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Have Ache in your Body? Stick it!

Posted on February 19th, 2016 by in New Materials & Applications

Medherant Patch

Image Source: Warwick University

You may say that is not nice.  It actually is!  Because now you can treat the pain with medicinal patches.  Let’s start with a little primer on pain relief pills.

Many people cannot take aspirin or another medicine from the NSAID family because of concerns about stomach and gastrointestinal (GI) issues.  They may even cause GI bleeding in individuals with “stomach ulcers or previous history of stomach ulcer bleeding” according to the Cleveland Clinic (Source: Cleveland Clinic).  NSAID stands for nonsteroidal anti-inflammatory drugs such as Aspirin, Ibuprofen, Celecoxib and Naproxen. These drugs reduce pain caused by inflammation quite effectively.  The adverse side effects prevent many people from taking these drugs.  Alternatives such as acetaminophen are usually analgesics (pain relievers) and antipyretics (fever reducers) but have no anti-inflammatory effect.

AA Chemical structure of Ibuprofen

Figure 1: AA Chemical structure of Ibuprofen

Inflammation is unavoidable because it is the body’s protective response to irritation or injury and is characterized by redness, warmth, swelling, and pain. NSAIDs are used to treat a variety of symptoms such as pain, inflammation, and stiffness caused by rheumatoid arthritis and tendonitis. NSAIDs are also used to treat a variety of other conditions, such as osteoarthritis, muscle aches, backaches, dental pain, pain caused by gout, bursitis, menstrual cramps. They may also be used to reduce fever or relieve minor aches caused by the common cold. (Source: Cleveland Clinic)

A good deal of development effort has been concentrated on developing alternative drug delivery means to bypass the GI system thus allowing a larger patient population to benefit from available drugs.  Transdermal (through the skin) delivery of medicine is one effective alternative that bypasses the GI system and the liver.  Ibuprofen gels are available that can be applied to the skin.  There are drawbacks to the gel because it delivers an uncontrolled dose and is inconvenient to apply and maintain on the skin for a length of time.  These two issues have spurred the development of controlled release patches of NSAID drugs to overcome those shortcomings.

In spite of being counterintuitive (to laymen), the transdermal delivery route is quite promising.  A drug crossing the skin successfully enters the blood stream by which it is delivered to the target pain point.  There are challenges to transdermal drug delivery including availability of a limited number of drugs amenable to administration by this route.  The exterior layer (stratum corneum) provides most of the excellent barrier properties of human skin (Figure 2).  The molecular size of a drug and its hydrophilic or hydrophobic nature are among the important factors affecting its ability to permeate through human skin.  Successful transdermal drugs have relatively smaller molecules (<a few hundred Daltons) and heavily favor lipids (Source: M. R. Prausnitz and R. Langer, Transdermal Drug Delivery, Nat Biotechnol, 26, 11, pp1261–1268, Nov 2008).

Micrograph of skin cross-section

Figure 2: Micrograph of skin cross-section.  (Image Source: M. R. Prausnitz and R. Langer, Transdermal Drug Delivery, Nat Biotechnol, 26, 11, pp1261–1268, Nov 2008)

Researchers at the University of Warwick in collaboration with Medherant, a Warwick spinoff company, have produced the first ever Ibuprofen patch delivering Ibuprofen directly through skin at a consistent dose rate.  They can incorporate significant amounts of the drug (up to 30% weight) into a polymer matrix that sticks the patch to the patient’s skin with the drug being delivered at a steady rate up to 12 hours.  The drug load by this new technology could be 5 to10 times more than the similar products.  In addition to high drug load capability the patch has an accurate drug release.  The patches would have to undergo testing and regulatory approval prior to being commercialized.

University of Warwick research chemist Professor David Haddleton said: “There are only a limited number of existing polymers that have the right characteristics to be used for this type of transdermal patches – that will stick to the skin and not leave residues when being easily removed. Furthermore, there are also only a limited number of drugs that will dissolve into these existing polymers. Medherant’s technology now opens up the field of transdermal drug delivery to previously non-compatible drugs.”  (Source: Warwick University)

Professor Haddleton’s statements appear to open the door for the development of additional drugs for transdermal delivery.  The size of the drug molecule has been one of the impediments to transdermal delivery of medicines.  There is also a need for developing non-allergenic adhesives and effective polymer vehicles for drug delivery.

To borrow from the American writer William S. Burroughs: Perhaps all pleasure is only [pain] relief.

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