Mechanism of action of hormonal preparations used for emergency contraception: a review of the literature

Contraception today

Modern contraceptive methods represent more than a technical advance: they are the instrument of a true social revolution-the "first reproductive revolution" in the history of humanity, an achievement of the second part of the 20th century, when modern, effective methods became available. Today a great diversity of techniques have been made available and-thanks to them, fertility rates have decreased from 5.1 in 1950 to 3.7 in 1990. As a consequence, the growth of human population that had more than tripled, from 1.8 to more than 6 billion in just one century, is today being brought under control. At the turn of the millennium, all over the world, more than 600 million married women are using contraception, with nearly 500 million in developing countries. Among married women, contraceptive use rose in all but two developing countries surveyed more than once since 1990. Among unmarried, sexually active women, it grew in 21 of 25 countries recently surveyed. Hormonal contraception, the best known method, first made available as a daily pill, can today be administered through seven different routes: intramuscularly, intranasally, intrauterus, intravaginally, orally, subcutaneously, and transdermally. In the field of oral contraception, new strategies include further dose reduction, the synthesis of new active molecules, and new administration schedules. A new minipill (progestin-only preparation) containing desogestrel has been recently marketed in a number of countries and is capable of consistently inhibiting ovulation in most women. New contraceptive rings to be inserted in the vagina offer a novel approach by providing a sustained release of steroids and low failure rates. The transdermal route for delivering contraceptive steroids is now established via a contraceptive patch, a spray, or a gel. The intramuscular route has also seen new products with the marketing of improved monthly injectable preparations containing an estrogen and a progestin. After the first device capable of delivering progesterone directly into the uterus was withdrawn, a new system releasing locally 20 microg evonorgestrel is today marketed in a majority of countries with excellent contraceptive and therapeutic performance. Finally, several subcutaneously implanted systems have been developed: contraceptive "rods," where the polymeric matrix is mixed with the steroid and "capsules" made of a hollow polymer tube filled with free steroid crystals. New advances have also been made in nonhormonal intrauterine contraception with the development of "frameless" devices. The HIV/AIDS pandemic forced policy makers to look for ways to protect young people from sexually transmitted diseases as well as from untimely pregnancies. This led to the development of the so-called dual protection method, involving the use of a physical barrier (condom) as well as that of a second, highly effective contraceptive method. More complex is the situation with antifertility vaccines, still at a preliminary stage of development and unlikely to be in widespread use for years to come. Last, but not least, work is in progress to provide effective emergency contraception after an unprotected intercourse. Very promising in this area is the use of selective progesterone receptor modulators (antiprogestins).

Contraception in Canada: a review of method choices, characteristics, adherence and approaches to counselling

Contraception is a significant concern for Canadian women of child-bearing age, their partners and their health care providers. In this narrative review we provide information on current trends and recent changes in Canadians' choices of contraceptive methods. We review the characteristics of contraceptive methods available in Canada, with an emphasis on hormonal methods and newer options such as the transdermal contraceptive patch, the vaginal contraceptive ring and the levonorgestrel-releasing intrauterine system. We also discuss adherence to contraception as well as approaches to counselling to promote adherence and to reduce the risk of sexually transmitted infections in the context of contraception.

Effectiveness of levonorgestrel emergency contraception given before or after ovulation--a pilot study

BACKGROUND

Although widely used, the mechanisms of action of the levonorgestrel emergency contraceptive pill (LNG ECP) are still unclear. There are increasing data to indicate that LNG is particularly effective as an ECP by interrupting follicular development and ovulation. An important outstanding question is whether it has any effect on fertilization or implantation.

METHOD

Ninety-nine women participated; they were recruited at the time they presented with a request for emergency contraception. All women took LNG 1.5 mg in a single dose during the clinic consultation. A blood sample was taken immediately prior to ingestion of the ECP for estimation of serum LH, estradiol and progesterone levels to calculate the day of ovulation. The specimens were analyzed in a single batch. Based on these endocrine data, we estimated the timing of ovulation to be within a +/-24-h period with an accuracy of around 80%. Women were followed up 4-6 weeks later to ascertain pregnancy status. The effectiveness of ECP when taken before and after ovulation was determined.

RESULTS

Three women became pregnant despite taking the ECP (pregnancy rate, 3.0%). All three women who became pregnant had unprotected intercourse between Days -1 and 0 and took the ECP on Day +2, based on endocrine data. Day 0 was taken as ovulation day. Among 17 women who had intercourse in the fertile period of the cycle and took the ECP after ovulation occurred (on Days +1 to +2), we could have expected three or four pregnancies; three were observed. Among 34 women who had intercourse on Days -5 to -2 of the fertile period and took ECP before or on the day of ovulation, four pregnancies could have been expected, but none were observed. We found major discrepancies between women's self-report of stage of the cycle and the dating calculation based on endocrine data.

CONCLUSION

These data are supportive of the concept that the LNG ECP has little or no effect on postovulation events but is highly effective when taken before ovulation.

