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Here's a chart or two as well as a PDF link to a scientific study examining the penetration efficacy of the VersaFoam used in Rogaine Foam as a number of people have questioned how well it penetrates given the fact that it "dries so fast" compared to the old, greasy formula...
Note that this is a study based only on the VersaFoam vehicle and not specifically Rogaine Foam...but it does clearly show the effectiveness of its penetration profile :
This graph also partly explains the minimum 4 hour timespan recommended before washing off...as the penetration characteristics seem to peak around the 4 to 6 hour mark.
Here's the PDF link to the study from which the above data was drawn :
http://www.versafoam.com/pdf/huang.pdf
Taken from the study :
Happy Reading...
Note that this is a study based only on the VersaFoam vehicle and not specifically Rogaine Foam...but it does clearly show the effectiveness of its penetration profile :
This graph also partly explains the minimum 4 hour timespan recommended before washing off...as the penetration characteristics seem to peak around the 4 to 6 hour mark.
Here's the PDF link to the study from which the above data was drawn :
http://www.versafoam.com/pdf/huang.pdf
Taken from the study :
The studies presented herein demonstrated that the new foam has the ability to deliver a greater amount of the active drug at an increased rate compared with other vehicles. This was true whether entry occurred into a synthetic lipophilic barrier (Silastic membrane) or into split-thickness skin samples (from live human donors). These findings also suggest that the new foam utilizes a nontraditional ‘‘rapid-permeation’’ pathway for the delivery of drugs. It is likely that components within the foam (probably the alcohols) act as penetration enhancers 8 and reversibly alter the barrier properties of the outer stratum corneum, thereby driving the delivered drug across the skin membrane via the intracellular route. This is in contrast to traditional topical delivery vehicles, which must first rely on hydration of the intercellular spaces in the stratum corneum to effect drug delivery. The latter mechanism reflects a hydration-dependent process, which may result in comparatively slower drug permeation. Researchers have speculated that the physical changes that a foam vehicle such as this new foam undergoes after release from the container has important implications for the rate of penetration and permeation of an agent through the stratum
corneum.12 It is well known that maximum drug transfer into the skin takes place when the drug is in a saturated solution at the vehicle-skin interface.12,21 The evaporation of volatiles from the foam, which
leaves behind little if any residue from the vehicle, may cause the active ingredient to concentrate at the interface, leading to the aforementioned saturation and then to supersaturation. This supersaturation,
although generally a transient condition, results in a drug delivery rate exceeding that of a saturated solution that may occur with other vehicles, further contributing to the enhanced rate of delivery seen
with the new foam. In addition, supersaturation may permit the formation of a drug reservoir within the stratum corneum.
Happy Reading...