The impact of polymeric excipients on the particle size of poorly soluble drugs after pH-induced precipitation

Monitoring of particle sizes distribution during Valsartan precipitation in the presence of nonionic surfactant

Particle size is a key parameter when dealing with drug particle formation, delivery or dissolution. The correct measurement of particle size depends on various factors, such as sample preparation or dilution, but also on the choice of method for its characterization. In this work, we study the process of precipitation of poorly water-soluble drug Valsartan from supersaturated solution in the presence of nonionic surfactant Tween 20. Several techniques including dynamic light scattering (DLS) operated in several measuring modes, optical microscope (OM) and static light scattering (SLS) were used to analyze the kinetics of particle formation. As concluded by the results, the increase in turbidity of the solution seriously limits the application of classical DLS to properly measure the particle size and polydispersity. One way to get around this restriction is by dilution, which however results in a decrease in the size of Valsartan particles in the studied population. In contrast, here we present for a first time technique based on modulated 3D cross correlation DLS equipped with the sample goniometer to determine size of submicron particles of the drug in highly turbid solutions. Additionally, a modified OM was used to measure micron-sized particles for samples without any dilution in a continuous mode. Measured particle sizes combined with measured Valsartan concentration allowed us to identify mechanism responsible for the particle formation from supersaturated solutions. The main mechanism, as it is shown in this work, is covering surface of precipitate particles by the amount of used Tween 20.

Multifunctional Role of Polyvinylpyrrolidone in Pharmaceutical Formulations

Polyvinylpyrrolidone (PVP), a non-ionic polymer, has been employed in multifarious fields such as paper, fibers and textiles, ceramics, and pharmaceutics due to its superior properties. Especially in pharmacy, the properties of inertness, non-toxicity, and biocompatibility make it a versatile excipient for both conventional formulations and novel controlled or targeted delivery systems, serving as a binder, coating agent, suspending agent, pore-former, solubilizer, stabilizer, etc. PVP with different molecular weights (MWs) and concentrations is used in a variety of formulations for different purposes. In this review, PVP-related researches mainly in recent 10 years were collected, and its main pharmaceutical applications were summarized as follows: (i) improving the bioavailability and stability of drugs, (ii) improving the physicomechanical properties of preparations, (iii) adjusting the release rate of drugs, and (iv) prolonging the in vivo circulation time of liposomes. Most of these applications could be explained by the viscosity, solubility, hydrophilicity, and hydrogen bond-forming ability of PVP, and the specific action mechanisms for each application were also tried to figure out. The effect of PVP on bioavailability improvement establishes it as a promising polymer in the emerging controlled or targeted formulations, attracting growing interest on it. Therefore, given its irreplaceability and tremendous opportunities for future developments, this review aims to provide an informative reference about current roles of PVP in pharmacy for interested readers.

A composite nanocarrier to inhibit precipitation of the weakly basic drug in the gastrointestinal tract

For weakly basic drugs, the sharp decrease of drug solubility and the following drug precipitation after drugs transferring from the gastric fluid to the intestinal fluid in the gastrointestinal (GI) tract is a main reason for the poor oral bioavailability of drugs. Here, an anticoagulant dabigatran etexilate (DE) was used as a model drug, and a composite nanocarrier system of DE was developed to improve the drug dissolution by decreasing the drug leakage in the stomach and inhibiting the drug precipitation in the intestinal tract. With the encapsulation of drugs in nanocarriers, the precipitation percentage of DE in composite nanocarriers was 22.25 ± 3.88% in simulated intestinal fluid, which was far below that of the commercial formulation. Moreover, the relative bioavailability of DE-loaded composite nanocarriers (456.58%) was greatly enhanced and the peak of its activated partial thromboplastin time was also significantly prolonged (p < .01) compared with the commercial formulation, indicating that the anticoagulant effect of DE was effectively improved. Therefore, the designed composite nanocarrier system of DE presents great potentials in improving the therapeutic efficiency and expanding the clinical applications of poorly water-soluble weakly basic drugs.

Preclinical evaluation of new formulation concepts for abiraterone acetate bioavailability enhancement based on the inhibition of pH-induced precipitation

Abiraterone acetate is a potent drug used for the treatment of metastatic castration resistant prostate cancer. However, currently marketed product containing crystalline abiraterone acetate exhibits strong positive food effect which results in strict dosing regimen. In the present work, a rational approach towards design of novel abiraterone acetate formulations that would allow increased bioavailability on a fasting stomach and thus decreased food effect is presented. Precipitation experiments in biorelevant media were designed to assess pH induced precipitation of the drug and a pool of polymeric excipients was then screened for their potential to inhibit precipitation. The best performing polymeric excipients were subsequently used as carriers for the preparation of amorphous solid dispersions. Two main approaches were followed in order to formulate the drug. The first approach relies on the suppression of precipitation from a supersaturated solution whereas the second one is based on the hypothesis that when the release of the drug is tuned, optimal uptake of the drug can be reached. Optimized formulation prototypes were tested in a rat animal model in an incomplete block, randomized bioequivalence study to assess their relative bioavailability under fasting conditions. We show that both formulation approaches lead to increased bioavailability of abiraterone acetate on a fasting stomach with bioavailability in rats being enhanced up to 250% compared to the original drug product containing crystalline drug.