Lipid-polyethylene glycol based nano-ocular formulation of ketoconazole
Graphical abstract
Introduction
Local delivery to the eye, though a preferred route with lower incidence of systemic side effects, cannot address internal eye diseases (Sigurdsson et al., 2007, Bucolo et al., 2012, Geroski and Edelhauser, 2000, Ahmed and Patton, 1985, Hughes et al., 2005). Nanostructured systems may however deliver drug successfully to the posterior segment of the eye (Kaur and Kakkar, 2014). Solid lipid nanoparticles (SLNs), comprising of a nanosized lipidic core stabilized by a layer of surfactants is now attaining popularity as a suitable system for ocular delivery (Leonardi et al., 2014, Seyfoddin et al., 2010). Both the nano size, and the lipidic nature of SLNs helps to improve ocular bioavailability of encapsulated drug; both due to prolonged ocular retention and improved permeation (Hippalgaonkar et al., 2013, Mohanty et al., 2015, Seyfoddin et al., 2010).
Fungal infections of the eye, though less common than infections with bacteria and viruses, are usually more severe and may lead to loss of vision. With an increased immunocompromised population, including HIV infected persons, patients undergoing surgeries/transplants, and those receiving chemotherapy, the ophthalmic mycosis is howsoever on the rise. Efficient administration of appropriate antifungal therapy can help to preserve vision, provided the agent reaches the affected tissue in sufficient concentration (Kaur et al., 2008b).
Ketoconazole (KTZ) is a broad spectrum antifungal agent, with high lipo-solubility (log P = 4.74) (Logua et al., 1997) but a short ocular half life (elimination half life is 19 min in aqueous humor and 43 min in cornea) (Zhang et al., 2008) and very poor solubility (0.04 mg/ml). It is recommended to be administered orally at a dose of 100 to 400 mg every 12 h (Müller et al., 2013). However, it is associated with low oral bioavailability (Baxter et al., 1986) and severe adverse effects like nausea, vomiting, gastrointestinal disturbance, hepatitis, gynecomastia, adrenal cortex suppression (O’Brien, 1999) and hepatotoxicity (FDA, 2013, Sharma et al., 1993). Its absorption from the gut is dependent on the gastric pH. Significant drug–drug interactions are also reported upon its oral administration (Thomas, 2003).
High lipophilicity of KTZ may promote permeation, however its large molecular weight (531.44 Da), tends to impede its transport across the biological membranes. Similarly, high lipid solubility although can help passage across corneal epithelium, however, its passage through the aqueous corneal stroma will be compromised (Barar et al., 2008) following topical administration. Furthermore, its limiting water solubility (0.04 mg/ml) makes it difficult to present KTZ in a solubilised form on the corneal surface, latter being an important pre-requisite for ocular formulations.
Presently SLN ocular dispersion of KTZ was designed to provide an alternate topical route rather than an oral route of administration, which is associated with significant adverse effects. Further intent of the study is to develop a nanocarrier system which can permeate upto the posterior eye in an intact form so as to carry the incorporated drug along with it. Fungal infection of the internal eye invariably leads to vision loss within a short span and achieving high drug concentration in the vitreous is difficult post oral administration due to the existence of blood-aqueous and blood-retinal barriers. Developed KTZ-SLN system was extensively characterized and confirmed to permeate the cornea via ex vivo corneal permeation studies. In vivo pharmacokinetic profile of KTZ-SLN was compared with the corresponding free drug dispersion. In vitro and in vivo safety and autoclavability of the developed KTZ-SLN system was confirmed. The dispersion was comprehensively developed as a suitable ocular formulation in terms of pH, refractive index, osmolarity, stability on keeping (both entrapment efficiency and particle size were evaluated upto 1 year) and preservation against contamination (using challenge test). Though a well established preservative benzalkonium chloride (BAK) was employed, but it is important to confirm that physical adsorption or interaction with any of the components does not compromise the activity of BAK.
