Levonorgestrel and estradiol release from an improved contraceptive vaginal ring

Development of Hormonal Intravaginal Rings: Technology and Challenges

Intravaginal rings (IVRs) are minimally invasive polymeric devices specifically designed to be used for the sustained and prolonged release of various type of drugs such as hormones. One of the benefits of using topical drug delivery systems (e.g., IVRs) is the fact that systemic drug delivery may cause drug resistance due to elevated drug levels. Topical drug delivery also provides higher concentrations of the drug to the target site and has fewer side effects. In addition, when a drug is administered vaginally, the hepatic first-pass effect is avoided, resulting in higher absorption. Contraception and treatments for specific diseases such as endometriosis and hormone deficiencies can be improved by the administration of hormones via an IVR. This article aims to classify and compare various designs of commercially available and non-commercial hormonal IVRs and to analyze their performance. Current challenges affecting the development of IVRs are investigated, and proposed solutions are discussed. A comprehensive search of publications in MEDLINE/PubMed and of commercial product data of IVRs was performed, and the materials, designs, performance, and applications (e.g., contraception, endometriosis, estrogen deficiency and urogenital atrophy) of hormonal IVRs were thoroughly evaluated. Most hormonal IVRs administer female sex hormones, i.e., estrogen and progestogens. In terms of material, IVRs are divided into 3 main groups: silicone, polyurethane, and polyethylene-co-vinyl acetate IVRs. As regards their design, there are 4 major designs for IVRs which strongly affect their performance and the timing and rate of hormone release. Important challenges include reducing the burst release and maintaining the bioavailability of hormones at their site of action over a prolonged period of administration as well as lowering production costs. Hormonal IVRs are a promising method which could be used to facilitate combination therapies by administering multiple drugs in a single IVR while eliminating the side effects of conventional drug administration methods. IVRs could considerably improve womenʼs quality of life all over the world within a short period of time.

Advances in contraceptive vaginal rings: what does the future hold?

INTRODUCTION

Contraceptive vaginal rings (CVRs) are good contraceptive options because they do not require skilled providers, are self-administered, and show a higher stability of drug diffusion.

AREAS COVERED

This article provides a review of the developments made with CVRs over the past number of years, while giving focus to the latest CVRs that have gone through clinical development. The author of the article also provides an expert perspective on the future of these useful therapeutic options.

EXPERT OPINION

Pharmacokinetic studies have shown that segesterone, an absorbable progestin that is used alone or in combination with ethinyl estradiol (EE) or E_2, is the CVR of choice at this present time. Indeed, segesterone has demonstrated safety and efficacy as a CVR and is also an appropriate option for lactating women, as they are not absorbed orally. However, good cycle control is important for improved CVR adherence. CVRs that allow the combination of more than one drug may unravel another multi-purpose use when combined with microbicides and could provide combined protection to women who wish to protect themselves from pregnancy and sexually transmitted infection.

Matrix and reservoir-type multipurpose vaginal rings for controlled release of dapivirine and levonorgestrel

A matrix-type silicone elastomer vaginal ring providing 28-day continuous release of dapivirine (DPV) - a lead candidate human immunodeficiency virus type 1 (HIV-1) microbicide compound - has recently demonstrated moderate levels of protection in two Phase III clinical studies. Here, next-generation matrix and reservoir-type silicone elastomer vaginal rings are reported for the first time offering simultaneous and continuous in vitro release of DPV and the contraceptive progestin levonorgestrel (LNG) over a period of between 60 and 180days. For matrix-type vaginal rings comprising initial drug loadings of 100, 150 or 200mg DPV and 0, 16 or 32mg LNG, Day 1 daily DPV release values were between 4132 and 6113μg while Day 60 values ranged from 284 to 454μg. Daily LNG release ranged from 129 to 684μg on Day 1 and 2-91μg on Day 60. Core-type rings comprising one or two drug-loaded cores provided extended duration of in vitro release out to 180days, and maintained daily drug release rates within much narrower windows (either 75-131μg/day or 37-66μg/day for DPV, and either 96-150μg/day or 37-57μg/day for LNG, depending on core ring configuration and ignoring initial lag release effect for LNG) compared with matrix-type rings. The data support the continued development of these devices as multi-purpose prevention technologies (MPTs) for HIV prevention and long-acting contraception.

