Nano- and microcrystals of griseofulvin subcutaneously administered to rats resulted in improved bioavailability and sustained release

Pharmacokinetics of nano- and microcrystal formulations of low solubility compounds after intramuscular injection to mice

OBJECTIVES

The aim of this study was to investigate the pharmacokinetics (PK) of poorly soluble compounds when administered intramuscularly (i.m.) as crystalline particles of different sizes.

METHODS

Three uncharged compounds (griseofulvin, AZ'72, and AZ'07) with varying aqueous solubility were dosed to mice at 10 and 50 mg/kg as nano- and microparticle formulations. The PK of the compounds was evaluated.

KEY FINDINGS

The smaller particles of the drugs resulted in higher maximum plasma concentration (Cmax) and area under the plasma concentration-time profile (AUC) at 50 mg/kg. There was a dose-proportional increase in AUC but less than dose dose-proportional increase in Cmax. The evaluation at 10 mg/kg was more complex as increased exposure for nanoparticles was only observed for griseofulvin which has the highest solubility. In addition, there was an increase in half-life with an increase in dose.

CONCLUSIONS

This study highlights that general expectations based on in vitro dissolution (i.e. that smaller particles dissolve faster than larger particles when surrounded by liquid) do not always translate to in vivo and demonstrates the importance of understanding the physicochemical properties of the drug, the characteristics of the formulations and the microphysiology at the delivery site.

Novel griseofulvin zinc nanohybrid emulsion for intensifying the antimicrobial control of dermatophytes and some opportunistic pathogens

Dermatophytosis is a critical sort of skin infection caused by dermatophytes. The long-term treatment of such skin infections may be improved through the application of nanotechnology. This study aimed to prepare griseofulvin zinc Nanohybrid emulsion (GF-Zn-NHE) to improve griseofulvin activity against dermatophytes and some opportunistic pathogenic yeasts and bacteria. The GF-Zn-NHE is prepared by ultra-homogenization ultra-sonication strategies and validated by UV-visible spectroscopy analysis that confirms presences of griseofulvin and Zn-NPs peaks at 265 and 360 nm, respectively. The GF-Zn-NHE has mean distribution size 50 nm and zeta potential in the range from -40 to -36 mV with no significant changes in size distribution and particle size within 120 day ageing. Fourier transform infrared spectroscopy spectrum confirmed the presence of griseofulvin and Zn-NPs stretching vibration peaks. Gamma ray has a negative influence on GF-Zn-NE production and stability. GF-Zn-NHE drug release 95% up to 24 h and 98% up to 72 h of GF was observed and Zinc 90% up to 24 h and 95% up to 72 h, respectively. High antimicrobial activity was observed with GF-Zn-NHE against dermatophytic pathogens in compare with GF, GF-NE, zinc nitrate and ketoconazole with inhibition zone ranged from 14 to 36 mm. The results have shown that the MIC value for Cryptococcus neoformans, Prophyromonas gingivalis and Pseudomonas aeruginosa is 0.125 mg ml -1 and for Trichophyton rubrum, L. bulgaricus and Escherichia coli value is 0.25 mg ml -1 and for Candida albicans, Malassezia furfur and Enterococcus faecalis is 0.5 mg ml -1 and finally 1 mg ml -1 for Streptococcus mutans. TEM of treated Cryptococcus neoformans cells with GF-Zn-NHE displayed essentially modified morphology, degradation, damage of organelles, vacuoles and other structures.

Development of Drug Release Model for Suspensions in ESCAR (Emulator of SubCutaneous Absorption and Release)

We recently developed an in vitro testing system, namely, ESCAR (Emulator of SubCutaneous Absorption and Release). The objective of this work was to investigate drug release behaviors of unmilled and milled suspensions in ESCAR. A mass transport-based model was developed to describe the multi-step drug release process, including drug dissolution, particle settling, drug distribution/partition, and drug permeation through the membrane(s). To address the particle settling effect, a correction factor was included in the model and its value was obtained by data fitting. It was found that, for both suspensions, (i) the experimental data of various dose/formulation combinations could be fit by the developed model; (ii) the dose effect on drug release was offset by the particle settling effect. This model may help to reduce experimental efforts and facilitate subcutaneous suspension formulation development using ESCAR.

