Pharmacokinetic study of different dosing regimens of levonorgestrel for emergency contraception in healthy women

Double Dosing Levonorgestrel-Based Emergency Contraception for Individuals With Obesity: A Randomized Controlled Trial

Increasing the dose of levonorgestrel-containing emergency contraception from 1.5 mg to 3 mg did not improve rates of ovulation delay in individuals with obesity.

OBJECTIVE:

To assess whether dose escalation (ie, doubling the dose) of emergency contraception that contains levonorgestrel (LNG) improves pharmacodynamic outcomes in individuals with obesity.

METHODS:

We enrolled healthy, reproductive-age individuals with regular menstrual cycles, body mass index (BMI) higher than 30, and weight at least 176 lbs in a randomized pharmacodynamic study. After confirming ovulation (luteal progesterone level greater than 3 ng/mL), we monitored participants with transvaginal ultrasonography and blood sampling for progesterone, luteinizing hormone, and estradiol every other day until a dominant follicle measuring 15 mm or greater was visualized. At that point, participants received either oral emergency contraception with LNG 1.5 mg or 3 mg (double dose) and returned for daily monitoring for up to 7 days. Our primary outcome was the difference in the proportion of participants with no follicle rupture 5 days postdosing (yes or no) between groups. The study had 80% power to detect a 30% difference in the proportion of cycles with at least a 5-day delay in follicle rupture (50% decrease).

RESULTS:

A total of 70 enrolled and completed study procedures. The two groups had similar baseline demographics (mean age 28 years, BMI 38). We found no difference between groups in the proportion of participants without follicle rupture more than 5 days post–LNG dosing (LNG 1.5 mg: 18/35 [51.4%]; LNG 3.0 mg: 24/35 [68.6%], P=.14). Among participants with follicle rupture before 5 days, the time to rupture did not differ between groups (day at 75% probability of no rupture is day 2 for both groups).

CONCLUSION:

Individuals with higher BMIs and weights experience a higher risk of failure of emergency contraception with LNG and exhibit an altered pharmacokinetic profile. However, the simple strategy of doubling the dose does not appear to be an effective intervention to improve outcomes.

CLINICAL TRIAL REGISTRATION:

ClinicalTrials.gov, 02859337.

Uterine flushings from women treated with levonorgestrel affect sperm functionality in vitro

Levonorgestrel (LNG), a synthetic 19 nor-testosterone derivative, is widely used for emergency contraception. It is well known that LNG prevents ovulation only when given prior to the surge of serum luteinizing hormone (LH) during the periovulatory phase of the menstrual cycle. This observation suggests that LNG, given its contraceptive efficacy, has additional effects other than those affecting ovulation. In this study, we have evaluated the effects on human sperm functionality of uterine flushings (UF) obtained from women at day LH + 1 of a control cycle (CTR-LH + 1) and after receiving LNG (LNG-LH + 1) two days before the surge of LH. Human sperm from normozoospermic donors were incubated with UF and protein tyrosine phosphorylation, sperm motility, acrosome reaction as well as zona pellucida (ZP) binding capacity were assessed. A significant decrease in total motility and tyrosine phosphorylation accompanied by an increase on spontaneous acrosome reaction was observed when sperm were incubated in the presence of LNG-LH + 1. None of these effects were mimicked by purified glycodelin A (GdA). Moreover, the addition of UF obtained during the periovulatory phase from LNG-treated women or the presence of purified GdA significantly decreased sperm-ZP binding. The data were compatible with changes affecting sperm capacitation, motility and interaction with the ZP. These results may offer evidence on additional mechanisms of action of LNG as an emergency contraceptive.

Pharmacokinetics of levonorgestrel and ulipristal acetate emergency contraception in women with normal and obese body mass index

OBJECTIVE

This study compares the pharmacokinetics (PK) of levonorgestrel (LNG) emergency contraceptive (EC) and ulipristal acetate (UPA)-EC between normal-body mass index (BMI) and obese-BMI women.

STUDY DESIGN

This prospective, randomized crossover study evaluates the PK of women after single doses of LNG-EC (1.5mg) and UPA-EC (30mg). Study procedures took place during clinical research unit admissions, where participants received a standardized meal and each study drug, in random order, during two separate 24-h admissions. Study staff collected 14 blood specimens (0, 0.5, 1.0, 1.5, 2, 3, 4, 6, 8, 10, 12, 16, 24 and 48h). We evaluated serum concentrations of LNG and UPA using liquid chromatography-tandem mass spectroscopy and estimated the PK parameters of both drugs using noncompartmental analysis. The main outcome of this study was a comparison of between-group differences in AUC_0-24.

