NORPLANT: levonorgestrel-releasing contraceptive implant

Successful Removal of Six Levonorgestrel Silastic Subcutaneous Implants (Norplant) 25 Years After Insertion: A Case Report

Levonorgestrel-releasing silastic implants are a form of subdermal contraception that utilizes implanted silastic rods to release levonorgestrel, providing long-acting reversible contraception over an extended period of time. This case report presents a female who had lost a significant amount of weight after receiving levonorgestrel-releasing implants 25 years prior. During the elapsed period, the rods were palpable and uncomfortable. She had previously been unable to find a provider willing to remove the implants. This case highlights the possible complications surrounding the removal of levonorgestrel silastic subcutaneous implants and the careful consideration required when the implant has been in place for an extended period.

Methods and considerations for the use of hormonal contraceptives in rat models of neurobehavior

Hormonal contraceptives (HCs), prescribed to millions of women around the world, alter the ovarian hormonal cycle resulting in neurobehavioral changes in HC users. Human epidemiological and experimental data has characterized some of these effects with oftentimes conflicting or irreproducible results, reflecting a dearth of research considering different compositions, routes of administration, or time-courses of HC use. Non-human animal research can model these effects and help elucidate the underlying mechanisms by which different HCs modulate neurobehavioral outcomes. Still, animal models using HCs are not well-established. This may be because the pharmacological profile of HCs - including the metabolism, receptor binding affinity, and neuromodulatory effects - is dynamic and not always clearly translatable between animals and humans. The current review addresses these issues and provides basic methods and considerations for the use of HCs in animal models of neurobehavior to help advance the field of behavioral neuroendocrinology and inform decisions regarding to women's health.

Determining the Exposure Threshold for Levonorgestrel Efficacy Using an Integrated Model Based Meta-Analysis Approach

Combined oral contraceptive pills are the most commonly used hormonal contraceptives for the prevention of unintended pregnancies in United States. They consist of a progestin (e.g., levonorgestrel (LNG)) and an estrogen component, typically ethinyl estradiol (EE). In addition to adherence issues, drug-drug interactions (DDIs) and obesity (women with body mass index (BMI) ≥ 30 kg/m² ) are prime suspects for decreased LNG efficacy. Therefore, we developed an integrated physiologically-based pharmacokinetic modeling and model-based meta-analysis approach to determine LNG's efficacy threshold concentrations and to evaluate the impact of DDIs and obesity on the efficacy of LNG-containing hormonal contraceptives (HCs). Based on this approach, co-administration of strong CYP3A4 inducers and LNG-containing HCs (LNG150: LNG 150 µg + EE 30 µg and LNG100: LNG 100 µg + EE 20 µg) resulted in a predicted clinically relevant decrease of LNG plasma exposure (women with BMI < 25 kg/m² : 50-65%; obese women: 70-75%). Following administration of LNG150 or LNG100 in the presence of a CYP3A4 inducer, there was an increase in mean Pearl Index of 1.2-1.30 and 1.80-2.10, respectively, in women with BMI < 25 kg/m² (incidence rate ratios (IRRs): 1.7-2.2), whereas it ranged from 1.6-1.80 and 2.40-2.85 in obese women (IRR: 2.2-3.0), respectively. Our results suggest that the use of backup or alternate methods of contraception is not necessarily required for oral LNG + EE formulations except within circumstances of both obesity and strong CYP3A4 inducer concomitance following administration of LNG100.

Correcting oral contraceptive pharmacokinetic alterations due to obesity: a randomized controlled trial

OBJECTIVE

To determine if increasing the hormone dose or eliminating the hormone-free interval improves key pharmacokinetic (PK) alterations caused by obesity during oral contraceptive (OC) use.

