The United States Food and Drug Administration (US FDA) has a developed a score for describing the degree of adhesion of a transdermal patch. A transdermal patch needs to be fully attached if it is going to be effective in drug delivery.
Selection: transdermal patch
Parameters:
(1) area of transdermal patch for attached to skin
(2) area of patch detached from skin
percent adherence =
= ((area of patch) - (detached area)) / (area of patch) * 100%
percent adherence =
= (area of patch attached) / (area of patch available) * 100%
Percent Attached
FDA Score
Interpretation
Drug Delivery
>= 90%
0
fully attached
good
75 to 89.9%
1
partially attached (edges loose)
fair
50 to 74.9%
2
partially detached
suboptimal
1 to 49.9%
3
mostly detached
poor
0%
4
completely detached
none
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