RESULTS

Thirty-two women completed the study (16 in each group). Among normal-BMI and obese-BMI participants, the mean BMIs were 22.0 (range 18.8-24.6) and 34.3 (range 30.6-39.9), respectively. After LNG-EC, mean AUC_0-24 and maximum concentration (C_max) were 50% lower among obese-BMI women than among normal-BMI women (AUC_0-24 100.8 vs. 208.5ng*h/mL, IQR_obese-BMI 35.8, IQR_normal-BMI 74.2, p≤.01; C_max 10.8 vs. 18.2ng/mL, p=.01). After UPA-EC, AUC_0-24 and C_max were similar between obese-BMI and normal-BMI women (AUC_0-24 362.5 vs. 293.5ng*h/mL, IQR_obese-BMI 263.2, IQR_normal-BMI 112.5, p=.15; C_max 95.6 vs. 89.3ng/mL, p=.70).

CONCLUSION

After a single dose of EC, obese-BMI women are exposed to lower concentrations of LNG and similar concentrations of UPA, when compared to normal-BMI women.

IMPLICATIONS

Differences in LNG-EC PK by BMI group may underlie and account for the lower LNG-EC efficacy reported among obese-BMI women, but modest differences in UPA-EC PK by BMI group provide less support for variable efficacy. A pharmacodynamic study may be able to clarify whether these PK differences account for observed differences in LNG-EC and UPA-EC efficacy.

Impact of obesity on the pharmacokinetics of levonorgestrel-based emergency contraception: single and double dosing

OBJECTIVE

To determine if differences exist in the pharmacokinetics (PK) of levonorgestrel-based emergency contraception (LNG-EC) in obese and normal body mass index (BMI) users and test whether doubling the dose of LNG-EC in obese women increases total and free (active) LNG serum concentrations.

STUDY DESIGN

Healthy, reproductive-age women with obese and normal BMIs received 1.5mg LNG orally (ECx1) and then in a subsequent menstrual cycle, the obese group also received 3mg LNG (ECx2). Dosing occurred during the follicular phase. Total and free LNG PK parameters were obtained via serum samples through an indwelling catheter at 0, 0.5, 1, 1.5, 2, and 2.5h. The primary outcome was the difference in total and free LNG concentration maximum (Cmax) between ECx1 and ECx2 in the obese group.

RESULTS

A total of 10 women enrolled and completed the study (normal BMI=5, median 22.8kg/m(2), range 20.8-23.7; obese BMI=5, 39.5kg/m(2), range 35.9-46.7). The total LNG Cmax for obese subjects following ECx1 (5.57±2.48ng/mL) was significantly lower than the level observed in normal BMI women (10.30±2.47, p=.027). Notably, ECx2 increased the Cmax significantly (10.52±2.76, p=.002); approximating the level in normal BMI subjects receiving ECx1. Free LNG Cmax followed a similar pattern.

CONCLUSION

Obesity adversely impacts both the total and free Cmax levels of LNG EC and this likely explains its lack of efficacy in obese women. Doubling the dose appears to correct the obesity-related PK changes but additional research is needed to determine if this also improves EC effectiveness in obese women.

IMPLICATIONS

This study demonstrates that obesity interferes with the pharmacokinetics of LNG EC, and that doubling the dose may be an effective strategy to improve its efficacy in obese women.

Association between levonorgestrel emergency contraception and the risk of ectopic pregnancy: a multicenter case-control study

Cases of ectopic pregnancy (EP) following levonorgestrel emergency contraception (LNG-EC) failure have been reported continuously, but whether there is an association between EP risk and LNG-EC is unclear. We concluded a case-control study to explore this association by recruiting 2,411 EP patients as case group, and 2,416 women with intrauterine pregnancy and 2,419 non-pregnant women as control groups. Odds ratios (ORs) and their 95% confidential intervals (CIs) were calculated and adjusted for potential confounding factors. Previous use of LNG-EC was not correlated with the EP. Compared to women who did not use contraceptives, current use of LNG-EC reduced the risk for intrauterine pregnancy (Adjusted OR [AOR] = 0.20, 95%CI: 0.14-0.27), but did not increase the risk for EP (AOR2 = 1.04, 95%CI: 0.76-1.42). Furthermore, compared to women who did not have further act of intercourse, women with unprotected further act of intercourse were at a higher risk of EP (AOR1 = 2.35, 95%CI: 1.17-4.71), and women with repeated use of LNG-EC for further intercourse during the same cycle was also associated with a higher risk for EP (AOR1 = 3.08, 95%CI: 1.09-8.71; AOR2 = 2.49, 95%CI: 1.00-6.19). A better understanding of the risk of EP following LNG-EC failure can optimize LNG-EC use and thus reduce the risk of EP.

