Both hormones prevent a woman's ovary from releasing an egg during her menstrual cycle called ovulation. They do this by changing the levels of the natural hormones the body makes. Progestins also make the mucus around a woman's cervix thick and sticky. This helps prevent sperm from entering the uterus. BCPs are also called oral contraceptives or just "the pill. All women who take BCPs need a check-up at least once a year. Women should also have their blood pressure checked 3 months after they begin to take the pill.
BCPs only work well if the woman remembers to take her pill daily without missing a day. Only 2 or 3 women out of who take BCPs correctly for a year will get pregnant. BCPs without estrogen are much less likely to cause these problems. The risk is higher for women who smoke or have a history of high blood pressure, clotting disorders, or unhealthy cholesterol levels. However, the risks of developing these complications are much lower with either type of pill than with pregnancy.
Regular menstrual cycles will return within 3 to 6 months after a woman stops using most hormonal birth control methods. Hormonal contraception. Williams Textbook of Endocrinology. Philadelphia, PA: Elsevier; chap American College of Obstetricians and Gynecologists website. Obstet Gynecol. PMID: pubmed. Textbook of Family Medicine. Philadelphia, PA: Elsevier Saunders; chap It has been used clinically for almost 40 years.
In , it was shown that 0. This concept of ovulation inhibition remained dormant until the synthesis of the nor progestogens, norethindrone and norethynodrel. Both of these compounds were made from estrone and contained mestranol as a not-easily removed contaminant. As a result, mestranol was used as the estrogen in the original norethindrone and norethynodrel combinations.
Improvements in the chemical process facilitated development of estrogen-free norethindrone, and it became possible to use EE in place of mestranol. In vivo , the methyl group is removed from mestranol, and the biologically active compound that binds to the estrogen receptor is EE. However, it may have an advantage over EE in that it is not metabolized to catechols or epoxides, and has less potential for inducing neoplastic transformation of its target cells.
EE has an enterohepatic circulation. That is, it is excreted as conjugates of glucuronic and sulfuric acid in the bile. The conjugates are hydrolyzed to a significant extent by microorganisms in the digestive tract, and the EE is then reabsorbed. This increases the mean residence time of EE in the body. Although it is possible that a change in the flora of the gut may increase or decrease the hydrolysis of the conjugates and thereby the reabsorption of EE, in general, alteration of the flora of the gut by antibiotics does not affect the availability of EE.
The time for maximal serum concentrations T max is 1 — 2 h. Estrogens and progestogens are antagonistic at the level of the uterus and vagina. In the breast, however, progesterone does not oppose the actions of estrogens, but directs the proliferative effects of prolactin and growth hormone toward the development of the lobulo-alveolar system.
Except for androgenic and estrogenic activities of the synthetic compounds, the progestogens presumably act similarly. At the hypothalamic—pituitary level, there also appear to be more complementary actions of estrogens and progestogens. To demonstrate the interaction of progestogen and estrogen at the hypothalamic—pituitary level, norethindrone, 0.
Together, the two agents provided total antiovulatory activity. It implies that higher doses of either or both components are able to create a degree of hypothalamic—pituitary suppression that exceeds the therapeutic need for ovulation inhibition.
It follows that an OC combining a progestogen at its ED antifertility dose with an estrogen in doses sufficient to control irregular cyclic bleeding will be as effective as higher dose products. This has proven to be the case. Serum progesterone levels remained uniformly low as expected, but serum SHBG levels varied with the preparation.
Since serum SHBG concentrations have been shown to be suppressed by androgen and increased by estrogens, the level of serum SHBG provides a good bioassay for the overall effect of the combined steroids. Nevertheless, the contribution of serum estradiol to the levels of SHBG and other estrogenic responses remain to be determined.
Monthly injectable preparations of Cycloprovera and estradiol cypionate 25 mg and 5 mg, respectively or HPR 50 mg norethindrone enanthate and 5 mg estradiol valerate provide suppression of ovulation for approximately 60 days and suppression of follicular development for a minimum of 30 days.
A newer mode of administration has been popularized for reducing menstrual periods to four times per year. Cycles are extended by Seasonale, composed of levonorgestrel and ethinyl estradiol Barr Laboratories, Inc. Bleeding or spotting averaged 8 days for the first cycle and 4 days in the eighth cycle. An association between and an increase in thromboembolic disease and the use of combined OCs has been demonstrated by several older epidemiologic studies.
