Anders Lundqvist

Particle size reduction for improvement of oral absorption of the poorly soluble drug UG558 in rats during early development

Background: The exposure of UG558 was not good enough using traditional microsuspensions. Aim: The aim of this study was to find out whether nanosuspensions were a better choice compared with a microsuspension, for an acidic substance with a water solubility in the order of 2 μM (pH 6.8, small intestinal pH) and no permeability limitations. Methods: UG558 was ground by a planetary ball mill. The particle size was measured by laser diffraction and the stability of the particle sizes was followed. The pharmacokinetic parameters of UG558 administered as nanosuspension have been compared with those from microsuspension using rat as in vivo specie. Both formulations were administered orally. The nanosuspension was also administered intravenously. Results: The particle size of the nanosuspensions was about 190 nm and about 12 μm for the microsuspensions. At the administered doses, solutions were no alternative (e.g. due to limited solubility). Already at the lowest dose, 5 μmol/kg (5 ml/kg), a significant difference was observed between the two suspensions. These results were further confirmed at a high dose (500 μmol/kg, 5 mL/kg). Thus, the study demonstrated a clear correlation between particle size and in vivo exposures, where the nanosuspensions provided the highest exposure. Furthermore, no adverse events were observed for the substance nor the nanosuspension formulations (i.e., the particles) in spite of the higher exposures obtained with the nanoparticles. To make it possible to calculate the bioavailability, 5 μmol/kg doses of the nanosuspensions (5 ml/kg) were also administered intravenously. No adverse events were observed. Conclusions: The nanoparticles have a larger surface, resulting in faster in vivo dissolution rate, faster absorption, and increased bioavailability, compared to microparticles. The lower overall bioavailability observed at the high dose, compared with the low dose, was due to a combination of low dissolution rate, low solubility, and a narrow intestinal absorption window for UG558.

Particle size reduction and pharmacokinetic evaluation of a poorly soluble acid and a poorly soluble base during early development

Aim: The aim of the present study was to find out if nanosuspensions were a better choice compared with microsuspensions, for the present substances with water solubility in the order of 2−3 μM (pH 6.8, small intestinal pH) and no permeability limitations. The ambition was also to understand what the higher solubility in the stomach for BA99 means in terms of absorption properties of the substance. Method: The pharmacokinetic parameters of a poorly soluble acid (AC88) and a poorly soluble base (BA99) administered orally as nanosuspensions have been compared with those from microsuspensions using rat as in vivo species. Results: A significant difference was observed between the two suspensions for AC88 already at the lowest dose, 5 μmol/kg (the particle size of the nanosuspensions and the microsuspensions was about 200 nm and 14 μm, respectively). These results were further confirmed at a high dose (500 μmol/kg). However, for BA99, there were no significant differences between the two formulations at any dose investigated (the particle size of the nanosuspensions and the microsuspensions was about 280 nm and 12 μm, respectively).Conclusions: The study demonstrated a clear correlation between particle size and in vivo exposures for an acidic compound, the nanosuspensions providing the highest exposure. For a basic compound, on the other hand, with the present properties and doses, a microsuspension was sufficient. In the latter case, the higher solubility at gastric pH, because of the basic pKa, limits the need for particle reduction.

Development of a Novel Lung Slice Methodology for Profiling of Inhaled Compounds.

The challenge of defining the concentration of unbound drug at the lung target site after inhalation limits the possibility to optimize target exposure by compound design. In this study, a novel rat lung slice methodology has been developed and applied to study drug uptake in lung tissue, and the mechanisms by which this occurs. Freshly prepared lung slices (500 μm) from drug-naive rats were incubated with drugs followed by determination of the unbound drug volume of distribution in lung (Vu,lung), as the total concentration of drug in slices divided by the buffer (unbound) concentration. Vu,lung determined for a set of inhaled drug compounds ranged from 2.21 mL/g for salbutamol to 2970 mL/g for dibasic compound A. Co-incubation with monensin, a modulator of lysosomal pH, resulted in inhibition of tissue uptake of basic propranolol to 13%, indicating extensive lysosomal trapping. Partitioning into cells was particularly high for the cation MPP+ and the dibasic compound A, likely because of the carrier-mediated transport and lysosomal trapping. The results show that different factors are important for tissue uptake and the presented method can be used for profiling of inhaled compounds, leading to a greater understanding of distribution and exposure of drug in the lung.

Systems Pharmacology Approach for Prediction of Pulmonary and Systemic Pharmacokinetics and Receptor Occupancy of Inhaled Drugs

Pulmonary drug disposition after inhalation is complex involving mechanisms, such as regional drug deposition, dissolution, and mucociliary clearance. This study aimed to develop a systems pharmacology approach to mechanistically describe lung disposition in rats and thereby provide an integrated understanding of the system. When drug‐ and formulation‐specific properties for the poorly soluble drug fluticasone propionate were fed into the model, it proved predictive of the pharmacokinetics and receptor occupancy after intravenous administration and nose‐only inhalation. As the model clearly distinguishes among drug‐specific, formulation‐specific, and system‐specific properties, it was possible to identify key determinants of pulmonary selectivity of receptor occupancy of inhaled drugs: slow particle dissolution and slow drug‐receptor dissociation. Hence, it enables assessment of factors for lung targeting, including molecular properties, formulation, as well as the physiology of the animal species, thereby providing a general framework for rational drug design and facilitated translation of lung targeting from animal to man.

