Novel inclusion complex of ibuprofen tromethamine with cyclodextrins: Physico-chemical characterization

Guest–host interactions of ibuprofen tromethamine salt (Ibu.T) with native and modified cyclodextrins (CyDs) have been investigated using several techniques, namely phase solubility diagrams (PSDs), proton nuclear magnetic resonance (¹H NMR), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffractometry (XRPD), scanning-electron microscopy (SEM) and molecular mechanics (MM). From the analysis of PSD data (A_L-type) it is concluded that the anionic tromethamine salt of ibuprofen (pK_a = 4.55) forms 1:1 soluble complexes with all CyDs investigated in buffered water at pH 7.0, while the neutral form of Ibu forms an insoluble complex with β-CyD (B_S-type) in buffered water at pH 2.0. Ibu.T has a lower tendency to complex with β-CyD (K₁₁ = 58 M⁻¹ at pH 7.0) compared with the neutral Ibu (K₁₁ = 4200 M⁻¹) in water. Complex formation of Ibu.T with β-CyD (ΔG° = −20.4 kJ/mol) is enthalpy driven (ΔH° = −22.9 kJ/mol) and is accompanied by a small unfavorable entropy (ΔS° = −8.4 J/mol K) change. ¹H NMR studies and MM computations revealed that, on complexation, the hydrophobic central benzene ring of Ibu.T and part of the isobutyl group reside within the β-CyD cavity leaving the peripheral groups (carboxylate, tromethamine and methyl groups) located near the hydroxyl group networks at either rim of β-CyD. PSD, ¹H NMR, DSC, FT-IR, XRPD, SEM and MM studies confirmed the formation of Ibu.T/β-CyD inclusion complex in solution and the solid state.     

Use of a nonlinear least-squares model for the kinetic determination of the stability constant of cyclodextrin inclusion complexes

The nonlinear least-squares model for the calculation of the stability constants (K_st) of drug:cyclodextrin complexes was used in kinetic studies. Complexation of riboflavin (R) with hydroxypropyl-β-cyclodextrin (HP:β-CD) was monitored kinetically by measuring the rate of photodegradation of R exposed to ultraviolet light in the presence of increasing concentrations of HP:β-CD. Formation of inclusion complex was confirmed in aqueous solution by proton nuclear magnetic resonance spectroscopy (¹H-NMR). The experimental K_st value (3321 M⁻¹), derived from the kinetic studies, appeared to fit well to a 1:1 drug: cyclodextrin molar ratio according to the nonlinear mathematical model. The model is particularly suitable for the study of cyclodextrin as a stabilizing system for compounds that are sensitive to light, oxygen, temperature or the media which contain them.     

Cyclodextrins as carriers for kavalactones in aqueous media: Spectroscopic characterization of (S)-7,8-dihydrokavain and β-cyclodextrin inclusion complex

Kavalactones represent the active constituents of kava–kava (Piper methysticum G. Forster), endowed with sedative and anaesthetic properties. Kavalactones are polar constituents, but poorly soluble in water with a low bioavailability. In this study, the formation of inclusion complexes of one of the most representative kavalactone isolated from kava–kava extract, (S)-7,8-dihydrokavain (DHK), with β-cyclodextrin (β-CyD) was investigated mainly by spectroscopic methods. NMR experiments were extensively used for the complete characterization of the complex and included ¹H NMR complexation shifts analysis, ¹H NMR diffusion measurements (DOSY), and ROESY experiments. In particular DOSY experiments demonstrated that in the presence of β-CyD the translational diffusion of kavalactone is sizably slowed down (2.5 × 10⁻¹⁰ m²/s) with respect to the free drug (4.4 × 10⁻¹⁰ m²/s) according to the inclusion of DHK in the cavity of (β-CyD). ROESY experiments confirmed the inclusion of DHK in the hydrophobic pocket of β-CyD through the primary hydroxyl rim, being the most relevant interactions between the H3′ of β-CyD and the ortho protons on the phenyl ring of the DHK, and between H5′ of β-CyD and the meta/para protons of DHK phenyl ring. The inclusion of the phenyl ring of DHK, leaving the lactone moiety outside of CyD was also confirmed by the induced CD effects. The binary solution DHK/β-CyD shows a 50% intensity increase of the negative band of the π–π* transitions of the phenyl ring with respect to the absorption observed with DHK alone. Molecular dynamics simulations results corroborated and further clarify observed spectroscopic data. It was found that the phenylethyl substituent at C6 has a preferential equatorial position in the free state, and an axial one in the complex, justifying the large downfield shift experienced by H6 of DHK upon binding. Finally the influence of β-CyD on water solubility of DHK was investigated by phase-solubility studies. In the range 2–4 mM of host, solubility of DHK was increased only two-fold, but being β-CyD also a penetration enhancer, in vivo studies will be performed to clarify a possible role of the complex on the bioavailability of DHK.     

