Solid state stabilisation of the orally delivered drugs atenolol, glibenclamide, memantine and paracetamol through their complexation with cucurbit[7]uril

The inclusion of the cardiovascular beta-blocker drug atenolol, the antidiabetic drug glibenclamide, the Alzheimer's NMDA glutamate receptor drug memantine and the analgesic/antipyretic drug paracetamol by cucurbit[7]uril (CB[7]) has been studied by H-1 nuclear magnetic resonance spectroscopy, electrospray ionisation mass spectrometry, molecular modelling, fluorescence displacement assays and differential scanning calorimetry. All four drugs form 1 : 1 host-guest complexes with CB[7], but the exchange kinetics and location of the binding is different for each drug. Atenolol is bound over the central phenyl ring with a binding constant of 4.2 x 10(4) M-1, whereas glibenclamide is bound over the terminal cyclohexyl group with a binding constant of 1.7 x 10(5) M-1, and memantine is totally bound within the CB[7]cavity. Paracetamol is bound in two locations, over the central phenyl ring and over the methyl group, with the CB[7]molecule shuttling quickly between the two sites. Inclusion by CB[7]was shown by differential scanning calorimetry to physically stabilise all four drugs, which has applications preventing drug degradation and improving drug processing and formulation.