Implanon: A Review of the Literature With Recommendations for Clinical Management

Pharmacokinetic Modeling to Guide Preclinical Development of an Islatravir-Eluting Reservoir-Style Biodegradable Implant for Long-Acting HIV PrEP

Long-acting injectable cabotegravir is more effective than daily oral PrEP at preventing HIV transmission due to improved adherence, but requires bi-monthly large-volume intramuscular injections. Subcutaneous (SC) contraceptive implants can be formulated with antiretrovirals for extended-duration HIV PrEP. Islatravir (ISL) is a first-in-class, investigational antiretroviral with pharmacologic properties well-suited for implant delivery. We performed preclinical studies for the development of a reservoir-style, poly(ε-caprolactone) ISL-eluting implant by conducting a single-dose SC ISL dose-ranging pharmacokinetic (PK) study of 0.1, 0.3, and 1 mg/kg in adult Wistar rats. Non-compartmental analysis was conducted, and dose proportionality assessed for ISL plasma and intracellular islatravir-triphosphate (ISL-tp). Population PK models estimated ISL's unit impulse response to deconvolve ISL-implant in vivo absorption rate (mg/day) and cumulative mass (mg) from published rat plasma PK (n = 10). Drug release was interpreted using four kinetic models. Dose proportionality was affirmed for ISL and ISL-tp. A first-order, two-compartment model fitted the SC ISL bolus data. Mean (SD) absorption rate from 0 to 154 days was 0.072 ± 0.024 mg/day, and cumulative mass at 154 days was 8.67 ± 3.22 mg. ISL absorption was well-described by zero-order (r2 = 0.95) and Ritger-Peppas (r2 = 0.98). Our zero-order ISL-release poly(ε-caprolactone) implant is projected to achieve clinical PK above ISL-tp's PrEP efficacy threshold. Continued development for HIV PrEP applications is warranted.

Long-acting reversible contraception with etonogestrel implants in female macaques (Macaca mulatta and Macaca fascicularis)

Introduction

Contraception is often required for management and population control purposes in group-housed and free-roaming non-human primates. Long-acting reversible contraceptives, including subdermal progestin-releasing implants, are preferred as they eliminate challenges associated with frequent administration. Etonogestrel (ENG)-releasing subdermal implants are reversible and long-acting for a minimum of 3 years, and are commercially available for human use as Implanon® or Nexplanon®.

Methods

A retrospective analysis was performed detailing the contraceptive effectiveness and reversibility of subdermal placement of one-fourth or one-third of an ENG implant (68 mg/implant) in 129 female rhesus macaques (Macaca mulatta) and 67 cynomolgus macaques (Macaca fascicularis) at the Biomedical Primate Research Centre (Rijswijk, Netherlands). Furthermore, single cross-sectional ENG serum concentrations were measured for 16 rhesus and 10 cynomolgus macaques, and hemoglobin and blood chemistry pre-ENG and at timepoints >0.5, >1.5, and > 2.5 years post-ENG insertion were evaluated for 24 rhesus macaques. Finally, data were obtained using trans-abdominal ultrasound regarding the influence of ENG on uterine volume and endometrial thickness in 14 rhesus and 11 cynomolgus macaques.

Results

As a contraceptive ENG was in 99.80% (CI 93.50-99.99) and 99.95% (CI 99.95-100) effective in rhesus and cynomolgus macaques, respectively. Prolonged ENG durations of implant use in 14 rhesus macaques (range 3.1-5.0 years) and eight cynomolgus macaques (range 3.2-4.0 years) resulted in no unintended pregnancies. A total of 17 female macaques were allowed to breed after ENG removal, and among them, 14 female macaques (82%) had an uneventful delivery. Serum ENG concentrations with a median ENG duration of 1.2 years (range 0.1-6.0 years) and 1.9 years (range 0.6-4.7 years) resulted in median concentrations of 112 pg./mL (range 0-305 pg./mL) and 310 pg./mL (range 183-382 pg./mL) for rhesus and cynomolgus macaques, respectively. ENG had no clinical effect on hemoglobin and blood chemistry parameters nor on the thickness of the endometrial lining or uterus volume.

Conclusion

This study indicates that both one-fourth and one-third of the ENG implants are effective, long-acting, reversible, and safe contraceptive to use in macaques.