Differential Effects of Modified β-Cyclodextrins on Pharmacological Activity and Bioavailability of 4-Biphenylacetic Acid in Rats after Oral Administration

Gastric tolerability, absorption and pharmacological activity of the non-steroidal anti-inflammatory drug 4-biphenylacetic acid (BPAA), as an inclusion complex with β-cyclodextrin (β-CyD) or chemically modified β-CyDs: 2,6-di-O-methyl-β-CyD (DM-β-CyD), 2,3,6-tri-O-methyl-β-CyD (TM-β-CyD) and 2-hydroxypropyl-β-CyD (HP-β-CyD), were investigated in the rat after oral administration. BPAA absorption, determined from area under the plasma concentration-time curve (AUC), was increased by complexation with all β-CyDs in the following order: DM-β-CyD > TM-β-CyD > HP-β-CyD > β-CyD. The carrageenan paw oedema test demonstrated a significant increase in anti-inflammatory activity of BPAA and the ED50 values, compared with BPAA alone, were reduced to about a third for the BPAA-DM-βCyD complex and halved for the others. BPAAA complexed with DM-β-CyD, HP-β-CyD or β-CyD showed better gastric tolerability compared with uncomplexed drug, whereas the BPAA-TM-β-CyD complex produced marked gastric lesions similar in extent to BPAA alone. TM-β-CyD (500mg kg^?1) and DM-β-CyD (1000mg kg^?1) caused gastric erosions 21 h after oral administration. The pharmacokinetic profiles of BPAA-β-CyD complexes have shown that DM-β-CyD is the most effective in enhancing the bioavailability of BPAA.     

Comparative Study on Inclusion Complexation of Maltosyl-β-cyclodextrin,Heptakis(2,6-di-O-methyl)-β-cyclodextrin and β-Cyclodextrin with Fucosterol in Aqueous and Solid State

Abstract— The complexation of fucosterol with three kinds of β-cyclodextrin (β-CyD) was investigated in aqueous solution and in the solid state. The solubility of fucosterol increased significantly on its complexation with maltosyl-β-CyD and heptakis(2,6-di-O-methyl)-β-CyD (DM-β-CyD), while no appreciable increase was observed when complexed with β-CyD. The stability constant of complexation with β-CyD estimated from solubility determinations was greater for a 1:2 complex than for a 1:1 complex. On the other hand, 1:1 complexation of fucosterol with maltosyl-β-CyD or DM-β-CyD was greater than 1:2 complexation. The solid complexes were obtained in molar ratios of 1:2 and 1:3 for β-CyD and maltosyl-β-CyD complexes, respectively. The inclusion behaviour of fucosterol with maltosyl-β-CyD was compared with β-CyD in the solid state using DSC, powder X-ray diffractometry and CP/MAS ¹³C NMR. Maltosyl-β-CyD showed different inclusion behaviour compared with β-CyD, and produced an amorphous structure of fucosterol on complex formation. The dissolution rate of fucosterol-maltosyl-β-CyD complex was significantly faster than other complexes due to its high aqueous solubility and amorphous structure.     