Refusals by pharmacists to dispense emergency contraception: a critique

Over the past several months, numerous instances have been reported in the United States media of pharmacists refusing to fill prescriptions written for emergency postcoital contraceptives. These pharmacists have asserted a "professional right of conscience" not to participate in what they interpret as an immoral act. In this commentary, we examine this assertion and conclude that it is not justifiable, for the following reasons: 1) postcoital contraception does not interfere with an implanted pregnancy and, therefore, does not cause an abortion; 2) because pharmacists do not control the therapeutic decision to prescribe medication but only exercise supervisory control over its dispensation, they do not possess the "professional right" to refuse to fill a legitimate prescription; 3) even if one were to grant pharmacists the "professional right" not to dispense prescriptions based on their own personal values and opinions, pharmacists "at the counter" lack the fundamental prerequisites necessary for making clinically sound ethical decisions, that is, they do not have access to the patient's complete medical background or the patient's own ethical preferences, have not discussed relevant quality-of-life issues with the patient, and do not understand the context in which the patient's clinical problem is occurring. We conclude that a policy that allows pharmacists to dispense or not dispense medications to patients on the basis of their personal values and opinions is inimical to the public welfare and should not be permitted.

Nonprescription Availability of Emergency Contraception in the United States: Current Status, Controversies, and Impact on Emergency Medicine Practice

In October 2004, the American College of Emergency Physicians Council joined more than 60 other health professional organizations in supporting the nonprescription availability of emergency contraception. This article reviews the history, efficacy, and safety of emergency contraception; the efforts toward making emergency contraception available without a prescription in the United States; the arguments for and against nonprescription availability of emergency contraception; and the potential impact nonprescription availability could have on the practice of emergency medicine in the United States.

Emergency contraception - a human rights issue

Emergency contraception is the only resource that women can use to avoid becoming pregnant after having sexual intercourse without contraceptive protection. It could be a powerful means to prevent unwanted pregnancies and their devastating consequences for women's health, social wellbeing and life project, and for the unwanted child, if all people had ample access to good quality information, education and services for sexual and reproductive health. In spite of the preventive medicine value of emergency contraception, conservative sectors oppose its availability, appealing to moral values that are not universally shared in pluralistic societies. Excluding the only contraceptive that can be used after intercourse because some consider the mechanism of action to be unacceptable would mean restricting the right of choice of others, and imposing one particular belief or set of values on all members of the community, thus violating the freedom of conscience. Authorities have a moral obligation to protect human rights.

Bioavailability of the Yuzpe and levonorgestrel regimens of emergency contraception: vaginal vs. oral administration

Separate crossover studies compared the bioavailability of oral vs. vaginal routes of administration for the Yuzpe (n=5) and levonorgestrel regimens (n=4) of emergency contraception. Twice the standard dose of the Yuzpe regimen (200 microg of ethinyl estradiol, 1000 microg of levonorgestrel) or the levonorgestrel regimen (1500 microg of levonorgestrel) was self-administered vaginally. One week later, each subject received orally the standard dose of the assigned medication. Serial blood samples were collected over 24 h and assayed for levonorgestrel and ethinyl estradiol (for the Yuzpe regimen only). Paired t tests were used to compare oral vs. vaginal administration for maximum concentration (Cmax), time to maximum concentration (Tmax) and area under the curve over 24 h (AUC0-24). Relative bioavailability (vaginal/oral) was derived from AUC0-24. Vaginal administration of double the standard dose of the Yuzpe regimen resulted in a lower Cmax (vaginal=5.4 vs. oral=14.6 ng/mL, p=.038) and a later Tmax (5.9 vs. 2.0 h, p=.066) for levonorgestrel, compared to oral administration. Corresponding ethinyl estradiol concentrations were higher (786 vs. 391 pg/mL, p=.039) and peaked later (4.0 vs. 1.9 hr, p=.154) with vaginal administration. Relative bioavailabilities for levonorgestrel and ethinyl estradiol were 58% and 175%, respectively. Similarly, vaginal administration of the levonorgestrel regimen resulted in a lower Cmax (vaginal=5.4 vs. oral=15.2 ng/mL, p=.006) and a later Tmax (7.4 vs. 1.3 h, p=.037) for levonorgestel, compared to oral administration. The relative bioavailability was 62%. Our preliminary data suggest that vaginal administration of these emergency contraception regimens appears to require at least three times the standard oral dose to achieve equivalent systemic levonorgestrel concentrations.

Women and postfertilization effects of birth control: consistency of beliefs, intentions and reported use

Background

This study assesses the consistency of responses among women regarding their beliefs about the mechanisms of actions of birth control methods, beliefs about when human life begins, the intention to use or not use birth control methods that they believe may act after fertilization or implantation, and their reported use of specific methods.

Methods

A questionnaire was administered in family practice and obstetrics and gynecology clinics in Salt Lake City, Utah, and Tulsa, Oklahoma. Participants included women ages 18–50 presenting for any reason and women under age 18 presenting for family planning or pregnancy care. Analyses were based on key questions addressing beliefs about whether specific birth control methods may act after fertilization, beliefs about when human life begins, intention to use a method that may act after fertilization, and reported use of specific methods. The questionnaire contained no information about the mechanism of action of any method of birth control. Responses were considered inconsistent if actual use contradicted intentions, if one intention contradicted another, or if intentions contradicted beliefs.

Results

Of all respondents, 38% gave consistent responses about intention to not use or to stop use of any birth control method that acted after fertilization, while 4% gave inconsistent responses. The corresponding percentages for birth control methods that work after implantation were 64% consistent and 2% inconsistent. Of all respondents, 34% reported they believed that life begins at fertilization and would not use any birth control method that acts after fertilization (a consistent response), while 3% reported they believed that life begins at fertilization but would use a birth control method that acts after fertilization (inconsistent). For specific methods of birth control, less than 1% of women gave inconsistent responses. A majority of women (68% or greater) responded accurately about the mechanism of action of condoms, abstinence, sterilization, and abortion, but a substantial percentage of women (between 19% and 57%) were uncertain about the mechanisms of action of oral contraceptives, intrauterine devices (IUDs), Depo-Provera, or natural family planning.

