Solubility Of Sulpiride In ME Components

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II. Results and discussion:
1. Screening of ME components:
1.1. Solubility of sulpiride in ME components:
In order to achieve maximum drug loading into ME formulation, the oil, which showed higher solubilization capacity for sulpiride is selected for ME preparation. The choice of oil for ME is often a compromise between its solubilization potential for the drug and its ability to microemulsify. Results in table 1 represent the solubility of sulpiride into different oils, surfactants and co-surfactants. Non-polar solvents possessing low dielectric constants can dissolve non-polar solutes with similar internal pressures via induced dipole interactions [23]. Labrafil isostearique showed the greatest solubilization power for sulpiride (16.02
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The area of the formed ME of each system is calculated relative to the whole area of the pseudo-ternary phase diagrams using AutoCAD program 2014. Figures 1 and 2 showed pseudo-ternary phase diagrams of various oils from different origin and fatty acid chain length such as vegetable oil (Avocado oil), long chain triglyceride (Labrafil isostearique) and GMO. These oils were tested for their effects on the area of ME formed. It was observed that the vegetable oil “Avocado” based systems gave no ME systems for all tested surfactants except for T80/Labrasol and the area of ME was the smallest among all S/CoS ratios compared to the other oil based systems (GMO or Labrafil) (Figures 1 and 2). This was reported because Avocado oil is a vegetable oil of high content of saturated and unsaturated fatty acids (15.8% Palmitic, 4.15% Palmitoleic, 49.5% Oleic, 25.1% Linoleic and 3.59% Linolenic) which are too bulky to penetrate the interfacial file to assist in the formation of an optimal surface curvature [28]. On the other hand, GMO has long side chains, with amphiphilic nature, can solubilize amounts of water forming stable monophasic solutions at room temperature, and could give wider ME areas [29]. Low polarity oils such as Avocado are considerably more difficult to form ME systems. In other words, oils of higher polarity can increase the …show more content…
Water content below 25% was found insufficient to hydrate the polyoxyethylene groups of surfactants, which are critical for the swelling of surfactant chains to demonstrate the gel structure. Gel was readily formed when the surfactant concentration was greater than 60%. The gel structure could break down upon dilution with water as the distance between the polyoxyethylene groups increased and the gel structure destabilized resulting in breaking of the swelled gel [10]. HLB of surfactants has a great effect on ME areas. A clear ME system formed readily when the HLB of the surfactant increased indicating that the formed MEs are o/w type [32]. The HLB of surfactant mixtures were calculated according to the equation:
HLB mix = WT × HLBT + WS × HLBS
Where WT, WS are the weight fractions and HLBT, HLBS are the HLB values of T80 (or T20) and Sp80, respectively.
It was observed that the water content increased linearly with HLB due to the increased hydration capacity and higher water retention by the more hydrophilic surfactants36. The obtained MEs areas were arranged in decreasing order according to HLB of the surfactant(area of ME not HLB) or the surfactant mixture used as following: T20 “HLB=16.7” > T80 “HLB=15” > Sp80/ T20 (1:3) “HLB=13.6” > Sp80/ T20 (1:1) “HLB=10.5”> Sp80/ T80 (1:1) “HLB=9.65”> Sp80/ T80 (1:3) “HLB=12.33” > Sp80/ T20 (3:1) “HLB=7.4”> Sp80/

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