Dose proportional drug products of multiple strengths are expected to have comparable dissolution profiles. However often they don’t – studies have shown that this dissimilarity could be attributed to differences in shape/size of these tablets, specifically the surface area by volume ratios.
Impact of Geometry on Drug Release
Studies have shown tablet geometry plays a key role in the drug release behavior of tablets. For immediate release tablets, study findings indicated the drug burst release was significantly decreased by decreasing the size of tablets. Studies have also shown the influence of tablet geometry on controlled release formulations.
Surface area/volume (SA/V) is one of the key variables in controlling drug releasefrom controlled-release matrix tablets containing hydrophilic polymers like hydroxypropyl methylcellulose (HPMC) and carbomer.
Tablets with larger SA/V typically had faster release profiles, regardless of the dose or shape. Studies on controlled release formulations have shown that it is always essential to keep the SA/V constant to get constant drug release profiles in different strengths.
Apparently, adapting a tablet surface area/volume ratio can produce a drug release profile similar to that of the reference tablet.
The current study indicated that by decreasing the size of tablets, the drug burst release was significantly decreased. Although the present study is based on a small sample of tablet shapes, the findings indicate that the initial burst and complete release occurred in large, biconvex tablets.
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