Conclusion

Women who believe that life begins at fertilization may not intend to use a birth control method that could have postfertilization effects. More research is needed to understand the relative importance of postfertilization effects for women in other populations, and in relation to other properties of and priorities for birth control methods. However, many women were uncertain about the mechanisms of action of specific methods. To respect the principles of informed consent, some women may need more education about what is known and not known about the mechanisms of action of birth control methods.

Emergency contraception for sexual assault victims: an advocacy coalition framework

A bill was introduced into the Tennessee legislature in the 2005 session that would require emergency departments to offer and dispense emergency contraception to sexual assault survivors who are at risk of pregnancy. Several advocacy groups collaborated to form the Women's Health Safety Network for the purpose of communicating as one voice. The advocacy coalition framework of policy development is applied to the political system and is used as a model to discuss issues impacting policy development for this particular bill. Key actors, proponents, and opponents to this bill are presented along with constraints to policy acceptance. The challenge for emergency contraception advocates on a state and national level is to keep the focus on public health science, the health and well-being of women, and out of the abortion debate.

Emergency contraception

Teen birth rates in the United States have declined during the last decade but remain much higher than rates in other developed countries. Reduction of unintended pregnancy during adolescence and the associated negative consequences of early pregnancy and early childbearing remain public health concerns. Emergency contraception has the potential to significantly reduce teen-pregnancy rates. This policy statement provides pediatricians with a review of emergency contraception, including a definition of emergency contraception, formulations and potential adverse effects, efficacy and mechanisms of action, typical use, and safety issues, including contraindications. This review includes teens' and young adults' reported knowledge and attitudes about hormonal emergency contraception and issues of access and availability. The American Academy of Pediatrics, as well as other professional organizations, supports over-the-counter availability of emergency contraception. In previous publications, the American Academy of Pediatrics has addressed the issues of adolescent pregnancy and other methods of contraception.

Cost savings from use of emergency contraceptive pills in Australia

BACKGROUND

Emergency contraception, which prevents pregnancy after unprotected sexual intercourse, has the potential to reduce significantly the incidence of unintended pregnancy and the consequent need for abortion and to reduce medical care costs.

AIM

To determine the savings generated by use of Postinor-2, the levonorgestrel regimen of emergency hormonal contraception, in Australia.

METHODS

We modelled the cost savings when women obtain Postinor-2 directly from a pharmacist where cost savings are measured as the cost of pregnancies averted by use of Postinor-2 per dollar spent on Postinor-2.

RESULTS

Each dollar spent on a single treatment with Postinor-2 saves A$2.27-A$3.81 in direct medical care expenditures on unintended pregnancy depending on assumptions about savings from costs avoided by preventing mistimed births. Postinor-2 is cost-saving even under the least favourable assumption that mistimed births when prevented today occur 2 years later. Results are robust even to large changes in model input parameters.

CONCLUSION

Emergency contraception is cost saving. More extensive use of emergency contraception could save considerable medical and social costs by reducing unintended pregnancies, which are expensive.

Failure of the emergency contraceptive levonorgestrel and the risk of adverse effects in pregnancy and on fetal development: an observational cohort study

OBJECTIVE

To determine pregnancy and neonatal outcome after the failure of levonorgestrel as an emergency contraceptive.

DESIGN

A retrospective observational cohort study.

SETTING

Telephone consultations concerning reproductive risk factors conducted by Telefono Rosso-Teratology Information Service, Catholic University of Sacred Heart, Rome, Italy.

PATIENT(S)

Women exposed to levonorgestrel (36 cases) compared with a control group (80 cases).

INTERVENTION(S)

Teratological counseling.

MAIN OUTCOME MEASURE(S)

The rate of congenital anomalies, the prepartum or peripartum complications, and the pregnancy outcomes.

RESULT(S)

Twenty-five exposed newborns with length and weight identical to that of the control group were shown to be without increased risk of congenital malformation. No statistical differences were observed in terms of spontaneous or legal abortion and pregnancy and neonatal complications, and there was no ectopic pregnancy in either group.

CONCLUSION(S)

Although the sample size was small, in our experience, the failure of levonorgestrel as an emergency contraceptive was not associated with an increased risk of major congenital malformations, prepartum or peripartum complications, or an adverse pregnancy outcome.

In vitro effect of levonorgestrel on sperm fertilizing capacity and mouse embryo development

The objectives of this study were to assess the expression of alpha-d-mannose binding sites in human spermatozoa, human sperm-oocyte interaction and the development of early stages of mouse embryo in the presence of levonorgestrel (LNG). Semen samples were obtained from 16 normozoospermic men. Spermatozoa were separated by Percoll gradient and incubated overnight for capacitation. The kinetic analysis of the expression of alpha-D-mannose binding sites was determined at 0, 4 and 22 h and in 22 h-capacitated spermatozoa that had been exposed to 1, 10 or 100 ng/mL of LNG or to a control medium for 30 min. Sperm binding sites for alpha-D-mannose were detected using commercial alpha-D-mannosylated bovine serum albumin conjugated with fluorescein isothiocyanate. To evaluate sperm-oocyte interaction, each oocyte was placed in a 100-microL droplet containing one of the three doses of LNG or control medium and inseminated with 1.0 x 10(5) motile spermatozoa/mL, after which the number of bound spermatozoa was evaluated. A total of 157 two-cell embryos recovered from eight mice was pooled and assigned randomly to treatment (1, 10 or 100 ng/mL of LNG) or control groups. There was a significant increase in the expression of specific alpha-d-mannose binding sites (Patterns II and III) during the incubation of spermatozoa under capacitating conditions. In the presence of LNG, results showed that there was no significant difference in the expression of specific alpha-d-mannose binding sites (Patterns II and III) at any LNG concentration tested compared with those spermatozoa in control medium. None of the LNG concentrations were capable of modifying the number of spermatozoa tightly bound to the human zona pellucida. There was no association between the presence or absence of LNG or the different doses of LNG evaluated and mouse embryo development. In conclusion, the hypothesis that in vitro exposure to LNG could interfere with sperm function and could contribute to the mechanism of action of this form of contraception was not confirmed but cannot be ruled out by the results of this study.

