Surfactant concentration-drug combination

Surfactant concentration-drug combination gave the greatest respirable fraction of the aerosols. ... 

This expression is obtained by combining equations (11.31) and (11.34) for a non-ionizable drug R when Kf is unaifected by co-former and = A surfactant concentration that increases drug solubility 100-fold is predicted to increase co-crystal solubility 10-fold. Equation (11.35) implies that a surfactant will increase the solubility of all 1 1 co-crystals of a drug by the same ratio as long as the stated assumptions are justified. 

The preferred method of delivery of oral microemulsion formulations is either as a combination of drug, lipid, and surfactant/cosurfactant (generally filled into soft or sealed hard gelatin capsules) that spontaneously microemulsify in the GIT, or as a microemulsion preconcentrate in which the dose form contains a small quantity of hydrophilic phase and is in itself a concentrated O/W or W/O microemulsion, which becomes diluted or phase inverted in the GI fluids. 

In both MEKC methods reported, the mobile phase consisted of borate buffer containing surfactant and acetonitrile. It was foimd that mobile phase prepared at pH 9.75 gave better resolution compared to other conditions, and increasing pH also increased the migration time of ezetimibe. An analyte concentration of 25 mM was chosen due to its lower current, and the sharp peaks observed [41]. In addition, for the analysis of ezetimibe in combination with another drug such as simvastatin, increasing the borate concentration increased both resolution and migration times. 

The combined effect of pH and surfactants on the dissolution of piroxicam has been reported. " In this system, the dissolution rate and solubility of the drug substance could be well estimated by a simple additive model for the effect of pH and surfactant, where the total dissolved concentration equaled the summation of the amoimt of dissolved non-ionized substance, the amount of dissolved ionized substance, and the amoimt of substance solubilized in the surfactant micelles. It was suggested that the model developed in this work could be useful in establishing an in vitro-in vivo correlation for piroxicam. 

Cetylpyridinium chloride is a quaternary ammonium cationic surfactant, used in pharmaceutical and cosmetic formulations as an antimicrobial preservative see Section 10. It is used therapeutically as an antiseptic agent used alone or in combination with other drugs for oral and throat care used in nonparenteral formulations licensed in the UK and used in oral and inhalation preparations at concentrations of 0.02-1.5 mg (see Section 16). 

Release of methotrexate, metoclopramide and sodium chloride from type A, B and C w/isopropyl myristate/w emulsions have been compared (Fig. 5 a,b,c). In all cases, release from the type C emulsion is not prolonged, which may be a reflection of stability or structure or a combination of these two parameters. In the case of methotrexate, variation of the concentration of secondary surfactant (polysorbate 80) from 0.5 to 20% had no significant effect on the rate of drug release from the system. 

In order to keep the use concentrations low, the solubilizing power of one surfactant is rarely utilized alone. Thus, combinations of two or more surfactants are used to optimize the solubilization effect by the formation of mixed micelles, especially with lecithin and bile acids. For injectable solutions mostly several solubilization principles are combined as can be seen in the examples. By employing pH adjustment and 5% sodium dodecyl sulfate, the solubility of the investigational cancer drug pyroxamide could thus be increased by a factor of nearly half a million over its intrinsic solubility. ... 

Although the micellar solubilization can be demonstrated in vitro there is no warrant for a corresponding enhancement of bioavailability by the oral route in any case. With particular combinations of drug substance and surfactant, even reduced instead of improved bioavailability has been observed. Such effects depend on the concentration of the surfactant and may have various reasons such as shift of equilibrium in favour of micellar inclusion or formation of other types of drug-surfactant aggregates. 

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