Low-dose transdermal HT just as good as oral for the heart?

Low-dose transdermal estradiol (E2)/norethisterone acetate (NETA) patches seem to elicit the same favorable effects on cardiovascular biochemical markers as low-dose oral E2/NETA after 12 and 52 weeks of treatment, according to the findings of a recent open-label study involving postmenopausal women with intact uteri.

Both hormone therapy regimens decreased serum concentrations of P-selectin, intercellular adhesion molecule (ICAM)-1, and monocyte chemoattractant protein (MCP)-1, all of which are molecules involved in the early stages of atherosclerosis. Both delivery methods also produced similar decreases in homocysteine, which is considered an independent risk factor for cardiovascular disease. Matrix metalloproteinase-9, thought to be involved in plaque stabilization, was increased only by oral HT, as was urodilatin excretion. Urinary concentrations of cyclic guanosine monophosphate, the ratio of prostacylin to thromboxane metabolite, and the serotonin metabolite were significantly increased by both HT delivery modes, although the oral treatment produced a significantly greater increase from baseline than the transdermal product.

The authors of the study are unsure whether these differences are purely the result of different delivery methods or the result of different pharmacokinetic properties. Because the transdermal route provides the added benefits of delivering a sustained release of estrogen with predictable absorption characteristics and eliminates the local gastrointestinal irritation experienced by some women taking the oral formulation, it may be preferred; however, the transdermal route doesn't seem to increase levels of high-density lipoprotein cholesterol the way oral administration does.

Mueck AO, Genazzani AR, Samsioe G, et al. Low-dose continuous combinations of hormone therapy and biochemical surrogate markers for vascular tone and inflammation: transdermal versus oral application. Menopause. 2007;14:978-984.