C

Time (min)

—*-LabrafacCM 10 BM 287 (C8-C10)—■— Labrafil M 10 BM355(C18:2) —Labrafil NA 10 BM 369 (C18:1)

Figure 3 Effect of chain length and saturation of fatty acid present in the glyceride on drug release of Ro 15-0778 from peanut oil based solution containing 60% of emulsifier with hydrophilic-lipophilic balance of 10 (Paddles, 50rpm, 900mL of 5% Cremophor EL aqueous solution).

The effect of the surfactant (Labrafac CM10) concentration on the drug oil-water partition coefficient, lipid droplet size, and drug release rate from a SEDDS formulation was investigated by Shah et al. (Fig. 4) (11). Increased surfactant concentrations were correlated with both a smaller lipid droplet size and a reduced oil-water partition coefficient for the drug, which in turn, were associated with more rapid drug release, as determined in 900 mL of 5% aqueous solution of Alkamuls EL-719, in a USP XXII, Dissolution Apparatus 2.

Dielectric Constant (e)

The dielectric constant that increases in proportion to the relative polarity of a molecule, is determined by oscillometry and is defined as the ratio of the capacity of a condenser (made with the test substance as the dielectric material) to the capacity of the same condenser with air as the dielectric, as determined at a frequency of 1 MHz (30). Given the general assumption that "like dissolves in like," substances with similar dielectric constants are typically miscible with one another.

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