any pharmacokinetic interaction in the clinic as a result of the displacement of binding to plasma proteins.

Safety and tolerability of mood-stabilising anticonvulsants in the elderly

The authors review current research on the safety and tolerability of anticonvulsant medications used for individuals over the age of 60 years with affective disorders, agitation and other psychiatric disorders. Three anticonvulsants currently approved in the US for treatment of bipolar affective disorder are reviewed: valproate, lamotrigine and extended-release carbamazepine. The authors discuss the pharmacokinetics, pharmacodynamics, drug-drug interactions and the impact of ageing for each drug. There are few studies of anticonvulsant medications in elderly patients with bipolar disorder or other psychiatric conditions. Therefore, the authors summarise adverse events of greatest prevalence and/or greatest severity based on data derived predominately from studies of geriatric patients with epilepsy and/or other non-psychiatric indications. Guidelines are offered for the safe use of these medications in the elderly, based on research literature.

Managing Bipolar Disorder in the Elderly

Clinical research in geriatric psychopharmacology has been a relatively neglected focus compared with the wealth of information on younger populations, and there is a dearth of published, controlled trials. Similarly, these are limited data in the area of geriatric bipolar disorder. Although there is an absence of rigorous, evidence-based information, preliminary data on older adults with bipolar disorder suggest some promising treatment options and important differences in older versus younger patients with bipolar illness. Lithium, while widely utilised in younger populations, is often poorly tolerated in the elderly. Clinical evidence regarding use of antiepileptic compounds in late-life bipolar disorder is generally compiled from bipolar disorder studies in mixed populations, studies in older adults with seizure disorders, and studies on dementia and psychotic conditions other than bipolar disorder. Valproate semisodium and carbamazepine are widely prescribed compounds in older adults with bipolar disorder. However, the popularity of these compounds has occurred in context of an absence of evidence-based data. The atypical antipsychotics have expanded the treatment armamentarium for bipolar disorder in mixed populations and may offer particular promise in management of bipolar illness in older populations as well. Olanzapine, risperidone, quetiapine, ziprasidone and aripiprazole are atypical antipsychotics that have been approved by the US FDA for the treatment of bipolar disorder; however, there are no published, controlled trials with atypical antipsychotics specific to mania in geriatric patients. Preliminary reports on the use of clozapine, risperidone, olanzapine and quetiapine suggest a role for the use of these agents in late-life bipolar disorder. Information with ziprasidone and aripiprazole specific to geriatric bipolar disorder is still lacking.

The interaction of human serum albumin with a novel antidiabetic agent—SU-118

SU-118 is a newly synthesized antidiabetic agent and shows the best hypoglycemic effect among a series of analogs. Its binding properties and binding sites located on human serum albumin (HSA) have been studied using UV absorption and fluorescence spectroscopy. The results of spectroscopic study and the thermodynamic parameters obtained suggest that SU-118 binds to the hydrophobic cavity of human serum albumin and the hydrophobic interaction is the predominant intermolecular force stabilizing the complex. Fluorescent probe displacement studies show that SU-118 can displace competitively both dansylamide and dansylsarcosine from HSA. It is suggested that SU-118 can bind to both site I and site II, but the primary interaction may take place at site I. A binding constant of 1.4 x 10(4) M(-1) and a binding site of 2.0 are obtained from absorbance titration data. The value of binding constant is of the same order of magnitude as that from fluorescence titration. This study provides a molecular basis for elucidating the mechanism of drug acting and predicting unfavorable drug interaction.

Stereoselective kinetics of warfarin binding to human serum albumin: effect of an allosteric interaction

Kinetic and equilibrium binding studies were performed on the interaction of warfarin enantiomers with human serum albumin (HSA) in the absence and presence of lorazepam acetate (LoAc) enantiomers. Binding kinetics were followed by recording changes in the fluorescence of warfarin upon binding to HSA using the stopped-flow technique. The binding of (R)-warfarin displayed an exponentially increasing fluorescence, satisfying the two-step mechanism reported previously for the racemate, i.e., a diffusion controlled pre-equilibrium is followed by a slower rearrangement of the complex. In the case of (S)-warfarin, the signal was biphasic: a fast fluorescence enhancement was followed by a slow decline. The different kinetic features indicate that the equilibrium conformations of the [(S)-warfarin-HSA] and [(R)-warfarin-HSA] complexes are achieved via different mechanisms. The phenomenon was seen in buffers of different pH and compositions. Equilibrium binding measurements indicated significantly lower molar intrinsic fluorescence for the (S)-warfarin complex, suggesting differences in the microenvironments of the bound enantiomers. In the presence of (S)-LoAc, the allosterically enhanced binding of (S)-warfarin manifested itself in accelerated relaxation kinetics. In accordance with the low molar intrinsic fluorescence determined for the stable ternary complex, the amplitude of the decline in fluorescence became larger.