A randomized study on pharmacodynamic effects of vaginal rings delivering the progesterone receptor modulator ulipristal acetate: research for a novel estrogen-free, method of contraception

OBJECTIVE

To determine whether a 3-month contraceptive vaginal ring (CVR) delivering ulipristal acetate (UPA) can inhibit ovulation in 90% of cycles.

STUDY DESIGN

This was a randomized dose-finding parallel group clinical trial. Fifty-five healthy women with normal ovulation at baseline were randomized to receive a low-dose (1500 μg/day) or a high-dose (2500 μg/day) UPA-CVR for two consecutive 12-week treatment periods, followed by a recovery cycle. A subgroup of women received levonorgestrel (LNG) 1.5 mg orally twice (at the end of both 12-week ring periods) or once (at the end of the 24-week treatment). The primary outcome was ovulation suppression assessed by transvaginal ultrasound and hormone levels. Secondary outcomes included endometrial safety and bleeding patterns.

RESULTS

All subjects showed normal ovulation at baseline and recovery. Ovulation suppression was seen in 81.8% (95% CI: 73.3%, 88.5%) and 86.1% (95% CI: 78.1%, 92%) of treatment cycles with low and high-dose, respectively. Benign progesterone receptor modulator associated endometrial changes (PAEC) were seen during treatment; 78.8% at week 24, but resolved at recovery cycle. A few cases of heavy bleeding occurred near the end of the 24-week treatment, but a single dose of LNG every 12 weeks reduced the increase in endometrial thickness during the second treatment period and prevented excessive bleeding.

CONCLUSION

The 3-month UPA-CVR may become an effective long-acting, user-controlled estrogen-free contraceptive. The greatest suppression of ovulation was seen with the 2500-μg/day ring.

IMPLICATIONS

The 3-month CVR delivering UPA 2500 μg/day can become an effective user-controlled estrogen-free contraceptive method. Benign PAEC during treatment returns to normal after discontinuation. The prevention of occasional excessive withdrawal bleeding, either by a progestin or by using higher UPA levels to increase follicle suppression may permit prolonged treatment.

A systematic review of effectiveness and safety of different regimens of levonorgestrel oral tablets for emergency contraception

BACKGROUND

Unintended pregnancy is a complex phenomenon which raise to take an emergency decision. Low contraceptive prevalence and high user failure rates are the leading causes of this unexpected situation. High user failure rates suggest the vital role of emergency contraception to prevent unplanned pregnancy. Levonorgestrel - a commonly used progestin for emergency contraception. However, little is known about its pharmacokinetics and optimal dose for use. Hence, there is a need to conduct a systematic review of the available evidences.

METHODS

Randomized, double-blind trials were sought, evaluating healthy women with regular menstrual cycles, who requested emergency contraception within 72 h of unprotected coitus, to one of three regimens: 1.5 mg single dose levonorgestrel, two doses of 0.75 mg levonorgestrel given 12 h apart or two doses of 0.75 mg levonorgestrel given 24 h apart. The primary outcome was unintended pregnancy; other outcomes were side-effects and timing of next menstruation.

RESULTS

Every trial under consideration successfully established the contraceptive effectiveness of levonorgestrel for preventing unintended pregnancy. Moreover, a single dose of levonorgestrel 1.5 mg for emergency contraception supports its safety and efficacy profile. If two doses of levonorgestrel 0.75 mg are intended for administration, the second dose can positively be taken 12-24 h after the first dose without compromising its contraceptive efficacy. The main side effect was frequent menstrual irregularities. No serious adverse events were reported.

CONCLUSIONS

The review shows that, emergency contraceptive regimen of single-dose levonorgestrel is not inferior in efficacy to the two-dose regimen. All the regimens studied were very efficacious for emergency contraception and prevented a high proportion of pregnancies if taken within 72 h of unprotected coitus. Single levonorgestrel dose (1.5 mg) can substitute two 0.75 mg doses 12 or 24 h apart. With either regimen, the earlier the treatment is given, the more effective it seems to be.

