News

Study suggests low-dose, transdermal hormone therapy may have lower stroke risk than oral hormone therapy

June 07, 2010

By Patricia Nicholson

A new study led by researchers at McGill University found that postmenopausal women taking low-dose hormone therapy (HT) using a transdermal patch did not have the increased stroke risk seen in women taking oral HT.

HT using estrogen, either alone or in combination with progesterone, is associated with a significant increase in stroke risk in postmenopausal women, according to background information in the study. However, most research on HT and stroke has looked at oral medications.

The McGill team wanted to compare oral and transdermal HT because transdermal formulations may have a different cardiovascular risk profile since they enter the bloodstream through the skin, rather than the digestive system. That means they go through different biochemical processes in order to reach the bloodstream. Most notably, transdermal drugs do not need to be broken down in the liver before entering the circulatory system. When drugs are processed through the liver, some of their potency is lost, and the concentration that enters the bloodstream is lower than the original dose. Therefore dosing may be very different for oral and transdermal formulations of the same drug.

The researchers studied data on HT use in more than 75,000 women in the U.K. All study subjects were between the ages of 50 and 79.

Starting with a cohort of 870,286 women who met the age criteria, the researchers identified 15,710 cases of stroke between 1987 and 2006. These cases were matched to a control group of almost 60,000 women of the same age who received care in the same medical practices as the stroke patients. The researchers then compared HT use in the stroke cases and the controls.

The results suggest that women using low-dose (50 micrograms or less of estrogen) transdermal patches did not have an increased stroke risk. There was no significant difference in stroke incidence in women using low-dose estrogen patches and women who did not use HT.

Oral HT containing either low-dose (0.625 milligrams or less of equine estrogen, or 2 milligrams or less of estriadol) or high-dose (anything more than the low-dose amount) estrogen were both associated with an increased risk of stroke.

High-dose transdermal patches (more than 50 micrograms estrogen) were also associated with increased stroke risk.

The study findings indicate that low-dose estrogen replacement therapy via transdermal patch may have a different risk profile than oral HT, and may provide an alternative for treating menopausal symptoms.

The study was published online in BMJ on June 3, 2010.

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