Micelle formation by some phenothiazine derivatives. II. Nuclear magnetic resonance studies in deuterium oxide

Nortriptyline Hydrochloride Solubility-pH Profiles in a Saline Phosphate Buffer: Drug-Phosphate Complexes and Multiple pHmax Domains with a Gibbs Phase Rule "Soft" Constraints

The solubility of a model basic drug, nortriptyline (Nor), was investigated as a function of pH in phosphate and/or a chloride-containing aqueous suspension using experimental practices recommended in the previously published "white paper" (Avdeef et al., 2016). The pH-Ramp Shake-Flask (pH-RSF) method, introduced in our earlier work (Marković et al., 2019), was applied. An improved and more detailed experimental design of the Nor solubility measurement allowed us to exploit the full capacity of the pH-RSF method. Complex equilibria in the aqueous phase (cationic and anionic complex formation between Nor and the phosphate) and solid-phase transformations (Nor free base, 1:1 Nor hydrochloride salt, 1:1 and 1:2 Nor phosphate salts) were characterized by a detailed analysis of the solubility measurements using the computer program pDISOL-X. The solid phases were characterized by thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, and elemental analyses. The results of the present investigation illustrate the influence of competing counterions, such as buffering agents, complexing agents, salt coformers, tonicity adjusters, and so forth, on the aqueous solubility of drugs and interconversion of salts. Careful attention given to these factors can be helpful in the formulation of drug products.

Antipsychotic phenothiazine drugs bind to KRAS in vitro

We used NMR to show that the antipsychotic phenothiazine drugs promazine and promethazine bind to GDP-KRAS. Promazine also binds to oncogenic GDP-KRAS(G12D), and to wild type GppNHp-KRAS. A panel of additional phenothiazines bind to GDP-KRAS but with lower affinity than promazine or promethazine. Binding is most dependent on substitutions at C-2 of the tricyclic phenothiazine ring. Promazine was used to generate an NMR-driven HADDOCK model of the drug/GDP-KRAS complex. The structural model shows the tricyclic phenothiazine ring of promazine associates with the hydrophobic pocket p1 that is bordered by the central β sheet and Switch II in KRAS. Binding appears to stabilize helix 2 in a conformation that is similar to that seen in KRAS bound to other small molecules. Association of phenothiazines with KRAS may affect normal KRAS signaling that could contribute to multiple biological activities of these antipsychotic drugs. Moreover, the phenothiazine ring represents a new core scaffold on which to design modulators of KRAS activity.

Interactions of phenothiazine drugs with surfactants: a detailed physicochemical overview

Phenothiazine drugs have been the subject of great interest due to their interesting aggregation properties and ability to interact with surfactants, model lipid bilayers, and biomembranes. Since these drugs show enormous pharmacological actions and deposits on the biomembranes, their pharmacological activities seem to be related to the drug-membrane interactions or to the absorbability on the membrane. Further, the mechanisms for the various biological activities of phenothiazines can be explained by exploring these drug-membrane interactions. Keeping these points in view, many researchers have investigated the interactions of these drugs with surfactants. This review describes the physicochemical aspects of the interactions between phenothiazine drugs and surfactants which have been discussed under three sections: (i) micellar and interfacial studies, (ii) spectroscopic studies, (iii) phase separation studies (CP) and (iv) miscellaneous.

Interactions of phenothiazine drugs with bile salts: micellization and binding studies

An evaluation of the interactions of phenothiazine tranquilizer drugs (promazine hydrochloride; PMZ and promethazine hydrochloride; PMT) with bile salts viz., sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous medium, investigated through different physicochemical measurements is presented in this work. The mixed micellization behavior and surface properties of the phenothiazine-bile salt systems have been analyzed by conductivity and surface tension measurements. Application of different theoretical approaches to all the phenothiazine-bile salt mixtures shows a non-ideal behavior. Further, the spectroscopic techniques such as UV-visible and steady state fluorescence have been employed to study the binding of phenothiazines with bile salts. The stoichiometric ratios, binding constants (K), and free energy change (ΔG) for the phenothiazine-bile salt complexes were estimated from the Benesi-Hildebrand (B-H) double reciprocal plots obtained by using the changes in spectral intensities of phenothiazines on addition of bile salts. The results are discussed in the light of use of bile salts as promising drug delivery agents for phenothiazines and hence improve their bioavailabilty.

Effects of calcium ions on solubility and aggregation behavior of an anionic sulfonate gemini surfactant in aqueous solutions

Effects of calcium ions on the solubility and aggregation behavior of an anionic sulfonate gemini surfactant 1,3-bis(N-dodecyl-N-propylsulfonate sodium)-propane (12-3-12(SO(3))(2)) have been studied in aqueous solution. Compared with single-chain surfactant sodium dodecylsulfate, 12-3-12(SO(3))(2) shows much better performance to the hardness tolerance with calcium ions. Moreover aggregates of the Ca(2+)/12-3-12(SO(3))(2) complexes in clear solutions influence the morphologies of the precipitates. At 12-3-12(SO(3))(2) concentrations lower than 1.5 mM, the small spherical micelles of Ca(2+)/12-3-12(SO(3))(2) in clear solutions generate precipitates of solid particles owing to complexation of surfactant monomers with Ca(2+). At 12-3-12(SO(3))(2) concentrations higher than 1.5mM, the Ca(2+)/12-3-12(SO(3))(2) complexes transform into large compact spherical aggregates and then into long wormlike micelles. These large aggregates are well dispersed in aqueous solutions and efficiently complex calcium ions. In particular, long wormlike micelles are entangled with each other at 100.0 mM CaCl(2) and 100.0 mM 12-3-12(SO(3))(2) exhibiting viscoelastic properties. In addition, the stacking of long wormlike micelles produces precipitates with ordered fibrillar structures. This work reveals that such anionic sulfonate gemini surfactants are better candidates than single-chain surfactants in applications with high hardness levels, and the ordered aggregate structures may have potential applications in materials science.