Inclusion complexation of metronidazole benzoate with β-cyclodextrin and its depression of anhydrate-hydrate transition in aqueous suspensions

Metronidazole benzoate was found to form an inclusion complex with β-cyelodextrin (β-CyD) in aqueous solution and in the solid phase. A phase solubility diagram was obtained and an apparent 1:1 formation complex constant of 1.3 × 10³ M^?1 was determined. A microcrystalline inclusion complex was isolated and shown to have the stoichiometric composition of 1:1.5 (drug: β-CyD). By inclusion complexation of the metronidazole ester with β-CyD the phase transition of the clinically used anhydrous form of the compound to the monohydrate occurring in aqueous suspensions was inhibited as was the marked crystal growth resulting from the phase transition. Besides increasing the physical stability of metronidazole benzoate suspensions the complexation with β-CyD protected the drug against photochemical degradation and decreased the rate of hydrolysis.     

Improvement of Solubility and Oral Bioavailability of Rutin by Complexation with 2-Hydroxypropyl-β-cyclodextrin

The object of this study was to enhance the solubility, dissolution rate, and oral bioavailability of rutin by complexation with 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD). The interaction of rutin with cyclodextrins (CyDs) was evaluated by the solubility, and ultraviolet (UV) and circular dichroism (CD) spectrophotometries. The chemical and enzymatic stability of rutin was examined in an alkaline buffer solution and in rat small intestinal homogenates, respectively. Dissolution rates of rutin and its CyD complexes were measured by the dispersed amount method. In vivo absorption studies of rutin after oral administration via conventional tablet containing rutin alone or its β-CyD complexes was performed on beagle dogs. The stability constants calculated from the phase solubility method increased in the order of HP-γ-CyD < G₂-β-CyD < β-CyD < HP-β-CyD. Spectroscopic studies also revealed that HP-β-CyD and β-CyD formed a relatively more stable inclusion complex with rutin. The dissolution rates of rutin increased by the complexation with CyDs in the order of rutin alone < HP-β-CyD ≤ β-CyD. HP-β-CyD inhibited the hydrolysis of rutin in the alkaline buffer solution and the small intestinal homogenates of rats, suggesting that HP-β-CyD may stabilize rutin in a gastrointestinal tract after oral administration. When the tablet containing rutin or its β-CyD complexes was administered to beagle dogs, the plasma levels of homovanillic acid (HVA) (a major stable metabolite of rutin) after oral administration of HP-β-CyD complex were much higher than in either that of rutin alone or in its β-CyD complex. The in vivo absorption study suggests that HP-β-CyD increased the oral bioavailability of rutin from the gastrointestinal tracts of beagle dogs because of the increase in solubility, faster dissolution rate, and gastrointestinal stability. HP-β-CyD has a significant advantage with respect to providing high aqueous solubility while maintaining a lack of toxicity in oral pharmaceutical preparations of rutin.     

Amorphous spironolactone-hydroxypropylated cyclodextrin complexes with superior dissolution and oral bioavailability

Inclusion complex formations of spironolactone (SP) with four cyclodextrins (parent β- and γ-CyDs and hydroxypropylated β- and γ-CyDs) in aqueous solution and in the solid state were investigated by the solubility method, spectroscopic methods, thermal analysis, powder X-ray diffractometry, and cross polarization/magic angle spinning ¹³C-nuclear magnetic resonance spectroscopy. Although the stability constant of the parent CyD complexes was larger than that of the corresponding hydroxypropylated CyD complexes, the solubilizing effect of hydroxypropyl CyDs was greater than that of parent CyDs. The solid complexes of SP were prepared by the spray-drying method in molar ratios of 1:2 and 2:3 (guest/host) with β-CyDs and γ-CyDs, respectively. The CyD complexes maintained an amorphous state for lengthy time periods (over 2 months at 75% relative humidity and 60°C), with the exception of the β-CyD complex which was converted to a crystalline complex after 1 month storage. The dissolution rate of hydroxypropyl CyD complexes was much faster than that of the parent CyD complexes, the rate being in the order of hydroxypropyl-β-CyD ⪢ hydroxypropyl-γ-CyD > γ-CyD > β-CyD > metastable SP forms > stable SP form. Plasma levels of canrenone, a major effective metabolite of SP, were monitored to estimate the absorption-enhancing effect of hydroxypropyl CyDs. The area under the plasma concentration-time curve after oral administration of the hydroxypropyl-β-CyD complex in dogs was 3.6 times that of SP alone, and this enhancement was higher than those of the parent CyD complexes reported previously (Seo, H., Tsuruoka, M., Hashimoto, T., Fujinaga, T., Otagiri, M. and Uekama, K., Enhancement of oral bioavailability of spironolactone by β- and γ-cyclodextrin complexations. Chem. Pharm. Bull., 31 (1983) 286–291).     

