Practical Method for Preparing Nanosuspension Formulations for Toxicology Studies in the Discovery Stage: Formulation Optimization and <i>in Vitro</i>/<i>in Vivo</i> Evaluation of Nanosized Poorly Water-Soluble Compounds

Abstract

The present study aimed to develop a practical method for preparing nanosuspension formulations of poorly water-soluble compounds for enhancing oral absorption in toxicology studies in the discovery stage. To obtain a suitable nanosuspension formulation for the intended purpose, formulations were optimized with a focus on the following characteristics: i) containing a high drug concentration, ii) consisting of commonly used excipient types in proper quantities for toxicology studies, iii) having long-term stability, and iv) having versatility for use with diverse compounds. Test compounds were milled with various excipients by wet media milling methods using a mixer mill (10 mg/batch) and a rotation/revolution mixer (0.5 g/batch). As a result, 100 mg/mL nanosuspensions of all 11 test compounds could be prepared with an optimized dispersing agent, 0.5% hydroxypropyl methylcellulose (HPMC) (3 cP)-0.5% Tween 80. Notably, it was found that the molecular weight of HPMC influenced not only particle size but also the stability of nanosuspensions and they were stable for 4 weeks at 5°C. The nanosuspensions increased in vitro dissolution rates and provided 3.9 and 3.0 times higher C max and 4.4 and 1.6 times higher area under the concentration-time curve from 0-24 h (AUC 0-24 h ) in rats (oral dose of 300 mg/kg) for cilostazol and danazol, respectively. In conclusion, applying a wet media milling method with the combination of HPMC of a small molecular weight and Tween 80 as a dispersing agent, nanosuspensions can be practically prepared and conveniently utilized for enhancing the oral absorption of poorly water-soluble compounds in toxicology studies in the discovery stage.Key words nanosuspension; toxicology study; wet media milling; mixer mill; rotation revolution mixer; oral absorptionThe proportion of poorly water-soluble compounds among drug candidates in the discovery stage has been increasing for the past decade.1,2) Because of the poor solubility of these compounds, sufficient oral absorption is not observed in animal studies, and the evaluation of pharmacological and toxicological profiles of drug candidates has therefore become more challenging. In particular, this problem frequently occurs in toxicology studies that require high oral absorption and is now a common problem in pharmaceutical companies.3)The application of formulation technologies such as solubilizing excipients, 4) solid dispersions, 5,6) and nanosuspensions 7,8) is an attractive strategy for improving oral absorption of poorly water-soluble compounds. However, the use of solubilizing excipients and solid dispersions for toxicology studies in the discovery stage is practically limited because of toxicities of excipients and amount of drug substances for formulation studies, respectively. On the other hand, nanosuspensions have the potential to solve these problems. Because nanosuspensions can be prepared as highly drug-loaded formulations with small quantities of excipients, adverse effects caused by excipients can be avoided. 9) In addition, n...

Nanosuspension formulations of poorly water‐soluble compounds for intravenous administration in exploratory toxicity studies: in vitro and in vivo evaluation

“…In contrast, Cil microsuspension dissolved slowly and did not reach saturation solubility after 60 min. Comparable results for particle size and dissolution speed in water, a fasted state simulated intestinal fluid, and a fed state simulated intestinal fluid were obtained for Cil in other studies (Jinno et al ., ; Komasaka et al ., ). The initial concentration of the compound is important for appropriately measuring the dissolution rate in plasma.…”

“…Recently, nanosuspension technologies have been developed to increase the bioavailability of poorly water‐soluble drugs (Gao et al ., ; Liversidge et al ., ; Müller et al ., ; Sutradhar et al ., ; Müller & Peters, ; Neervannan, ; Yadollahi et al , ). In a previous study, we optimized a preparation method of nanosuspensions for oral administration using a rotation/revolution mixer and confirmed its enhancing effect on exposure in rats (Komasaka et al ., ). However, the solubility limits of compounds prevent administration routes such as intravenous (IV) injection in preclinical toxicological and pharmacological studies.…”

“…At the same time, a sterilization method was preliminarily investigated and autoclaving was selected because filtration of the resulting suspension was impossible and poloxamer 338 aqueous solution is thought to be stable during autoclaving. Autoclaving was then combined with wet‐media milling using a mixer mill and zirconia beads (Komasaka et al ., ), and this “mill–autoclave–mill method” was investigated using the poorly soluble compounds Cil, spironolactone (Spi) and probucol (Pro). To confirm the effect of nanosuspensions, the Cil nanosusupension was administered to dogs IV, and the exposure was compared with that of Cil saline solution after measurement of the solubility of nanosuspended Cil in dog plasma.…”

Three-dimensional aspects of formulation excipients in drug discovery: a critical assessment on orphan excipients, matrix effects and drug interactions

“…Solid dispersion and nano suspension approaches are effective in solubilizing highly lipophilic compounds; however, they are much difficult and labor intensive to be adopted in early drug discovery stages. Advantages of both of these strategies are extensively reported in the literature [ [29] , [30] , [31] , [32] , [33] ].…”

Improved oral absorption of cilostazol via sulfonate salt formation with mesylate and&nbsp;besylate

“…5 – 7 A number of techniques have been reported to increase the aqueous solubility of poorly soluble drugs, 8 such as salt formation, 9 micronization, the solid dispersion technique, and emulsification. Various formulations of cilostazol have been examined to overcome the problems outlined above, such as using β-cyclodextrin inclusion complex, 10 , 11 nanosized crystalline particles, 12 formation of nanoemulsions, 13 – 15 microemulsions, 16 and spray-dried solid dispersions. 17 However, to our knowledge, there have been no previous studies regarding salt formation of cilostazol.…”