Hydrophilic excipients

Spherical pellets containing 5% triamcinolone acetonide were prepared by Villar-Lopez and co-workers [59] by extrusion/spheronization following formulation with microcrystalline cellulose and/or a hydrophilic excipient like lactose, sodium earbox-ymethylcellulose, or P-cyclodextrin. Their suitability for coating, with a view toward colonic drug deliveiy, was assessed in terms of their size, sphericity, and dissolution test response. The best results were afforded by a 5 90 5 composition of microcrystalline cellulose, P-cyclodextrin, and triamcinolone acetonide, prepared by complex-ation of triamcinolone acetonide with P-cyclodextrin prior to the addition of microcrystalline cellulose. 

Pore-building, hydrophilic excipient hydroxyethylcellulose ( ), viscosity grades of 2% aqueous solution 300, 6000, 30000 mPas, (Natrosol 250 G, H, M, Hercules BV, Den Haag, The Netherlands) ... 

Pore building, hydrophilic excipient bovine serum albumin (Sigma Chemical Company, St. Louis, MO) of high and low dissolution rates (the dissolution rate of the product could be reduced by special treatment) ... 

Table 3 The Effect of Hydrophilic Excipients on the Dissolution Rates of Griseofulvin (a Biophannaceutical Classification System Class II Drug)...

Table 4 The Dissolution and Release of Biopharmaceutical Classification System Class II and IV Drugs Are Enhanced by Hydrophilic Excipients...

For the preparation of a micellar solution, the water-insoluble drug and lipophilic excipients can be dissolved in a liquid surfactant by mixing at a relatively high temperature (43S 6flntil a clear solution is obtained. If necessary, a cosolvent can be added to aid solubility in the surfactant. Then a water or buffer solution containing hydrophilic excipients is added to the desired volume while mixing. In some cases, the aqueous solution needs to be heated to the same temperature as that > the surfactant to obtain desirable results. 

The wetting behavior of powders is an also important factor for drug dissolution. If the wetting is not satisfactory, hydrophilic excipients (lactose) and surfactant (sodium lauryl sulfate or polysorbate) are combined in the powder mixtures. The contact angle is used as an index of wetting. The lower the contact angle, the better the wetting occurs. 

IVIVCs are often indicated only for obtaining oral formulations. Various data have been presented in the cases of less-classical formulations such as intrauterine devices, chewing gums, ocular inserts, suppositories, etc. For example, for suppositories two main types of formulations exist one based on hydrophilic excipients and the second on lipophilic excipients. The first step is the dissolution of the mass. This means a fusion of the lipophilic base at human body temperature (36-39.5°C) or dissolution for the water-soluble base (even with a high melting point) in the rectal fluid. 

In this era of automatic titrators, microprocessor-controlled thermal analysis, and definitive spectral techniques, one of the most powerful techniques, that is, optical microscopy, is frequently overlooked. The value of direct sample observation, preferably while it is exposed to different relative humidities, cannot be overstated. In the author s laboratory, a plexiglass chamber was constructed that can be placed on the stage of the microscope, through which air of known humidity can be circulated. This simple technique has been very useful in examining the swelling (or lack) of disintegrants and the influence of very hydrophilic excipients in combination with a moisture sensitive drug. ... 

Finally, the complicated situation faced when a moisture sensitive drug is combined with an hydrophilic excipient is shown in Fig. 24. In this study, aspirin... 

A Mitrevej andR G. Hollenbeck, Influence of hydrophilic excipients on the interaction of aspirin and water, Int. J. Pharm. 14, 243-250(1983). 

Precirol ATO 5 Stearic acid Compritol 888 ATO Glycerol monosterate Precirol WL2155 Hydrophilic excipients ... 

In extmded products, plasticizers play the usual role of process additive and component which adds elasticity to the product. In addition to these typical roles, plasticizers were found to perform some roles typical of the product into which they were incorporated. In pharmaceutical products, dmg controlled-release properties were regulated with the amount of the plasticizer present in tablet coating. In addition, the type of plasticizer could also change properties of coating by affecting the balance between hydrophobic polymer component and hydrophilic excipients. ... 

Capsules disintegrate when the capsule shell dissolves and the powder mixmre is wetted. Hydrophilic excipients promote the wetting of the powder bed (Fig. 4.1). Due to the low compaction of the encapsulated powder, and the easy dissolution of most diluents for capsules, the addition of a disintegrating agent is often not needed for pharmacy preparations. However, when excipients compact easily (e.g. calcium monohydrogen phosphate dihydrate) a disintegrant is recommended. 

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