Expressions of candidate molecules in the human fallopian tube and chorionic villi of tubal pregnancy exposed to levonorgestrel emergency contraception

BACKGROUND

Cases of ectopic pregnancy (EP) following levonorgestrel (LNG) emergency contraception (EC) failure were reported, however, the effects of LNG on tubal microenvironment or chorionic villi in EP have not yet been documented.

METHODS

Fifty-five women with tubal pregnancy were divided into two groups according to whether LNG-EC was administrated during the cycle of conception. The serum concentrations of beta-hCG, E2 and P were measured. The mRNA and protein expressions of estrogen and progesterone receptors, leukemia inhibitory factor, vascular endothelial growth factor, inducible nitric oxide synthase, and endocannabinoid receptor - CB1 in the ectopic implantation site and chorionic villi were examined.

RESULTS

Compared to those unexposed to LNG-EC, women with tubal pregnancy exposed to LNG-EC during the cycle of conception had no statistically significances in the serum concentrations of beta-hCG, E2 P, nor in the pathological types of tubal pregnancy or the expressions of ER-alpha, PR, LIF, VEGF, iNOS and CB1.

CONCLUSIONS

The expressions of candidate molecules in the fallopian tube and chorionic villi were not altered by exposure to LNG-EC. A routine therapy with no additional intervention might thus be applied to tubal pregnancy exposed to LNG-EC.

In vitro assessment of some sperm function following exposure to levonorgestrel in human fallopian tubes

BACKGROUND

The mechanism of action of levonorgestrel (LNG) as emergency contraception (EC) remains a subject of debate and its effect on sperm function has been only partially explained. The aim of this study was to assess whether LNG at a similar dose to those found in serum following oral intake for EC could affect spermatozoa when exposed to human fallopian tubes in vitro.

METHODS

Fifteen mini-laparotomies were performed, the side on which ovulation occurred was recorded, and both tubes were removed and perfused with a suspension containing 1 × 10(6) motile spermatozoa, with or without LNG. Following 4-hour incubation, the tubes were sectioned to separate the isthmus and the ampulla. Each segment was flushed and the material was evaluated to quantify the number of motile sperm, the number of spermatozoa adhering to the oviductal epithelium and the acrosome reaction (AR) rate.

RESULTS

The addition of LNG did not significantly alter the number of recovered motile spermatozoa either at the isthmus or at the ampulla, nor did it have any effect on the number of recovered spermatozoa adhered to the human tubal epithelium. Furthermore, LNG did not affect the AR rate. No significant differences were found even when the side on which ovulation occurred was taken into account.

CONCLUSIONS

In a similar dose to that observed in serum following oral intake for EC, LNG had no effect on the number of motile spermatozoa recovered from the human fallopian tubes in vitro, on their adhesion to the tubal epithelium, distribution or AR rate. The possible effect of LNG as EC on sperm function remains poorly understood.

Therapeutic levels of levonorgestrel detected in blood plasma of fish: results from screening rainbow trout exposed to treated sewage effluents

Pharmaceuticals are found in surface waters worldwide, raising concerns about effects on aquatic organisms. Analyses of pharmaceuticals in blood plasma of fish could provide means to assess risk for pharmacological effects, as these concentrations could be compared with available human therapeutic plasma levels. In this study we investigated if fish exposed to sewage effluents have plasma concentrations of pharmaceuticals that are approaching human therapeutic levels. We also evaluated how well the bioconcentration of pharmaceuticals into fish blood plasma can be predicted based on lipophilicity. Rainbow trout were exposed to undiluted, treated sewage effluents at three sites in Sweden for 14 days. Levels of 25 pharmaceuticals in blood plasma and effluents were analyzed with liquid chromatography-mass spectrometry/mass spectrometry and gas chromatography-high resolution mass spectrometry. The progestin pharmaceutical levonorgestrel was detected in fish blood plasma at concentrations (8.5-12 ng mL(-1)), exceeding the human therapeutic plasma level. In total 16 pharmaceuticals were detected in fish plasma at concentrations higher than 1/1000 of the human therapeutic plasma concentration. Twenty-one pharmaceuticals were detected in either plasma or effluent, and 14 were detected in both compartments, allowing plasma bioconcentration factors to be determined. For 11 of these, theoretically calculated and experimentally measured values were in reasonably good agreement. However a few drugs, including levonorgestrel, did not bioconcentrate according to the screening model used. This study shows that rainbow trout exposed to sewage effluents have blood plasma levels of pharmaceuticals similar to human therapeutic concentrations, suggesting a risk for pharmacological effects in the fish. There is a particular concern about effects of progestin pharmaceuticals. For levonorgestrel, the measured effluent level (1 ng/L) was higher than water levels shown to reduce the fertility of fish.