Determinants of Implanon discontinuation among women who use Implanon at Debre Berhan town public health institutions in Northeast Ethiopia: a case-control study

Background

Discontinuation of the most effective methods of contraception such as Implanon has now become a worldwide problem, which is significantly associated with mistimed and unwanted pregnancies and unsafe abortion, leading to an increased risk of maternal and child mortality and morbidity. However, studies on factors associated with Implanon discontinuation in Ethiopia, particularly in the area under this study, are limited. Therefore, this study aims to identify the determinants of Implanon discontinuation among women who used Implanon at Debre Berhan town public health institutions.

Methods and materials

A facility-based unmatched case-control study was conducted among 312 study participants (78 cases and 234 controls) from February 1, 2021, to April 30, 2021. The study participants were selected by using a systematic random sampling method for controls, and cases were selected consecutively until the required sample size was reached, during the data collection period. The data were collected by using a structured face-to-face interviewer-administered questionnaire and entered into Epidata version 4.6 and transferred to SPSS version 25 for analysis. Variables with a p-value of <0.25 in the bivariable analysis were entered into the multivariable logistic regression model. In the final model variables, a p-value of <0.05 was considered statistically significant at a 95% confidence interval (CI) and the strength of association was measured using an adjusted odds ratio (AOR).

Results

In this study, the determinants of Implanon discontinuation were the following: women who had no formal education (AOR: 3.57; 95% CI, 1.62-7.87), who had no children (AOR: 2.8; 95% CI, 1.50-5.17), who had no counseling about side effects (AOR: 2.43;95% CI, 1.30-4.55), who had no discussion with their partner (AOR: 2.7; 95% CI, 1.34-5.46), who had no follow-up appointment (AOR:2.81; 95% CI, 1.54-5.12), and who had side effects (AOR:1.91; 95% CI, 1.13-3.53).

Conclusion and Recommendations

Women's educational status, having no children during the insertion of Implanon, received no counseling about the side effects of insertion, no follow-up appointment, experiencing side effects, and no discussion with a partner were determinants of Implanon discontinuation. Hence, healthcare providers and other health sector stakeholders should provide and strengthen pre-insertion counseling, and follow-up appointments to increase the retention rates of Implanon.

Perspective Chapter: Modern Birth Control Methods

This chapter focuses on various modern birth control methods, including combined oral contraceptives, progestogen-only pills, progestogen-only injectables, progestogen-only implants, intrauterine devices, barrier contraceptives, and emergency contraceptive pills. Each contraceptive method is covered in detail, including mechanism of action, effectiveness, health benefits, advantages, disadvantages, risks, and side-effects.

Safety and pharmacokinetics of islatravir subdermal implant for HIV-1 pre-exposure prophylaxis: a randomized, placebo-controlled phase 1 trial

Islatravir (MK-8591) is a highly potent type 1 human immunodeficiency virus (HIV-1) nucleoside reverse transcriptase translocation inhibitor with a long intracellular half-life that is in development for the prevention and treatment of HIV-1. We conducted a randomized, double-blind, placebo-controlled, phase 1 trial in adults without HIV-1 infection. Participants received islatravir or placebo subdermal implants for 12 weeks and were monitored throughout this period and after implant removal. The co-primary end points were safety and tolerability of the islatravir implant and pharmacokinetics, including concentration at day 85, of islatravir triphosphate in peripheral blood mononuclear cells (PBMCs). Secondary end points included additional pharmacokinetic parameters for islatravir triphosphate in PBMCs and the plasma pharmacokinetic profile of islatravir. Based on preclinical data, two doses were assessed: 54 mg (n = 8, two placebo) and 62 mg (n = 8, two placebo). The most frequently reported adverse events were mild-to-moderate implant-site reactions (induration, hematoma, pain). Throughout the 12-week trial, geometric mean islatravir triphosphate concentrations were above a pharmacokinetic threshold of 0.05 pmol per 10⁶ PBMCs, which was estimated to provide therapeutic reverse transcriptase inhibition (concentration at day 85 (percentage of geometric coefficient of variation): 54 mg, 0.135 pmol per 10⁶ cells (27.3); 62 mg, 0.272 pmol per 10⁶ cells (45.2)). Islatravir implants at both doses were safe and resulted in mean concentrations above the pharmacokinetic threshold through 12 weeks, warranting further investigation of islatravir implants as a potential HIV prevention strategy.

