Surfactants polyoxyethylene stearates

Surfactants Polyoxyethylene stearate, Renex, Poloxamer 188, Texafor AIP, deoxycholic acid. Tweens, Spans Miscellaneous Pentaerythritol, pentaerythrityltetracetate, urea, urethane, hydroxyalkylxanthins. 

Some studies reported that polyoxyethylene (POE) stearates (under the brand name Myrj) and alkyl-polyethyleneoxide (PEO) surfactants (under the brand name Brij) can inhibit efflux pumps. The oral bioavailability of the P-gp substrate cyclosporine A administered in a solid dispersion of polyoxyethylene 40 stearate (Myrj 52) was in the same range as the oral bioavailability of the commercial product Sandimmune Neoral (Liu et al. 2006). In a study by Lo, it has been shown that apical to basolateral epirubicin transport across Caco-2 cells was enhanced in the presence of polyoxyethylene 40 stearate and the basolateral to apical transport was decreased. These results indicate that polyoxyethylene stearates effect efflux pumps (Lo 2003). Similar results were gained when using polyoxyethylene laurylether (Brij 30). In another study, tablets based on polyoxyethylene 40 stearate containing the P-gp substrate rhodamine 123 increased the oral bioavailability in rats by about 2.4-fold (Foger et al. 2006a). 

Materials that are solubilized in polyethylene glycol can be solubilized in the polyoxyethylene chains on the surface of a nonionic micelle. Ismail, Gouda, and Motawi found that the micellar partition coefficients of barbiturates in polysorbates 20, 40, 60, and 80 is a function of the solute substituents and is proportional to the octanol-water partition coefficient of the barbiturate. Similarly, Ikeda, Kato, and Tukamoto showed that the solubilization of alkyl barbiturates by polyoxyethylene lauryl ether is not dependent upon the number of carbons in the substituents. Since the different polysorbates contain different aliphatic groups, the rather small dependence of solubilization upon polysorbate number (i.e., upon alkyl chain length) suggests that the barbiturates are not solubilized primarily in the hydrocarbon portion of the micelle. Gouda, Ismail, and Motawi showed that the solubilization of barbiturates in polyoxyethylene stearates is proportional to the number of polyoxyethylene units in the surfactant. 

Several non-ionic surface-active materials have been developed as suppositories vehicles. Many of these bases, known as water-dispersible bases, can be used for the formulation of both water-soluble and oil-soluble drugs. The surfactants most commonly used are thepolyoxyethylene sorbitan fatty acid esters (Tweens), the polyoxyethylene stearates, and the sorbitan fatty acidesters (Spans). These surfactants may be used alone, blended, or with other suppository base materials to yield a wide range of melting points and consistencies. 

Polyoxyethylene stearates are nonionic surfactants produced by polyethoxylation of stearic acid. Two systems of nomenclature are used for these materials. The number 8 in the names poloxyl 8 stearate or polyoxyethylene 8 stearate refers to the approximate polymer length in oxyethylene units. 

Polyoxyethylene stearates are particularly useful as emulsifying agents when astringent salts or other strong electrolytes are present. They can also be blended with other surfactants to obtain any hydrophilic-lipophilic balance for lotions or ointment formulations. See Table III. 

A relationship between the lipophilicity of the solubilisate, expressed by the partition coefficient between octanol and water, Poctanoi (see Chapter 5), and its extent of solubilisation has been noted for the soluhilisation of substituted barbituric acids by polyoxyethylene stearates, of substituted benzoic acids by polysorbate 20, and of several steroids by polyoxyethylene nonionic surfactants. An exhaustive survey of data for the solubilisation of some 64 dmgs by bile salt micelles revealed linear relationships between log (partition coefficient between micelles and water) and log Poctanoi ach of seven bile salts... 

Figure 5.8 Micellar solubilization in polyoxyethylene stearates. The number of equivalents solubilized per equivalent of oxyethylene group is plotted as the ordinate against the stearate-ethylene oxide mole ratio for the surfactants. , p-hydroxybenzoic acid O, benzoic acid A, o-hydroxybenzoic acid V, methyl p-hydroxybenzoate andt>, propyl p-hydroxybenzoate. From Mukerjee [81] with permission.