Pharmacokinetic evaluation of poorly soluble compounds formulated as nano- or microcrystals after intraperitoneal injection to mice

Intraperitonial (i.p.) delivery during initial stages of drug discovery can allow efficacy readouts for compounds which have suboptimal pharmacokinetics (PK) due to poor physiochemical properties and/or oral bioavailability. A major limitation for widespread use of i.p. administration is the paucity of published data and unclear mechanisms of absorption, particularly when using complex formulations. The aim of the present study was to investigate the PK of poorly soluble compounds with low oral bioavailability when administered i.p. as crystalline nano- and microsuspensions. Three compounds, with varying aqueous solubility (2, 7, and 38 µM, at 37 °C), were dosed to mice at 10 and 50 mg/kg. In vitro dissolution confirmed that nanocrystals dissolved faster than microcrystals and hence were expected to result in higher exposure after i.p. dosing. Surprisingly, the increase in dissolution rate with decrease in particle size did not result in higher in vivo exposure. In contrast, the microcrystals showed higher exposure. The potential of smaller particles to promote access to the lymphatic system is hypothesized and discussed as one plausible explanation. The present work demonstrates the importance of understanding physicochemical properties of drug formulations in the context of the microphysiology at the delivery site and how that knowledge can be leveraged to alter systemic PK.

Experimental design, development and evaluation of extended release subcutaneous thermo-responsive in situ gels for small molecules in drug discovery

The objective of this work is to develop extended release subcutaneous thermo-responsive in situ gel-forming delivery systems using the following commercially available triblock polymers: poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA-PEG-PLGA, copolymer A & B) and poly (lactide-co-caprolactone)-poly (ethylene glycol)-poly (lactide-co-caprolactone) (PLCL-PEG-PLCL, copolymer C). Performance of two optimized formulations containing ketoprofen as a model compound, was assessed by comparing in vitro drug release profiles with in vivo performance following subcutaneous administration in rats. This work employs a Design of Experiment (DoE) approach to explore first, the relationship between copolymer composition, concentration, and gelation temperature (GT), and second, to identify the optimal copolymer composition and drug loading in the thermo-responsive formulation. Furthermore, this work discusses the disconnect observed between in vitro drug release and in vivo pharmacokinetic (PK) profiles. In vitro, both formulations showed extended-release profiles for 5-9 days, while PK parameters and plasma profiles were similar in vivo without extended release observed. In conclusion, a clear disconnection is observed between in vitro ketoprofen drug release and in vivo performance from the two thermogel formulations tested. This finding highlights a remaining challenge for thermogel formulation development, that is, being able to accurately predict in vivo behavior from in vitro results.

Picking up good vibrations: Exploration of the intensified vibratory mill via a modern design of experiments

The aim of this work was to strengthen the understanding of the intensified vibratory mill by unravelling the milling process in terms of the particle size reduction and heat generation via a modern design of experiments approach. Hence, the influence of five process parameters (acceleration, breaks during milling, bead size, milling time and bead-suspension ratio) was investigated via an I-optimal design. Particle size was measured via laser diffraction and the temperature of the sample after milling was computed. To advance our understanding, a mechanistic model for the set-up of wet-stirred media milling processes was applied on the observed milling trends. A generic approach for the optimisation of the milling process was retrieved and included the optimisation of the bead size and intermittent pausing for effective cooling. To finetune the remaining process parameters, the present work provides contour plots and strong predictive models. With these models, the particle size and the temperature after milling of suspensions manufactured with the intensified vibratory mill could be forecasted for the first time.

