Effects of film thickness and alkaline concentration on dissolution kinetics of poly(4-hydroxystyrene) in alkaline aqueous solution

The dissolution behavior of a simple combination of poly(4-hydroxystyrene) (PHS) films and tetramethylammonium hydroxide (TMAH) aqueous solution was analyzed to gain a fundamental understanding of the effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists (CARs). Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance (QCM). Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900- and 500-nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films.

Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro

Atorvastatin and lisinopril are a successful combination for the treatment of patients with chronic heart failure and hypertension. Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro were described. In medium with hydrochloric acid pH 1.2, in the medium of acetate buffer solution with a pH of 4.5 and in the medium phosphate buffer solution with a pH of 6.8 for 15 min more than 85% of the active substance passes into solution, hence the dissolution profiles these drugs in these environments are similar, and the drugs in them are “very quickly soluble”. Among the in vitro models that make it possible to assess the degree of absorption of API, the most widely used culture of adenocarcinoma cells of the colon – Caco-2. The development of the analytical methodology and its validation is the final stage of both the dissolution study and the Caco-2 test, as well as the biowaver procedure. It plays the most important role in the reliability of the results for all the above procedures and tests. To study permeability, method LC-MS/MS was developed. According to the obtained results, atorvastatin and lisinopril showed low permeability. The values ​​of recovery of transport of test and control substances through the monolayer of cells of the Caco-2 line indicate that the results of the experiment can be considered reliable. The equivalence of the drugs “Lisinopril”, tablets of 10 mg and “Atorvastatin”, tablets of 10 mg, belongs to class III BCS proven by in vitro studies.

Modelling the Plant Uptake of Metals from Release Rates Obtained by the EUF Method

In this study, soil dissolution kinetics were evaluated to predict the metal uptake of lettuce plants under varying conditions of fertilisation and metal pollution. Velocities and time dependencies of soil dissolution obtained by electro-ultrafiltration (EUF), which prevents back reaction, were modelled in three ways, obtained from suspensions in 0.002 M DTPA at determined soil pH levels, for cases in which sampling versus time led to decreasing concentrations. The models yielded a maximum achievable concentration, a timespan needed for it to be reached, a slope, and an intercept of the respective fitted curves. Three geogenically metalliferous soil samples and one ambient soil sample, both as originals, fertilised with PK or soaked with a Cd-Ni-Pb solution, were used as solid samples. The resulting kinetic parameters were correlated with the amounts absorbed by lettuce plants grown with these substrates in pot experiments, which yielded fairly good correlations with Zn, but also with Li and Sr, as well as Ni and Pb, mainly because of differences due to the addition of a metallic salt solution. Plant growth was hardly influenced by the additions.

In vitro Comparative Dissolution Studies of Different Propranolol Generic Tablets Available in Bangladesh

The present study focused to assess in vitro dissolution profiles of four different products of propranolol 10 mg Tablets (Randomly coded as PRP1-PRP4) available in Bangladesh comparing with the reference brand (coded as REF). Propranolol is a competitive non selective beta-adrenergic receptor antagonist used to amend or restore normal heart rhythm in cardiovascular diseases. An in vitro dissolution study was carried out using the United States Pharmacopoeia (USP) paddle method at 75 rpm with 500 mL of 0.1N HCl dissolution media at 37.0± 0.5 0C. All the tested locally manufactured propranolol products; PRP1, PRP2, PRP3, PRP4 showed compatible dissolution (87%, 86%, 87%, and 80%, respectively) pattern (dissolution criterion Q=80% in 30 minutes) compared with the reference brand (88% dissolution in 30 minutes). The dissolution behavior was estimated with the reference brand using a model dependent and model-independent approach (f2>50, f1 < 15). A mechanistic mathematical release kinetics was also evaluated. The best-fit kinetic model was Hixon-Crowell release kinetics for reference brand and PRP1; and first order release kinetics was predominant for PRP2, PRP3 and PRP4. Keywords: propranolol, dissolution, similarity factor, difference factor, dissolution kinetics

Modelling of the Erosive Dissolution of Metal Oxides in a Deep Eutectic Solvent—Choline Chloride/Sulfosalicylic Acid—Assisted by Ultrasonic Cavitation

Here we report on the results concerning the influence of ultrasound on the dissolution process of metal oxides CoO, Ni2O3 and Mn2O3 in choline chloride/sulfosalicylic acid as a deep eutectic solvent. The mechanism of dissolution under cavitation conditions with ultrasonic assistance is described. Theoretical research resulted in equations describing the dissolution process kinetics and linking its basic parameters. Optimal conditions for the most effective ultrasound application were found. Experimental data on dissolution kinetics of metal oxides in deep eutectic solvents was also obtained. It was discovered that experimental data correlates well with theoretical calculations, which confirms the correctness of developing a picture about the physicochemical nature of the process under study.

Study of Dissolution Kinetics of Mefenamic Acid Solid Dispersion with Polyvinylpyrrolidone

The low solubility of a biologically active substance in an aqueous medium is often the main reason for the reduced therapeutic effect of drugs. The most common approach to solve this problem is to obtain a watersoluble salt of the active substance and an appropriate preparatory formulation based on it. In this case, the solubility of the obtained compound in hydrophobic systems decreases dramatically, which decreases the rate of transmembrane transport and changes the pharmacokinetic laws of the process. In practice, not only the dependence of the therapeutic effect on the salt compound properties, but also a complete loss of the drug active ingredient activity can be observed. The use of biologically active compound solid dispersions in watersoluble polymers is the most promising approach to increase the therapeutic effect of drugs while maintaining the hydrophobic nature of the active component, to reduce the dose load on the patient’s body and obtain prolonged action. In experiments we obtained solid dispersions of mefenamic acid in polyvinylpyrrolidone and studied kinetic regularities of solubility of this promising drug form in aqueous solution of phosphate buffer. By means of mathematical modelling it was found that the phenomenon under study is well described by Ritger --- Peppas model, which considers diffusion of biologically active component into solution according to Fick's law with possible influence on mass transfer at swelling and degradation of polymer matrix