Several authors have noted a relationship between the lipophilicity of the solubilizate, expressed as its partition coefficient between octanol and water, Pocianob its Saturation distribution between micelles and the aqueous phase. Rank-order correlations between the amount of substituted barbituric acid solubilized by polyoxyethylene stearates and their Poctanoi values have been reported by Ismail et al. [133]. Similarly the partition coefficients of several steroids between water and micelles of long-chain polyoxyethylene non-ionic surfactants have been correlated with their ether/water partition coefficients [145], Fig. 5.18 shows a linear relationship between the partition coefficient of a... 

Chlorobutanol, benzyl alcohol, and phenylethyl alcohol-non-ionic systems have been studied at two temperatures [205], as was the binding of benzoic acid by polyoxyethylene stearates [206]. The latter confirmed that solubilization was greatest in the least hydrophilic surfactant (on percentage basis) and there was no evidence of interaction below the CMC. 

Gluten was obtained from ProVim, a gluten-enriched flour, by a conventional dough-and-wash procedure (16). Gliadin was separated from the gluten by the method of Jones et al. (17). The surfactants selected for study were Myrj 45 [polyoxyethylene (8) stearate], Tween 60 [polyoxyethylene (20) sorbitan monostearate], Brij 35 [polyoxyethylene (23) lauryl ether], Brij 76 [polyoxyethylene (10) stearyl ether], Brij 78 [polyoxyethylene (20) stearyl ether], and calcium stearoyl-2-lactylate. (Note that the numbers in parentheses indicate the number of monomer units of ethylene oxide.) Working solutions were made up in 70% ethanol at 2.5 mg per 100 ml solution. 

If the solubility of a surfactant is highly temperature-dependent, as is the case for many nonionic polyoxyethylene surfactants and long chain fatty acid soaps such as sodium stearate, it will be found that foaming ability will increase in the same direction as its solubility. Nonionic POE surfactants, for example, exhibit a decrease in foam production as the temperature is increased and the cloud point is approached (solubility decreases). Long-chain carboxylate salts, on the other hand, which may have limited solubility and poor foaming properties in water at room temperature, will be more soluble and will foam more as the temperature increases. 

Anionic surfactants are the most commonly used type in the emulsion polymerization. These include sulfates (sodium lauryl sulfate), sulfonates (sodium dodecylbenzene sulfonate), fatty acid soaps (sodium or potassium stearate, laurate, palmitate), and the Aerosol series (sodium dialkyl sulphosuccinates) such as Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) and Aerosol MA (AMA, sodium dihexyl sulphosuccinates). The sulfates and sulfonates are useful for polymerization in acidic medium where fatty acid soaps are unstable or where the final product must be stable toward either acid or heavy-metal ions. The AOT is usually dissolved in organic solvents to form the thermodynamically stable reverse micelles. [22] Nonionic surfactants usually include the Brij type, Span-Tween 80 (a commercial mixture of sorbitol monooleate and polysorbate 80), TritonX-100[polyoxyethylene(9)4-(l,l,3,3-tetramethylbutyl)-phenyl... 

Although in many cases a particular location is preferred, the lifetime of a solubilizate within the micelle is long enough for a rapid interchange between different locations [80]. Mukerjee [81] has discussed the solubilization of benzoic acid derivatives by a series of polyoxyethylene surfactants (the Myrj class of non-ionic surfactants) in terms of an equilibrium distribution between two loci-the polyoxyethylene shell and the hydrocarbon core. The amount of the solubilizate solubilized in the core and polyoxyethylene region was assumed to be proportional to the number of equivalents of the alkyl chain moiety (stearate), Cr, and the number of equivalents of oxyethylene groups, respectively. The... 

Table 6.11 Relation between HLB of polyoxyethylene glycol stearates and polyoxyethylene glycol sorbitan fatty acid esters and the minimum bactericidal concentration of tyrothricin. Surfactant concentration 2x lO- moir ...

Figure 10.20(a) Reciprocal time of death of planarian as a function of surfactant concentration at 20° C. polyoxyethylene 20 stearate O, polyoxyethylene 30 stearate , polyoxyl 40 stearate , polyoxyethylene 50 stearate and , polyoxyethylene 100 stearate, (b) Reciprocal time of death of planarian as a function of surfactant concentration at 20 °C., polysorbate 20 O, polysorbate 40 A, polysorbate 60 and , polysorbate 80. From Isomaa and Ahlroth [192] with permission. 

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