University of Warwick chemist develops world's first ibuprofen patch

Materials World magazine
,
1 Feb 2016

Having recently created the world’s first ibuprofen skin patch, David Haddleton talks to Natalie Daniels about developing the new drug delivery system

Tell me about your background and what led to your work on the ibuprofen patch?

I am a Professor of Polymer Chemistry at the University of Warwick, and have worked on patch technology for many years, but mainly on electrocardiography electrodes. At the university, we have been working with Medherant Ltd, a Warwick spinout company, and Bostik, which has developed a new adhesive for industrial applications. We discussed with Bostik whether it would be applicable as a transdermal or medical adhesive, which could be applied with a polymer matrix, and that's where it all started. 

What are the main characteristics for these adhesives and why are they important?  

The characteristics required of adhesives applied to skin for either a transdermal system or wound care, similar to an Elastoplast, are the need to stick to the skin for a prolonged period even when exposed to water, to release with ease, have no skin irritancy and leave no residues on removal – the adhesive we are using has all of these properties. Currently, there are no commerical patches available for ibuprofen – there are gels and pain relief patches, but these will often contain no active ingredients, and if they do, it is not ibuprofen. We asked ourselves – why is there no ibuprofen patch? The probable reason is that the ibuprofen doesn't dissolve in the adhesive currently used in any other patches. We were then faced with how to apply this new adhesive into a transdermal application.

What were the steps to create this patch? 

The first test was to assess whether the drug dissolves into the polymer. Many active drugs are hydrophilic, meaning they are often salts, so you would have an ibuprofen gel with a salt of ibuprofen. Around 25 of these are available in gels, creams or patches, including over-counter prescription drugs, and 22 of them dissolve in our polymer, which means they can be used in our patch. The formulation works by dissolving a small molecule in a pre-polymer that has a high viscosity, and the adhesive is cured following formulation by water. 

What is the polymer matrix you used? 

The polymer is a silyl modified polymer adhesive produced by Bostik for use in industrial applications. It is relatively inexpensive to use and it is produced with no solvent, which is good for medical applications where those residues or small molecules would have the potential to be harmful, as well as great characteristics that make it comfortable on the skin. 

How does the patch work?

For a transdermal system, you dissolve the drug in the adhesive, so it is essentially a molecular solution, then the adhesive is applied to the skin. Because you have a reservoir of a small molecule that is then able to pass through the skin, it diffuses into the skin to deal with either local pain or in some cases diffuses into blood systems in systemic applications such as for hormone replacement therapy – for example, it could also be applied for alternative nicotine patches. These type of patches can also be used to treat common conditions including back pain and arthritis, without the need for a cream or oral tablet. 

We believe that the polymer we are using is superior to any other adhesive being used in patch technology. We can get in excess of 30% weight of ibuprofen in our patches, whereas it is often between 5–10% in gels. We can get very high loading, which means we can have increased application of the drug or smaller patches. If we have 10x the loading, the patch can be 10x smaller for the same delivery.

When can we expect to see these patches in the market?

We hope to see these patches in shops by the end of 2017. 

To find out more about the work on the ibuprofen patch, contact David at D.M.Haddleton@medherant.co.uk