Suppression of ovulation by a synthetic progestin in the capuchin monkey

BACKGROUND

From the limited research in New World monkeys it is not clear whether they are as sensitive to the antiovulatory effects of synthetic progestins as noted in human beings. We examined whether levonorgestrel prevented ovulation in the capuchin monkey.

METHODS

Cebus apella monkeys were treated orally with two doses of 2 mg of levonorgestrel, 8-9 hours apart, in four periovulatory stages assessed by laparoscopy.

RESULTS

Levonorgestrel-induced luteinization of the follicle prevented oocyte release up to 8 hours before ovulation. Unhealthy oocytes were recovered from 46% of unruptured follicles. Luteal progesterone was reduced by 55%, 35%, and 25% according to when levonorgestrel was given -2, -1, and 0 day from estradiol peak respectively.

CONCLUSION

The capuchin monkey, a neotropical primate in which progesterone circulates at levels much higher than in Old World primates and human beings, is sensitive to the antiovulatory effects of synthetic progestins.

Ectopic pregnancy following levonorgestrel emergency contraception: a case report

Use of levonorgestrel as emergency contraception is a safe and effective measure to prevent unwanted pregnancy. However, ectopic gestation in case of failure is a known risk. Access to levonorgestrel without a prescription in many countries has made it impossible to estimate the exact incidence of this potential adverse event. Thus, spontaneous reporting of cases serves to alert physicians to this possibility. We present a case of ectopic pregnancy following use of levonorgestrel emergency contraception. To our knowledge, this is the first case report from India following introduction of levonorgestrel emergency contraception in 2001.

Effect of a single vaginal administration of levonorgestrel in Carraguard® gel on the ovulatory process: a potential candidate for “dual protection” emergency contraception

OBJECTIVE

The study was conducted to evaluate the effect of Carraguard vaginal gel containing 0.75 mg of levonorgestrel (CARRA/LNG gel) administered in a single dose at different stages of follicle development over subsequent follicle rupture and hormonal levels.

METHOD

Randomized, blinded, cross-over study comparing the effects of a single administration of CARRA/LNG gel or Carraguard (CARRA) gel. Twenty-four healthy women were enrolled in two centers. The gels were administered when the follicle had reached diameters of 12-14, 15-17 and > or =18 mm in eight women each. Volunteers were followed for one treatment, one washout cycle and a second treatment cycle. Follicle rupture or nonrupture was assessed by transvaginal ultrasound. Luteinizing hormone, estradiol and progesterone levels were measured daily for 5 days following treatment, and three times per week until menses.

RESULTS

No follicular rupture within the 5-day period following administration was observed in 74% and 30% of the CARRA/LNG and CARRA gel treatment cycles, respectively, while ovulation was documented in 4% and 61%, respectively. The overall proportion of cycles with lack of follicular rupture or ovulatory dysfunction (follicle rupture preceded by an inadequate LH surge) was 96% for CARRA/LNG and 39% in the CARRA gel cycles.

CONCLUSION

Single vaginal administration of 0.75 mg LNG in CARRA gel in the late follicular phase is effective for interfering with the ovulatory process.

Pharmacokinetic study to compare the absorption and tolerability of two doses of levonorgestrel following single vaginal administration of levonorgestrel in Carraguard gel: a new formulation for "dual protection" contraception

OBJECTIVE

The study was conducted to assess levonorgestrel (LNG) serum levels achieved after a single administration of two different doses of Carraguard vaginal gel containing LNG (CARRA/LNG), designed for use as microbicide and contraceptive for potential dual protection.

MATERIALS AND METHODS

This was a randomized double-blind pharmacokinetic study conducted in 12 subjects enrolled at two centers. Each subject received a single vaginal administration of CARRA/LNG containing either 0.75 or 1.5 mg LNG per 4 mL of gel on Days 10-12 of the menstrual cycle. LNG serum levels were measured at 0, 1, 2, 4, 8 and 12 h after administration and for the following 7 days. LH and progesterone (for a preliminary evaluation of effect on the ovarian function) as well as SHBG were measured in the daily samples.

