Surfactants in Pharmaceutical Formulations

Surfactants are used in all disperse systems employed in pharmaceutical formulations. Several types of disperse systems can be identified (Table 13.1). 

This chapter deals with the use of surfactants in the first three classes, namely suspensions, emulsions and gels. Such disperse systems cover a wide size range Colloidal (1 nm-1 pm) to non-colloidal ( 1 pm). Generally speaking they are prepared by two main processes [1]  

Applied Surfactants Principle and Applications. Tharwat F. Tadros Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30629-3 

All disperse systems are thermodynamically unstable, i.e. the free energy of their formation is positive, as illustrated below. 

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The permeability of two peptides, P-gp substrate and non P-gp substrate, across caco-2 cells in the presence or absence of polysorbate 80 and cremophor EL, commonly used surfactants in pharmaceutical formulations, was investigated. The permeability of the P-gp substrate peptide across caco-2 cells was enhanced in the presence of polysorbate 80 and cremophor EL, whereas the non-P-gp substrate peptide was not affected by these surfactants [94]. Another commonly used lipidic excipient that has been shown to inhibit P-gp mediated efflux is D-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) [95]. The insertion of a known CYP3A4 and P-gp inhibitor to the formulation is another approach to elevate bioavailability. 

Docusate sodium and docusate salts are widely used as anionic surfactants in pharmaceutical formulations. Docusate sodium is mainly used in capsule and direct-compression tablet formulations to assist in wetting and dissolution. Docusate salts are also used in oral formulations as laxatives and fecal softeners see Table I. 

I 73 Surfactants in Pharmaceutical Formulations c) Polyoxyethylated glycol monoethers... 

Biological Implications of the Presence of Surfactants in Pharmaceutical Formulations... 

Biological implications of the presence of surfactants in pharmaceutical formulations... 

A fluorinated surfactant in toothpastes containing potassium fluoride enhances fluoroapatite formation and inhibits caries [204]. A fluorinated surfactant formulation (1% Lodyne S-110), which consists of an amphoteric fluoroalky-laminocarboxylic acid and a nonionic fluoroalkylamide synergist, in the toothpaste increases enamel-fluoride interactions. A fluorinated surfactant in pharmaceutical formulations and in toothpaste must be nontoxic for the intended purpose. 

El-Khateeb, S. Z., E. M. Abdel-Moety, Quaternary ammonium surfactants in pharmaceutical formulations by the hypochromic effect, Talanta, 1988,35, 813-815. 

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