Estrogen replacement therapy: Old treatment, new effects

By William T. Elliott, MD, FACP

The list of new and surprising findings from studies of postmenopausal estrogen replacement therapy (ERT) in healthy women grows longer almost weekly. A recent study indicated that healthy postmenopausal women have better blood pressure regulation while on ERT. This suggests that estrogen plays a role in the ability of the nervous system to control blood pressure. In the study appearing in Circulation, none of the women had hypertension at baseline. A separate study in the same journal found that transdermal estrogen was better at regulating blood pressure than oral estrogen. Researchers postulated that since transdermal estrogen bypasses enterohepatic circulation, more of the hormone is systemically available (Circulation 2001; 103:2,903-2,908; Circulation 2001; 103:2,909-2,914).

ERT may reduce the risk of cataracts according to an analysis of data from the Framingham Heart Study and the Framingham Eye Study I and II. Researchers examined the data for an association between lens opacities and postmenopausal estrogen use. Results indicated that women who took ERT the longest were the least at risk for developing cataracts. Women taking estrogen for 10 years or more had a 60% reduction in risk compared with nonusers (95% confidence interval). (Arch Intern Med 2001; 161:1,448-1,454).

Women with hypothyroidism who are being treated with thyroxine may need to increase their dose when they start begin using ERT. Estrogen leads to an increase in thyroxine-binding globulin and a decrease in serum-free thyroxine. Researchers suggest checking thyroid functions 12 weeks after initiating ERT and appropriately adjusting thyroxine doses (N Engl J Med 2001; 344:1,743-1,785).

Insulin

The search for a noninjectable insulin product looks promising. Pfizer and Aventis Pharmaceu-ticals are partnering on the development of an inhaled insulin product. Phase III data presented at the American Diabetes Association’s (ADA) 61st Annual Scientific Sessions suggest that a single bedtime injection of ultralente with daytime inhaled insulin (Exubera) to replace meal-related injections is at least as effective as subcutaneous insulin injections. The inhaled insulin was evaluated in both Type 1 and Type 2 diabetics. Inhaled insulin-induced insulin antibodies developed higher levels of insulin antibodies, but the clinical significance of this finding is unclear. Researchers suggest that the inhaled insulin may result in earlier introduction of insulin therapy in Type 2 diabetes based on patients’ acceptance and improved glycemic control.

Progress on an oral insulin product also was presented at the ADA session. The insulin molecule is susceptible to degradation in the intestines, but by attaching various polymeric oligomers, the molecule can be absorbed. Oral insulin also is in phase III trials.

Antibiotics

Aventis Pharmaceuticals’ telithromycin (Ketek), the first of a new class of antibiotics known as ketolides, has received an "approvable" letter from the Food and Drug Administration (FDA). The drug, which can be taken orally once a day, will be indicated for upper and lower respiratory tract infections including community acquired pneumonia. An approvable status from the FDA outlines additional information or conditions that must be met before the FDA will approve a drug.

Statin Therapy

High C-reactive protein (CRP) levels are a predictor of future coronary events and stroke. Studies have suggested that statins reduce CRP levels. A new study shows that this effect translates into lower rates of heart disease, even in patients with high CRP levels and low lipids. More than 5,700 patients were randomized to treatment with lovastatin or placebo. Researchers found that in patients with low lipids, lovastatin reduced CRP levels by 14.8%, and those patients also had a lower incidence of coronary events. An accompanying editorial suggests that measuring CRP levels along with lipid levels may become routine in healthy adults. (N Engl J Med 2001; 344:1,959-1,965; N Engl
J Med
2001; 344:2,016-2,018).

Lyme Disease

A single 200-mg dose of doxycycline given within 72 hours of a tick bite is highly effective at preventing Lyme disease. Researchers from New York randomized 482 patients who had been bitten by Ixodes scapularis to doxycycline or placebo. Of those tested, a significantly smaller proportion (P < 0.04) of the doxycycline-treated patients (3.2%) than of the placebo patients (0.4%) developed erythema migrans at the site of the tick bite. One-third of doxycycline patients noted side effects, primarily nausea and vomiting. See Lyme disease patient education insert in this issue (N Engl J Med 2001; 345:79-84).

Synthroid under attack

The FDA status of levothyroxine (Synthroid) is in limbo despite a 40-year safety record. Prior to1962, it was not necessary to file a New Drug Application (NDA) when seeking FDA approval. Synthroid was released in 1958 and, therefore, never was required to submit a NDA. The FDA recently notified Abbott Labs that the company needed to file documentation showing the safety and efficacy of Synthroid. Abbott requested a waiver, but the FDA denied their request. In the meantime, two advocacy groups, the National Organization of Women and the Grey Panthers, are demanding that the drug be withdrawn from the market because its safety and efficacy hasn’t been demonstrated.