Excipients, drug complexation with

The drug may be incorporated in a slowly eroding matrix of waxy materials, embedded in a plastic matrix, complexed with anion exchange resins or incorporated in a water-insoluble hydrophilic matrix. Drug release from these systems occurs by several mechanisms diffusion, dissolution, ionic exchange or osmotic pressure [1,2], depending on the type of polymeric excipient present and the formulation used. 

Oguchi and coworkers examined the decarboxylation behavior of -aminosalicylic acid (PAS) as a freeze-dried solid under thermal stress conditions (80°C) in the presence of the excipients pullulan (a linear polysaccharide which can not form inclusion complexes with PAS) and a-cyclodextrin (39). The solid-state stability was shown to correlate with the fraction of amorphous PAS. Increasing relative amounts of pullulan resulted in higher fractions of amorphous PAS. Rapid freezing (liquid nitrogen) was shown to result in a greater relative amount of amorphous drug, as expected. 

Excipients used in the formulation usually include a mixture of a water-soluble polymer and a crystalline sugar. Mannitol and natural polysaccharides such as gelatin and alginates are used. Microencapsulation and complexation with ion exchange resins can be combined with additional flavors and sweeteners for taste masking of bitter drugs. The fairly complex nature of manufacture and scale-up contributes to... 

Complexation Drug is entrapped or complexed with excipients that can mask the lipophilic groups of the drug and enhance drug solubility in water. Cyclodextrins are commonly used to entrap hydrophobic drugs in the core, while the hydrophilic groups on the periphery help to solubilize the drug. 

Excipients. Most tablets and capsules are complex mixtures containing a small amount of one or more drugs together with a larger amount of excipients. The following substances are frequently used as sxcipients. 

Excipients such as cyclodextrins, which form inclusion complexes with drug substances, can have a significant effect on drug stability. These effects will be described in... 

Z. Lu, W. Chen, E. Olivier, J.H. Hamman, Matrix polymeric excipients Comparing a novel interpolyelectrolyte complex with hydroxypropylmethylcellulose. Drug Deliv, 15 (2),... 

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