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. More on interfacial bonding of bi-layered tablets

Conclusions

The complex trend in IBS of bilayer tablets prepared with mixtures of MCC and lactose can be understood by considering BA-BS interplay of particles at the interface. The addition of a small amount of MCC to lactose increased the BS at the interface, resulting in a higher IBS. However, when too much MCC was in the mixture, the negative effect on IBS due to reduction of BA of the more plastic mixture outweighed the positive contribution to IBS by higher BS. Consequently, continuous decreased in IBS was observed when MCC amount increased. The effects of BA-BS interplay on IBS depended on P1, where higher P1 aggravated the negative effects of lower BA on IBS, thus changing the dependence of IBS on MCC%. The addition of HPMC weakens BS, thus also shifts the dependence of IBS on MCC%. This work confirmed the usefulness of the BS – BA interplay model in explaining IBS of formulated bilayer tablets. More on interfacial bonding of bi-layered tablets