Comparison of the vaginal microbial communities in women with recurrent genital HSV receiving acyclovir intravaginal rings

Vaginally administered antiviral agents may reduce the risk of HIV and HSV acquisition. Delivery of these drugs using intravaginal rings (IVRs) holds the potential benefits of improving adherence and decreasing systemic exposure, while maintaining steady-state drug levels in the vaginal tract. Elucidating how IVRs interact with the vaginal microbiome constitutes a critical step in evaluating the safety of these devices, as shifts the vaginal microbiome have been linked with several disease states. To date, clinical IVR trials have relied on culture-dependent methods that omit the high diversity of unculturable microbial population. Longitudinal, culture-independent characterization of the microbiota in vaginal samples from 6 women with recurrent genital HSV who used an acyclovir IVR was carried out and compared to the communities developing in biofilms on the IVR surface. The analysis utilized Illumina MiSeq sequence datasets generated from bar-coded amplicons of 16S rRNA gene fragments. Specific taxa in the vaginal communities of the study participants were found to be associated with the duration of recurrent genital HSV status and the number of HSV outbreaks. Taxonomic comparison of the vaginal and IVR biofilm communities did not reveal any significant differences, suggesting that the IVRs were not systematically enriched with members of the vaginal microbiome. Device usage did not alter the participants' vaginal microbial communities, within the confines of the current study design. Rigorous, molecular analysis of the effects of intravaginal devices on the corresponding microbial communities shows promise for integration with traditional approaches in the clinical evaluation of candidate products.

Mathematical modeling of drug delivery from torus-shaped single-layer devices

A mathematical modeling of controlled release of drug from torus-shaped single-layer devices is presented. Analytical solutions based on the pseudo-steady state approximation are derived. The reliability and usefulness of the model are ascertained by comparison of the simulation results with matrix-type vaginal ring experimental release data reported in the literature. A good agreement between the model prediction and the experimental data is observed. An analysis of the effect of the variation in torus design parameters on the solute release is also presented. The model is applicable only to torus-shaped single-layer systems wherein the initial load of drug is higher than its solubility in the polymer.

Comparing Patient Telephone Callback Rates for Different Hormonal Birth Control Delivery Systems

This study was conducted to determine the number of office telephone callbacks in the first 3 months after initiating use of the vaginal ring, the transdermal patch, or an oral contraceptive. If a patient called back, the reason for her call was noted. Patients were prospectively followed from sites in New Jersey and Florida for 3 months after initiation of hormonal contraception (oral, transdermal, vaginal) and the number of callbacks for each method was assessed. Before study recruitment, the patients had either never used or discontinued hormonal contraception for at least 1 month. All patients were given standard counseling, which included reference handouts specific to their chosen form of contraception. The number of callbacks for patients on oral contraceptives was 30/96 (26 patients, 4 of the 26 with 2 callbacks each); for the transdermal patch, 20/40 (17 patients, 3 of the 17 with 2 callbacks each); and for the vaginal ring, 11/72 (11 patients). Pearson chi2 analysis revealed that all 3 groups were significantly different from each other (P = 0.0004). Most patients called back for side effects related to their method of choice, and some patients called back more than once. Rate of callbacks after initiation of hormonal contraception was the least with the vaginal ring. Use of oral contraception, often considered the gold standard, resulted in a callback rate that was midway between the number of callbacks for the vaginal ring and the number of callbacks for the transdermal patch. The lower observed rate of callbacks with the vaginal ring compared with oral and transdermal contraception may provide clinicians the confidence that this method is well tolerated by their patients.