抗癌药物马蔺子素的β-环糊精包络物研究

目的研究抗癌药物马蔺子素与β-环糊精的主-客体包络行为。方法在悬汞电极上用循环伏安法考察β-环糊精不存在和存在时马蔺子素还原波的变化。结果在0.04 mol·L^-1 KH₂PO₄-Na₂HPO₄ (pH 6.8)近生理介质中,β-环糊精的引入使马蔺子素的还原波峰电流降低,峰电位正移。结论电活性客体分子马蔺子素与主体分子β-环糊精生成1∶1的包络物。用“电流法”测得其形成常数K_f值为1.92×10³ L·mol^-1。包络物的生成增强了马蔺子素的稳定性。     

Immunoliposomes Directed Toward VCAM-1 Interact Specifically with Activated Endothelial Cells—A Potential Tool for Specific Drug Delivery

Purpose Immunoliposomes can be potentially used as carriers for drug delivery to specific cells. The aim of this paper was to exploit the overexpression of vascular cell adhesion molecule-1 (VCAM-1) on activated human endothelial cells (HEC) for targeting of anti-VCAM-1 coupled liposomes with the intent for further use as drug carriers. Methods TNF-α-activated HEC were exposed to liposomes, either plain or coupled with antibodies to VCAM-1 (L-VCAM-1) or to irrelevant IgG (L-IgG); nonactivated HEC subjected to the same conditions were used as control. For binding studies, the cells were incubated with fluorescently labeled liposomes at 4°C, and after 2 h, fluorescence intensity was assessed by flow cytometry; specificity of binding was determined by performing the experiments in the presence of excess anti-VCAM-1. Cellular internalization of liposomes was studied employing radioactively or fluorescently labelled liposomes; to detect the mechanisms of uptake, experiments were performed in the presence of agents that interfere in the endocytotic pathway. Transmigration of liposomes was monitored in a two-chamber culture model. The effect of L-VCAM-1 binding to HEC on intracellular calcium ([Ca²⁺]_i) and distribution of actin was determined by fluorimetry and fluorescence microscopy. Results (1) L-VCAM-1 binds selectively and specifically to TNF-α activated HEC. (2) Approximately 50% of L-VCAM-1 is taken up by receptor-mediated endocytosis via clathrin-coated vesicles. (3) Binding of L-VCAM-1 to HEC surface induces a rise in [Ca²⁺]_i and reorganization of actin filaments. (4) A small percentage of liposomes migrates across HEC. Conclusion The data indicate that VCAM-1 may be an appropriate target for specific drug delivery to activated HEC using immunoliposomes.     

Influence of γ-aminobutyric acid on baclofen intestinal absorption

Since previous studies suggested that baclofen absorption in the rat middle intestine was inhibited by β-alanine and therefore mediated, at least in part, by the β-aminoacid carrier, we focused our new studies on the analysis of the possible inhibition of the drug by a γ-aminoacid model compound, γ-aminobutyric acid (GABA). A rat jejunum in situ study was undertaken in order to evaluate the effect of GABA on baclofen absorption and to establish the inhibition model. Assays using isotonic perfusion solutions of 0.5 mM baclofen with starting GABA concentrations ranging from 0 to 100 mM are reported. The results show that the absorption rate pseudoconstants of the drug decrease as the GABA concentration increases, with a limiting value of 0.65 h^?1 (±0.01). A partial competitive inhibition or complete competitive inhibition in the presence of a passive component could define the interaction phenomena between the two substances. Kinetic absorption parameters for GABA in the presence and absence of baclofen (K_i = 5.67 ± 1.54, K_m = 3.87 ± 0.63) suggest the existence of more than one intestinal carrier system for baclofen or GABA.     

