Nanoemulsion drug delivery systems are advanced modes for delivering and improving the bioavailability of hydrophobic drugs and the drug which have high first pass metabolism. The nanoemulsion can be prepared by both high energy and low energy methods. High energy method includes high-pressure homogenization, microfluidization, and ultrasonication whereas low energy methods include the phase inversion emulsification method and the self-nanoemulsification method. Low energy methods should be preferred over high energy methods as these methods require less energy, so are more efficient and do not require any sophisticated instruments. However high energy methods are more favorable for food grade emulsion as they require lower quantities of surfactant than low energy methods. Techniques for formulation of nanoemulsion drug delivery system are overlapping in nature, especially in the case of low energy methods. In this review, we have classified different methods for formulation of nanoemulsion systems based on energy requirements, nature of phase inversion, and self-emulsification.
Solid dispersions in water-soluble carriers have attracted considerable interest as a means of improving the dissolution rate, and hence possibly bioavailability, of a range of hydrophobic drugs. The poor solubility of carvedilol leads to poor dissolution and hence variation in bioavailability. The purpose of the present investigation was to increase the solubility and dissolution rate of carvedilol for enhancement of oral bioavailability. In the present investigation solid dispersions with poloxamer 188 were prepared by fusion method. The physical mixture and solid dispersion(s) were characterized for drug-carrier interaction, drug content, solubility and dissolution rate. The solubility of drug increased with increasing polymer concentration. The dissolution rate was substantially improved for carvedilol from its solid dispersion compared with pure drug and physical mixture. As indicated from X-ray diffraction pattern, DSC thermograms and SEM photographs, carvedilol was in the amorphous form, which confirmed the better dissolution rate of solid dispersions. FTIR results proved no chemical interaction between carvedilol and poloxamer 188. SEM images showed a novel morphology of solid dispersion compared with pure drug. The solid dispersion was stable under accelerated storage conditions.
Niosomes (nonionic surfactant-based vesicles) containing rifampicin were prepared using various nonionic surfactants of sorbitan ester class and cholesterol in 50:50 percent mol fraction ratio. The drug-entrapped vesicles were characterized for their shape, size, drug entrapment efficiency and in vitro release rate. On the basis of in vitro characterization, the niosomes showing maximum entrapment and minimum release rate were selected for in vivo performance evaluation. Cumulative percent doses of rifampicin recovered in thoracic lymph following intravenous and intraperitoneal administrations of free rifampicin solution and niosome-encapsulated rifampicin were compared. The study revealed that effective compartmentalisation of the drug took place in the lymphatic system following intraperitoneal administration of niosome-encapsulated rifampicin. Thus rifampicin encapsulated in niosomes could successfully be used for treatment of tuberculosis along lymphatic system.
Niosomes (non-ionic, surfactant-based vesicles) containing rifampicin of 8-15 microns in diameter were prepared using Span-85 and cholesterol in various molar fractions. The process variables that could affect the physical characteristics of niosomes and in vitro release of the drug from the niosomes were studied and optimized. In vivo distribution studies of the prepared niosomes found that 65% of the drug could be localized in the lungs by controlling the niosome size.
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