STUDY DESIGN

Obese [body mass index (BMI)≥30 kg/m(2)], ovulatory, otherwise healthy, women received an OC containing 20 mcg ethinyl estradiol (EE)/100 mcg levonorgestrel (LNG) dosed cyclically (21 days active pills with 7-day placebo week) for two cycles and then were randomized for two additional cycles to the following: continuous cycling (CC, a dose neutral arm using the same OC with no hormone-free interval) or increased dose (ID, a dose escalation arm using an OC containing 30 mcg EE/150 mcg LNG cyclically). During Cycles 2, 3 and 4, outpatient visits were performed to assess maximum serum concentration (Cmax), area under the curve (AUC0-∞) and time to steady state as well as pharmacodynamics. These key PK parameters were calculated and compared within groups between baseline and treatment cycles.

RESULTS

A total of 31 women enrolled and completed the study (CC group, n=16; ID group, n=15). Demographics were similar between groups [mean BMI: CC, 38 kg/m(2) (S.D. 5.1); ID, 41 kg/m(2) (S.D. 7.6)]. At baseline, the key LNG PK parameters were no different between groups; average time to reach steady state was 12 days in both groups; Cmax were CC: 3.82±1.28 ng/mL and ID: 3.13±0.87 ng/mL; and AUC0-∞ were CC: 267±115 h ng/mL and ID: 199±75 h ng/mL. Following randomization, the CC group maintained steady-state serum levels whereas the ID group had a significantly higher Cmax (p<.001) but again required 12 days to achieve steady state. However, AUC was not significantly different between CC (412±255 h ng/mL) and ID (283±130 h ng/mL). Forty-five percent (14/31) of the study population had evidence of an active follicle-like structure prior to randomization and afterwards this decreased to 9% (3/31).

CONCLUSION

Both increasing the OC dose and continuous dosing appear to counteract the impact of obesity on key OC PK parameters.

IMPLICATIONS

Obesity adversely affects the pharmacokinetics of very low dose OC pills. Although the impact of these changes on OC efficacy is still under debate, PK parameters can be normalized in obese users by continuous dosing or increasing to a low-dose pill.

In vivo absorption of steroidal hormones from smart polymer based delivery systems

The purpose of this study was to develop smart polymer based controlled delivery systems to deliver steroidal hormones after single subcutaneous (s.c.) injection at predetermined rates over extended period of time. In vivo absorption and pharmacokinetics of levonorgestrel (LNG) and testosterone (TSN) were investigated from the thermosensitive and phase sensitive polymeric controlled delivery systems. A selective, reliable, and rapid method for determination of serum LNG concentration was developed using high-performance liquid chromatography-tandom mass spectrometry with atmospheric pressure chemical ionization interface (HPLC-MS-MS with APCI), while TSN in serum samples was detected and quantified by a competitive immunoassay. The delivery systems controlled the absorption of LNG in rabbits up to 6 weeks from thermosensitive and approximately 4 weeks from phase sensitive polymeric delivery systems. In vivo study of TSN delivery systems in castrated rabbits controlled the release of TSN for at least 2 months from both thermosensitive and phase sensitive polymers. Thermosensitive and phase sensitive polymer formulations significantly (p < 0.05) increased relative bioavailability of steroidal hormones compared to control. In conclusion, thermosensitive and phase sensitive polymer based delivery systems controlled the release in vivo in rabbits for longer duration after single s.c. injection.

In vitro release of levonorgestrel from phase sensitive and thermosensitive smart polymer delivery systems

