Corneal targeted nanoparticles for sustained natamycin delivery and their PK/PD indices: An approach to reduce dose and dosing frequency Hardik Chandasana a, d,1 , Yarra Durga Prasad a, e,1 , Yashpal S. Chhonker a, d , Telaprolu K. Chaitanya a, e , Nripendra N. Mishra b , Kalyan Mitra c, d , Praveen K. Shukla b, e , Rabi S. Bhatta a, d, e, * a Pharmacokinetics & Metabolism Div., CSIR-Central Drug Research Institute, Lucknow 226031, India b Microbiology Div., CSIR-Central Drug Research Institute, Lucknow 226031, India c Electron Microscopy Unit, CSIR-Central Drug Research Institute, Lucknow 226031, India d Academy of Scientific and Innovative Research (AcSIR), Anusandhan Bhawan, Rafi Marg, New Delhi 110001, India e Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Raebareli 229010, India A R T I C L E I N F O Article history: Received 14 July 2014 Received in revised form 10 October 2014 Accepted 11 October 2014 Available online 16 October 2014 Keywords: Mycotic keratitis Natamycin Ocular drug delivery Polycaprolactone Nanoparticles Pharmacokinetic/pharmacodynamic indices A B S T R A C T Natamycin is the only approved medication for the treatment of mycotic keratitis. Current dosage regimen include one drop of natamycin suspension (5% w/v) instilled in the conjunctival sac at hourly or two hourly intervals for several days which has poor patient compliance. The purpose of the present study was to design a corneal targeted nanoformulation in order to reduce dose and dosing frequency of natamycin and evaluate its pharmacokinetic/pharmacodynamic indices in comparison with clinical marketed preparation. The nanoparticles prepared by nanoprecipitation method were in nanometer size range with high entrapment efficiency and positive surface charge. In-vitro release studies indicated prolonged release of natamycin up to 8 h. In-vitro antifungal activity was comparable with marketed preparation. The performance of nanoformulations was evaluated in rabbit eyes. The concentration of natamycin in tear fluid was determined by using LC–MS/MS. The pharmacokinetic parameters such as area under the curve, t1 / 2 and mean residence time were significantly higher and clearance was significantly lower for nanoformulations with that of marketed preparation. The optimized dosing schedule to maintain natamycin concentration above tenfold of MIC 90 was one instillation in every 5 h. Moreover, 1/5th dose reduction of nanoformulation was also effective. ã 2014 Elsevier B.V. All rights reserved. 1. Introduction Mycotic keratitis (MK) is a corneal fungal infection character- ized by decreased vision, photophobia, feathery-edged infiltrates and satellite lesions across the cornea. It can lead to blindness and loss of the affected eye if not diagnosed early and treated rapidly (Chang and Chodosh, 2011; Chowdhary and Singh, 2005; Gopinathan et al., 2002; Liu et al., 2013; Shokohi et al., 2006; Xie et al., 2006). The predisposing factors involve ocular trauma associated with vegetable matter in rural areas and contact lens use in developed countries. Other risk factors include disproportionate use of broad spectrum antibiotics, steroid drops, increased number of eye surgeries (e.g. penetrating keratoplasty or laser assisted in situ keratomileusis (LASIK)) that lead to compromised corneal surface (Patel and Hammersmith, 2008; Rosa et al., 1994; Yildiz et al., 2010). Across the world Aspergillus, Candida and Fusarium species have been known to cause MK, out of which the most commonly implicated pathogen isolated from MK is filamentous Aspergillus (Tanure et al., 2000). Natamycin (pimaricin), the most valuable antifungal agent till date, has been considered as the drug of choice for filamentous MK. It is the only commercially available US-FDA approved agent for the treatment of MK. Natamycin 5% w/v suspension prescribed as one drop instilled in the conjunctival sac at hourly or two hourly intervals for several days (USFDA, 2008). Current therapy with natamycin appears unsatisfactory for several reasons such as high dosing frequency, long treatment duration (4–6 weeks), short residence time at the ocular mucosa due to quick clearance by the naso- pharyngeal drainage. This prolonged dosing schedule is difficult to * Corresponding author at: CSIR-Central Drug Research Institute, Pharmacoki- netics and Metabolism Div., 10/1, Sector-10, Jankipuram Extension, Lucknow, Uttar Pradesh 226031, India. Tel.: + 91 522 2772974x4853; fax: +91 0522 2771942. E-mail addresses: rabi.cdri@gmail.com, rabi_bhatta@cdri.res.in (R.S. Bhatta). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.ijpharm.2014.10.035 0378-5173/ ã 2014 Elsevier B.V. All rights reserved. International Journal of Pharmaceutics 477 (2014) 317–325 Contents lists available at ScienceDirect International Journal of Pharmaceutics journal homepage: www.elsev ier.com/locate /ijpharm