Systems biology approach to study permeability of paracetamol and its solid dispersion

Effects of paracetamol/acetaminophen on the expression of solute carriers (SLCs) in late-gestation fetal rat brain, choroid plexus and the placenta

Solute carriers (SLCs) regulate transfer of a wide range of molecules across cell membranes using facilitative or secondary active transport. In pregnancy, these transporters, expressed at the placental barrier, are important for delivery of nutrients to the fetus, whilst also limiting entry of potentially harmful substances, such as drugs. In the present study, RNA-sequencing analysis was used to investigate expression of SLCs in the fetal (embryonic day 19) rat brain, choroid plexus and placenta in untreated control animals and following maternal paracetamol treatment. In the treated group, paracetamol (15 mg/kg) was administered to dams twice daily for 5 days (from embryonic day 15 to 19). In untreated animals, overall expression of SLCs was highest in the placenta. In the paracetamol treatment group, expression of several SLCs was significantly different compared with control animals, with ion, amino acid, neurotransmitter and sugar transporters most affected. The number of SLC transcripts that changed significantly following treatment was the highest in the choroid plexus and lowest in the brain. All SLC transcripts that changed in the placenta following paracetamol treatment were downregulated. These results suggest that administration of paracetamol during pregnancy could potentially disrupt fetal nutrient homeostasis and affect brain development, resulting in major consequences for the neonate and extending into childhood.

Integration of Placental Transfer in a Fetal-Maternal Physiologically Based Pharmacokinetic Model to Characterize Acetaminophen Exposure and Metabolic Clearance in the Fetus

BACKGROUND AND OBJECTIVE

Although acetaminophen is frequently used during pregnancy, little is known about fetal acetaminophen pharmacokinetics. Acetaminophen safety evaluation has typically focused on hepatotoxicity, while other events (fetal ductal closure/constriction) are also relevant. We aimed to develop a fetal-maternal physiologically based pharmacokinetic (PBPK) model (f-m PBPK) to quantitatively predict placental acetaminophen transfer, characterize fetal acetaminophen exposure, and quantify the contributions of specific clearance pathways in the term fetus.

METHODS

An acetaminophen pregnancy PBPK model was extended with a compartment representing the fetal liver, which included maturation of relevant enzymes. Different approaches to describe placental transfer were evaluated (ex vivo cotyledon perfusion experiments, placental transfer prediction based on Caco-2 cell permeability or physicochemical properties [MoBi^®]). Predicted maternal and fetal acetaminophen profiles were compared with in vivo observations.

RESULTS

Tested approaches to predict placental transfer showed comparable performance, although the ex vivo approach showed highest prediction accuracy. Acetaminophen exposure in maternal venous blood was similar to fetal venous umbilical cord blood. Prediction of fetal acetaminophen clearance indicated that the median molar dose fraction converted to acetaminophen-sulphate and N-acetyl-p-benzoquinone imine was 0.8% and 0.06%, respectively. The predicted mean acetaminophen concentration in the arterial umbilical cord blood was 3.6 mg/L.

CONCLUSION

The median dose fraction of acetaminophen converted to its metabolites in the term fetus was predicted. The various placental transfer approaches supported the development of a generic f-m PBPK model incorporating in vivo placental drug transfer. The predicted arterial umbilical cord acetaminophen concentration was far below the suggested postnatal threshold (24.47 mg/L) for ductal closure.

A Comparative Study on Dissolution Enhancement of Acetaminophen by Cooling, Anti-solvent, and Solvent Evaporation Crystallization

The aim of this study was to prepare APAP crystals by cooling, anti-solvent, and solvent evaporation crystallization to enhance its dissolution rate and to make comparisons of the three methods. Agitating speeds and types were regarded as factors affecting crystallization procedure. Samples were made with different ratios of PEG4000. They were characterized by X-ray diffraction and scanning electron microscopy. Dissolution tests were conducted to assess their dissolution property. The proportions of carriers existing in crystals by cooling and anti-solvent crystallization ranged from 1.3 to 5.1%. Mean dissolution time (MDT) of samples by the two methods was about 3 min, which was 17.2 min for untreated APAP. Addition of too much PEG4000 in solvent evaporation crystallization could decrease dissolution rate of APAP. Samples agitated by a rotor with speed of 100, 500, and 1000 rpm dissolved faster than those by a high shear mixer with speed of 3400 and 5000 rpm or by a glass rod. Agitating speed and type could affect particle size and drug dissolution. Dissolution enhancement of APAP might be attributed to decrease of fine particles and increase of particle wettability.

Evaluation of the recrystallization kinetics of hot-melt extruded polymeric solid dispersions using an improved Avrami equation

The recrystallization of an amorphous drug in a solid dispersion system could lead to a loss in the drug solubility and bioavailability. The primary objective of the current research was to use an improved kinetic model to evaluate the recrystallization kinetics of amorphous structures and to further understand the factors influencing the physical stability of amorphous solid dispersions. Amorphous solid dispersions of fenofibrate with different molecular weights of hydroxypropylcellulose, HPC (Klucel™ LF, EF, ELF) were prepared utilizing hot-melt extrusion technology. Differential scanning calorimetry was utilized to quantitatively analyze the extent of recrystallization in the samples stored at different temperatures and relative humidity (RH) conditions. The experimental data were fitted into the improved kinetics model of a modified Avrami equation to calculate the recrystallization rate constants. Klucel LF, the largest molecular weight among the HPCs used, demonstrated the greatest inhibition of fenofibrate recrystallization. Additionally, the recrystallization rate (k) decreased with increasing polymer content, however exponentially increased with higher temperature. Also k increased linearly rather than exponentially over the range of RH studied.