The objective of this research is to develop injectable controlled delivery systems for the contraceptive hormone, levonorgestrel (LNG), using phase sensitive and thermosensitive polymers. A combination of poly (lactide) (PLA) and a solvent mixture of benzyl benzoate (BB) and benzyl alcohol (BA) was used in the phase-sensitive polymer delivery systems. The effects of solvent systems and polymer concentrations on the in vitro LNG release were evaluated. In the case of thermosensitive polymer delivery systems, a series of low-molecular-weight poly (lactide-co-glycolide)-poly (ethylene glycol)-poly (lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers with varying ratios of lactide/glycolide (LA/GA, 2.0-3.5) were used. The effects of varying block length of copolymers 1, 2, 3, and 4 on the in vitro LNG release were evaluated. Phosphate buffer saline (pH 7.4) containing 0.5% w/v Tween-80 was used as in vitro release medium. The amount of the released LNG was determined by an high pressure liquid chromatography (HPLC) method. A controlled (zero-order) in vitro release of LNG was observed from both phase-sensitive and thermosensitive-polymer delivery systems. Increasing the concentration of the phase-sensitive polymer from 5% to 30% significantly (p < 0.05) decreased the release rate of LNG from 38.32 microg/day to 31.45 microg/day; and increasing the hydrophilic fraction of the solvents mixture (i.e., BA) significantly (p < 0.05) increased the release rate of LNG. In the case of the thermosensitive polymer delivery system, increasing the hydrophobic PLGA block length of copolymers significantly (p < 0.05) decreased the release rate of LNG (98.65 microg/day to 67.60 microg/day). It is evident from this study that both the phase sensitive and thermosensitive polymers are suitable for developing prolonged-release injectable delivery systems for the contraceptive hormone.

Effect of intermittent treatment with mifepristone on bleeding patterns in Norplant® implant users

A double-blind, placebo-controlled, randomized trial, was carried out in 120 Norplant users to evaluate the effect of mifepristone, 100 mg/day administered for 2 consecutive days every 30 days, on the vaginal bleeding pattern. Treatment was given from months 2-7 of implant use. Volunteers recorded bleeding and spotting days, during treatment and for the ensuing 6-month period. During treatment, women on mifepristone recorded the same frequency of bleeding/spotting episodes but significantly less prolonged bleeding episodes than placebo controls (mean +/- SD: 11 +/- 3 vs. 22 +/- 23 days) and their total number of bleeding days was 35% lower than in the placebo group. After the end of mifepristone use, bleeding patterns were similar in both groups. One pregnancy occurred in the mifepristone-treated group, in month 6 of treatment, the outcome was a healthy male baby. We conclude that intermittent administration of mifepristone can offer a clinically significant improvement of the vaginal bleeding pattern in Norplant users.

Risk factors for discontinuation of Norplant implant use due to menstrual problems

The objective of the analysis reported here was to examine risk factors for early discontinuation of Norplant implant use due to perceived menstrual problems. Cox's proportional hazard regression model was used to calculate adjusted hazard ratios that would reflect the relationship of selected subject characteristics to the risk of early discontinuation due to perceived menstrual problems. Approximately 13% of the study population discontinued for perceived menstrual problems. At the end of year 2, the gross cumulative life table discontinuation rate for perceived menstrual problems was 9.4 per 100 women and it rose to 16.4 per 100 women at the end of year 5. Women in this study were significantly more likely to discontinue Norplant implant use due to perceived menstrual problems if they had a higher education level (> 12 years), had used no contraceptives in the month before Norplant implant insertion, or had a relatively long average duration of menstrual flow at admission. identifying potential risk factors such as these may help providers to counsel and prepare women to use the Norplant implant method.

An enzyme immunoassay for serum and urinary levonorgestrel in human and non-human primates

