Enhanced chartreusin solubility by hydroxybenzoate hydrotropy

Role of Hydrotropes in Sparingly Soluble Drug Solubilization: Insight from a Molecular Dynamics Simulation and Experimental Perspectives

Drug molecules' therapeutic efficacy depends on their bioavailability and solubility. But more than 70% of the formulated drug molecules show limited effectiveness due to low water solubility. Thus, the water solubility enhancement technique of drug molecules becomes the need of time. One such way is hydrotropy. The solubilizing agent of a hydrophobic molecule is generally referred to as a hydrotrope, and this phenomenon is termed hydrotropy. This method has high industrial demand, as hydrotropes are noninflammable, readily available, environmentally friendly, quickly recovered, cost-effective, and not involved in solid emulsification. The endless importance of hydrotropes in industry (especially in the pharmaceutical industry) motivated us to prepare a feature article with a clear introduction, detailed mechanistic insights into the hydrotropic solubilization of drug molecules, applications in pharma industries, and some future directions of this technique. Thus, we believe that this feature article will become an adequate manual for the pharmaceutical researchers who want to explore all of the past perspectives of the hydrotropic action of hydrotropes in pharmaceutics.

Development and validation of spectrophotometric method of cefpodoxime proxetil using hydrotropic solubilizing agents

Purpose:

To develop and validate specific and accurate UV spectrophotometric method of cefpodoxime proxetil by using different hydrotropic solubilizing agents.

Materials and Methods:

The present study deals with spectrophotometric analysis of cefpodoxime proxetil by utilizing 4 different hydrotropic agents such as ammonium acetate (6 M), sodium citrate (1.25 M), sodium gycinate (1 M), sodium chloride (1 M), and urea (1 M).

Results:

From different hydrotropic agents, urea showed best aqueous solubility of cefpodoxime proxetil. The linearity was observed in the concentration range of 10-120 μg/ml. The method was validated and found to be precise. Accuracy (percent recovery) for cefpodoxime proxetil was found to be 99.82 ± 0.106.

Conclusion:

Urea as hydrotropic agent showed best aqueous solubility of cefpodoxime proxetil, which can be used as solubilizing agent. The proposed method is new, simple, safe, eco-friendly, economic, accurate, and cost-effective and can be successfully employed in routine analysis.

Spectrophotometric Determination of Poorly Water Soluble Drug Rosiglitazone Using Hydrotropic Solubilization technique

In the present investigation, hydrotropic solution of urea was employed as a solubilizing agent for spectrophotometric determination of poorly water-soluble drug rosiglitazone maleate. In solubility determination study, it was found that there was more than 14-folds enhancement in solubility of rosiglitazone maleate in a 6M solution of urea. Rosiglitazone maleate obeys Beer's law in concentration range of 5-300 μg/ml. Linearity of rosiglitazone maleate was found in the range of 80-120% of the label claim. The proposed method has been applied successfully to the analysis of the cited drug in pharmaceutical formulations with good accuracy and precision. The method herein described is new, simple, eco-friendly, economic, and accurate and can be utilized in routine analysis of rosiglitazone maleate in bulk drug and tablet dosage form.

Novel application of hydrotropic solubilizing additives in the estimation of aspirin in tablets

Highly concentrated aqueous solutions of various hydrotropic agents like sodium benzoate, sodium salicylate, sodium acetate, sodium citrate, nicotinamide and sodium ascorbate have been observed to enhance aqueous solubilities of a large number of poorly water-soluble drugs. In the present investigation hydrotropic solubilization technique has been employed to solubilize poorly water-soluble aspirin (analgesic and antipyretic drug) by 0.5 M ibuprofen sodium solution to carry out titrimetric analysis of aspirin in tablet dosage form. Results of analysis by proposed method and Phamacopoeial method are very comparable. Proposed method is new, rapid, simple, accurate, and reproducible. Statistical data proved the accuracy, reproducibility and the precision of proposed method.

New spectrophotometric estimation of indomethacin capsules with niacinamide as hydrotropic solubilizing agent

BACKGROUND

Hydrotropic solubilization process involves cooperative intermolecular interaction with several balancing molecular forces, rather than either a specific complexation event or a process dominated by a medium effect, such as co-solvency or salting-in.

MATERIALS AND METHODS

In the present investigation, hydrotropic solution of 2 M niacinamide was employed as the solubilizing agent to solubilize the poorly water-soluble drug, indomethacin, from the capsule dosage form for spectrophotometric determination in ultraviolet region.

RESULTS

Hydrotropic agent used did not interfere in the spectrophotometric analysis. In preliminary solubility studies, it was found that there was more than fivefold enhancement in the aqueous solubility of indomethacin (poorly water-soluble drug) in 2 M niacinamide solution as compared to its aqueous solubility at 28 ± 1°C.

CONCLUSION

The proposed method is new, simple, safe, environmentally friendly, economic, accurate and cost-effective and can be successfully employed in routine analysis.

New spectrophotometric estimation of ornidazole tablets employing urea as a hydrotropic solubilizing additive

Quantitative spectrophotometric analysis of poorly water-soluble drugs involves use of various organic solvents. Major drawbacks of organic solvents include high cost, volatility and toxicity. Safety of analyzer is affected by toxicity of the solvent used. In the present investigation the use of organic solvent has been avoided, making the method environmentally friendly. Urea has demonstrated enhancement in aqueous solubilities of a large number of poorly water-soluble drugs, thereby widely used as a hydrotropic agent. There was more than 10-fold enhancement in the solubility of ornidazole in 10 M urea solution as compared to its solubility in distilled water. In the present investigation, hydrotropic solution of urea (10 M) was employed as solubilizing agent to solubilize the poorly water-soluble drug, ornidazole, from fine powder of its tablet dosage form for spectrophotometric determination in ultraviolet region at 319 nm. Beer's law was obeyed in the concentration range of 5-25 μg/ml in presence of urea. Presence of urea did not interfere in the analysis. Proposed method is new, rapid, simple, accurate, and reproducible. Statistical data proved the accuracy, reproducibility and the precision of the proposed method.

