Estradiol topical formulations

Typical patches of estradiol contain 50 micrograms, but there are important differences between the wanted and unwanted effects of the available products, because of the ways in which they are formulated. The wash-out period of estradiol after transdermal administration is about 6 weeks. Transdermal estrogens can also be supplemented periodically by an oral progestogen (222). New topical formulations of estrogens continue to be studied and... 

The use of conventional topical formulations for transdermal drag delivery is presently limited to classic ointments for nitroglycerin, and some gel formulations of estradiol and progesterone. Although of demonstrated efficacy, these vehicles are often inelegant and result in poor reproducibility of the delivered dose (and hence of the provoked pharmacological effect). This variability, of course, originates in the... 

Terpenes continue to be a popular choice as experimental enhancers for delivering materials across skin membranes. For example, L-menthol facilitated in vitro permeation of morphine hydrochloride through hairless rat skin [37], imipramine hydrochloride across rat skin [59], and hydrocortisone through hairless mouse skin [60]. Recently, niaouli oil was found to be the most effective of six essential oils in promoting estradiol penetration through hairless mouse skin [61]. It is noteworthy that there is currently little control on the topical use of most terpenes, and many aromatherapy oils and formulations contain appreciable quantities of these chemicals. Their excessive use offers potential for permeation of hazardous compounds from the same formulations into the skin some terpenes also have pharmacological activity. 

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