Probabilistic modeling of an injectable aqueous crystalline suspension using influence networks

Probabilistic modeling using influence networks is an efficient, intuitive, and easy to communicate strategy in the development of complex pharmaceutical products. This study was aimed to use a risk-based approach to explore the complex interactions between product and process design parameters affecting size and shape of the particles in injectable aqueous crystalline suspensions (ACS). Based on a risk assessment, a design of experiments (DOE) was applied to evaluate the most important parameters, i.e., four critical material attributes and two critical process parameters. A model hydrophobic drug (carbamazepine) was milled and homogenized in a multistep process (dispersion and milling steps). The final formulations were characterized with automated at-line image analysis of thousands of individual particles. The particle size and shape distributions were summarized with descriptive parameters, and the relationship of these parameters and the DOE was modeled using influence networks (INs). This approach was compared and contrasted with a classical modeling approach based on multivariate linear regression (MVLR). INs had a superior visual interpretation capability of the complex and multivariate ACS system making the risk-based decision making more accessible. The probability and causality were included in the IN, i.e., the relationships between size and shape. Moreover, IN allowed to incorporate prior knowledge in a systematic way by implementing a 'black and white list'. An IN based model was created with the following model performance: a mean absolute percentage error of 1.7% and 1.1% for the size and 6.2% and 5.0% for the shape, respectively for dispersed and milled ACS. Parameters with the highest and lowest probability to control the critical quality attributes of ACS could be identified. Consequently, the parameter settings giving the optimum particle size and shape could be predicted using a Monte Carlo simulation to calculate the probability of success including the uncertainty of the model. The cubic MVLR model for the size of milled ACS was comparable to the IN in terms of the mean absolute percentage error, i.e., 1.1%. However, IN was more efficient in visualizing the complex and multivariate data set, including all the critical quality attributes and formulation/process parameters of the ACS at the same time. Moreover, the prior knowledge used in probabilistic modeling of IN could be systematically documented.

A candidate drug administered subcutaneously to rodents as drug particles showing hepatic recirculation which influenced the sustained release process

The aim of the present study was to evaluate and interpret the pharmacokinetic profiles after subcutaneous (s.c.) administration of crystalline AZ'72 nano- and microsuspensions to rodents. Both formulations were injected at 1.5 and 150 mg/kg to rats. For the lower dose, the profiles were similar after s.c. injection but extended as compared to oral administration. The overall exposure was higher for nanoparticles compared with microparticles during the investigated period. For the higher dose, injection of both suspensions resulted in maintained plateaus caused by the drug depots but, unexpectedly, at similar exposure levels. After addition of a further stabilizer, pluronic F127, nanosuspensions showed improved exposure with dose and higher exposure compared to larger particles in mice. Obviously, a stabilizer mixture that suits one delivery route is not necessarily optimal for another one. The differences in peak concentration (C_max) between nano- and microparticles were mainly ascribed to differences in dissolution rate. Plasma profiles in mice showed curves with secondary absorption peaks after intravenous and oral administration, suggesting hepatic recirculation following both administration routes. This process, together with the depot formulation, complicates the analysis of absorption from s.c. administration, i.e. multiple processes were driving the plasma profile of AZ'72.

Advanced modification of drug nanocrystals by using novel fabrication and downstream approaches for tailor-made drug delivery

Drug nanosuspensions/nanocrystals have been recognized as one useful and successful approach for drug delivery. Drug nanocrystals could be further decorated to possess extended functions (such as controlled release) and designed for special in vivo applications (such as drug tracking), which make best use of the advantages of drug nanocrystals. A lot of novel and advanced size reduction methods have been invented recently for special drug deliveries. In addition, some novel downstream processes have been combined with nanosuspensions, which have highly broadened its application areas (such as targeting) besides traditional routes. A large number of recent research publication regarding as nanocrystals focuses on above mentioned aspects, which have widely attracted attention. This review will focus on the recent development of nanocrystals and give an overview of regarding modification of nanocrystal by some new approaches for tailor-made drug delivery.