Absorb This: Delivering Drugs Through the Skin

By Lila Abassi — Dec 31, 2015
Researchers at the University of California have been able to successfully create a liquid blood pressure medication that can be absorbed through the skin, without the requisite skin toxicity. The implications for transdermal drug delivery are multiple and profound.
nicotine patch via shutterstock nicotine patch via shutterstock

Very cool things are being discovered at the University of California, Santa Barbara and not just because it s my alma mater. Researchers there have been able to develop a new, safe and effective method for delivering a common blood pressure medication through the skin without causing any skin toxicity which previously was a major roadblock for this drug delivery method.

A report published in the journal Technology, discusses how UCSB scientists have been able to convert the antihypertensive (or blood pressure reducing) drug, propranolol hydrochloride, into a form that is able to penetrate the skin without causing skin irritation. Studies previously done had shown that liquid salts may enhance drug delivery through the skin, but this study is unique in that researchers were able to design a formulation that does not cause skin toxicity, as is often the case.

Propranolol is positively charged which is a likely source of its toxicity. Shielding of this charge by association with a counter species in the liquid salt reduces its toxicity. These findings are broadly applicable to many charged drugs, said Professor Samir Mitragotri, PhD, the senior author of the paper.

The study s co-first author, Michael Zakrewsky, adds, An ideal drug liquid salt would need to permeate through the skin as an associated ion pair. Eventually, however, the drug and the counter ion must dissociate in blood to preserve the drug s therapeutic efficacy. We show that these attributes can be balanced through careful selection of counter ions. This technology presents an exciting new, patient compliant solution for treating diseases.

Transdermal or through the skin drug delivery has been an important contribution to some medical practice, but it has faced some difficulty in achieving its full potential as an alternative to oral or injections routes.

The first transdermal delivery of a drug systemically was scopolamine in 1979, which was used to treat motion sickness. About a decade later, nicotine patches, probably the most notable drug to be available transdermally, were approved. Currently, there are 19 Federal Drug Administration-approved medications such as hormones (estradiol, testosterone, contraception), pain killers such as fentanyl, and numbing medicine such as lidocaine.

Scheduled to make an appearance in a few years, as we previously reported, is the first ibuprofen patch. There are key reasons why medications that can be delivered in a patch form are preferable:

  • They bypass what is called first pass metabolism. This is where the liver breaks down much of the drug where only a small percentage of it becomes available for therapeutic purposes.
  • Preventing needle-stick injuries in healthcare and at home you can almost hear the sigh of collective relief from the millions of insulin-requiring diabetics.
  • Reducing dangerous medical waste.
  • Safely and effectively administered by patients without the need for specialized help; for those individuals with any physical/mental impairment that would prevent them from self-administering medications (i.e. vision problems, arthritis, dementia).
  • They can be formulated for longer-term drug delivery (up to one week).
  • It is predicted that compliance with medications for many would go through the roof.

Lastly, but certainly not least, are vaccines. Smaller doses of a vaccine would be needed to elicit a strong immune response as the skin itself contains specialized immune cells. Anyone caring for a child (as a parent, I admit to bias I saved the best for last) will appreciate that a trip to the pediatrician s office may no longer be equated with forced torture, tears and lollipop bribes.

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