[Pharmacokinetic and pharmacodynamic studies on vaginally administered levonorgestrel].
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Asia↗
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[Comparison of drug release rate between Chinese subcutaneous implants and Norplant in vitro].
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Asia↗
Long-acting steroidal contraception: an update.
Long-acting, injectable contraceptives first became available in the 1960s. It is currently estimated that almost 3.5 million women are now using depo-medroxyprogesterone acetate (DMPA); 800,000 are using norethindrone enanthate (NET-EN), and another few hundred thousand are using a variety of once-a-month injectables comprised of progestin plus estrogen. The advantages of injectable contraceptives are that they are highly effective, independent of coitus, easily administered, and they ensure regular contact with health services personnel. The last factor may be considered a disadvantage by some, since contact is more frequent than would be required for routine health services. The major disadvantage of the progestin-only formulations is disruption of normal menses, giving rise to unpredicted episodes of bleeding and spotting. With the once-a-month formulation, on the other hand, there are few discontinuations due to disruption of menses. For a long-acting method to be used longer than 6 months, it is desirable to choose an implant, since the method can be discontinued at will. The first implant system to be developed was Norplant, a set of six rubber capsules filled with levonorgestrel and implanted under the skin. The implant releases sufficient levels of medication to protect against pregnancy. For the first 5 years, the average failure rate was four or five per thousand users per year. The failure rate for women using standard oral contraceptives is approximately 20 to 50 per thousand. The most common side effect of the implant method is the disruption of the menstrual cycle, an effect that is particularly marked in the first month of use.(ABSTRACT TRUNCATED AT 250 WORDS)
Contraception↗
Ovarian function in amenorrheic and menstruating users of a levonorgestrel-releasing intrauterine device.
The ovarian function of 20 healthy users of a levonorgestrel-releasing intrauterine device was studied by measurements of plasma estradiol, progesterone, and levonorgestrel concentrations. Eight subjects were amenorrheic, and 12 had regular menstrual bleeding. Seventy-five percent of the subjects in both groups had ovulatory cycles. There was no difference between the mean levonorgestrel concentrations in the amenorrheic and regularly menstruating subjects. Estradiol function was undisturbed in the amenorrheic subjects with ovulatory cycles. The effect of levonorgestrel as a cause of amenorrhea is thought to be mainly of local nature. The intrauterine administration of levonorgestrel had only an occasional and weak effect on ovarian function.
Adult↗
Sex hormone levels and intestinal absorption of estradiol and D-norgestrel in women following bypass surgery for morbid obesity.
A report of reduced serum levels of progestins, following oral administration after jejunoileal bypass, promoted the present investigation of the absorption of D-norgestrel and estradiol following different types of intestinal bypass surgery for morbid obesity. A group of non-operated obese patients served as control. Apart from significantly higher gonadotrophin levels, which could be attributed to periovulatory sampling in the non-operated group, there was no significant differences in basal levels of estradiol, estrone, conjugated estrone, androstendione, testosterone, and progesterone. The operation did not influence the pattern of the menstrual cycle. Following a single oral dose of 4 mg micronized estradiol and 125 microgram D-norgestrel, serum levels of estradiol and estrone were equal in the three groups. serum D-norgestrel was equal in the two operated groups, but was significantly higher in the bypass group with 1:3 jejunoileal ratio, compared with the non-operated group. Further, a significant negative correlation between peak levels and weight was found. It is suggested that one year following bypass surgery, obesity - but not intestinal bypass - might be associated with reduced serum levels of exogenous sex steroids following oral administration.
Adult↗