Genomic study of the absorption mechanism of p-coumaric acid and caffeic acid of extract of Ananas comosus L. leaves

Cardiac disease has emerged as the leading cause of death worldwide, and food rich in phenolic acids has drawn much attention as sources of active substances of hypolipidemic drug. Ananas comosus L. (pineapple) is one of the most popular tropical and subtropical fruits. Isolated from pineapple leaves, EAL(Extract of Ananas Comosus L. Leaves) is rich in phenolic acids, such as p-coumaric acid, caffeic acid, and other phenolics, highly relevant to the putative cardiovascular-protective effects, which suggests its potential to be a new plant medicine for treatment of cardiac disease, but little is known about absorption, distribution, metabolism, and excretion of EAL in animals or human beings. In this study, we employed cDNA microarray, Caco-2 cell lines, and rat intestinal model to explore the absorption behavior of p-coumaric acid and caffeic acid in EAL. The permeation of 2 substances was concentration and time dependent. Results also indicated that monocarboxylic acid transporter was involved in the transepithelial transport of p-coumaric acid and caffeic acid.

Stabilization of amorphous paracetamol based systems using traditional and novel strategies

There is a special interest in having pharmaceutical active ingredients in the amorphous state due to their increased solubility and therefore, higher bioavailability. Nevertheless, not all of them present stable amorphous phases. In particular, paracetamol is an active ingredient widely known for its instability when prepared in the amorphous state. In the present work thermally stable amorphous binary paracetamol based systems were obtained showing stability on a wide range of temperatures: below its glass transition temperature (Tg) as amorphous solids in the glassy state and above their glass transition temperature, where these materials exist as stable supercooled liquids. To achieve stabilization of the binary paracetamol based system several strategies were applied and optimized, being the selection of the container material a key and novel approach to control the mechanical stress during cooling, eliminating cracks which act as nucleation centers leading to crystallization.

A novel concentration dependent amino acid ion pair strategy to mediate drug permeation using indomethacin as a model insoluble drug

Assessment of oral drug bioavailability is an important parameter for new chemical entities (NCEs) in drug development cycle. After evaluating the pharmacological response of these new molecules, the following critical stage is to investigate their in vitro permeability. Despite the great success achieved by prodrugs, covalent linking the drug molecule with a hydrophobic moiety might result in a new entity that might be toxic or ineffective. Therefore, an alternative that would improve the drug uptake without affecting the efficacy of the drug molecule would be advantageous. The aim of the current study is to investigate the effect of ion-pairing on the permeability profile of a model drug: indomethacin (IND) to understand the mechanism behind the permeability improvement across Caco-2 monolayers. Arginine and lysine formed ion-pairs with IND at various molar ratios 1:1, 1:2, 1:4 and 1:8 as reflected by the double reciprocal graphs. The partitioning capacities of the IND were evaluated using octanol/water partitioning studies and the apparent permeabilities (Papp) were measured across Caco-2 monolayers for the different formulations. Partitioning studies reflected the high hydrophobicity of IND (LogP=3) which dropped upon increasing the concentrations of arginine/lysine in the ion pairs. Nevertheless, the prepared ion pairs improved IND permeability especially after 60 min of the start of the experiment. Coupling partitioning and permeability results suggest a decrease in the passive transcellular uptake due to the drop in IND portioning capacities and a possible involvement of active carriers. Future work will investigate which transport gene might be involved in the absorption of the ion paired formulations using molecular biology technologies.

Physicochemical characterisation, drug polymer dissolution and in vitro evaluation of phenacetin and phenylbutazone solid dispersions with polyethylene glycol 8000

Poor water solubility leads to low dissolution rate and consequently, it can limit bioavailability. Solid dispersions, where the drug is dispersed into an inert, hydrophilic polymer matrix can enhance drug dissolution. Solid dispersions were prepared using phenacetin and phenylbutazone as model drugs with polyethylene glycol (PEG) 8000 (carrier), by melt fusion method. Phenacetin and phenylbutazone displayed an increase in the dissolution rate when formulated as solid dispersions as compared with their physical mixture and drug alone counterparts. Characterisation of the solid dispersions was performed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). DSC studies revealed that drugs were present in the amorphous form within the solid dispersions. FTIR spectra for the solid dispersions of drugs suggested that there was a lack of interaction between PEG 8000 and the drug. However, the physical mixture of phenacetin with PEG 8000 indicated the formation of hydrogen bond between phenacetin and the carrier. Permeability of phenacetin and phenylbutazone was higher for solid dispersions as compared with that of drug alone across Caco-2 cell monolayers. Permeability studies have shown that both phenacetin and phenylbutazone, and their solid dispersions can be categorised as well-absorbed compounds.