Effect of cyclodextrins on the solubility and stability of candesartan cilexetil in solution and solid state

Guest-host interactions of candesartan cilexetil (CAND) with cyclodextrins (CyDs) have been investigated using phase solubility diagrams (PSD), X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC) and molecular mechanical modelling (MM). Estimates of the complex formation constant (K(11)) show that the tendency of CAND (pK(a)=6.0) to complex with CyDs follows the order: β-CyD>HP-β-CyD>γ-CyD>α-CyD. Complex formation of CAND with β-CyD (ΔG°=-31.5 kJ/mol) is largely driven by enthalpy change (ΔH°=-32.8 kJ/mol) and slightly retarded by entropy change (ΔS°=-4.6J/mol K). The HPLC results indicate that complex prepared by freeze drying method is chemically not stable due to the formation of amorphous CAND. Also it may suggest formulating CAND with β-CyD by kneading (dispersion) or co-evaporation (real inclusion complex) methods into capsule rather than compressed in tablets, where the compression enhances the instability of CAND. DSC thermograms for CAND/β-CyD complexes proved the formation of inclusion complexes with new solid phase. MM studies indicate the partial penetration of CAND into the β-CyD cavity.     

Inclusion complex of a new propiconazole derivative with β-cyclodextrin: NMR, ESI–MS and preliminary pharmacological studies

A novel inclusion complex of the propiconazole nitrate (NO₃PCZ) with β-cyclodextrin (β-CD) was prepared by treatment of propiconazole (PCZ) with an acidic nitrating agent. The formation of NO₃PCZ and its inclusion complex with β-CD has been studied by NMR, ESI–MS, TGA, DSC methods. Using the undecoupled signal in the HMBC correlation spectra, almost identical coupling constants of CH from trizolic ring of PCZ and NO₃PCZ compounds (¹J(HC)3=207 Hz, ¹J(CH)5=214 Hz, for PCZ; ¹J(HC)3=208 Hz and ¹J(CH)5=215 Hz, for NO₃PCZ) were determined, confirming that the geometry of the heterocyclic skeleton is identical in both the forms. The 1:1 stoichiometry of the complex was determined by ESI–MS and was confirmed using Scott's equation in DMSO and Higuchi and Connors equation in water. The solubility curve obtained for NO₃PCZ in presence of β-CD in distilled water was constructed, resulting in a solubility diagram of AL type. Solubility of NO₃PCZ in water was determined by DLS studies. The results showed that NO₃PCZ was encapsulated within the β-CD cavity with a binding constant of 330 M-1 in DMSO and 975 M-1 in water. Preliminary pharmacological studies showed higher antifungal activities for NO₃PCZ and its inclusion complex, compared with its PCZ analog. The acute toxicity of the complex is smaller than the pure or modified drug, recommending the inclusion complex as future promising therapeutic agents.     

Combination effects of O-carboxymethyl-O-ethyl-β-cyclodextrin and penetration enhancer HPE-101 on transdermal delivery of prostaglandin E1 in hairless mice

An inclusion complex of prostaglandin E₁ (PGE₁) with β-cyclodextrin (β-Cyd) or O-carboxymethyl-O-ethyl-β-cyclodextrin (CME-β-CyD) was made as topical preparations in a fatty alcohol/propylene glycol ointment base. When the PGE₁ preparations were applied onto the skin of hairless mice, the vasodilating effect of the PGE₁-CME-β-CyD complex supplemented with a penetration enhancer, 1-[2-(decylthio)ethyl] azacyclopentane-2-one (HPE-101) was approximately 100 times that of the PGE₁ alone and approximately 10 times that of PGE₁ with HPE-101 or the PGE₁-β-CyD complex with HPE-101. The combination of CME-β-CyD and HPE-101 enhanced the percutaneous penetration of PGE₁ in a synergistic manner; CME-β-CyD assisted the release of HPE-101 from the ointment base and its entry into the skin which may facilitate the percutaneous penetration of PGE₁. Furthermore, this combination suppressed the bioconversion of PGE₁ to give less pharmacologically active metabolites during the passage through the skin, a situation delivering intact PGE₁ more effectively to the site of action. The present data suggest that the combination of CME-β-CyD and HPE-101 is particularly useful for improving topical bioavailability of PGE₁.     

