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 β-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 ¹H 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 × 10⁴ M⁻¹, whereas glibenclamide is bound over the terminal cyclohexyl group with a binding constant of 1.7 × 10⁵ 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.