Ovarian function during use of vaginal rings delivering three different doses of Nestorone

Contraceptive vaginal rings delivering various progestins alone or in combination with estrogen have been previously studied, showing adequate steroid vaginal absorption and acceptability by the users. Nestorone progestin (NES) is a potent 19-nor-progesterone derivative, inactive by the oral route, but an excellent option for vaginal delivery. The purpose of this study was to evaluate ovarian function during 6 months of continuous use of progestin-only vaginal rings delivering 3 different doses of NES: 50, 75, and 100 microg per day. Blood samples were taken twice a week for 5 consecutive weeks during a control cycle and on months 1, 3 and 6 of use, for the measurement of estradiol (E2), progesterone (P), and NES. A total of 87 volunteers randomly received each of the 3 doses. After an initial peak, NES serum levels remained fairly constant throughout the duration of the study at about 125, 200 and 250 pmol/L, respectively, decreasing slightly with time. Luteal activity occurred very rarely (1.2-2.6% of sampling periods) with no apparent difference between doses. Low E2 levels (< or =100 pmol/L) in all samples of a run were rare (5%) and only with the high dose ring (100 microg/day). E2 remained within normal levels (101-1500 pmol/L) in most of the segments studied. We conclude that the 50 and 75 microg/day NES rings provide adequate ovulation inhibition without hypoestrogenism, while the 100 microg/day ring may deliver an unnecessarily high dose.

Vaginal contraceptive rings

Steroids diffuse through polysiloxone at a constant rate, and steroids placed in the vagina rapidly pass through the vaginal epithelium into the circulation. Combining these principles led to the development of contraceptive vaginal rings (CVR) consisting of various progestins, with and without oestrogen, placed in flexible polysiloxone, doughnut-shaped devices. As occurs with oral contraceptives, the CVRs containing progestin plus oestrogen are left in the vagina for 3 weeks and removed for 1 week to allow withdrawal bleeding, while CVRs releasing a small dose of progestins without oestrogen are left in the vagina continuously for several months. Large-scale, clinical trials were performed with a low dose levonorgestrel-releasing-only CVR by the WHO. At 1 year, continuation rates were about 50 per 100 women with 17.2 per 100 discontinuing for menstrual problems and 4.5 for pregnancy. Two sizes of a CVR containing levonorgestrel and oestradiol were studied in a multinational trial organized by the Population Council. At the end of 1 year, about half the women were continuing with the method, one-quarter had discontinued because of bleeding problems, and pregnancy rates were between 1 and 2 per 100 women. The CVR was well accepted by women and their partners, but because of lowered HDL-cholesterol levels and accelerated atherosclerosis in female monkeys, further development of this formulation was discontinued. Recently, phase II clinical trials with CVRs containing combinations of NET-acetate plus ethinyloestradiol and 3-ketodesogestrel plus ethinyloestradiol have been undertaken. These CVRs provide good bleeding control, inhibit ovulation consistently and do not have an adverse effect on serum lipids. Phase III trials with these two types of CVRs will be initiated shortly.

The in vivo release characteristics of a multi-compartment vaginal ring releasing 3-keto-desogestrel

The results of a stage I study of a new vaginal ring releasing 3-keto-Desogestrel [3kDOG] is reported. The study design consisted of one study cycle, where the ring was used continuously for 21 days and then removed. Twenty healthy volunteers were randomly allocated to each of two study groups. On day 5 of the menstrual cycle, group A used a vaginal ring releasing 30 micrograms 3kDOG per 24 hours and group B used a 15 micrograms 3kDOG per 24 hours ring. After initial absorption of the 3kDOG a plateau phase was reached in 46 hours [group A] and 49 hours [group B]. On reaching the plateau phase, the overall decline in plasma levels during the 21 days of use was 5.24% for group A and 5.27% for group B. This represents a daily decline in plasma levels of 0.27% and 0.28% for the 30 micrograms and 15 micrograms per 24 hours rings, respectively. The plasma levels achieved by the rings were significantly different throughout (p = 0.011). On removal after 21 days, the mean removal half-life for both ring types was similar at 20.9 hours for group A and 21.1 hours for group B. It is concluded that the characteristics of the delivery system are worthy of further study as a potential means of contraception using 3kDOG delivered from a vaginal ring.