Pharmacokinetics and endometrial tissue levels of levonorgestrel after administration of a single 1.5-mg dose by the oral and vaginal route

OBJECTIVE

To determine the pharmacokinetics and endometrial tissue levels of levonorgestrel when taken as a single dose of 1.5 mg either orally or vaginally by healthy women in the periovulatory phase of their menstrual cycle.

DESIGN

Prospective randomized study.

SETTING

Academic research institution.

PATIENT(S)

Thirty women with regular cycles allocated to control (n = 5), oral (n = 13), and vaginal (n = 12) groups.

INTERVENTION(S)

Blood samples were drawn before (0 time) and at 0.5, 1, 2, 4, 6, 8, 24, 48, and 168 hours after levonorgestrel administration. Endometrial samples were collected 24 and 168 hours after levonorgestrel administration.

MAIN OUTCOME MEASURE(S)

Plasma and endometrial tissue levels of levonorgestrel.

RESULT(S)

Plasma concentrations of levonorgestrel were significantly greater during the first 48 hours after oral administration. However, 7 days after levonorgestrel administration, the plasma levels were similar for both treatments (3-5 nmol/L). Compared with vaginal administration, oral administration resulted in higher peak plasma concentrations (Cmax 64 vs. 10.7 nmol/L), with a shorter time to reach the maximal concentrations (Tmax 1.4 vs. 6.6 hours) and with a greater AUC (509 vs. 175 nmol/L). Interestingly, the half-life of levonorgestrel was shorter after oral administration (25 hours vs. 32.6 hours). Levonorgestrel tissue concentrations were not related to the plasma levels. Levonorgestrel values tended to be higher in endometrial tissue after vaginal administration. The ratio between plasma and endometrial concentrations of levonorgestrel differed significantly between the groups.

CONCLUSION(S)

These data indicate that orally administered levonorgestrel achieves higher plasma levels sooner than vaginally administered levonorgestrel. However, plasma levels after vaginal administration are more sustained and were likely to be sufficient for ovarian suppression. Therefore, the vaginally administered levonorgestrel could be considered as an alternative option for emergency contraception.

Late follicular phase administration of levonorgestrel as an emergency contraceptive changes the secretory pattern of glycodelin in serum and endometrium during the luteal phase of the menstrual cycle

This study examined serum glycodelin concentrations and endometrial expression during the luteal phase following oral administration of levonorgestrel (LNG) at different stages of the ovarian cycle. Thirty women were recruited and allocated into three groups. All groups were studied during two consecutive cycles, a control cycle and the treatment cycle. In the treatment cycle, each woman received two doses of 0.75 mg LNG taken 12 h apart on days 3-4 before the luteinizing hormone (LH) surge (Group 1), at the time of LH rise (Group 2) and 48 h after the rise in LH was detected (Group 3). Serum progesterone (P) and glycodelin were measured daily during the luteal phase, and an endometrial biopsy was taken at day LH +9 for immunohistochemical glycodelin-A staining. In Group 1, serum P levels were significantly lower, serum glycodelin levels rose earlier and endometrial glycodelin-A expression was weaker than in Groups 2 and 3, in which no differences were found between control and treatment cycles. Levonorgestrel taken for emergency contraception (EC) prior to the LH surge alters the luteal phase secretory pattern of glycodelin in serum and endometrium. Based on the potent gamete adhesion inhibitory activity of glycodelin-A, the results may account for the action of LNG in EC in those women who take LNG before the LH surge.

Emergency contraception: the politics of post-coital contraception

The literature and events related to the politicization of emergency contraceptive pills (ECPs) in the United States is reviewed. The basis of opposition to the regimen, rooted in the mode of action of ECPs, the confusion with mifepristone, and the challenges this presents for ECP advocates is also discussed. Legislative actions that impact availability of ECPs are described, as well as efforts to increase access and availability through innovate programs, legislation, and changes in medical practice. Recommendations for future research, service delivery, and public policy are also presented.

Late follicular phase administration of mifepristone suppresses circulating leptin and FSH - mechanism(s) of action in emergency contraception?

OBJECTIVE

Low dose mifepristone (RU486) is highly effective in emergency post-coital contraception (EC), although the mechanism(s) of action remains unclear. We studied the endocrine actions of 10 mg mifepristone administered orally as a single dose to eight healthy volunteers (aged 20-45 years) during the late follicular phase.