Nanoparticles in plant extracts: influence of drugs on the formation of nanoparticles and precipitates in black tea infusions

The influence of the neuroleptics fluphenazine and promethazine on the formation of nanoparticles in aqueous tea infusions was investigated using photon correlation spectroscopy. Formation of nanoparticles and of precipitates was observed in decaffeinated tea and caffeine-containing tea. The amount of drug in the nanoparticle fraction was determined at different starting concentrations using high-performance liquid chromatography. In the case of fluphenazine, between 8 and 30% are assigned to the nanoparticles fraction, in the case of promethazine between 30 and 56%. The concentration of free active principle is reduced by about 99% for fluphenazine or by about 90% for promethazine. A loss of pharmacological activity of the neuroleptics is probable. The addition of promethazine to infusions of caffeine containing tea resulted in the formation of nanoparticles with a small size distribution; their mean size was comparable to the diameter of nanoparticles in pure tea infusions. In the case of fluphenazine the mean particle size grew with increasing concentration. Adding promethazine to infusions of decaffeinated tea resulted in the formation of nanoparticles with a broad size distribution. Two different size classes were formed after addition of fluphenazine. Caffeine and neuroleptics both take part in the formation of nanoparticles in caffeine containing tea. The particles were visualized using scanning electron microscopy. Molecular modelling calculations were performed to investigate probable geometries between neuroleptics and thearubigins.

Self-association and solubility behaviors of a novel anticancer agent, brequinar sodium

To aid in the selection of appropriate excipients to formulate brequinar sodium [6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinolinecarboxyli c acid sodium salt; DuP 785], studies were initiated to characterize thoroughly its solubility behavior. The measured solubilities at RT (approximately 23 degrees C) agreed with the theoretical values in the pH range from 0.5 to 7.2, but became significantly greater than theoretical values at pH values above 7.2. This deviation was likely due to the vertical stacking-type self-association between brequinar molecules in water. The NMR and pH methods determined a critical association concentration of 15 mg/mL. Sodium salicylate, which has been proven to interfere with molecular self-association, reduced drug solubility from 116 to 10 mg/mL. But urea, another deaggregative agent, gave about a twofold increase rather than a decrease in solubility. Addition of sodium chloride caused a 226-fold decrease in solubility. The apparent solubility product did not remain constant but decreased as sodium chloride concentration increased, suggesting that the added salt decreased the degree of self-association between brequinar molecules. Among four surfactants examined (a bile salt with a rigid fused ring versus three ordinary surfactants with a flexible chain structure), only sodium cholate significantly increased the aqueous solubility of brequinar sodium.

Photon correlation spectroscopy of surface active cationic drugs

Photon correlation spectroscopy (PCS) has been used to examine the aggregation in aqueous NaCl solution of a series of antidepressant and antihistamine drugs (hydrochlorides of imipramine, clomipramine, amitriptyline, butriptyline, protriptyline, doxepin, dothiepin, iprindole, diphenhydramine, bromodiphenhydramine, orphenadrine) propranolol hydrochloride and propantheline bromide. Critical micelle concentrations were measured by surface tension and PCS. Micellar sizes were investigated as functions of drug structure and drug and NaCl concentration. Generally, antidepressants formed the largest micelles. We propose that the antidepressants aggregate in a similar fashion to the phenothiazines by stacking with size increasing by addition of single monomers to stacks and by addition of more stacks to the aggregate.

Cmc of mixtures of chlorpromazine hydrochloride and polysorbate 80 determined by pH measurements

The cmc of mixtures of chlorpromazine hydrochloride and polysorbate 80 was determined by pH titration. The values thus obtained coincided with those determined by the surface tension method. The mixtures studied could be divided into two groups according to the shape of their pH concentration curves. For mixtures containing less than 0.8 mole fraction chlorpromazine, the curves suggest that some interaction occurs in the premicellar concentration range. For mixtures containing more than 0.8 mole fraction chlorpromazine, the curves suggest that the micellar process occurs in more than one step.

The effect of drug concentration on the thermal (dark) degradation of promethazin hydrochloride in aqueous solution

The thermal (dark) degradation of promethazine hydrochloride in aqueous solution presents a complex kinetic picture. The process is oxygen dependent and is modified by EDTA. In citrate buffer, pH 4.0, ionic strength 0.5M, containing 0.1% EDTA, the thermal degradation at 90 degrees can be fitted to first order rate plots at drug concentrations up to 1.56 x 10.27 (0.5%) and to zero order rate plots at drug concentrations greater than 9.35 x 10.2M (3.0%). At intermediate concentrations no simple equation can describe the data. These effects have been correlated with the formation of drug micelles and the rate date have been interpreted on the basis of a first order monomer process and a half order micellar process occurring simultaneously.

Aggregation of antihistamines in aqueous solution: micellar properties of some diphenylmethane derivatives

The micellar properties of the antihistamine drugs, diphenhydramine hydrochloride, bromodiphenhydramine hydrochloride, chlorcyclizine hydrochloride and diphenylpyraline hydrochloride, have been studied in aqueous solution. The zeta potentials of the micelles were calculated from their electrophoretic mobilities as determined by a dye-tracer technique. Estimates of the degree of ionization of the micelles using a combination of conductivity and electrophoresis data were in reasonable agreement with values previously determined by light scattering. The extent of micellar hydration has been calculated from viscosity data. The hydrophobic and electrical contributions to the free energy of micellization have been calculated and related to the chemical structure.