Synthesis, processing and solid state excipient interactions of cucurbit[6]uril and its formulation into tablets for oral drug delivery

The synthesis, processing, and solid state excipient interactions of cucurbit[6]uril (CB[6]) and its formulation into oral tablets has been examined using a range of physical chemistry techniques. Rapid precipitation from HCl by the addition of water yields microcrystalline CB[6] with smaller and more consistent particle size (30-165 μm) compared with the sieved CB[6] (50-540 μm) produced from large crystals grown by slow evaporation from HCl. The microcrystalline particles also contain fewer water molecules in the crystal compared with the sieved particles: 10 and 16% respectively. Microcrystalline CB[6] can be formulated into tablets suitable for oral delivery with a CB[6] content of 1-50% w/w, with the other excipients including lactose, talc, Avicel, magnesium stearate and Ac-Di-Sol. In the solid state microcrystalline CB[6] does not interact significantly with the talc, Ac-Di-Sol or Avicel, but significant interactions are observed when mixed or ground with either magnesium stearate or lactose, resulting in the lowering of the melting points of both excipients. This work represents the first study of the physical processing and solid state chemistry of CB[n]s for pharmaceutical formulation and represents an important development step in the use of CB[n]s as drug delivery vehicles.