These drugs including https://pillintrip.com/medicine/noranelle are the most common form of hormonal contraception in the world. Since the beginning of their use, OCs have undergone significant changes in steroid dosage. Doses of ethinyl estradiol and mestranol (estrogens used in OCs) have been greatly reduced over the past three decades from 150 to 30 mcg. The newest preparations contain 20 mcg of ethinylestradiol. The dose of the gestagenic component has also been reduced. The tablets produced today contain 0.4-1 mg of norethisterone, 125 mg of levonorgestrel or even smaller doses of the most potent and selective progestins. A change in the type of gestagens in OCs has allowed three generations to be distinguished. The first generation of OCs includes preparations containing noretinodrel acetate. The second generation of progestins contains levonorgestrel, whose progestin activity is 10 times higher than that of noretinodrel.
The third generation includes OCs containing desogestrel (Marvelon), norgestimat (Cilest), gestoden, which is part of the drug Femoden. These gestagens are used in micrograms, do not cause disturbances in lipid metabolism, have less androgenic activity, do not increase the risk of cardiovascular disease. Depending on the dose of the estrogenic and type of gestagenic components, OCs can have predominantly estrogenic, androgenic or anabolic effects.
The mechanism of action of oral contraceptives. The mechanism of action of OCs is based on the blockade of ovulation, implantation, changes in gamete transport and corpus luteum function.
Ovulation. The primary mechanism of ovulation blockade is the suppression of gonadotropin-releasing hormone (GTR) secretion by the hypothalamus. The secretion of gonadotropic hormones of the pituitary gland (FSH and L) is inhibited. An indicator of hormonal suppression of ovulation is the absence of estrogen, FSH and LH peak in the middle of the menstrual cycle, inhibition of the normal postovulatory increase in serum progesterone. Throughout a menstrual cycle, estrogen production in ovaries remains at the low level corresponding to an early follicular phase.
Cervical mucus. Thickening and thickening of cervical mucus becomes evident 48 h after the start of progestin administration. Mobility and ability of sperm to penetrate cervical mucus is impaired due to thickening and thickening; cervical mucus becomes reticular and characterized by reduced crystallization.
Implantation. Implantation of the developing blastocyst occurs approximately 6 days after fertilization of the egg. Sufficient maturation of the superficial endometrial glands with adequate secretory function and appropriate endometrial structure for implantation is required to ensure successful implantation and development of the blastocyst. Changes in the levels and disruption of the ratio of estrogen and progesterone lead to impaired functional and morphological properties of the endometrium. All this disturbs the implantation process. Transport of the fertilized egg is altered by the effects of hormones on the secretion and peristalsis of the fallopian tubes. These changes disrupt the transport of sperm, egg or developing embryo.
Efficacy and acceptability of OCs. OCs are the only means of preventing pregnancy with 100% efficacy. A distinction is usually made between theoretical efficacy, which is the use of the method without errors or missed pills, and clinical efficacy, which is calculated on the basis of the number of pregnancies that have occurred in real life, taking into account the errors made by women. The most objective measure of clinical efficacy is the Pearl Index, which measures the number of pregnancies that occur in 100 women per year. The Pearl Index is defined by the number of pregnancies per 100 women who used a contraceptive method within 12 months, by the following formula: number of pregnancies x 1200/number of menstrual cycles. For OC the Perl index is 0.2-1.
Thus, OCs meet all the requirements for modern contraceptives:
high effectiveness in preventing pregnancy;
ease of use (coitus-independent);
Reversibility of the effect.
Principles of use of oral contraceptives. Despite the fact that modern contraceptives contain low doses of sex hormones and are well tolerated, they are still medicines whose use has various limitations. The basic therapeutic principle is that each woman should be prescribed the lowest dose of steroids that can provide optimal contraceptive security. For continuous use in healthy women, OCs containing no more than 35 mcg of ethinylestradiol and 150 mcg of levonorgestrel or 1.5 mg of norethisterone are recommended. The most important task of the doctor is to identify women for whom hormonal contraception is contraindicated, which makes a thorough collection of medical history and careful examination of each patient necessary.
Absolute contraindications to the use of OCs are the following diseases that the patient currently has, or has a history of them:
confirmed or suspected pregnancy;
A history of thromboembolism;
varicose veins with a history of thrombophlebitis;
diseases of the cerebral vessels;
malignant tumors of genitals and mammary glands;
severe forms of gestosis in the anamnesis;
Blood pressure over 160/95 mm Hg.
diseases of the gallbladder;
smoking; – trophic ulcers of the lower leg;
Long-term plaster casts;
significant excess weight;
Age 40 or older;
Oral contraceptives and fertility. After stopping OCs, ovulation is quickly restored and more than 90% of women are able to become pregnant within two years. The term “post-pill” amenorrhea is used to describe cases of secondary amenorrhea for more than 6 months after stopping OC. Amenorrhea for more than 6 months occurs in about 2% of women and is especially common in early and late reproductive periods of fertility. Oral contraceptives and pregnancy. Women who have used OCs do not have an increased incidence of spontaneous miscarriage, ectopic pregnancy or fetal abnormalities. In those rare cases where a woman accidentally took OCs during early pregnancy, their damaging effects on the fetus have also not been identified. Oral contraceptives and age. An important issue is the age at which a woman can start taking OCs to prevent unplanned pregnancy. Previously, there was a prejudice against the prescription of oral contraception for adolescent girls. Nowadays, such notions are rejected. In any case, taking the contraceptive pill is the best alternative to pregnancy and even more so to teenage abortion. OCs have been proven to have no effect on body growth and do not increase the risk of amenorrhea. The need for effective contraception is also evident in the period leading up to menopause. In those cases when other methods of contraception are unacceptable for the woman and her partner, when the risk factors of cardiovascular and metabolic complications, such as hypertension, diabetes, obesity, hyperlipidemia are excluded, OC can be taken before the menopause. A woman’s age is not as important in the absence of risk factors. The development of modern OCs with low doses of hormones allows women under 45 years of age and older to use them. The drug of choice at this age may be preparations containing only gestagens. Duration of OC use. With constant medical supervision, the absence of contraindications, women can continue taking OCs for many years. There is no sufficiently justifiable reasons for periodic abstinence from taking oral contraceptives. Interaction of OCs with medications. In case of prescription of OC it is necessary to take into account the possibility of their drug interaction with a number of drugs, manifested in weakening of the contraceptive effect, in case of their simultaneous use.