Experimental Solubility, Thermodynamic/Computational Validations, and GastroPlus-Based In Silico Prediction for Subcutaneous Delivery of Rifampicin.

We focused to explore a suitable solvent for rifampicin (RIF) recommended for subcutaneous (sub-Q) delivery [ethylene glycol (EG), propylene glycol (PG), tween 20, polyethylene glycol-400 (PEG400), oleic acid (OA), N-methyl-2-pyrrolidone (NMP), cremophor-EL (CEL), ethyl oleate (EO), methanol, and glycerol] followed by computational validations and in-silico prediction using GastroPlus. The experimental solubility was conducted over temperature ranges T = 298.2-318.2 K) and fixed pressure (p = 0.1 MPa) followed by validation employing computational models (Apelblat, and van't Hoff). Moreover, the HSPiP solubility software provided the Hansen solubility parameters. At T = 318.2K, the estimated maximum solubility (in term of mole fraction) values of the drug were in order of NMP (11.9 × 10-2) ˃ methanol (6.8 × 10-2) ˃ PEG400 (4.8 × 10-2) ˃ tween 20 (3.4 × 10-2). The drug dissolution was endothermic process and entropy driven as evident from "apparent thermodynamic analysis". The activity coefficients confirmed facilitated RIF-NMP interactions for increased solubility among them. Eventually, GastroPlus predicted the impact of critical input parameters on major pharmacokinetics responses after sub-Q delivery as compared to oral delivery. Thus, NMP may be the best solvent for sub-Q delivery of RIF to treat skin tuberculosis (local and systemic) and cutaneous related disease at explored concentration.

Enhanced stability and permeation potential of nanoemulsion containing sefsol-218 oil for topical delivery of amphotericin B.

AIM: To characterize the enhanced stability and permeation potential of amphotericin B nanoemulsion comprising sefsol-218 oil at varying pH and temperature of aqueous continuous phase. METHODOLOGY: Several batches of amphotericin B loaded nanoemulsion were prepared and evaluated for their physical and chemical stability at different pH and temperature. Also, a comparative study of ex vivo drug permeation across the albino rat skin was investigated with commercial Fungisome® and drug solution at 37 °C for 24 h. The extent of drug penetrated through the rat skin was thereby evaluated using the confocal laser scanning microscopy (CLSM). RESULTS AND CONCLUSIONS: The optimized nanoemulsion demonstrated the highest flux rate 17.85 ± 0.5 µg/cm(2)/h than drug solution (5.37 ± 0.01 µg/cm(2)/h) and Fungisome® (7.97 ± 0.01 µg/cm(2)/h). Ex vivo drug penetration mechanism from the developed formulations at pH 6.8 and pH 7.4 of aqueous phase pH using the CLSM revealed enhanced penetration. Ex vivo drug penetration studies of developed formulation comprising of CLSM revealed enhanced penetration in aqueous phase at pH 6.8 and 7.4. The aggregation behavior of nanoemulsion at both the pH was found to be minimum and non-nephrotoxic. The stability of amphotericin B was obtained in terms of pH, optical density, globular size, polydispersity index and zeta potential value at different temperature for 90 days. The slowest drug degradation was observed in aqueous phase at pH 7.4 with shelf life 20.03-folds higher when stored at 4 °C (3.8 years) and 5-fold higher at 25 °C (0.951 years) than at 40 °C. The combined results suggested that nanoemulsion may hold an alternative for enhanced and sustained topical delivery system for amphotericin B.

Elastic liposome-based gel for topical delivery of 5-fluorouracil: in vitro and in vivo investigation.

OBJECTIVE: This investigation has focused to characterize the elastic liposome containing 5-fluorouracil (5-FU) and to enhance drug permeation across stratum corneum (SC) of the skin (rat) using various surfactants and in vivo dermal toxicity evaluation. METHODOLOGY: 5-FU-loaded elastic liposomes were developed, prepared and characterized for their entrapment efficiency, vesicle size, number of vesicles, morphological characteristics, surface charge and turbidity. In vitro drug release profile, in vitro skin permeation potential and in vitro hemolytic ability of the formulation have been evaluated to compare with drug solution for 24 h. In vitro skin permeation potential was also compared with marketed cream. Furthermore, in vivo skin irritation potential, drug penetration into the skin using confocal laser scanning microscopy (CLSM) and in vivo toxicity studies were performed. RESULTS AND CONCLUSIONS: The optimized elastic liposomes demonstrated maximum drug entrapment efficiency, optimum vesicular size and considerable elasticity. In vitro skin permeation studies showed the highest drug permeation flux like 77.07 ± 6.34, 89.74 ± 8.5 and 70.90 ± 9.6 µg/cm(2)/h for EL3-S60, EL3-S80 and EL3-T80, respectively, as compared to drug solution (8.958 ± 6.9 µg/cm(2)/h) and liposome (36.80 ± 6.4 µg/cm(2)/h). Drug deposition of optimized elastic liposome EL3-S80 was about three fold higher than drug solution. Skin irritation and CLSM studies suggested that optimized gel was free from skin irritation and capable to deliver 5-FU into the epidermal area for enhanced topical delivery than drug solution. The in vitro study showed minimum hemolysis in the optimized formulation. Finally, in vivo toxicity studies followed with hisptopathological assessment showed that elastic liposome was able to extract SC to improve drug permeation without changing general anatomy of the skin.