METHODS

Serum levels of LH, FSH, oestradiol, progesterone, leptin, mifepristone, cortisol, and gluco-corticoid bioactivity (GBA) were measured before and 1, 2, 4 and 8 h after ingestion of mifepristone on cycle day 10 or 11 (study day 1), and follow-up was continued for 10 days. Ovarian ultrasonography was performed on study days 1 and 7. Similar measurements were carried out during a control cycle.

RESULTS

Mifepristone postponed ovulation, as evidenced by a 3.4+/-1.1 day (means+/-s.d.) delay (P < 0.005) in the LH surge and 3.6+/-4.0 day prolongation of the treatment cycle (P = 0.08). During the mifepristone cycle, an LH surge was displayed by five subjects when serum mifepristone levels had declined to 9.5+/-7.1 nmol/l. During the day of mifepristone administration, circulating GBA (P < 0.001) and leptin (P < 0.001) levels declined. On the day after mifepristone administration, mean serum FSH and leptin levels were lower than pretreatment values (3.8+/-1.8 IU/l vs 5.2+/-1.1 IU/l, n = 7, P < 0.05; 28.9+/-6.7 microg/l vs 33.2+/-9.0 microg/l, n = 7, P < 0.05 respectively), and the corresponding difference in the mean serum oestradiol concentration was borderline (452+/-252 pmol/l vs 647+/-406 pmol/l, n = 7, P = 0.056). In contrast to the control cycle, individual leptin levels declined during the follow-up after ingestion of mifepristone (n = 8, P < 0.01).

CONCLUSIONS

These data showed that the commonly employed dose of mifepristone for EC delays ovulation and prolongs the menstrual cycle, when given during the late follicular phase. The mechanism of action of mifepristone may include a reduction of FSH secretion via a decrease in circulating leptin.

Changes in young women's awareness, attitudes, and perceived barriers to using emergency contraception

BACKGROUND

In a 1996 survey, most young women ages 13-20 years from an urban, hospital-based clinic and a drug treatment center had inadequate awareness of emergency contraception (EC), and perceived several barriers to its use. Since that time, the FDA has approved two products for EC, media coverage has increased, and physicians have provided more counseling about EC.

PURPOSE

The purpose of this study is to compare the awareness, attitudes, and perceived barriers to using EC among a sample of young women from 1996 with a different sample of women from 2002.

METHODS

We recruited 139 young women (mean age 16.7 +/- 1.8 yrs) from the same adolescent clinic and drug treatment center as the 1996 sample. They had similar demographic characteristics, with the majority (63%) being African-American or multi-ethnic; 85% had ever been sexually active. They were interviewed using a questionnaire about their sexual and contraceptive history as well as their knowledge of and experience with EC. They then watched a 4(1/2) minute video and received a 5-minute didactic review of EC. Following the educational intervention, participants' knowledge, attitudes, and perceived barriers to using EC were assessed. The questionnaire used to guide the interviews was nearly identical to that used in 1996.

RESULTS

Between 1996 and 2002, the percentage of participants reporting that they had ever heard of EC grew (44% vs. 73%, P < 0.001), as well as the percentage reporting that they had ever used EC (4% vs. 13%, P = 0.02). Of those participants who had ever heard of EC, fewer 1996 participants knew where to obtain it compared to 2002 participants (78% vs. 95%, P = 0.002) and fewer 1996 participants knew the correct time limits for use (20% vs. 51%, P < 0.001). The above data were collected prior to a didactic review session about EC. After receiving information about EC, the percentage of participants reporting a positive attitude toward EC grew between 1996 and 2002 (72% vs. 96%, P < 0.001). Young women also had fewer concerns about safety and side effects in 2002. The 1996 participants were more likely to report barriers to using EC compared to the 2002 participants. In 1996, EC side effects and impact on fertility were the most commonly perceived barriers to EC use. However, in 2002 the frequency of all reported barriers decreased and cost had become the number one perceived barrier.

CONCLUSION

Since 1996, young women at an urban hospital-based adolescent clinic and drug treatment center increased their awareness, use, and positive attitudes towards EC, as well as decreased their perceived barriers to using EC. Educational interventions that focus on improving knowledge among younger adolescents, specifically about correct time limits and identifying ways to find affordable EC, will address the most common knowledge deficits and perceived barriers to EC use among adolescents.

[Emergency contraception--current trends, possibilities and limitations]

INTRODUCTION

Emergency contraception has been used for over three decades. Indications for emergency contraception are intercourse without contraceptive protection or inadequate application of other contraceptive means. Also, this method is the only way out in situations when sexual intercourse has proceeded not only without protection, but also without voluntary agreement of both partners.

CONTRACEPTION MEANS

Despite of their proven efficiency, it is thought that application of contraception means, even in countries with highly developed systems of health care, is far below optimal. Contemporary studies have pointed out some new posibilities and novel, modified methods of emergency contraception have been proposed. Basic methods of emergency contraception include use of hormonal preparations and postcoital insertion of intrauterine copper devices. Hormonal preparations that are used in emergency contraception are: combined hormonal contraceptive pills, levonorrgestrel and antiprogestin mifepristone. In 1998, the method with levonogestrel only, was indicated by World Health Organization as a "golden standard" in hormonal emergency contraception. The article gives a survey of new trends, possibilities and limitations of modern emergency contraception, with the aim of popularization of this form of contraception in our country.