Vaginal rings for continuous low-dose release of oestradiol in the treatment of urogenital atrophy

Silicone vaginal rings for the continuous release of 17 beta-oestradiol (E2) with 2 constant in vitro release rates were used for the treatment of symptoms of urogenital atrophy in 2 groups of postmenopausal women. The very low dose of 7 micrograms/24 h was found to alleviate atrophic symptoms effectively and to induce significant maturation of vaginal and urethral epithelium. After a brief initial peak, the serum levels of E2 over 3 mth of treatment remained close to the detection limit. The 'undetectable' E2 release pattern was reflected only in increased levels of oestrone sulphate. There was no evidence of a systemic metabolic response and patient acceptance of the method was excellent. Continuous low-dose release of E2 via vaginal rings consequently offers an alternative means of administering local oestrogen therapy which may be particularly suitable for geriatric patients.

Contraceptive steroids and coronary artery atherosclerosis in cynomolgus macaques

The influence of two types of steroidal contraception on the extent of coronary, aortic, carotid, and iliaco-femoral atherosclerosis was assessed in 57 cynomolgus macaques with moderate diet-induced hyperlipoproteinemia. Thirteen animals were treated with an intravaginal ring that released 17 beta-estradiol and levonorgestrel. Fifteen females were treated with an oral contraceptive (OC) composed of ethinyl estradiol and norgestrel. Fifteen females received placebo vaginal rings, and 14 males were untreated. The contraceptive treatments resulted in similar large reductions in plasma high-density lipoprotein (HDL) cholesterol concentrations. Neither treatment influenced the prevalence of coronary artery atherosclerosis. However, treatment with the contraceptive vaginal ring was associated with increased extent of coronary artery atherosclerosis (plaque size) relative to untreated females, whereas treatment with the OC was not. The contrasting effects of the two treatments could not be explained by differences in total plasma cholesterol, HDL cholesterol, or blood pressure. The results suggest that the greater estrogenic influence associated with the ethinyl estradiol-containing OC resulted in inhibition of coronary artery atherosclerosis despite a pronounced progestin-induced lowering of plasma HDL cholesterol concentration and, further, that hormonal balance may have a marked influence on the relationship between plasma lipids and atherogenesis.

Bioavailability of levonorgestrel from intravaginal rings in women of low income groups

Two types of intravaginal rings (IVR) containing 50-128 mg of levonorgestrel (LNOG) and 28-60 mg of estradiol were inserted in 18 apparently normal subjects belonging to the low socioeconomic group on day 5 of the cycle. A total of 120 cycles were studied with cyclic insertion and withdrawal. Data on menstrual cycle changes were noted. For bioavailability study, blood samples were collected twice weekly for a period of one month in the first cycle in 8 women. All the plasma samples were analysed for LNOG and progestrone by RIA. Cycle control was excellent in IVR users. Expulsion of the ring was noted in 4 instances. The plasma LNOG levels were found to reach a peak level ranging from 2.7-7.5 ng/ml within 4 days after the IVR insertion. In between day 9 to 24, the plasma levels appeared to be almost steady, and once the ring was removed, the levels dropped off rapidly. The mean plasma LNOG calculated during the steady-state period of the cycle ranged from 1.6-5.1 ng/ml. These mean LNOG levels were found to be inversely correlated with skin-fold at triceps. In all the subjects ovulation was found to be inhibited, as reflected by plasma progesterone values. The range of release rates calculated from plasma steady-state values was 51-119 micrograms/day. The average release rates over the entire period of observation based on area under curve were 102-200 micrograms/day. On the other hand, the release rates obtained from the residual drug in the ring after a period of use ranged from 184-259 micrograms/day.