Interaction studies of a novel Co(II)-based potential chemotherapeutic agent with human serum albumin (HSA) employing biophysical techniques

Novel macrocyclic cobalt(II) complex C₃₆H₂₄N₈O₄S₄CoCl₂ with a butterfly topology was synthesized and characterized by spectroscopic (IR, ¹H, ¹³C NMR, EPR, UV-Vis, ESI-MS) and analytical methods. The complex exhibits distorted octahedral geometry around Co(II) metal ion, which was confirmed by EPR measurements with g_a, g_b, and g_c values (8.01, 2.20, and 1.66), respectively, and molar extinction coefficient ε = 58 M⁻¹cm⁻¹. The Interaction studies with human serum albumin (HSA) in phosphate buffer (0.1 M, pH 7.0) were studied by electronic absorption titration, fluorescence titration, circular dichroism, and cyclic voltammetry. Hyperchromism in fluorescence intensity indicates binding of complex with HSA near tryptophan residue in IIA subdomain leading to less polar microenvironment around tryptophan and more at tyrosine. The intrinsic binding constant K _b obtained from absorption spectral titrations was found to be 9.3 × 10⁴ M⁻¹, suggesting medium binding affinity of HSA with complex. CD spectrum indicates α-helical structure up to β-pleated secondary structure. CV data confirmed medium reversible binding with HSA. The binding of complex with HSA shows typical reversible mode of binding, which enables the delivery of drug candidate to the tissue enzymes and receptors in an efficient manner, and thereby affects the uptake of the drug.     

Modified β-Cyclodextrin (SBE7-β-CyD) with Viscous Vehicle Improves the Ocular Delivery and Tolerability of Pilocarpine Prodrug in Rabbits

The complexation of pilocarpine prodrug, O,O'-dipropionyl-(1,4-xylylene) bispilocarpate, with various β-cyclodextrin (β-CyD) derivatives was studied by the phase solubility method. The effects of coadministered sulphobutyl ether β-CyD (SBE7-β-CyD) with and without poly(vinyl alcohol) (PVA) on the miotic response and eye irritation of the prodrug were investigated in pigmented rabbits. The pilocarpine prodrug formed 1:1 inclusion complexes with variably substituted sulphobutyl ether derivatives of β-CyD (SBE4-β-CyD and SBE7-β-CyD), and 1:1 and 1:2 complexes with hydroxypropyl-β-CyD (HP-β-CyD) at pH 7:4. Coadministered SBE7-β-CyD eliminated the eye irritation due to the pilocarpine prodrug, but also decreased the miotic response. Ocular absorption of the prodrug was improved by increasing the viscosity of prodrug/SBE7-β-CyD solution with PVA without inducing any eye irritation. Eye irritation due to viscous prodrug/SBE7-β-CyD solutions was comparable with isotonic NaCl solution. We conclude that administration of pilocarpine prodrug in viscous SBE7-β-CyD solution decreases substantially eye irritation while ocular absorption is not affected.     

