metrogel: how it gets into your skin

Two recently published papers look at the processes involved when you apply metrogel topically. The first abstract just tells us that they undertook some new ways of measuring metronidazole absorption, but doesn’t reveal their results.

The second abstract suggests that a cream based metronidazole formulation (presumably metrocream, but could also include Noritate) had the greatest absorption when tested with human skin. They suggest that future research is needed to determine if indeed this makes any difference to rosacea symptoms.

Previously Rosacea News reported ;

metrogel, metrolotion, metrocream, noritate, once and twice per day – all the same same

“Despite quite a lot of activity in the marketing and development of the metronidazole treatments (lotion, cream, gel, generic equivalents, metrogel 1%, once per day, twice per day) this research suggests that the formulation and treatment frequency make little difference to the treatment outcome. So if you can tolerate one of the available formulations, there is likely marginal benefit from changing to another.”

Metronidazole based treatments do seem to attract a lot of research, maybe even too much research given the marginal improvement that many rosacea sufferers experience from the metro triplets. Imagine if the research poured in metronidazole was directed to new, leading edge treatments.

As background, from `measuring niacinamide (vitamin B3) moisturizer and skin barrier‘: 

“Confocal Raman microspectroscopy (CRS), in contrast, is a new technique that combines the well attested method of Raman spectroscopy (the study of inelastic scattering of light, rather than its absorption) with confocal microscopy, allowing noninvasive, realtime, in vivo measures of molecular concentration profiles.”


Follow-up of drug permeation through excised human skin with confocal Raman microspectroscopy. Eur Biophys J., 2007 Jun 13, Tfayli A, Piot O, Pitre F, Manfait M.

Skin is a multilayered organ which covers and protects the surface of human body by providing a barrier function against exogenous agents. Meanwhile, the efficacy of several topically applicated drugs is directly related to their penetration through the skin barrier. Several techniques are commonly used to evaluate the rate, the speed and the depth of penetration of these drugs, but few of them can provide real-time results. Therefore, the use of nondestructive and structurally informative techniques permits a real breakthrough in the investigations on skin penetration at a microscopic scale.

Confocal Raman microspectroscopy is a nondestructive and rapid technique which allows information to be obtained from deep layers under the skin surface, giving the possibility of a real-time tracking of the drug in the skin layers. The specific Raman signature of the drug enables its identification in the skin. In this study, we try to follow the penetration of Metronidazole, a drug produced by Galderma as a therapeutic agent for Rosacea treatment, through the skin. The first step was the spectral characterization of Metronidazole in the skin. Then micro-axial profiles were conducted to follow the penetration of the drug in the superficial layers, on excised human skin specimens. For more accurate information, transverse sections were cut from the skin and spectral images were conducted, giving information down to several millimeters deep. Moreover, the collected spectra permit us to follow the structural modifications, induced by the Metronidazole on the skin, by studying the changes in the spectral signature of the skin constituents.


Percutaneous absorption kinetics of topical metronidazole formulations in vitro in the human cadaver skin model, Adv Ther. 2007 Mar-Apr;24(2):239-46, Elewski BE

Topical formulations containing identical active agents are available in various vehicles and concentrations, which may affect percutaneous absorption. This study was undertaken to evaluate the in vitro percutaneous absorption pharmacokinetics of metronidazole in different vehicles and concentrations as the active agent in 6 topical formulations. Formulations were applied to sections from 3 cadaver skin donors, and percutaneous absorption of metronidazole was measured over a 48-h test period through the finite dose technique and the use of Franz diffusion cells. Metronidazole penetrates into and through human cadaver skin.

Data show the general ranking of delivery of similar concentrations of metronidazole according to vehicle as cream > lotion > gel. The 48-h penetration of metronidazole in the human cadaver skin model was greatest with cream formulations and lowest with gel formulations. These results reveal the importance of the vehicle selected for penetration of metronidazole into the skin. The relevant target zone in rosacea is the dermis because this is the area where inflammation takes place. Additional studies are warranted to examine absorption of metronidazole into the relevant target zone and the correlation of absorption with efficacy.

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