RESULTS

Serum LNG maximum concentrations (Cmax) were 14.1+/-2.1 and 11.7+/-2.7 nmol/L and Tmax was 12.0 and 6.0 h for the low and high dose, respectively, with large intersubject variability within the first 48 h. Mean levels at 96 h were 10% of Cmax. Differences in AUC between both doses were not statistically significant. SHBG levels decreased approximately 25% by Day 4 after administration. Luteal activity was observed in 3/6 and 5/6 of the subjects in the low- and high-dose group, respectively.

CONCLUSION

This study demonstrates that the CARRA/LNG gel can sustain elevated serum levels of the contraceptive steroid for up to 96 h after a single application. The serum levels attained with the 0.75-mg formulation are in the range expected to perturb the ovulatory process as observed in some subjects. The lack of correlation between the administered dose and serum concentrations of the steroid may be related to a rate-limiting absorption of LNG from the vaginal mucosa. The results reported here suggest that the CARRA/LNG formulation has good potential to become a dual-protection method, possibly preventing conception and sexually transmitted infections.

Levonorgestrel pharmacokinetics in plasma and milk of lactating women who take 1.5 mg for emergency contraception

BACKGROUND

Progestin-only methods are among the contraceptive options available for breastfeeding women, however the doses of progestin used in emergency contraception (EC) have not been evaluated in nursing mothers. We therefore investigated the pharmacokinetics of 1.5 mg levonorgestrel (LNG) in lactating women.

METHODS

Twelve healthy exclusively breastfeeding volunteers received 1.5 mg LNG. Women refrained from nursing for 72 h after dosing and fed their infants with milk frozen beforehand. Serial blood and milk samples were collected for 120 h and assayed for LNG and sex hormone binding globulin.

RESULTS

LNG concentrations peaked in plasma and in milk 1-4 h and 2-4 h after dosing, respectively. Concentrations in milk (M) paralleled those in plasma (P) but were consistently lower (mean M:P ratio 0.28). Estimated infant exposure to LNG is 1.6 microg on the day of dosing (1 microg in the first 8 h), 0.3 microg on the second day and 0.2 microg on the third day.

CONCLUSIONS

Nursing mothers may need EC. These results suggest that to limit infant exposure to the period of maximum LNG excretion in milk, mothers should discontinue nursing for at least 8 h, but not more than 24 h, after EC.

Levonorgestrel-Only Dosing Strategies for Emergency Contraception

The United States Food and Drug Administration-approved progestin-only dosing strategy for emergency contraception is levonorgestrel 0.75 mg taken as soon as possible within 72 hours of unprotected intercourse, with a second 0.75-mg dose taken 12 hours later. However, different dosing strategies have been studied and promoted by various organizations. The American College of Obstetricians and Gynecologists recommends a single dose of levonorgestrel 1.5 mg for emergency contraception as one option. As another option, they recommend two doses of levonorgestrel 0.75 mg may be effective when taken 12-24 hours apart. We performed a search of MEDLINE and International Pharmaceutical Abstracts from 1967-2006 to evaluate and describe the existing pharmacokinetic and patient outcome data regarding administration of levonorgestrel as a 1.5-mg single dose or two 0.75-mg doses taken 12 or 24 hours apart. Additional studies were identified from the bibliographies of the selected literature. Several pertinent articles were identified. All of the studies demonstrated that emergency contraception effectively prevented pregnancy. In addition, evidence supports the safety and efficacy of a single dose of levonorgestrel 1.5 mg for emergency contraception. Furthermore, when two doses of levonorgestrel 0.75 mg are administered, the second dose can confidently be taken 12-24 hours after the first without compromising efficacy. Understanding the evidence that supports the different emergency contraception dosing strategies is critical for clinicians, and especially pharmacists, who have interactive roles in dispensing emergency contraception.

Pharmacokinetics of single-dose levonorgestrel in adolescents

PURPOSE

The purpose of this study is to compare the pharmacokinetics of levonorgestrel, a drug used for emergency contraception between female adolescents and adults.

METHODS

Twenty-two female subjects, aged 13-16 years, received a single 0.75-mg dose of the drug. Serial blood samples were collected for 72 h and used to measure plasma levonorgestrel concentrations. Previously published data from 16 adults, aged 18-45 years, served as comparison.