Effect of 2-Hydroxypropyl-β-cyclodextrin on Percutaneous Absorption of Methyl Paraben

A potential use of 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) to solubilize methyl paraben and to suppress its percutaneous absorption was examined, and compared with nonionic surfactant HCO-60. HP-β-CyD significantly increased the solubility of methyl paraben in water, where the apparent 1:1 stability constant of the soluble complex was determined to be 2150 M^?1. The in-vitro cutaneous permeability of methyl paraben through an isolated skin of hairless mouse was suppressed by HP-β-CyD, thus promoting the bioconversion of methyl paraben to the less toxic metabolite, p-hydroxybenzoic acid (p-HBA) in the epidermis. These effects of HP-β-CyD were greater than those of HCO-60. HP-β-CyD (2% w/v) reduced the in-vivo percutaneous absorption of methyl paraben by 66% 24 h after the topical application of a solution containing [¹⁴C]methyl paraben to hairless mouse skin. Additionally, the percutaneous absorption of [¹⁴C]HP-β-CyD was confirmed to be extremely low. These results suggest that HP-β-CyD is useful in liquid preparations of methyl paraben for topical application.     

Population pharmacokinetics of phenytoin in Singapore Chinese

Summary The pharmacokinetics of phenytoin was studied in 66 epileptic Chinese children and adults. The data were analysed by the population approach, using the non-linear mixed effect model, in the MULTI (ELS) program. There was no age or gender-related effect on either the apparent maximum elimination rate (k_max) or Michaelis-Menten constant (K_M). K_max was related to body weight 0.656. The population pharmacokinetics was similar in children and adults. K_max and K_M were estimated to be 30.72 mg·kg^–0.656 day^–1 and 2.307 mg·l^–1, respectively. K_max was higher than reported values, and K_M was comparable to that reported in a study in Japanese, but was much lower than that reported in studies of European patients. The inter-individual variability of K_M (CV 65.58%) was substantially higher than that of k_max (CV 28.49%), and the residual (intra-individual) variability was found 21.33% (CV).     

Stabilization of isosorbide 5-mononitrate in solid state by β-cyclodextrin complexation

Inclusion complexation of isosorbide 5-mononitrate (5-ISMN) with β-cyclodextrin (β-CyD) was investigated by the solubility method, X-ray diffractometry and thermal analysis. An analysis of the phase solubility diagram indicates that the stoichiometry for the complex of 5-ISMN with β-CyD is 1:1 in the solid state. The volatility of 5-ISMN and the whisker-growth from tablet or powder were significantly retarded by the binding to β-CyD. In addition, the degradation of 5-ISMN stored at 60°C and 75% relative humidity was remarkably inhibited by the β-CyD complexation. The improvement of physicochemical properties of 5-ISMN by β-CyD complexation in the solid state may solve problems encountered by the storage.     

Synthesis and receptor binding analysis of dermorphin hepta-, hexa- and pentapeptide analogues

Sixteen dermorphin analogues were synthesized and characterized for μ- and δ-opioid receptor binding properties using [³H]DAGO and [³H]DPDPE, respectively. The analogues included the following: substitutions at position 4 and/or the C-terminal residue; deletions of Gly⁴ or Pro⁶-Ser⁷; inclusion of Z or an acetyl group on the β-amino group of Lys⁷; and the presence of either a C-terminal amide or free acid group. Two peptides, [Lys7-OH]- and [Lys⁷-NH₂]dermorphin, had μ-affinities (K_iμ= 0.15–0.13 nm ) and μ-selectivities (K_iδ/K_iμ= 1158–1482) higher than dermorphin (K_iμ= 0.28 nm ; K_iδ/K_iμ= 295) and best fitted a one-site binding model similar to dermorphin. Significantly better (P <0.0001) fits to a two-site binding model vs. a one-site model were observed with four dermorphin analogues: [Lys(Z)⁷-OH]heptapeptide, [des-Gly⁴(Tyr⁴,Pro⁵,Asn⁶-OH)]hexapeptide and two pentapeptides, [Tyr⁵-NH₂] and [Trp⁴,Asn⁵-OH]. Our data revealed a complex binding pattern for dermorphin analogues to brain μ-receptors in which Hill coefficients less than 0.85 generally suggest heterogeneity of μ-receptors; however, only detailed analyses of the data derived from the non-linear regression fits for one- or two-components gave evidence for the possible existence of two separate [³H]DAGO binding sites. Eight of our dermorphin analogues had significantly better fits for a two-site model (P <0.05), but only four seemed to have two distinct Kⁱ, values (P <0.0001).