Section snippets
Materials and selection of components
Ketoconazole was a kind gift from Torrent Pharmaceuticals Pvt. Ltd., H.P., India; Compritol® 888 ATO was a gift sample from Gattefosse, France; and Phospholipon 90 G (soya lecithin) was gifted by Lipoid, Germany. Phosphotungstic acid (PTA) and BAK were procured from Sigma–Aldrich, USA. All other reagents used in the study were of analytical grade.
Compritol® 888 ATO was presently chosen as the lipid component, because it is reported to result in stable SLN formulations with small particle size (
Characterization of SLNs
Transmission electron microscopy indicated SLNs to be small in size (between 70 and 135 nm) and spherical in shape, with no aggregation/irregularities in the system (Fig. 1). Particle size, total drug content, EE, zeta potential, pH, osmolarity and RI of the developed KTZ-SLNs is included in Table 1.
The PDI of <0.3 (presently 0.28 ± 0.02) indicates narrow particle size distribution (Madheswaran et al., 2013). No micronized particles were observed in the entire population and majority (90%) of the
Discussion
Majority of fungal pathogens including Aspergillus sp., Candida sp., and Fusarium sp. and their clinical isolates are susceptible and sensitive to KTZ (Therese et al., 2006). Inspite of showing effectiveness against the commonly occurring infections of the eye (Therese et al., 2006, Grossman and Lee, 1989), no ocular formulation of KTZ is in the market. Effective concentrations of KTZ have been established, but only in the debrided cornea (Hemady et al., 1992), indicating that permeation
Conclusion
Ketoconazole was successfully entrapped in lipidic core providing enhanced permeation through cornea and higher bioavailability both in the aqueous and vitreous humor. The developed nanoparticles were able to cross ocular barrier, reach posterior segment of the eye and had significant antifungal potential. Thus, the developed SLNs can be used both for the treatment of keratitis and endophthalmitis. Corresponding safety in corneal and retinal cell lines followed by in vivo acute and subchronic
Declaration of interest
The authors report no declarations of interest.
Acknowledgments
The funding provided by DST, New Delhi, India, is highly acknowledged. Dr Jayant Raut is thankful for the UGC-D S Kothari post doctorate fellowship.
Characterization studies conducted at PU-SAIF centre are highly acknowledged. Special thanks are due to Mr. Avtar Singh and Mr. Manish Kumar for interpretation of NMR data and to Mr. Dinesh Sharma for TEM pictures.
References (98)
Influence of intestinal efflux pumps on the absorption and transport of furosemide
Saudi Pharm. J.
(2010)- et al.
Diclofenac sodium delivery to the eye: in vitro evaluation of novel solid lipid nanoparticle formulation using human cornea construct
Int. J. Pharm. Res.
(2008) - et al.
Solid lipid nanodispersions containing mixed lipid core and a polar heterolipid: characterization
Eur. J. Pharm. Biopharm.
(2007) - et al.
Pharmacokinetics of ketoconazole administered intravenously to dogs and orally as tablet and solution to humans and dogs
J. Pharm. Sci.
(1986) - et al.
New surface-active polymers for ophthalmic formulations: evaluation of ocular tolerance
Eur. J. Pharm. Biopharm.
(2004) - et al.
Pharmacokinetics, tissue distribution and relative bioavailability of isoniazid-solid lipid nanoparticles
Int. J. Pharm.
(2013) - et al.
Crystallization tendency and polymorphic transitions in triglyceride nanoparticles
Int. J. Pharm.
(1996) - et al.
Solid lipid nanoparticles (SLN) as ocular delivery system for tobramycin
Int. J. Pharm.
(2002) - et al.
P-Glycoprotein expression in human retinal pigment epithelium cell lines
Exp. Eye Res.
(2006) - et al.
Development of a nanostructured lipid carrier formulation for increasing photo-stability and water solubility of phenylethyl resorcinol
Appl. Surf. Sci.
(2014)