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This study aims to improve gatifloxacin bioavailability to the eye using solid-lipid nanoparticles (SLN). Cationic SLNs were prepared by o/w-microemulsion method using stearylamine. The generated formulations were optimized by three-factor, three-level Box-Behnken statistical design. The independent variables were the lipid(mix) concentration (X1), poloxamers-188 (X2), and sodium-taurocholate (X3), while the dependent variables were drug release (Y1), encapsulation efficiency (EE) (Y2), and particle size (Y3 ) with applied constraints of maximizing drug release and EE and minimizing particle size. Response surface plots were drawn, statistical validity of the polynomials was established, optimized formulations were selected by feasibility and grid search, and the optimization process was validated. Particle size, polydispersity index, and zeta-potentials were measured by photon correlation spectroscopy. Particle's morphology was evaluated by transmission electron microscopy. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXRD) studies were performed to characterize state of drug and lipid modification. SLN size was (250-305 nm) and zeta-potential (29-36 mV) after 3-month storage. Entrapment efficiencies were 46.58 and 78.55%, and loading efficiencies were 29.60 and 20.70 for SLN-C and SLN-D, respectively. DSC and WXRD analyses showed low-crystalline SLN and amorphous drug dispersion in SLN. In vitro release data were fitted to release kinetics equations, where the release pattern was found to follow Korsmeyer-Peppas model.

This study describes corneal permeation of gatifloxacin from solid lipid nanoparticle (SLN) through the cornea and its effect on corneal hydration level. The aqueous humor levels of gatifloxacin after single topical instillation in Gate(®) Eyedrops and positively charged SLN-C were determined. A 3.37-fold increase in the relative bioavailability was observed with the SLN-C (AUC0→∞ 2.192 μg mL(-1) h) (AUC, area under the curve) as compared to Gate(®) Eyedrops (AUC0→∞ 0.651 μg mL(-1) h). The t1/2 of drug in SLN-C exhibited a 2.34-fold higher than Gate(®) Eyedrops seem to be significantly increased (p > 0.05), Cmax of gatifloxacin from SLN-C showed 1.09-fold higher concentration as compared to Gate(®) Eyedrops. The results suggested that SLNs could enhance ocular bioavailability of gatifloxacin and prolong its residence time in the eyes. Moreover, no signs of ocular irritation were seen with the SLN formulations, indicating their relative safety compared to the marketed drops.

The purpose of this study was to determine the pharmacokinetics (PK) of the 5-HT(2A) receptor antagonist ketanserin in healthy adult horses, and to develop a computational model that could be used to optimize dosing. Plasma concentrations of ketanserin were determined using liquid chromatography with mass spectrometry after single and multiple intravenous administration in the horse. A two-compartment linear pharmacokinetic model described the plasma concentration-time profile of ketanserin after single and multiple doses in healthy horses; the terminal half-life was 11.5 h; steady-state volume of distribution was 10.5 L/kg; AUC was 115 ng · h/mL; and clearance was 0.87 L/h/kg. Model simulations followed by the examination in three healthy horses suggest 0.3 mg/kg q.8 h exhibited linear PK and produced consistent systemic blood concentrations of ketanserin above 3 ng/mL.