Flunitrazepam, a 7-nitro-1,4-benzodiazepine that is unable to bind to the indole-benzodiazepine site of human serum albumin

Benzodiazepine (BDZ) is generally thought to bind to site II of human serum albumin (HSA), also known as the indole-BDZ site, which is located at subdomain III A of the molecule. However, differences in the binding characteristics of BDZ drugs with HSA have been reported. The photolabeling profiles of HSA with [(3)H]flunitrazepam (FNZP) in the presence and absence of diazepam (DZP) were shown to be identical, suggesting that each drug primarily binds to different regions. The results of fluorescent probe displacement experiments showed that FNZP failed to decrease the fluorescence of dansylsarcosine to an extent similar to that of DZP. In the photoinhibition experiment, site I and site II ligands failed to inhibit the photoincorporation of [(3)H]FNZP to HSA. In order to evaluate the photolabeling specificity of FNZP, an attempt was made to photolabel alpha(1)-acid glycoprotein (AGP) which also binds BDZ with similar affinity as HSA. The effect of myristate (MYR) and DZP on the FNZP photolabeling of these two major drug binding plasma proteins was examined. Photoincorporation was inhibited when HSA was photolabeled with [(3)H]FNZP in the presence of MYR but not in the presence of DZP. Conversely, DZP inhibited the photolabeling of [(3)H]FNZP to AGP. These results suggest that FNZP interacts with HSA at regions which are not located in the preformed binding pocket of subdomain III A.

Spectroscopic analysis of the binding of amylobarbitone, secbutobarbitone, pentobarbitone, phenobarbitone and quinalbarbitone to human serum albumin

The binding of five barbiturates: amylobarbitone, secbutobarbitone, pentobarbitone, phenobarbitone and quinalbarbitone to human serum albumin (HSA) was studied by difference spectroscopy and spectrofluorimetric titrations. There were no changes in the HSA spectral properties. Our result suggest that there are two classes of binding sites on HSA for these barbiturates. A detailed investigation of the effect of their binding to HSA by deconvoluted spectra, suggests that the interaction of barbiturate-HSA takes place principally on the subdomain IIIA of HSA.

Binding of (+)- and (-)-isomers and racemate of etomoxir to human serum albumin and effect of stearic acid and stanozolol

Binding of (+)- and (-)-isomers and the racemate of sodium 2[6-(4-chlorophenoxy)-hexyl]-oxiran-2-carboxylate dihydrat (etomoxir) to the human serum albumin (HSA) was studied by the gel filtration method. The experimental results are presented graphically using the method of Scatchard. Measurements revealed the following data on the binding: (a) for either of the isomers there are two independent and nonequivalent classes of binding sites on the HSA molecule; (b) the binding constants calculated for both isomers were of the same order of magnitude (K1/n approximately 20 x 10(5) L.mol-1 for the concentration range 3.48-4.0 x 10(-5) mol.L-1, and K2/n approximately 2 x 10(5) L.mol-1 for the concentration range 4.28-10 x 10(-5) mol.L-1, for the high and low affinity binding sites, respectively); (c) statistically significant difference (p < or = 0.05) between the low affinity binding constant estimated for the (+)-isomer K2 = 1.9 +/- 0.1 x 10(5) L.mol-1) compared with the constants evaluated for the (-)-isomer and racemic etomoxir (2.6 +/- 0.1 and 2.9 +/- 0.2 x 10(5) L.mol-1, respectively); and (d) both isomers are bound into a high extent to the HSA molecule (i.e., at a ligand concentration of 3.48 x 10(-5) mol.L-1, the percent of binding was approximately 95% for the compound tested. When plotting the percent binding (% Cb) against the total concentration (Ctot), a statistically significant difference (p < or = 0.05) was obtained between the slope of the straight line for the (+)-isomer and those for other two compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of drug binding sites on mammalian albumins

The fluorescent probes warfarin and dansylsarcosine are known to selectively interact with binding sites I and II, respectively, on human albumin. This paper investigates whether similar binding sites exist on bovine, dog, horse, sheep and rat albumins. Binding sites on albumins were studied by: (1) displacement of warfarin and dansylsarcosine by site I (phenylbutazone) and site II (diazepam) selective ligands; (2) the effects of non-esterified fatty acids (carbon chain lengths: C5-C20) and changes in pH (6-9) on the fluorescence of warfarin and dansylsarcosine; and (3) the ability of site selective ligands to inhibit hydrolysis of 4-nitrophenyl acetate. For bovine, dog, horse, human and sheep albumins the fluorescence of bound warfarin and dansylsarcosine was selectively decreased by phenylbutazone and diazepam, respectively. For these albumins medium chain fatty acids (C1-C12) reduced the fluorescence of dansylsarcosine (maximum inhibition with C9) whereas long chain acids (C12-C20) enhanced the fluorescence of warfarin (maximum increases with C12). In addition, changes in pH from 6 to 9 increased the fluorescence of warfarin and although site I ligands (warfarin/phenylbutazone) had no pronounced effects on 4-nitrophenyl acetate hydrolysis, site II ligands (dansylsarcosine/diazepam) significantly inhibited this reaction. Rat albumin behaved differently from the other albumins studied in that the C12-C20 fatty acids and changes in pH did not enhance the fluorescence of warfarin. Moreover, the differential effects of site I and site II ligands on the fluorescence of warfarin/dansylsarcosine and hydrolysis of 4-nitrophenyl acetate were less apparent with rat albumin. The results suggest bovine, dog, horse and sheep albumins have binding sites for warfarin and dansylsarcosine with similar properties to sites I and II on human albumin. By contrast, the warfarin binding site and to a lesser degree the dansylsarcosine site, of rat albumin have different characteristics from these sites on the other albumins studied.