Safety and Benefits of Contraceptives Implants: A Systematic Review

Progestin-only contraceptive implants provide long-acting, highly effective reversible contraception. We searched the medical publications in PubMed, CENTRAL, and EMBASE for relevant articles on hormonal implants published in English between 1990 and 2021. Levonorgestrel (LNG) 6-capsule subdermal implants represented the first effective system approved for reversible contraception. The etonogestrel (ENG) single rod dispositive has been widely employed in clinical practice, since it is a highly effective and safe contraceptive method. Abnormal menstrual bleeding is a common ENG side effect, representing the main reason for its premature discontinuation. Emerging evidence demonstrated that it is possible to extend the use of the ENG implant beyond the three-year period for which it is approved. The ENG implant could be an effective and discrete alternative to the IUD in young girls, such as post-partum/post-abortion. Implants should be inserted by trained skilled clinicians who previously provide adequate counselling about their contraceptive effect, benefits, and any possible adverse events. More studies are needed to validate the extended use of the ENG implant for up to 5 years.

Retrospective Analysis of the Effectiveness and Reversibility of Long-Acting Contraception Etonogestrel (Implanon®) inCommon Marmosets (Callithrix jacchus)

Simple Summary

Due to the breeding success of common marmosets in captivity, colony managers need to achieve a balance between maintaining sustainable population numbers while preventing the breeding of surplus animals. Population control can be achieved by various methods, reversible and nonreversible. Long-acting reversible contraceptives are preferred, as they are not permanent and eliminate the logistical problems associated with the daily or weekly administration of oral or injectable contraceptives. Implanon^® (etonogestrel) is a widely used progestin-based contraceptive in marmosets with the theoretical advantages of being reversible and long-acting. However, no dose and efficacy data are available yet. In this study, we examined, by using electronic health records, the relationship between the use of one-fourth or one-third of an etonogestrel implant in female marmosets and the number of parturitions, interbirth interval, litter size, body weight, stillbirths and unintended pregnancies. We have concluded that etonogestrel implants are efficacious and safe to use in marmosets. Our data result in recommendations about the use of etonogestrel implants in marmosets. Our data can probably be extrapolated to other callitrichids.

Abstract

Contraception is an important population control method for the colony management of primates housed in captivity. Etonogestrel (ENG) implants (i.e., Implanon^®) are a widely used progestin-based contraceptive in common marmosets (Callithrix jacchus) with the theoretical advantages of being reversible and long-acting. However, no dose and efficacy data are available yet. Therefore, data from 52 adult female marmosets contracepted with ENG (one-fourth or one-third of an implant) housed at the Biomedical Primate Research Centre (BPRC, Rijswijk, The Netherlands) over the past 18 years were analyzed. Using an electronic database, a retrospective longitudinal cohort study was conducted to calculate the reproductive data before, during and after ENG use. The data show an effectiveness in preventing pregnancy of 99%. The implant was effective within one week after insertion. Unintended pregnancies did occur, but in 60% of these cases, the animals were already pregnant at the time of implant insertion. In these cases, healthy offspring were born despite the use of the implant. No stillbirths, neonatal deaths or maternal deaths could be linked to ENG use. After implant removal, 83% of the animals delivered healthy offspring. No difference in contraception efficacy was observed between the use of one-fourth or one-third of an implant. ENG achieved a contraceptive protection exceeding 99% and was shown to be reversible concerning fertility. To our knowledge, this is the first detailed analysis on the use of ENG in marmosets.

Influence of age on tolerability, safety and effectiveness of subdermal contraceptive implants

The use of long-acting contraceptive methods is on the rise. The aim of this study was to describe the main variables (effectiveness, tolerability, menstrual bleeding) associated with the use of subdermal contraceptive implants and to investigate the influence of age on these variables. This was a descriptive, retrospective, observational study of 221 cases of contraceptive implants inserted at a Spanish hospital between 2006 and 2015. The mean age of implant users was 31.2 ± 7.5 years. Effectiveness was 100% and good tolerability was recorded for 86.5%. Infrequent bleeding was the most common bleeding pattern, followed by amenorrhoea. Of the 221 implants inserted, 47.5% were removed. The main reasons were expiration (54.3%) and discomfort due to bleeding alterations and other adverse effects (25.7%). Nulliparity and weight gain were significantly associated with an increased probability of implant removal. This study shows that implants were highly effective, safe and well-tolerated in our population. The age of users had no influence on any of the study variables analysed. Impact Statement What is already known on this subject? Subdermal contraceptive implants are long-acting reversible contraceptives which are both safe and effective. What do the results of this study add? The age of users had no influence on any of the study variables analysed. Nulliparity and weight gain were significantly associated with an increased probability of implant removal. What are the implications of these findings for clinical practice and/or further research? Subdermal contraceptive implants were a safe and effective long-acting progestin contraceptive method for women from all age groups in our series because no significant age-related differences were observed for the tolerability, vaginal bleeding patterns, the effectiveness, the adverse effects or any other variables.