Pituitary–ovarian function following the standard levonorgestrel emergency contraceptive dose or a single 0.75-mg dose given on the days preceding ovulation

We assessed to what extent the standard dose of levonorgestrel (LNG), used for emergency contraception, or a single dose (half dose), given in the follicular phase, affects the ovulatory process during the ensuing 5-day period. Fifty-eight women were divided into three groups according to timing of treatment. Each woman contributed with three treatment cycles separated by resting cycles. All received placebo in one cycle, and standard or single dose in two other cycles, in a randomized order. The diameter of the dominant follicle determined the time of treatment. Each woman had the same diameter assigned for all her treatments. Diameters were grouped into 33 categories: 12-14, 15-17 or 18-20 mm. Follicular rupture failed to occur during the 5-day period in 44%, 50% and 36% of cycles with the standard, half dose and placebo, respectively. Ovulatory dysfunction, characterized by follicular rupture associated with absent, blunted or mistimed gonadotropin surge, occurred in 35%, 36% and 5% of standard, single dose or placebo cycles, respectively. In conclusion, LNG can disrupt the ovulatory process in 93% of cycles treated when the diameter of the dominant follicle is between 12 and 17 mm. It is highly probable that this mode of action fully accounts for the contraceptive efficacy as well as the failure rate of this method. The present data suggest that half the dose may be as effective as the standard dose.

A short-term in vitro gill culture system to study the effects of toxic (copper) and non-toxic (cortisol) stressors on the rainbow trout, Oncorhynchus mykiss (Walbaum)

A short-term (24 h) method of gill filament culture system was developed to predict the effects of environmental contamination and stress in fish. Gill culture system containing two or three rainbow trout gill filaments in sterile glutamine supplemented Leibovitz 15 (L-15) media was submitted for 24 h to six different treatments: (i) CONT (control, medium only); (ii) CORT (cortisol, 0.28 microM cortisol); (iii) BLOCK (glucocorticoid receptor blocker, 14 microM RU 486); (iv) CORT+BLOCK (cortisol and blocker, 0.28 microM cortisol+14 microM RU 486); (v) CORT+CU (cortisol and copper, 100 microM CuSO4+0.28 microM cortisol); (vi) CU (copper, 100 microM CuSO4). After 24 h, the overall gill structure and cellular components resembled those of salmonids in vivo. Lactate dehydrogenase (LDH) activity in the culture media increased in the CORT+CU and CU groups but was significantly lower in the CORT+CU compared to CU group. Apoptotic cells increased in the CORT and CORT+BLOCK. The numbers of glucocorticoid (GR) receptor-positive cells were lower in the CU group. This short-term culture system seems to be suitable for studying the effects of both external and internal stress effectors (toxicants and hormones respectively), as it contains all cell types found in the gills and the cells give similar biological response as in vivo.

Trends in the use of emergency contraception: An epidemiological study in Barcelona, Spain (1994–2002)

We conducted a retrospective review of the medical records of women requesting emergency contraception (EC) at our emergency department over a 9-year period (1994-2002). EC accounted for 5.9% of all visits (n = 95,288) and increased from 1.26% in 1994 to 9.82% in 2002 (p < 0.001). Reasons for EC were condom problems in 79.5% of cases. EC was used only once by 93% of women. The mean daily number of visits was significantly higher in August (2.46), July (2.01) and September (2.02) than in other months (p < 0.05), and was more frequent on Sunday (3.26), Saturday (2.92) and Monday (2.05) compared to other week days (p < 0.001). New Year's Day and the St. John's Night registered the highest number of visits (mean of 17.2 and 11.7, respectively), with significant differences compared to the remaining days of the year (p < 0.001).

The role of emergency contraception

Emergency contraception is an underused therapeutic option for women in the event of unprotected sexual intercourse. Available postcoital contraceptives include emergency contraceptive pills (ECPs) both with and without estrogen, and copper-bearing intrauterine devices. Each method has its individual efficacy, safety, and side effect profile. Most patients will experience prevention of pregnancy, providing they follow the treatment regimen carefully. There are concerns that women who use ECPs may become lax with their regular birth control methods; however, reported evidence indicates that making ECPs more readily available would ultimately reduce the incidence of unintended pregnancies. In addition, it is typically conscientious contraceptive users who are most likely to seek emergency treatment. Patient education is paramount in the reduction of unintended pregnancies and there are numerous medical resources available to women to assist them in this endeavor. Finally, ECPs are associated with financial and psychologic advantages that benefit both the individual patient and society at large.

The pharmacokinetics of mifepristone in humans reveal insights into differential mechanisms of antiprogestin action

The pharmacokinetics of mifepristone is characterized by rapid absorption, a long half-life of 25-30 h, and high micromolar serum concentrations following ingestion of doses of >/=100 mg of the drug. The serum transport protein-alpha 1-acid glycoprotein (AAG)-regulates the serum kinetics of mifepristone in man. Binding to AAG limits the tissue availability of mifepristone, explaining its low volume of distribution and low metabolic clearance rate of 0.55 L/kg per day. In addition, the similar serum levels of mifepristone following ingestion of single doses exceeding 100 mg can be explained by saturation of the binding capacity of serum AAG. Mifepristone is extensively metabolized by demethylation and hydroxylation, the initial metabolic steps being catalyzed by the cytochrome P-450 enzyme CYP3A4. The three most proximal metabolites, namely, monodemethylated, didemethylated and hydroxylated metabolites of mifepristone, all retain considerable affinity toward human progesterone and glucocorticoid receptors. Also, the serum levels of these three metabolites are in ranges similar to those of the parent mifepristone. Thus, the combined pool of mifepristone-plus its metabolites-seems to be responsible for the biological actions of mifepristone. Recent clinical studies on pregnancy termination and emergency contraception have focused on optimization of the dose of mifepristone. In these studies it has become apparent that the doses efficient for pregnancy termination differ from those needed in emergency contraception-mifepristone is effective in emergency contraception at a dose of 10 mg, which results in linear pharmacokinetics. However, the >/=200 mg doses of mifepristone needed for optimal abortifacient effects of mifepristone result in saturation of serum AAG and thus nonlinear pharmacokinetics. In view of the pharmacokinetic data, it may be speculated that dosing of mifepristone for pregnancy termination and for emergency contraception could be reduced to approximately 100 mg and 2-5 mg, respectively. It remains to be seen whether the newly synthesized, more selective antiprogestins will prove more efficacious in the clinical arena.

