Transdermal estradiol patches are primarily designed for adult women. No low-dose patches are licensed for pubertal induction in hypogonadal girls. Low doses can be achieved by cutting a matrix patch into smaller pieces. However, the manufacturers do not guarantee stability or utility of cut estradiol patches. The aim of the study was to assess 1-month stability of cut estradiol patches from four different manufacturers in the laboratory at room temperature (+21°C) and at an elevated temperature (+35°C).
Estraderm MX 50 µg, Systen 50 µg and Oesclim 25 µg matrix patches were cut into eight pieces while Estradot 50 µg small patches were cut in half. The cut patches were stored in their respective pouches at +21°C or at +35°C for up to 1 month. The estradiol drug was extracted from the patch by ethyl acetate n-hexane and determined by radioimmunoassay.
Storage at +21°C or +35°C up to 1 month did not reduce the estradiol concentration in Estraderm MX, Systen and Oesclim patches. However, although the estradiol in Estradot patches was not affected by storage at +21°C, at +35°C, estradiol decreased by 57% (±1%) in cut pieces.
Unused Estraderm MX, Systen and Oesclim patch pieces may be stored for at least 1 month at ≤+35°C. Where estradiol patches for children are not available, cut pieces of these or similar patches can be used for pubertal induction. The Estradot patch was too small to properly cut into low doses and not stable in elevated temperatures.