Sociodemographic profiles and use-dynamics of Jadelle (levonorgestrel) implants in Jos, Nigeria

Background:

Contraceptive implants (including Jadelle) are highly effective, safe, and easy to use and have a long duration of action. They do not interfere with intercourse with immediate return to fertility after removal. However, disruption of the menstrual bleeding pattern is almost inevitable and coercive prescription may be a problem because insertion and removal of implants are provider dependent. The objective of this study was to determine the sociodemographic profiles of acceptors of Jadelle and the reasons for discontinuation in Jos, Nigeria.

Materials and Methods:

This was a 6-year retrospective chart review carried out at the Jos University Teaching Hospital.

Results:

About 1401 women accepted Jadelle with a mean (±standard deviation) of 33.4 ± 5.9 years. About 88% of the women were Christians and almost three-quarters (73.5%) had at least secondary school education. The means of parity and number of children still alive at the time of accepting Jadelle were 4.1 and 3.8, respectively. Half of the women (49.5%) were breastfeeding and over half (55.9%) had future fertility desires at the time of commencing Jadelle. About 82% had previously used other contraceptives (mostly short-acting methods such as injectables, pills, and condoms), with only 18% starting Jadelle as the first-ever contraceptive method. About 90% of the women had regular menstrual cycles. The major reason for discontinuation of Jadelle was desire for pregnancy although menstrual pattern disruption was the most common reason for removal in the first 6 months of use.

Conclusion:

The main reason for discontinuation of Jadelle was to have more children although menstrual pattern disruptions accounted for earlier discontinuation.

Contraception and the obese woman

PURPOSE

Obesity has reached epidemic rates among U.S. women of reproductive age, many of whom want to use contraception. However, some forms of contraception can have adverse effects on an obese woman's health. This article explores risks of contraception available in the United States and provides clinical recommendations for use by obese women.

DATA SOURCES

Information was compiled by reviewing the scientific literature on contraception and female obesity using CINAHL, MEDLINE, PubMed search engines.

CONCLUSIONS

The evidence is largely supportive of combined oral contraceptive (COC) use in carefully screened obese women without known risks factors for cardiovascular disease. The efficacy of COCs may be slightly reduced in obese women because of increased body mass. Other types of hormonal contraceptives have varying safety and efficacy reports when used by obese women. Intrauterine devices do not have reduced efficacy nor increased risks for obese women but insertion may be more difficult. Obesity has no effect on efficacy of barrier methods of contraception.

IMPLICATIONS

Clinicians should conduct a careful history and physical exam with selected supporting laboratory tests when considering prescription of hormonal contraceptives for obese women. Obese women require health counseling to carefully follow directions for contraceptive use to avoid unintended pregnancy.

Menstrual bleeding patterns in adolescents using etonogestrel (ENG) implant

BACKGROUND

Etonogestrel (ENG) implant is an effective method of contraception. The implant is designed to provide contraceptive efficacy for 3 years with a relatively quick return of fertility upon its removal. Menstrual irregularities are not uncommon on long-acting progestins and can often be the factor for discontinuation or removal. A retrospective chart analysis was done on 58 patients who chose to be on the ENG implant. Age ranged from 12 to 24 years. The cycle ranged from 1 to 17 months. The mean length of use of the implant was 10.9 months. Over the 20-month period, 13 ENG implants were removed because of menstrual bleeding problems.

METHOD

We conducted a chart review of the adolescent patients who received the ENG implant in our adolescent clinic. An analysis was done based on symptoms experienced by patients who were on the ENG implant and their management, which in some cases resulted in its removal.

SETTING

The data is presented on adolescent and young adult patients who receive their reproductive care in the Adolescent Medicine Clinic at the University of Kentucky, Lexington, KY, USA.

