From the Guidelines
It is not recommended to apply an estradiol transdermal patch under the arm due to potential interference with proper adhesion and medication delivery. The application sites for estradiol patches are typically limited to areas such as the lower abdomen, buttocks, or upper outer thigh, as these provide consistent absorption of the medication into the bloodstream 1.
Key Considerations for Patch Application
- The underarm area has different skin characteristics, including more sweat glands and potential for friction, which could interfere with proper adhesion and medication delivery.
- Residue from deodorants or antiperspirants in the underarm area could further interfere with absorption.
- Proper patch placement is crucial for maintaining steady hormone levels throughout the treatment period.
Guidance from Relevant Studies
While the provided study 1 discusses the use of a combination hormone transdermal contraceptive patch, the principles of patch application and the importance of proper skin site selection can be applied to estradiol patches as well. The study highlights the need for correct placement to ensure efficacy and minimize side effects, which supports the recommendation against applying estradiol patches under the arm.
Clinical Implications
Always follow the specific instructions provided with your prescription, rotate application sites to prevent skin irritation, and consult your healthcare provider before making any changes to how you use your medication. This ensures that you receive the full therapeutic benefit of the estradiol patch while minimizing potential side effects.
From the Research
Application Sites for Estradiol Transdermal Patches
- The studies 2, 3, 4, 5 investigated the application of transdermal patches at various sites, including the buttocks, abdomen, arm, and torso.
- According to the study 3, the buttocks seem to be an acceptable site for the application of a once-weekly 17-beta estradiol transdermal delivery system, with higher absorption rates compared to the abdomen.
- The study 4 found that the relative bioavailability of ethinyl estradiol and gestodene was higher when the patch was applied to the outer, upper arm compared to the lower abdomen and buttocks.
- The study 5 demonstrated that absorption of norelgestromin and ethinyloestradiol from a contraceptive patch was equivalent when applied to the buttock, arm, and torso, while absorption from the abdomen was approximately 20% less.
Application Under the Arm
- The study 4 specifically investigated the application of a transdermal patch to the outer, upper arm and found that the relative bioavailability of ethinyl estradiol and gestodene was 31% and 24% higher, respectively, compared to application on the abdomen.
- The study 5 also found that absorption of norelgestromin and ethinyloestradiol from a contraceptive patch was equivalent when applied to the arm compared to the buttock and torso.
- However, it is not explicitly stated in the studies whether the patch can be applied under the arm, but rather on the outer, upper arm.
- Based on the available evidence 4, 5, it can be inferred that the arm may be a suitable site for the application of a transdermal estradiol patch, but the specific location under the arm is not directly addressed.