![]() ![]() ![]() In separate experiments on molecular weight of the polymer, they saw the usual trend in drug release rates: K100 LV > K4M > K15M » K100M But the higher molecular weight polymer did increase the lag (hold-up) time before establishment of quasi-steady state. However, there have been several instances in the literature that report no difference in release for different molecular weights. It is generally accepted that drug dissolution from tablets is slower for higher molecular weight HPMC polymers. Fast polymer hydration and gel layer formation are particularly critical when formulating with water-soluble drugs and water-soluble excipients. ![]() This prevents the tablet from immediately disintegrating, resulting in premature drug release. In most studies, increased polymer level in the formulation results in decreased drug-release rates.īased on studies examining the effect of substitution on release rate from hydrophilic matrix tablets, K-chemistry results in the slowest release compared to other polymers of similar molecular weight.Ī fast rate of hydration followed by quick gelation and polymer/polymer coalescing is necessary for a rate-controlling polymer to form a protective gelatinous layer around the matrix. If the polymer level is too low, a complete gel layer may not form. This barrier protects the drug from immediately releasing into the dissolution medium. There must be sufficient polymer content in a matrix system to form a uniform barrier. The mechanisms by which drug release is controlled in matrix tablets are dependent on many variables: Insoluble drug is released primarily through tablet erosion.Soluble drug is released primarily by diffusion through the gel layer. ![]() At the same time, other soluble excipients or drugs will also- wet, dissolve, and diffuse out of the matrix while insoluble materials will be held in place until the surrounding polymer/excipient/drug complex erodes or dissolves away. That's why before going to formulate such product few factors should be considered -Ī hydrophilic matrix, controlled-release system is a dynamic one involving- polymer wetting, polymer hydration, gel formation, swelling, and polymer dissolution. Sustained release/ Extended release/ Modified release/ Controlled release drug formulation is a most critical formulation for a pharmacist. ![]()
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