Oral contraceptives and antithrombin III: variations by dosage and ABO blood group

Article Abstract:

One of the most serious side effects of oral contraceptives is the formation of blood clots. If the blood clots travel to the brain or heart, they can cause a stroke or death. Antithrombin III is a substance that is made in the blood that prevents the blood from clotting. Therefore, a deficiency in antithrombin III may be associated with an increased risk of blood clot formation (thrombosis). Previous studies have reported that women with type O blood have a lower risk of thromboembolism from oral contraceptive use than women with type A, B or AB blood. Therefore, a study was performed to determine the relationship between blood levels of antithrombin III and blood type in women using oral contraceptives. Sixty-seven women were given 50 micrograms (ug) of ethinyl estradiol and 1.0 milligrams (mg) of norethindrone; 61 women received 35 ug of ethinyl estradiol and 1.0 mg of norethindrone; and 64 received 35 ug of ethinyl estradiol and 0.5 mg of norethindrone. Blood levels of antithrombin III were measured before and during oral contraceptive use. After nine months of oral contraceptive use, blood levels of antithrombin III decreased by 20 to 30 percent in all three treatment groups. The greatest decreases in antithrombin III (39 percent) were observed in women who did not have type O blood and were treated with the lowest dose of progestin (35 ug of ethinyl estradiol and 0.5 mg of norethindrone). The women with type O blood who were treated with the highest doses of estrogen (50 ug of estradiol and 1.0 mg of norethindrone) experienced a 32 percent decrease in antithrombin III. These findings suggest that use of oral contraceptives can reduce the amount of antithrombin III in the blood. However, at the present time, it is difficult to determine if this increases the risk of thromboembolism in women who use oral contraceptives. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Complications and side effects, Risk factors, Thromboembolism, Blood chemical analysis, blood, Antithrombin III

---

The effect of tetracycline on levels of oral contraceptives

Article Abstract:

Combined use of oral contraceptives and certain antibiotics can reduce the effectiveness of the contraceptives, possibly because antibiotics reduce the reabsorption of estrogen (a female hormone) by the digestive tract. However, this is debated. To learn more concerning this issue, seven healthy women were studied while taking oral contraceptives and tetracycline (an antibiotic often prescribed for pelvic inflammatory disease and some sexually transmitted diseases). Blood was sampled at regular intervals to determine the concentrations of estradiol, norethindrone (steroid hormones that are the active ingredients of the contraceptive pill), and tetracycline. The sampling began on day 0, after only the contraceptive had been ingested; the next day, both drugs were taken, and were continued until day 10. Four other women took tetracycline only (controls). Results showed that the amount of norethindrone in the blood did not decrease after tetracycline had been added to the regimen, nor were peak levels of the compound reduced. Tetracycline levels were no different for women who also took the contraceptive than for control subjects. The results support further investigation of the importance of the digestive tract in the metabolism of oral contraceptives. But the lack of effect of tetracycline, with either short- or long-term ingestion, on the metabolism of oral contraceptives makes it less likely that the two agents interfere with one another's effectiveness. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Physiological aspects, Drug interactions, Tetracycline, Tetracyclines, Drug metabolism

---

A randomized trial of three oral contraceptives: comparison of bleeding patterns by contraceptive types and steroid levels

Article Abstract:

A comparison of three different combinations of birth control pills found that irregular bleeding occurred most often in women taking pills with the lowest total dose of hormonal steroids. Combination birth control pills are made with both norethindrone, a progestin, and ethinyl estradiol, an estrogen. These are both hormonal steroids. Women using oral contraceptives were randomly assigned to one of three groups. Each group took a pill that combined different doses of the hormonal steroids. Of the 316 women initially participating in the study, 192 remained in the study and were followed for the full nine months. At an interview three months after the study began, 80% of the women on the lowest total dose pill complained of bleeding between their periods. Concentrations of the hormones in the blood plasma were measured by radioimmunoassay. No relationship was found between the amount of hormones in the blood and bleeding between periods. Bleeding between periods seems to be associated with both the estrogen and progestin in birth control pills.

Uterine bleeding, Uterine hemorrhage

Similar abstracts:

• Abstracts: Oral contraceptives in risk groups: exclusion or monitoring? Oral contraceptives and thrombosis: an overview of study methods and recent results
• Abstracts: Evaluating periodontal status of US employed adults. Variations in the prevalence and extent of periodontitis
• Abstracts: Effectiveness and tolerance of long-term malaria prophylaxis with mefloquine. Imported Plasmodium falciparum malaria in American travelers to Africa: implications for prevention strategies
• Abstracts: Elimination of coincident Staphylococcus aureus nasal and hand carriage with intranasal application of mupirocin calcium ointment
• Abstracts: Overexpression of HER-2/neu in endometrial cancer is associated with advanced stage disease. The effect of antibodies and immunotoxins reactive with HER-2/neu on growth of ovarian and breast cancer cell lines

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.