Fertility regulation in nursing women: VIII. Progesterone plasma levels and contraceptive efficacy of a progesterone-releasing vaginal ring

The objectives of this trial were to test the contraceptive efficacy and measure progesterone plasma levels of women using progesterone-releasing rings during lactation. Two types of rings delivering an average of about 5 mg or 10 mg of progesterone per day were tested in 128 healthy nursing women. A control group was formed by 127 Copper T users. Rings were inserted at day 60 postpartum and replaced every 3 months with a new one. Initially progesterone plasma levels were around 10 nmol/l and 15 nmol/l for rings releasing 5 and 10 mg per day, respectively, and decreased slightly after 30 days. Levels observed in subsequent segments of use approximated those of the first segment. These levels are within the range shown to inhibit fertility in lactating women. One pregnancy was diagnosed in 739 woman-months of progesterone ring use, and none occurred in 794 woman-months of Copper T use, which contrasts with the high incidence of pregnancy in a group of untreated nursing women where 19 pregnancies resulted during 677 woman-months. No deleterious effects were detected lactation and infant growth or maternal and infant health. It is concluded that the vaginal rings releasing progesterone are a suitable contraceptive method for lactating women.

Measurement of ethynylestradiol and levonorgestrel incorporated into sustained release contraceptive formulations

High performance liquid chromatography was used to measure the concentrations of ethynylestradiol (EE) and levonorgestrel (LNG) released from contraceptive devices into aqueous medium containing the cationic detergent, benzalkonium chloride. Most of the detergent was removed after solvent extraction of the steroid, although small amounts of it remained in the steroid phase. Over the course of many injections into octasilyl (C8) or octadecylsilyl (C18) reversed-phase columns, the chromatographic profile of EE was gradually altered with multiple peaks emerging. The profile of LNG was not changed. EE chromatographed as a double peak on a fully end-capped C18 column. Rechromatography of each peak yielded a mixture of the two. Mass spectral analysis showed that the peaks differed only in the gain or loss of an equivalent of water. Introduction of a cation exchange column before the analytical column removed residual benzalkonium ions, and by thus preventing deterioration of the column, permitted EE to consistently emerge as a single, symmetrical peak.

The progestagen releasing vaginal ring

The results of the Manchester study and its reinforcement from data from the multicenter study indicate that the ring is a well-tolerated delivery system for low-dose progestagens. The expulsion rate is low and vaginal tolerance satisfactory. The pregnancy rate and bleeding pattern is of the same order as oral low-dose progestagens. Indeed, there is an indication that the pregnancy rate and abnormal bleeding rate may be even lower. Data from other more extensive phase 3 studies will be required to confirm this impression. The subjective assessment is that the majority of patients are enthusiastic about this method of contraception, bearing in mind that many of them had become disenchanted with existing marketed contraceptive methods. Because of its high level of acceptability, the gap between theoretical and use-effectiveness in narrowed and once inserted, a high degree of motivation is not required since the existing ring only needs to be reinserted after 90 days of use. The acceptability of vaginal methods of contraception as evidenced by the rapid uptake of the vaginal sponge suggests that there is considerable potential for increased use of vaginal methods. In the present state of knowledge, it would appear that the woman for whom the progestagen only conception is particularly appropriate is the one who is lactating or for the older woman whose fertility is on the wane. For the woman who wishes to space her family, the progestagen only contraceptive is also appropriate. With increased refinements and experience of this method, there is a likelihood that the ring may extend the use and application of progestagen only contraception to a wider range of potential patients.

Pharmacodynamics of a contraceptive vaginal ring releasing norethindrone and estradiol: ovarian function, bleeding control and lipoprotein patterns