RESULTS

There was a statistically significant higher total plasma clearance divided by the bioavailability (CL/F) of levonorgestrel in adolescents compared to adults, resulting in lower maximum and average total plasma concentrations. There was a trend for a larger volume of distribution divided by bioavailability (V/F), but there was no significant difference in the half-life of levonorgestrel in adolescents relative to adults (p=.098).

CONCLUSION

The differences between adolescents and adults are unlikely to be clinically significant because specific changes in total concentrations suggest that unbound concentrations are probably not affected. Furthermore, empirically high doses of levonorgestrel are given for emergency contraception.

The in vitro effect of emergency contraception doses of levonorgestrel on the acrosome reaction of human spermatozoa

INTRODUCTION

The aim of this study was to evaluate the effect of three concentrations of levonorgestrel (LNG) comparable to the levels found in serum following ingestion of LNG as emergency contraception (EC) on the acrosome reaction (AR) of capacitated and noncapacitated spermatozoa of fertile men.

MATERIALS AND METHODS

A total of 24 semen samples from three fertile men were evaluated. The spermatozoa were selected by Percoll gradient. Twelve samples were subsequently incubated with human tubal fluid medium supplemented with bovine serum albumin (HTF/BSA) for 20 h under capacitating conditions. The capacitated spermatozoa and the spermatozoa from the remaining 12 samples were exposed to LNG at 1, 10 and 100 ng/mL, to follicular fluid (FF) (20 %v/v) and to HTF medium. The ratio of live to dead spermatozoa was assessed after 1, 2 and 3 h of incubation at 37 degrees C and 5% CO2. After 30 min of exposure to the different LNG concentrations, aliquots were divided into two parts. In the first part, spermatozoa were immediately stained with Hoescht 33258 and fluorescein isothiocyanate-pisum sativum agglutinin (FITC-PSA) in order to assess AR rate and to repeat evaluation of the live-to-dead ratio. After 3 h of incubation, the remaining part of the aliquots were submitted to the same procedures. Each concentration of LNG was then compared with FF and HTF medium as positive and negative controls, respectively.

RESULTS

The results showed that in vitro exposure to the three different LNG concentrations did not induce AR.

CONCLUSION

This study failed to show any in vitro effect on AR of LNG concentrations similar to those found in serum following intake of LNG as EC. If this effect exists or if there is any other that influences sperm fertilizing capacity, in vitro experiments are probably not an appropriate way of testing it.

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.

[Emergency contraception: user's profile in primary care emergency services]

OBJECTIVES

To establish the emergency contraception (EC) users profile and whether she perceives this type of contraception as an emergency. Design. Cross sectorial study (over one year period: March 2002-March 2003).

SETTING

Emergency Services in Primary Care. Usera and Carabanchel; 11th Area; Madrid.

PARTICIPANTS

Women requesting EC in these centres.

MAIN OUTCOME MEASURES

A questionary was filled out for all participants with their age, how many hours had spent since sexual intercourse took place (within 24 h), usual method of contraception used, previous use of EC, level of education, and reason for this request.

RESULTS

89 women. Drops out: 0. Average age: 23.7+/-48 years (range: 16-40 years). 79.8% of them came to medical emergency services in less than 24 h after sexual intercourse. Usual anticonceptive method was the condom (88.8%), 2.2% used hormones, 9% no contraceptive method at all and none of them had used the intrauterine device. 34.8% were previous users of EC. Education levels: 2.2% of women only could read and write, elementary school (37.1%), secondary school (34.8%) and high school (25.8%). Reasons for requesting EC: 91% condom failure, 7.9% not to have used any contraceptive method, and 1.1% wrong use of natural birth control methods. Among the women who had went to the emergency services within the 24 h of the sexual intercourse the 77.4% of all of them had requested EC previously and the 93% of those had requested EC for the first time (P=.032). Likewise all of them with high school level and who could write and read, the 93.9% with elementary school level, and the 71% with secondary studies went to the emergency services within the 24 h of the non protected sexual intercourse (P=.05).

CONCLUSIONS

Most of the women were young, they perceived the unprotected sexual intercourses as an emergency, the condom was the most frequently used anticonceptive method, they requested EC due to condom breakage. In 1/3 of the cases the EC had been requested previously and this group and the young women with secondary studies one were who requested it later.

A randomized trial of mifepristone (10 mg) and levonorgestrel for emergency contraception

OBJECTIVE

To compare the efficacy, patient acceptability and adverse effects of low-dose mifepristone (10 mg) with the levonorgestrel regimen (2 doses of 750 microg given 12 hours apart) for emergency contraception.