Hydrotropic solubilization of nimesulide for parenteral administration

Nimesulide is a non-steroidal anti-inflammatory drug (NSAID) that exhibits analgesic, antipyretic and anti-inflammatory activities. It is practically insoluble in water. The effect of various hydrotropes such as nicotinamide, sodium ascorbate, sodium benzoate, sodium salicylate and piperazine on the solubility of nimesulide was investigated. The solubility enhancement of nimesulide by the hydrotropes was observed in decreasing order as piperazine > sodium ascorbate > sodium salicylate > sodium benzoate > nicotinamide. In order to elucidate the probable mechanism of solubilization, various solution properties of hydrotropes such as viscosity, specific gravity, surface tension, refractive index, specific conductance of hydrotropic solutions were studied at 25 +/- 2 degrees C on the basis of earlier studies. The hydrotropic solubilization of nimesulide at lower hydrotrope concentration may be attributed to weak ionic interactions while that at higher hydrotrope concentration may be due to molecular aggregation. Parenteral formulations using piperazine as a hydrotrope were developed and studied for physical and chemical stability.

The Hydrotrope Action of Sodium Xylenesulfonate on the Solubility of Lecithin

The activity of sodium xylenesulfonate in aqueous solution was determined by vapor pressure measurements, the results of which were transformed to mean activities. In addition, surface tension, conductivity, and partial molar volume were determined to obtain complementary information about potential association structures. No sudden change was observed, indicating the association to take place in the concentration range where the increased solubility of lecithin was observed, contrary to the case of surfactant micellization. The solubilization of lecithin in the aqueous solutions of sodium xylenesulfonate showed the association to be cooperative between the two amphiphiles. A model is proposed for the interpretation of the catastrophic incorporation threshold concentration observed in the solubility curve of lecithin. Copyright 2001 Academic Press.

Surface active drugs: self-association and interaction with membranes and surfactants. Physicochemical and biological aspects

Many pharmacologically active compounds are of amphiphilic (or hydrophobic) nature. As a result, they tend to self-associate and to interact with biological membranes. This review focuses on the self-aggregation properties of drugs, as well as on their interaction with membranes. It is seen that drug-membrane interactions are analogous to the interactions between membranes and classical detergents. Phenomena such as shape changes, vesiculation, membrane disruption, and solubilization have been observed. At the molecular level, these events seem to be modulated by lipid flip-flop and formation of non-bilayer phases. The modulation of physicochemical properties of drugs by self-association and membrane binding is discussed. Pathological consequences of drug-membrane interaction are described. The mechanisms of drug solubilization by surfactants are reviewed from the physicochemical point of view and in relation to drug carrying and absorption by the organism.

Effects of hydrotropic agents on the solubility, precipitation, and protein binding of etoposide

Etoposide, a commonly used anticancer agent, has an aqueous solubility of 0.2 mg/mL. It is formulated for intravenous use as a more concentrated solution (Vepesid; 20 mg/mL) with polysorbate 80 and with cosolvents. In this work, hydrotropic agents such as sodium benzoate, sodium o-hydroxybenzoate (sodium salicylate), sodium 2,5-dihydroxybenzoate (sodium gentisate), and the sodium salts of 2,4-dihydroxy- and 2,6-dihydroxybenzoic acid and of 2,4,6-trihydroxybenzoic acid have been used as alternative solubilizers of etoposide. The weakest and strongest interactants with etoposide were, respectively, sodium benzoate and sodium 2,4,6-trihydroxybenzoate. The effect of mono- and dihydroxybenzoates on etoposide solubility was intermediate. Although sodium 2,4,6-trihydroxybenzoate is the most efficient solubilizer, its use is limited by its own low aqueous solubility. The effect of sodium salicylate and other formulation ingredients on the in vitro protein binding and precipitation of etoposide upon dilution with normal saline and human plasma has been studied. Etoposide binds to the extent of 94% to human serum albumin (HSA) and human plasma, but only 24% to bovine serum albumin (BSA) in vitro. Sodium salicylate significantly decreased the binding of the drug to both HSA and human plasma, whereas the components of Vepesid did not. Dilution of Vepesid (1:2 and 1:3) with plasma in vitro resulted in immediate precipitation, while the corresponding dilutions of etoposide aqueous solution (20 mg/mL in 2 M sodium salicylate) produced no precipitate for the first hour.

Interactions in the solid state. II: Interaction of sodium bicarbonate with substituted benzoic acids in the presence of moisture

The interaction of an organic acid with sodium bicarbonate in water produces an effervescent reaction. The reaction products are carbon dioxide, water, and the sodium salt of the acid. The kinetic rate-determining step for this reaction is the dehydration of carbonic acid. The solid-solid interaction with known amounts of moisture was followed by quantitatively determining carbon dioxide evolution as a function of time. The aqueous solubilities, diffusion coefficients, dissociation constants, and solid-solid interaction rates of six different substituted benzoic acids were determined. Using a model based on diffusion of the organic acid through the aqueous layer coupled with chemical reaction, predicted rates and levels of carbon dioxide production were compared with experimental results. Included in the model were the effects of the reaction products on the solution properties of the reactants. It was found that high concentrations of substituted sodium benzoate were generated very quickly and affected the solubility of the reactants, diffusion coefficient of the acid, and the carbonic acid dehydration rate constant. Moisture content was found to have a profound influence on the interaction rate. Water provides a medium for diffusion of the reacting species as well as the reaction solvent.