A new contraceptive vaginal ring (CVR), releasing approximately 700 micrograms of norethindrone (NET) and approximately 140 micrograms of estradiol (E2) daily, was studied in eleven women for a total of 61 21-day cycles. Ovarian function, as judged by plasma progesterone (P) and E2 levels, and plasma NET levels were studied by weekly blood samples in 30 cycles. The lipoprotein pattern was studied before, after two and six months of treatment and one month after completed treatment. The CVR gave rise to stable plasma NET levels which however varied considerably between individuals. Signs of luteal activity/ovulation were encountered in 4/30 cycles, all in subjects with the lowest NET plasma levels. E2 levels above 250 pmol/l, indicating follicular activity, were encountered in 22/30 cycles. Breakthrough bleeding and spotting appeared in 40/61 cycles and in 12 per cent of the treatment days. Bleeding control was significantly better in the same subjects when using a CVR releasing levo-Norgestrel and E2. Serum and HDL cholesterol concentrations decreased significantly by 10-12 per cent during treatment. The ratios between apolipoproteins A-I and A-II on one hand and HDL cholesterol on the other increased significantly and the ratio apolipoprotein A-I:A-II decreased significantly, indicating a change in the lipoprotein composition. These changes are qualitatively similar but quantitatively not as pronounced as with the more extensively studied 1-Ng/E2 CVR. The difference in clinical performance and in the effects on the lipoprotein pattern between the presently studied CVR and the 1-Ng/E2 CVR is most likely the result of not using equipment doses of gestagen in the CVRs.

Ovarian function, bleeding control and serum lipoproteins in women using contraceptive vaginal rings releasing five different progestins

Ovarian function, bleeding patterns and serum lipoproteins were studied in women using contraceptive vaginal rings (CVRs) of dimethyl-polysiloxane impregnated with steroids. The different CVRs were used for about 10 cycles each. The following groups were studied, with the daily steroid dosage given in parentheses. Women using CVRs delivering levonorgestrel (290 micrograms), norethisterone (850 micrograms), medroxyprogesterone acetate (700 micrograms) or megestrol acetate (1.9 mg), all of which were in combination with estradiol (200 ug). Women using CVRs delivering progesterone (5.2 mg). Women taking megestrol acetate orally (15 mg/day) for three weeks. In all women except those using the levonorgestrel CVR, there were indications of incomplete suppression of ovarian activity as shown by elevated levels of progesterone and/or estradiol peaks. Bleeding control seemed to be good with the levonorgestrel CVR and rather poor with the others. Levonorgestrel treatment was associated with a decrease in high density lipoprotein cholesterol (32%) and triglycerides (25%) and a 16% decrease in apolipoprotein A-I. Norethisterone induced a 10% decrease in A-I and a reduction of cholesterol in very low density lipoprotein. All other lipid and apolipoprotein B, A-I and A-II values were unaltered with the administration of the CVRs and with oral megestrol acetate. Levonorgestrel was given in a higher dose than the other progestins, but the absence of effects of the high oral dose of megestrol acetate on the serum lipoproteins indicates that the progesterone-derived progestins in adequate doses probably would not alter the lipoprotein metabolism. Higher doses of progestins are needed to achieve acceptable control of ovarian activity and bleeding patterns than seen with these CVRs.

Influence of a levonorgestrel-containing contraceptive vaginal ring on plasma lipids and lipoproteins in cynomolgus monkeys

The effect of a contraceptive vaginal ring (CVR) containing levonorgestrel on plasma lipid and lipoprotein concentrations and characteristics was assessed in ten cynomolgus monkeys. The animals were fed a diet similar to the average American diet in fat (40% of calories) and cholesterol (0.2 mg/kcal) content. The objective of this study was to determine if changes in lipids and lipoproteins caused by progestogen administration parallel those seen in human females. A parallel pattern would recommend the cynomolgus monkey as a model for studying the effects of progestogens on the atherosclerotic process. Treatment with the CVR resulted in significant decreases in total plasma, VLDL + ILDL + LDL, and HDL cholesterol concentrations and a decrease in the percentage of HDL2 in total HDL. Plasma triglyceride concentrations were low throughout the study and consistent effects of the CVR were not seen. CVR treatment resulted in increases in TPC:HDL-C ratios and in the flotation rate of the LDL particle. The patterns of effects on HDL cholesterol, total plasma cholesterol, and HDL2 concentrations were similar to the progestogen-induced changes observed in human plasma lipids and lipoproteins. Based on these effects, the cynomolgus monkey appears to be a suitable model for the study of progestogen-induced changes in plasma lipids and lipoproteins and their consequent influences on coronary artery atherosclerosis.