Liquid aspirin could be possible using pharmaceutically active ionic liquids claim researchers in Northern Ireland. 

Aspirin is typically administered orally but can suffer from problems such as poor solubility, bitter taste and large tablets required for the dosage. A liquid salt form of aspirin could overcome these issues and offer new delivery forms. This could be possible using ionic liquids say Robin Rogers and colleagues at Queen's University Belfast. 

The team prepared the novel ionic liquids by using simple ion exchange reactions between salts of the active component of aspirin (acetyl salicylate), or the chemically similar salicylic acid, and pharmaceutically active ammonium salts. The counter ions could be used to add a second function to the ionic liquid drug such as anti-bacterial or anti-microbial behaviour, says Rogers. 'Another option would be to mask the taste with a counter ion used for that purpose,' he adds. 

Ralf Giernoth, an expert on the synthesis of new ionic liquids at the University of Cologne, Germany, was excited by the possibilities. 'The idea of incorporating pharmaceuticals into ionic liquids is fascinating and inspiring. One could imagine easy application of drugs through the skin, since many of the common ionic liquid cations bearing long alkyl chains are known to penetrate the skin and the cell membranes.' 

The aspirinate ionic liquids were much less stable than the salicylate ones, owing to aspirin's tendency to hydrolyse in the presence of water, explains Rogers, which may limit their therapeutic applications. This problem could be overcome with appropriate care in manufacturing and packaging he says, but 'there would have to be a reason to need an ionic liquid form of aspirin and I believe this may reside in overcoming side effects by delivery of a particular active ingredient at the same time,' he adds. 

Rogers concludes that the work shows that pharmaceutical ionic liquids could provide another tool in drug development, design and delivery. 'In theory, any combination of two or more drugs that have appropriate and opposite ionic forms are possible, as long as both active ingredients form a stable cation and anion - for example, an anti-inflammatory ion with an active species known to cause an inflammatory response as a side effect.' 

Christina Hodkinson 

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