Co-administration of a nanosuspension of a poorly soluble basic compound and a solution of a proton pump inhibitor-the importance of gastrointestinal pH and solubility for the in vivo exposure

In Sigfridsson et al. (2011, Drug Dev Ind Pharm, 37:243–251), there was no difference in plasma concentration of BA99 when administering the drug as nanosuspension or microsuspension and analyzing the blood samples by liquid chromatography–mass spectrometry. This was related to the dissolved amount of drug in the gastric tract, which was high enough to support fast absorption when the drug reached the small intestine. One single physicochemical property (pKa, about 3 for BA99) abolished the benefit of small particles. These results were further confirmed in the present study, where a proton pump inhibitor, AZD0865, was used to elevate the gastric pH and then drastically decreased the gastric solubility. In this way, BA99 could be considered as a model compound for a neutral substance. By increasing the gastric pH to 5–6 and 8–9, respectively, in rats, the plasma concentrations of BA99, after administering nanosuspensions, were unchanged compared with untreated (i.e. no AZD0865) animals. For microsuspensions of the test compound, on the other hand, the exposure of BA99 was 2- to 3-fold lower than for nanosuspensions at both pHs. Moreover, the blood concentrations of BA99 administered as microsuspension were also 2- to 3-fold lower compared with untreated (no AZD0865) individuals receiving both nanoparticles and microparticles of BA99. Obviously, for neutral compounds, with similar physicochemical properties as the present compound, size reduction will be crucial for increased plasma exposure. For basic compounds, with similar physicochemical properties as the present compound, the crucial step for absorption is the dissolution and solubility in the gastric tract.

Evaluation of exposure properties after injection of nanosuspensions and microsuspenions into the intraperitoneal space in rats

In the present paper, BA99 and AC88 were used as model compounds for intraperitoneal (i.p.) administration to Sprague-Dawley rats. A major problem for the compounds, like many others newly developed pharmaceutical drugs, is the poor solubility in water. To solve solubility related problems, development of nanosuspensions is an attractive alternative. Both compounds are suitable for nanosuspensions, using the milling approach. After 2 weeks in freezer, the nanoparticles aggregated to form particles in the 400–2000 nm interval. However, following a 20 s ultrasonication step, the original particle sizes (about 200 nm) were obtained. Adding 5% mannitol before the samples were frozen abolished aggregation. It is also possible to freeze-dry the nanosuspension in the presence of 5% mannitol and re-disperse the formulation in water. Nanosuspensions of both compounds were injected i.p. to rats at 5 and 500 µmoL/kg. At the low dose, also a microsuspension was administered. I.p. administration resulted in overall improved Cmax for both AC88 and BA99 compared to s.c. and oral administration. I.p. is the preferred route of administration of tolerable drugs when a fast onset of action is desired and when a significant first passage metabolism occurs. The net charge of the active molecule appeared to affect the absorption kinetics. In the present work, the neutral molecule was favored over the negatively charged one.

Dapagliflozin‐lowered blood glucose reduces respiratory Pseudomonas aeruginosa infection in diabetic mice

Hyperglycaemia increases glucose concentrations in airway surface liquid and increases the risk of pulmonary Pseudomonas aeruginosa infection. We determined whether reduction of blood and airway glucose concentrations by the anti‐diabetic drug dapagliflozin could reduce P. aeruginosa growth/survival in the lungs of diabetic mice.

Subcutaneous administration of nano- and microsuspensions of poorly soluble compounds to rats

Abstract The aim of the present study was to evaluate and interpret the pharmacokinetic profiles of two compounds after subcutaneous (s.c.) administration. The compounds have similar physicochemical properties, but are a base (BA99) and an acid (AC88), respectively. The compounds were administered as nano- (5 and 500 µmol/kg) and microsuspensions (5 µmol/kg) s.c. to Sprague–Dawley rats. At the low dose, the exposure was higher for both compounds administered as nanocrystals compared to microparticles. The high dose of the compounds resulted in even higher exposure, but not in a dose-linear manner. The differences in exposure between nano- and microparticles were mainly ascribed to higher dissolution rate and improved solubility for smaller particles. In addition to differences in exposure, there were also differences in the elimination pattern. After s.c. injection of 5 µmol/kg of BA99 as nano- and microsuspensions, the elimination profile was similar as observed earlier after oral administration. However, after injection of the higher dose of BA99 and all formulations of AC88, an extended elimination profile was observed, forming a maintained plateau under the investigated time-period. Essentially, constant plasma levels were caused by a balanced equilibrium between total body clearance of the drug and supply rate of drug from the formulations.