Emulsion drug absorption

The role of droplet size on drug stability stems from the correlation between droplet size and surface area, and between surface area of droplets and exposure of drug to the aqueous media. If the drug is relatively insensitive to aqueous media, this may not be a major issue however, for the converse situation, development of emulsions with relatively coarser droplet size may offer improved drug stability. Nonetheless, this should be balanced with physical stability of the emulsion as well as the efLciency of drug absorption after oral administration (Toguchi et al., 1990). 

Surfactants have been the most investigated chemicals to promote drug absorption from all body tracts. In this section, we will focus on work carried out from the early stages on the enhancing effects of surfactants on drug GI absorption as well as on their interactions with the GI membrane and their toxicity. Systems with multifactorial effects such as emulsions and microemulsions are not the focus of this review. 

Yang, S. C., and Benita, S. (2000), Enhanced absorption and drag targeting by positively charged submicron emulsions, Drug Dev. Res., 50,476 186. 

Usually, dmgs dissolved in oils are absorbed mainly via the aqueous phase. Transport from one phase to the other and partitioning are therefore important. In the absorption of drugs from o/w emulsions when the dmg partition coefficient is greater than 1, the amount of dmg in the aqueous phase (rather than the concentration) is a critical factor for absorption. In the absorption of poorly oil-soluble drugs, drug absorption from emulsions is greater than from aqueous solution. In an emulsion of volume ratio, O, the dmg concentration in the aqueous phase (C ) is related to the overall concentration of the dmg (C) by the expression ... 

Percutaneous preparations (gels, creams, and emulsions) are convenient, but variability in drug absorption is common. This form of estrogen is used for systemic therapy. Topical emulsion and gel formulations were approved for use recently in the United States. 

T. Honda. M. Okamoto, M. Maeda. T, Kawagoshi, H, Nihonmaisu. 1. Yamashita. M. Yoshida. K. Tazawa. M. Fujimaki. DDS with MFGM (milk fat globule membrane) intestinal absorption of MFOM-insulin emulsion. Drug Deliv Syst 7 4,1-46. 1992. 

Figure 8.44 The effect of aqueous phase volume on drug absorption from emulsions when the drug has a partition coefficient of less than unity.

As with micelle-facilitated dissolution, emulsion-facilitated dissolution has gained renewed interest due to its application to water-insoluble drug delivery and enhanced absorption. Over the years, emulsion systems have been developed and used to either model the in vivo dissolution process or mimic the intestinal surfactant system to enhance drug delivery of poorly soluble compounds [54-66], Emulsions have also been used as vehicles for drug delivery, e.g., to protect... 

Spontaneous emulsification of oils carrying drugs make SEDDS good candidates for the oral delivery of hydrophobic drugs with adequate oil solubility since the drug will be presented as a fine (submicron) emulsion that has a large surface area across which diffusion can take place rapidly, thereby facilitating absorption into the body. 

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