The benefits and risks of over-the-counter availability of levonorgestrel emergency contraception

Removing the prescription requirement for Plan B will help ensure that the product plays a larger role nationally in the reduction of unintended pregnancy and abortion-important public health goals. Over-the-counter (OTC) sale of Plan B should present no serious safety issues. OTC consumers are able to understand and follow the instructions for proper use of Plan B. Efficacy of the OTC product is likely to be the same as, or better than, the prescription product, given more timely access to treatment. Based on the results of a growing body of literature and foreign marketing experience, the risk of unintended health consequences also appears to be minimal. There is no evidence to suggest that American women will abuse Plan B as an OTC product.

Emergency contraception--clinical and ethical aspects

Emergency contraception (EC) consists of either 1.5 mg of levonorgestrel (LNG) in one or two doses, or a combination of LNG with ethinylestradiol, administered for up to 5 days after unprotected intercourse. Clinical studies indicate that LNG alone is more effective and has less side effects. Its effectiveness decreases the longer after coitus it is taken. EC is indicated when there is non-compliance or accidents with the use of regular methods of contraception, or when women have had voluntary or imposed unprotected intercourse. The ethics of providing EC has been questioned by some, arguing that it acts by preventing implantation. Scientific evidence does not support this concept, but shows that EC acts mostly before fertilization. Placing obstacles to the access of EC is unethical as it transgresses the ethical principles of autonomy, non-maleficence beneficence and justice. Far from inducing abortions, EC reduces unwanted pregnancies and prevents abortion.

Canadian Contraception Consensus

This document has been archived because it contains outdated information. It should not be consulted for clinical use, but for historical research only. Please visit the journal website for the most recent guidelines.

Minimum effectiveness of the levonorgestrel regimen of emergency contraception

The standard method for estimating the effectiveness of emergency contraceptive pills (ECPs) uses external data to calculate the proportion of expected pregnancies averted by the treatment. Because these data may not be applicable to ECP study populations, this approach could result in substantial overestimation of effectiveness. We used data from two published randomized trials of the levonorgestrel and Yuzpe ECP regimens to calculate the minimum effectiveness of the levonorgestrel regimen. Conservatively assuming that the Yuzpe regimen was entirely ineffective in these trials, we estimate that the levonorgestrel regimen prevented at least 49% of expected pregnancies (95% confidence interval: 17%, 69%). Because physiologic data suggests that the Yuzpe regimen does, in fact, have some efficacy, the effectiveness of the levonorgestrel regimen is likely to be higher than our minimum estimate.

Pharmacokinetics of 10 mg of mifepristone

The results of several randomized studies have verified the efficacy of 10 mg mifepristone in emergency contraception. In the present study we characterized the pharmacokinetics of 10 mg mifepristone. Eight healthy female volunteers received a single oral dose of mifepristone on the day 10 or 11 of their menstrual cycle. Blood samples were collected at 0, 1, 2, 4 and 8 h, daily for the next 6 days and on day 10 after mifepristone. Mifepristone concentrations were determined by radioimmunoassay preceded by column chromatography. A peak level of 1.41 +/- 0.31 micromol/L (mean +/- SD) was measured at 1 h. Individual elimination phase half-lives varied from 15.3 to 26.8 h, the mean (+/- SD) value being 19.6 +/- 4.50 h. Serum mifepristone concentrations exceeded 10 nmol/L in all volunteers for an average of 4.9 days. The pharmacokinetic data on 10 mg mifepristone are in line with previous pharmacokinetic and clinical data, and encourage further development of the 10-mg dose in emergency contraception.

A multiparametric study of the action of mifepristone used in emergency contraception using the Rhesus monkey as a primate model

