Results and discussion
In vitro dissolution study of core tablets. Figure 1 and Figure 2 show the release profiles of salbutamol sulfate from the uncoated tablets prepared with Starlac and
Avicel PH 101 as a filler, respectively. Upon contact with the dissolution medium, core tablets prepared using Starlac as
a filler started to erode and released the drug. Starlac is a coprocessed excipient consisting of lactose monohydrate and
maize starch (85:15) (10). As a result of both hydration and disintegrant properties of Starlac, upon contact with the dissolution
medium, this core tablet erodes and provides release within 12 min. No significant effect from Ac-Di-Sol was observed on the
release pattern of the drug. Core tablets prepared with Avicel PH 101 as a filler, upon contact with the dissolution medium
tablets, swelled, disintegrated, and released the drug. As the amount of Ac-Di-Sol increased, the drug release increased.
Figure 3 shows the release pattern of albutamol sulfate from the uncoated tablets prepared using Starlac and Avicel PH 101
as a filler.
In vitro dissolution study of press-coated tablets.
Rupturable polymer (EC) combined with erodible polymer (HPC EXF). As shown by Figure 4 and Figure 5, when rupturable polymer (EC N 22 F) combined with erodible polymer (HPC EXF), lag time
increased with an increasing weight ratio of EC N 22 F to HPC EXF. Using EC N 22 F alone resulted in the shortest lag time
compared to any weight ratio of EC N 22 F to HPC EXF. This occurs because EC is semipermeable in nature and, although it is
naturally insoluble in the dissolution medium, it penetrates the coating layer of the tablet when used alone. After hydration
of the core, the drug was released.
For tablets in which EC was used with HPC EXF, and as a result of the solubility of HPC EXF, upon contact with the dissolution
medium, HPC EXF hydrated and formed a compact with EC. In addition, the hydrophobicity of EC retards the hydration of HPC
EXF. Therefore, the dissolution medium did not penetrate the outer-coating layer but the coating eroded slowly.