CONCLUSIONS

ENG implant when used correctly and as indicated is extremely effective in providing contraception for up to 3 years. However, menstrual irregularities can be very troublesome and often a reason for its removal. In our experience, 22.4% (13 out of the 58 subjects) had menstrual problems post-insertion that led to its removal. It is crucial for a clinician to inform and be informed about such side effects.

[Tolerance of the contraceptive implant by prescription context (postabortion or not): Prospective study on 127 consultants]

AIM

While contraceptive methods increased in number, the number of abortions has remained stable. The aim of this study was to estimate the satisfaction of women toward a contraceptive implant (Implanon(®)) available in France in order to clarify prescription.

METHOD

The survey concerned 127 women who visited Angers and Nantes family planning centres between January2009 and January2010 in two implant prescription contexts (postabortion or not). They agreed to answer a first questionnaire describing the reasons for their choice. A second questionnaire was sent six months after to assess its tolerance.

RESULTS

In our study, 82% of patients were using a contraceptive method prior to implant (68% in postabortion and 88% in the other group). The first reason for choosing the implant was the fear of forgetting - it was more important in the postabortion group (88% vs. 61%). The main side effects were amenorrhea (50%), weight gain (30%) and mood disorders (19%). More than one in two women (54%) was very satisfied by the implant. It should be noted that in one quarter of cases, women seek early withdrawal of the contraceptive implant (23% in postabortion and 21% in the other group), a rate that is 39% in patients under 25years and 47% in patients who reported a mood disorder.

CONCLUSION

There is a tendency to better tolerance of the implant out of a context of abortion. Furthermore, mood disorders appear to be poorly tolerated. These elements encourage greater caution in prescribing the contraceptive implant in postabortion, situation in which patients have already psychological disorders, and even more among younger patients.

[General practitioners' (GPs) practice regarding the line to take in case of missed pill]

OBJECTIVE

To explore general practitioners' (GPs) practice face of missed pill and prevention of such missings.

MATERIAL AND METHOD

Twenty-five GPs from Sarthe Department (Western France) took part in semistructured interview during which they expressed themselves on the prevention of missed pill and its consequences.

RESULTS

Twelve out of 20 physicians stated positively that their female patients often forget their pill. However, they noted that missed pill was seldom a reason for phone call or consultation. During the initial pill prescription, GPs insisted on how to take the pill (14/25) as well as advice in case of a missed pill (22/25), their availability (12/25) and the instruction leaflet (16/25). But only five quoted the importance of involving women in the choice of contraception. On prescription renewal, only nine out of 25 ask their patients about observance defect and eight out of 25 repeated the information. If patients asked for further explanation, only two doctors out of 25 had practices in line with the French National Authority for Health's (HAS) recommandation guidelines.

CONCLUSION

GPs' attitudes are partly due to a lack of practice's knowledge in primary and emergency contraception methods. It seems essential to promote GPs' training and to take into account their expectations and needs. Furthermore, female patient must be actor of the choice of her contraceptive method in order to improve compliance and, therefore, effectiveness.

Effect of etonogestrel implant on serum lipids, liver function tests and hemoglobin levels

BACKGROUND

This study aimed to assess the possible effects of etonogestrel implant (Implanon, Organon, Oss, The Netherlands) on total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and Hb levels in a sample of Turkish population.

STUDY DESIGN

Healthy women of childbearing potential who had applied to our Family Planning Clinic for a contraceptive method and had chosen to have an Implanon insertion after thorough counseling about all family planning methods and screening for eligibility for Implanon use were enrolled in the study. Serum concentrations of TC, TG, HDL-C, LDL-C, AST, ALT and Hb levels were tested before and at 3 and 6 months after insertion. Baseline mean parameters were compared with mean parameters at 3 and 6 months for statistical significance using paired-samples t test.

RESULTS

Eighty-two women eligible for the study were included. Mean age of the patients was 27.5+/-4.8 years. When compared to the baseline values, there was a statistically significant decrease in the TC (p<.001), HDL-C (p<.001) and TG (p=.006) at the end of the third month, while there was a significant increase in Hb values (p=.01). The decrease in TC (p=.001) and HDL-C (p<.001) and increase in Hb value (p=.03) persisted by the end of sixth month while the decrease in TG was transient. A statistically significant increase in mean ALT level was observed at 6 months (p=.03).

CONCLUSION

The effect of Implanon on liver functions and lipid metabolism does not lead to unhealthy alterations. Increase in Hb can be attributed to the high frequency of amenorrhea in patients.