Interfacial bonding in formulated bilayer tablets

To take full advantage of the drug delivery benefits offered by bilayer tablets, the common issue of weak interfacial bonding strength (IBS) with manufacturing must be overcome. This work seeks to characterize the effects of composition in individual layers and compaction pressure on the IBS. Mixtures of MCC and lactose in different ratios with and without HPMC were used where the first layer was compacted with two different pressures (20 and 100 MPa) followed by a second layer compaction pressure of 200 MPa. After identifying the failure mode as either at the interface or within a layer, the complex trends of bilayer tablet IBS as a function of MCC content were explained by considering the interplay between particle bonding strength and bonding area at the interface.