TLDR Rubbing skin increases absorption of water-soluble drugs from lotions and creams, but not oil-soluble drugs.
The study examined how rubbing affects the absorption of caffeine (CAF), a hydrophilic drug, and rhododendrol (RD), a lipophilic drug, from lotions and creams into the skin. It was discovered that rubbing significantly increased the permeation of CAF into the skin for both types of formulations, especially when rubbed against hair growth direction. However, rubbing did not enhance the permeation of RD. The increase in CAF permeation may be due to the enlargement of hair follicle openings caused by rubbing, while RD's lack of enhancement could be attributed to its high distribution in the outer skin layer (stratum corneum). The study, which used porcine skin as a model and had an average sample size of three (n = 3), suggests that rubbing can influence the effectiveness of topical drug delivery, but more research is needed to understand the effects with different drugs and formulations.
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February 2018 in “International Journal of Pharmaceutics” Researchers developed a method to measure drugs in hair follicles and found that both water-loving and fat-loving drugs can be detected after being applied to the skin.
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February 2009 in “European journal of pharmaceutics and biopharmaceutics” Hair follicles help absorb and store topical compounds, aiding targeted drug delivery.
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December 2007 in “BJCP. British journal of clinical pharmacology/British journal of clinical pharmacology” Hair follicles significantly increase the speed and amount of caffeine absorbed through the skin.
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May 2009 in “BJCP. British journal of clinical pharmacology/British journal of clinical pharmacology” Caffeine penetrates human skin in lab tests similarly to real-life conditions, but actual skin use is still essential for accurate results.
