Preparation, characterization and pharmacokinetics of cyadox nanosuspension

www.nature.com/scientificreports OPEN Received: 3 November 2016 Accepted: 29 March 2017 Published: xx xx xxxx Preparation, characterization and pharmacokinetics of cyadox nanosuspension Adeel Sattar1, Dongmei Chen1, Lishun Jiang1, Yuanhu Pan1, Yanfei Tao1, Lingli Huang1,3, Zhenli Liu2, Shuyu Xie1 & Zonghui Yuan1,2,3 An increase in number of newly developed synthetic drugs displays bioavailability constraints because of poor water solubility. Nanosuspensions formulation may help to overwhelm these problems by increasing dissolution velocity and saturation solubility. In the present study, cyadox (Cyx) nanosuspension was successfully prepared by recrystallization based on acid–base neutralization combined with high pressure homogenization method using Polyvinylpyrrolidone K30 (PVP) as stabilizer. The nanosuspension had uniform particle distribution, excellent sedimentation rate and redispersibility. The nanosuspension significantly improved the solubility, dissolution and bioavailability. The saturation solubility of Cyx nanocrystal was higher than that of bulk Cyx and released the total drug in very short time. Further, pharmacokinetics of Cyx nanosuspension and normal suspension following oral administration was investigated in beagle dogs. Nanosuspension improved the bioavailability of Cyx which could be beneficial for intestinal bacterial infection in animals. Maximum concentration and area under concentration time curve were increased with particles size reduction which might give rise to pronounce fluctuations in plasma concentration and more intensified antibacterial effects. The terminal half-life and mean resident time of Cyx nanosuspension had also increased compared to normal Cyx suspension. In conclusion, nanosuspensions may be a suitable delivery approach to increase the bioavailability of poorly soluble drugs. Quinoxaline 1, 4-di-N-oxides (QdNOs) are widely used synthetic antibacterial derivatives in animals to treat many gram-negative and gram-positive bacterial infections1–3. The important members of this group including carbadox, olaquindox and mequindox have been strictly limited to use due to potential toxicity in animals. Cyadox (Cyx) is believed to be safer and effective antibacterial agent of QdNOs with much lower toxicity in animals compared to other members of this group4, 5. It has been used as an effective antibacterial agent against most of pathogenic bacterial species in animals including Salmonella, Escherichia coli, Pasturella and Staphylococcus species6, 7. Dogs are generally considered to more likely to these type of bacterial infections8, 9. Considering its exceptional safety as well as efficacy, Cyx might be a promising antibacterial agent to treat infectious diseases in various animal species, including canines. However, the Cyx has a poor solubility in aqueous medium as well as simultaneously in organic solvents, which is becoming its major challenge in the clinic application for animal infection treatment. The low solubility leads to drug delivery complications like erratic absorption and unsatisfactory oral bioavailability. Due to large requirement of volume, intravenous delivery is also not possible. Currently, there is no effective formulation for Cyx except the premix. Therefore, the enhancement of Cyx solubility should be firstly solved in its development. Many traditional approaches are adopted to enhance the drug solubility i.e co-solvents, micronization and cyclodextrin. But, bioavailability problem remains as such in many cases, as micronization does not produce a sufficient surface in order to increase the dissolution velocity of poorly soluble drugs. Consequently, the industry has moved forward from micronization to nanonization (production of drug nanocrystals)10–12. Production of nanocrystals revolutionized the pharmaceutical industry by improving the performance of poorly soluble drugs. 1 National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, 430070, China. 2MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China. 3MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China. Adeel Sattar and Dongmei Chen contributed equally to this work. Correspondence and requests for materials should be addressed to S.X. (email: ) or Z.Y. (email: ) Scientific Reports | 7: 2289 | DOI:10.1038/s41598-017-02523-4 1 www.nature.com/scientificreports/ Figure 1. The stability of cyadox nanosuspension prepared with different stabilizer. (A) Poloxamer 407; (B) Poloxamer 188; (C) Sodium alginate; (D) Pluronic F-68; (E) Polyvinyl pyrrolidone; (F) Polyvinyl alcohol. ® Homogenization pressure (bar) Cycle times Particle sizes (nm) 300 1 738.9 ± 103.0 300 3 636.0 ± 49.32 300 6 645.1 ± 55.14 300 10 652.0 ± 50.27 1200 1 524.1 ± 58.12 1200 3 460.9 ± 29.52 1200 6 364.3 ± 34.28 1200 10 325.7 ± 40.61 Table 1. Effect of homogenization pressure and cycle times on the sizes of nanosuspension. Nanocrystals enhance the saturation solubility as well as dissolution velocity, improved bioavailability, proportionality and oral absorption13, 14. Nanocrystals are considered to be a good choice in those conditions where low absorption of the drug is mainly due to dissolution velocity. Not only for oral route of administration, nanosuspension can also be effectively used intravenously as well as other routes like ocular, dermal or pulmonary routes15. Because of relatively cheaper cost, larger drug loading capability, production in scale up, and none or fewer carrier-associated side effects, the nanosuspension are easily commercialized16. There is currently several related nanocrystal production in human medicine clinic after the first product Emend introduced in the market in 2000. Therefore, the nanocrystal might an effective way to improve the solubility and bioavailability. Nanocrystals can be generated by two basic approaches, bottom-up (controlled precipitation/crystallization) and top-down technologies as well as nanonizing (reduction of large size drug particles to smaller ones by mechanical grinding down)17. In case of bottom-up technique, organic solvent is used to dissolve the drug and precipitated by adding an anti-solvent in the presence of a stabilizer. As a result, homogenous and smaller size particles are formed18. In addition, it may result in the production of amorphous drug nanoparticles which have high dissolution rate as well as saturation solubility19. Whereas, top-down technique involves the reduction of particle size by using various processes like micro-fluidization, high pressure homogenization and media milling20. The combination techniques, combining a pre-treatment with a subsequent size reduction step are also widely employed for obtaining more homogenous nanoparticles. In this study, th (...truncated)