The evidence suggests that the incidence of venous thromboembolism correlates with the EE dosage and the arterial complications with the type and dose of progestogen. Estrogen has a dose-dependent suppressive effect on natural inhibitors of clotting factors, including antithrombin III and proteins C and S. The effect of the progestogens on carbohydrate metabolism also is a risk factor for vascular disease because impaired glucose tolerance raises serum insulin levels and results in the associated angiopathy.
However, the newer epidemiologic studies now indicate that the incidence of cardiovascular disease with the low dose current OCs has been substantially reduced. In part, this is due to better drugs and, in part, to a better selection of patients for steroidal contraception. A metaanalysis of newer combination pills has concluded that there is no significant association of OCs with cardiovascular disease regardless of duration of use. There appears to be little or no increased risk of breast cancer associated with OC use.
The relative risk in the WHO studies was 1. Cervical cancer is difficult to attribute to the use of OCs since the effects of confounding factors are difficult or impossible to eliminate. Nevertheless, the WHO report concluded that the use of OCs for more than 5 years was associated with a relative risk of cervical cancer from 1.
Endometrial cancer risk is lower in women who have used oral contraception. Relative risks as low as 0. Specific pharmacologic interactions between OCs and other drugs have been shown to increase or decrease the effectiveness of the contraceptive agents. Drugs may reduce the efficacy of OCs by induction of liver enzymes that metabolize steroid hormones. Other drugs may interfere with intestinal absorption or the enterohepatic circulation.
Factors known to induce liver enzymes of steroid metabolism are the antibiotics: rifampin, penicillin, chloramphenicol, cephalosporins, metronidazole, and tetracyclines; the sulfonamides; nitrofurantoin; the anticonvulsants: phenobarbital, primidone, carbamazepine, ethosuximide, and phenytoin; and the antifungal griseofulvin. The list is not comprehensive but is an indication of the number and types of compounds that may affect activity of the OCs.
By inducing enzymes that hydroxylate steroids in the liver, these compounds increase the clearance and thereby decrease the average blood levels of the OCs. Potentially, a change in the intestinal flora, for example by antibiotic medication, may decrease the enterohepatic circulation of EE by decreasing the hydrolysis of glucuronide and sulfate conjugates of the estrogen. This results in less unconjugated EE that can be reabsorbed into the bloodstream; lower serum levels of EE; and a higher proportion of conjugated steroid that is readily excreted.
Plasma levels of EE may be increased by some drugs. Ascorbic acid and paracetamol acetaminophen compete with EE for sulfation. With less sulfate conjugates formed, more EE is available for reabsorption from the gut and serum levels are increased. On the other hand, it should be realized that the drugs that decrease the efficacy of OCs compete for the same enzyme systems in the liver that metabolize the OCs.
Such drugs may, therefore, be metabolized more slowly in the presence of OCs, resulting in elevated blood levels of the drugs. The presence of OCs may, therefore, decrease the rate at which the antibiotics, anticonvulsants, and antifungals are metabolized, and may increase their concentrations to toxic levels. Other drugs which themselves are not good inducers of liver enzymes may also be affected similarly; antidepressants, beta blocking agents, some antianxiety agents, and theophylline preparations may be increased in blood by OCs.
The opposite effect, that of decreased efficacy, may result from concomitant administration of OCs and other drugs: EE results in decreased efficacy of anticoagulants; the progestogens decrease the effectiveness of insulin and anti-diabetogenic agents. The steroidal contraceptives have been greatly improved over time. The nor progestogens have good pharmacokinetic properties. They are efficiently absorbed, have long biological half-lives, and have high affinity for the progesterone receptor.
Some compounds had undesirable side-effects, which were primarily related to the androgenic activity they possessed. Such side-effects as weight gain, blood pressure increase, undesirable lipoprotein profiles, and diabetogenic properties have been largely eliminated by exceedingly small modifications in the levonorgestrel molecule and by the use of smaller doses. The problem of determining the minimal effective dose is one that could only be determined with considerable experience in clinical investigations and could not be ascertained from preclinical animal studies.
The estrogenic component remains an essential part of the OCs to control menstrual and intermenstrual bleeding. Mestranol has largely been replaced by EE, although EE is the active product of both. The thromboembolic disease associated with OCs is primarily due to the estrogen component. This has been minimized by decreasing the dose of EE but remains the primary concern of OC users. It is clear that steroidal contraceptives decrease the incidence of endometrial and ovarian cancer, and the possible increase in the incidence of breast and cervical cancer is too small to ascertain with certainty.
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Novel oral contraception combination. U S Patent 3,,, September 17, Effects of a low-oestrogen oral contraceptive on urinary excretion of luteinizing hormone and ovarian steroids.
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