METHODS

This randomized controlled trial compared mifepristone (10 mg) to levonorgestrel (2 doses of 750 microg given 12 hours apart) in the context of emergency contraception within 120 hours of unprotected intercourse. The primary outcome measure was unintended pregnancy. Secondary outcomes included adverse effects experienced by women, acceptability of the method of emergency contraception used, and the timing of the first menstrual cycle after treatment.

RESULTS

The total number of women recruited was 2,065. The crude pregnancy rates were 1.3% and 2.0% for mifepristone and levonorgestrel (P = .46), with 77% and 64% of expected pregnancies prevented, respectively. Women receiving mifepristone were more likely to have a delayed onset of the subsequent menstrual cycle after treatment (P < .001), whereas those having levonorgestrel were more likely to have an early onset of the subsequent menstrual cycle (P < .001). Acceptability levels were high for both methods, with 94% of women receiving mifepristone and 91% receiving levonorgestrel expressing satisfaction. There was no difference in adverse effects (nausea, vomiting, breast tenderness, abdominal pain, lethargy, headache, hot flushes, and dizziness) experienced by women in the 2 groups.

CONCLUSION

This study suggests that a small dose of mifepristone is not less effective than levonorgestrel for emergency contraception. Both regimens were highly acceptable to women.

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 randomized trial to compare 24 h versus 12 h double dose regimen of levonorgestrel for emergency contraception

BACKGROUND

Levonorgestrel (0.75 mg given for two doses 12 h apart) has been proven to be an effective regimen for emergency contraception when the first dose is given within 72 h of unprotected coitus. However, the dosing interval is inconvenient for those taking the first dose in the afternoon. We conducted a randomized study to evaluate two levonorgestrel dosing regimens for emergency contraception. Two doses of levonorgestrel 0.75 mg were administered with the first dose given up to 120 h after unprotected intercourse. The second dose was given 12 h later in the first regimen and 24 h later in the second regimen.

METHODS

We conducted a double-blind, randomized trial between 1997 and 2003 at five centres in China. A total of 2071 women requesting emergency contraception within 120 h of unprotected intercourse were recruited. They were randomized to receive two doses of 0.75 mg of levonorgestrel, given either 24 h apart or 12 h apart.

RESULTS

Outcome was unknown for 53 women (24 in the 24 h group and 29 in the 12 h group). Among the remaining 2018 women, the crude pregnancy rate was 1.9% in the 24 h group [95% confidence interval (CI) 1.17-2.94] and 2.0% in the 12 h group (95% CI 1.19-2.99). The proportion of pregnancies prevented was estimated to be 72% in the 24 h group and 75% in the 12 h group. Side-effects were mild in both groups. The efficacy of the 12 h regimen declined significantly when there were further acts of intercourse after treatment (5.0 versus 1.0%, P<0.01). This was not observed in the 24 h group.

CONCLUSIONS

Two doses of 0.75 mg levonorgestrel given either 24 or 12 h apart are effective for emergency contraception up to 120 h after unprotected intercourse. Further research to investigative more effective methods of emergency contraception is warranted.

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.

The in vitro effect of levonorgestrel on the acrosome reaction of human spermatozoa from fertile men

The objective of the study was to evaluate the effect of levonorgestrel (LNG) on the occurrence of acrosome reaction (AR) of capacitated spermatozoa from fertile men. A total of 20 semen samples from four fertile men were evaluated. The spermatozoa were separated by swim-up, and subsequently incubated for 20 h under capacitating conditions. Capacitated spermatozoa were exposed to three different concentrations of LNG (200, 400 and 800 ng/mL), follicular fluid (20% v/v), and ethanol or human tubal fluid medium (HTF) as a control. The AR rate and the ratio of live to dead spermatozoa were assessed after 15 and 30 min of incubation at 37 degrees C and 5% CO(2). The different treatments were compared with follicular fluid and HTF medium as positive and negative controls. The main results showed that the AR rate after 15 min of exposure was not affected by LNG and was significantly higher with follicular fluid than with all the other treatments. At 30 min of exposure, the three LNG concentrations induced a greater rate of AR than the HTF and a trend of higher AR rate with greater concentration was observed. Follicular fluid induced a significantly higher rate of AR than the other treatments. In conclusion, the addition of LNG in vitro to capacitated human spermatozoa is associated with a dose-dependent increased rate of AR, but such increase was not as great that induced by follicular fluid.

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.