Mifepristone is a potent agent used in emergency contraception (EC). In the present study, we examined the contraceptive efficacy of mifepristone used in EC and then, using the model of mifepristone-based EC, we investigated its mechanism of action in the rhesus monkey. Sexually mature females were allowed to cohabitate with male animals from 1600 to 900 h of any one day of days 8-17 of cycle without (Group I; n = 6) and with a single dose of mifepristone (Group II, n = 31, 25 mg per animal, subcutaneous) 72 h postcoitus. Blood samples from all animals of Groups I and II were used to determine the concentrations of estradiol (E), progesterone (P) and chorionic gonadotrophin in peripheral circulation for retrospective analysis of the days of ovulation and blastocyst implantation. Four out of six animals (66.6%) in Group I became pregnant, while all 31 monkeys in Group II failed to establish pregnancy along with marginal changes in serum concentrations of E and P. In the second part of the study, animals were subjected to the same experimental protocol followed by collection of endometrial tissue samples on cycle day 22 from animals of both Group I (n = 6) and Group II (n = 24). Endometrial samples were subjected to morphological analysis including mitotic index, immunohistochemistry for vascular endothelial growth factor (VEGF), leukemia inhibitory factor (LIF), transforming growth factor beta1, estradiol receptor (ER), progesterone receptor (PR), proliferating cell nuclear antigen, placental protein 14 (PP 14) and detection of apoptosis by terminal nick end labeling method followed by histometric analysis. The results were retrospectively analyzed between the two groups on the basis of the day of treatment after ovulation: early luteal phase (days 0-3 postovulation) and mid-luteal phase (days 4-7 after ovulation). Mifepristone used in EC in the present study resulted in general loss of functional integrity of epithelial compartment characterized by loss of secretory maturation, increased apoptosis and higher degree of degeneration along with decreased expression of VEGF, LIF, PP14 and ER, while PR level increased as compared to control samples. The vascular compartment appeared to be compromised along with affected morphological features and decreased expression of VEGF, LIF, ER and PR following the administration of mifepristone. It appears that mifepristone used in EC alters the physiological homeostasis in epithelial and vascular compartments of implantation stage endometrium rendering it hostile to blastocyst implantation. Furthermore, the degree to which the endometrial function is affected largely depends on the day of mifepristone treatment in a parameter-specific manner resulting in a higher degree of degenerative changes in samples obtained from animals who received mifepristone during mid-luteal phase of cycles.

A single dose of mifepristone (200 mg) in the immediate preovulatory phase offers contraceptive potential without cycle disruption

A single dose of mifepristone is an effective emergency contraceptive and has potential as a regular "once-a-month" pill. If given in the early luteal phase, the formation of a secretory endometrium is inhibited or delayed and implantation of the embryo prevented. We have explored the effect of giving the mifepristone just prior to ovulation on the ovarian and endometrial cycle. Seven women with regular menstrual cycles were studied during a control cycle and then in a second cycle when 200 mg mifepristone was given within 24 h of ovulation, i.e., when luteinizing hormone (LH) in serum was >15 IU/L and the dominant follicle was >18 mm. Ovulation was confirmed within 48 h by ultrasound in five of the seven women. The remaining two women had luteinized unruptured follicle. Following mifepristone, menses occurred after a normal luteal phase compared to control cycle (13.7 +/- 0.7 vs. 13.7 +/- 0.9 days). In all subjects the endometrium on LH + 6 in the treatment cycle showed no, or very little, secretory changes, suggesting it was unlikely that pregnancy would have occurred. We conclude that mifepristone could be given as a "once-a-month" contraceptive pill without causing significant disruption in the menstrual cycle in the majority of women for a 4-day period from just prior to ovulation until LH + 3.

Recent Advances in Hormonal and Barrier Contraception

Hormonal and barrier contraceptive choices have undergone unprecedented expansion over the past decade. Oral contraceptives have been joined by products with alternative hormone delivery systems, including transdermal, injectable, and intravaginal. In addition, the doses and chemical structures of the estrogen and progestin components have been altered to improve tolerability. Barrier methods continue to offer nonhormonal options with varied levels of protection from sexually transmitted infections. With the expansion of choices, consideration of individual needs is key to maximizing effectiveness and tolerability. Future advancements will continue to focus on individualized options as well as expanded male contraceptive devices.

Emergency contraception: models to increase accessibility

Much of the recent focus on emergency contraception (EC) has been on the need to increase the availability of EC without a prescription. Barriers to the wider accessibility of EC include the need to use the medication within a 72-hour window, cost, and knowledge about its availability. Concerns about the non-prescription accessibility of EC include missing the opportunity to see a physician, possible reduced use of barrier contraceptives and the resulting increase in sexually transmitted infections, and overuse of EC and underuse of regular contraception. As the wider availability of EC is a reality, and pressure to further increase its access is growing, it is timely that issues surrounding accessibility of EC be discussed. This paper explores the issues around making EC more accessible and the various models of obtaining EC, namely, prescription medication, pharmacist-physician collaboration, pharmacist-dispensed medication, schedule II (behind the counter) medication, or on-the-shelf medication. The ideal model will be the one that provides improved accessibility for adolescents, other low-income women, and indeed for all women. Increased accessibility of EC should also lead to cost savings for the health-care system because of fewer unwanted pregnancies.

Postcoital treatment with levonorgestrel does not disrupt postfertilization events in the rat

Levonorgestrel (LNG), a progestin widely used for regular hormonal contraception, is also used for emergency contraception (EC) to prevent pregnancy after unprotected intercourse. However, its mode of action in EC is only partially understood. One unresolved question is whether or not EC prevents pregnancy by interfering with postfertilization events. Here, we report the effects of acute treatment with LNG upon ovulation, fertilization and implantation in the rat. LNG inhibited ovulation totally or partially, depending on the timing of treatment and/or total dose administered, whereas it had no effect on fertilization or implantation when it was administered shortly before or after mating, or before implantation. It is concluded that acute postcoital administration of LNG at doses several-fold higher than those used for EC in women, which are able to inhibit ovulation, had no postfertilization effect that impairs fertility in the rat.

Ectopic pregnancies following emergency levonorgestrel contraception

There are little or no data on the risk of ectopic pregnancy following levonorgestrel treatment as an emergency contraception. We encountered three cases of ectopic pregnancy following the use of levonorgestrel administered peri- or postovulation. Here we report these cases and discuss the clinical and epidemiologic implications of this association. Health providers should be alert to the possibility of an ectopic pregnancy in women who become pregnant or complain of lower abdominal pain after taking levonorgestrel.