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Solubility suspended drugs

Bisrat et al. concluded that for sparingly soluble, suspended drugs, diffusional transport plays a major role in the dissolution kinetics [19]. They studied the effect of particle size and viscosity on dissolution rate and apparent diffusional distance (.h-App) of oxazepam and griseofulvin. The term apparent diffusional distance was used as a simplified measure of the distance over which diffusion dominates and was calculated as follows ... [Pg.193]

Povidone is additionally used as a suspending, stabilizing, or viscosity-increasing agent in a number of topical and oral suspensions and solutions. The solubility of a number of poorly soluble active drugs may be increased by mixing with povidone. See Table II. [Pg.611]

One complication which arises when we are carrying out stability testing of suspensions is the changes in the solubility of the suspended drug with increase in temperature. With suspensions, the concentration of the drug in solution usually remains constant because, as the decomposition reaction proceeds, more of the dmg dissolves to keep the solution saturated. As we have seen, this situation usually leads to zero-order release kinetics. If the acmal decomposition of dissolved dmg is first-order, then we can express the decrease of concentration, c, with time, t, as... [Pg.132]

Exact dose is sometimes difficult to determine (soluble fractions versus suspended drug versus the amount of drug that will eventually dissolve)... [Pg.242]

M. Bisrat, E. K. Anderberg, M. I. Barnett, C. Nystrom. Physicochemical aspects of drug release. XV. Investigation of diffusional transport in dissolution of suspended, sparingly soluble drugs. Int. J. Pharm. 1992, 80, 191-201. [Pg.211]

When drug polymorphs cannot interconvert as a result of being suspended in aqueous solution, a different bioavailability of the two forms usually results [126], For instance, the peak concentration of chloramphenicol in blood serum was found to be roughly proportional to the percentage of the B-polymorph of chloramphenicol palmitate present in a matrix of the A-polymorph [133]. The same concept has been found to apply to hydrate species, where the higher solubility and dissolution rate of the anhydrous phase relative to the trihydrate phase resulted in measurably higher blood levels when using the anhydrate as... [Pg.367]

Although determination of a complete pH-degradation rate profile is desired, it may not always be practical due to limitations of drug supply and time. Also, insufficient solubility in purely aqueous systems may limit determination of pH-degradation rate profiles. Organic cosolvents may be used to increase solubility however, extrapolation to aqueous conditions must be done with caution. Stability of the drug in a suspended form in the desired buffer can be tested in lieu of solution stability. The stress test results must however, be interpreted in relation to the solubility in the suspension medium. The test may provide an empirical indication of pH stability in the presence of excess water. Satisfactory stability in the GI pH range (1 to 7.5) is important for oral absorption. While there are examples of... [Pg.24]

Delivery systems that use a multicompartment core can theoretically deliver drugs of any solubility [48,49], A basic Push-Pull System consists of two layers the Lrst contains the drug, osmotically active hydrophilic polymer(s), and other pharmaceutical excipients the second layer, often called the push layer, contains a hydrophilic expansion polymer, other osmotically active agents, and the excipients, as shown in Figure 22.6. Poorly water-soluble compounds can be delivered using an ORO Push-Pull tlelivery system by incorporating drug as a micronized form, or as a hot-melt material suspended in a polymer matrix. [Pg.622]

The active ingredients in MDIs are usually water-soluble and chlorofluorocarbon- or hydrofluorocarbon-insoluble. Some CFC and HFA formulations use ethanol as a suspending agent by using an ethanol-insoluble salt form of the drug. Since the vehicle in MDIs must be propellant-based, a product with the drug suspended in the propellant may be the most stable dosage form. [Pg.367]

Coacervation phase separation. This technique is used to microencapsulate water-soluble drugs. The core material (drug) is suspended in a nonaqueous polymer solution (coating material), and the polymer is made to form a uniform coat by various approaches, such as temperature change, addition of an incompatible polymer, addition of a nonsolvent, or addition of a salt. [Pg.294]

Solvent evaporation. This is the most commonly used method for microencapsulation of the drugs that are soluble or suspended in the organic phase. In this method, a solution or suspension of drug in an organic solvent containing dissolved polymer is emulsified to form o/o or o/w dispersion, possibly with the aid of a surfactant. The organic... [Pg.294]


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See also in sourсe #XX -- [ Pg.193 ]




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Drug solubility

Drugs Soluble

Drugs suspended

Suspending

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