A microtiter plate enzyme immunoassay (EIA) is reported for the measurement of levonorgestrel (LNG) in serum and urine samples of human and non-human primates, and the results are compared to data obtained by radioimmunoassay (RIA). Rabbit polyclonal antibodies were raised against the bovine serum albumin conjugate of the 3-O-carboxymethyl oxime (CMO) derivative of LNG. The enzyme label was produced by the conjugation of horseradish peroxidase to LNG at the 3-position by the same CMO bridge used for the immunogen. The assay requires 2.5 hours to perform using 2.2-azino-di-(3-ethylbenzthiazoline sulfonic acid) diammonium salt as the chromogenic substrate. Serum (100 microliters) is extracted with petroleum ether prior to assay, whereas urine samples (25 microliters) are diluted and measured directly. The sensitivity of the assay is 0.25 pg/well with a 50% displacement of label at 7.5-9.5 pg and a linear response through 250 pg/well. Minimum levels of 8.7 and 10.0 pg/ml can be detected in serum and urine samples, respectively. Changes in serum LNG concentrations were measured in women and non-human primates following LNG implantation or injection. In the non-human primate study, serum LNG concentrations began to rise rapidly following i.m. injection of LNG, with peak levels occurring on days 3 to 5, then decreasing to approximately 25-35% of peak levels for the duration of the study. Circulating concentrations of 1.86 +/- 0.18 ng/ml LNG were reached in women the first week post-insertion of Norplant implants and decreased by 50% at 7-10 days, 75% after 14-21 days, followed by a steady decrease during the next 60-70 days to constant low levels that exhibited a high individual variation. Correlation coefficients of EIA and RIA results were 0.988 for human serum, 0.926 for human urine, and 0.972 for non-human primate serum.

Characteristics and experiences of American women electing for early removal of contraceptive implants

The study describes the experiences of 430 women who had Norplant(R) contraceptive implants removed prior to the five years of method effectiveness. Each subject was surveyed when the implants were inserted and again at the time of removal. Descriptive data are presented concerning perceptions of the method before insertion and after removal, reactions to the contraceptive and experiences associated with the removal procedure. Subjects' use of Norplant implants ranged from 14 days to 40 months, with a mean of 13.3 and median of 13 months. Over 95% reported changes in menstrual bleeding patterns and 95% experienced other non-bleeding related side effects. Non-bleeding side effects were the most frequently indicated reasons for removal, followed by bleeding changes. The mean removal time was 34 minutes with a median of 25 minutes. Over 48% reported experiencing significant pain during the removal procedure, and 27% stated that the pain was greater than expected. Despite electing for early removal of implants,the majority of women surveyed indicated satisfaction with all aspects of the method save its effect on their overall health. Although method-related side effects were intolerable for most subjects, their overall perception of the method was generally satisfactory.

Subdermal contraceptive implants

Subdermal contraceptive implants involve the delivery of a steroid progestin from polymer capsules or rods placed under the skin. The hormone diffuses out slowly at a stable rate, providing contraceptive effectiveness for 1-5 years. The period of protection depends upon the specific progestin and the type of polymer. Advantages of progestin implants include long term contraceptive action without requiring the user's or provider's attention, low dose of highly effective contraception without the use of estrogen, and fertility is readily reversible after the removal of implants. The levonorgestrel implant Norplant R system is the only one that has been approved for distribution. The contraceptive efficacy of Norplant is the highest observed amongst the most effective methods with an annual pregnancy rate of 0.2 during the first and second year and 1.1 on the fifth year. Menstrual problems are the main reason for the discontinuation of Norplant and 9% of women stopped using it during the first year of treatment. Other implants are still under development trying to simplify the method by reducing the number of units and to introduce other progestins that may minimize side effects. Norplant-2 was designed to release the same dose of progestin from only two covered rods. Evaluation of 1400 women enrolled, indicates that over 2 years the cumulative pregnancy rate is below 0.5 per 100 women. There are three single implants under development: Nestorone, 3-Keto-desogestrel and Uniplant that are expected to be effective for 1-2 years. Phase II clinical trials with Nestorone have been completed and no pregnancies have been observed in 1570 woman-months of use. Bleeding irregularities occurred in 20-30% of the women but there were only four terminations because of bleeding problems. A multricentric study is ongoing with a newly designed 3-keto-desogestrel implant named Implanon, which releases approx. 60 micrograms/day of the hormone. The objectives of this study are to assess contraceptive efficacy, safety and acceptability of Implanon. Another multricentric study is ongoing with Uniplant, which releases nomegestrol acetate with a duration of action for only 1 year. The objectives of the trial are to study the endocrine profile of Uniplant users and to evaluate the efficacy and acceptability of the method.