The first uterine pass effect

Vaginal mifepristone for the treatment of symptomatic uterine leiomyomata: an open-label study

OBJECTIVE

To evaluate the efficacy and safety of 3 months of vaginal mifepristone treatment on leiomyoma volume and related symptoms.

DESIGN

Prospective, open-label, two tertiary centers, phase II clinical trial.

SETTING

Two tertiary medical centers in Israel.

PATIENT(S)

Thirty-three enrolled women, ages 30-53 years, diagnosed with symptomatic uterine fibroids.

INTERVENTION(S)

Patients received 10 mg mifepristone vaginally daily for 3 months.

MAIN OUTCOME MEASURE(S)

Reduction in uterine leiomyoma volume. Improvement in symptoms related to uterine fibroids was assessed with the use of the "Uterine Fibroid Symptoms Quality of Life Questionnaire" (UFS-QoL). The number of bleeding days, safety, and tolerability were secondary measures.

RESULT(S)

Mifepristone treatment significantly reduced leiomyoma volume from 135.3 ± 22.9 cc at enrollment to 101.2 ± 22.4 cc after 3 months of treatment. The UFS-QoL Score significantly decreased from 20.7 ± 0.7 at enrollment to 14.0 ± 0.8 after 3 months of treatment. The number of bleeding days significantly decreased by 3.5 days. Endometrial biopsies showed no evidence of endometrial hyperplasia or cellular atypia. There were no major side effects during the course of the study, and treatment was well tolerated.

CONCLUSION(S)

Vaginal mifepristone may offer an effective treatment option for women with symptomatic uterine leiomyoma and can improve the patients' quality of life.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00881140.

The vagina as a route for drug delivery: a review

Overactive bladder (OAB) syndrome has a significant deleterious impact on quality of life. After conservative therapy and bladder retaining, antimuscarinic drugs remain the mainstay of OAB management. Oral therapy is associated with frequent side effects, leading to the development of alternative agents and formulations or the use of novel routes of drug administration, such as the vaginal route. The vagina is often ideal for drug delivery because it allows the use of lower doses, maintains steady drug administration levels, and requires less frequent administration than the oral route. With vaginal drug administration, absorption is unaffected by gastrointestinal disturbances, there is no first-pass effect, and use is discreet. The aim of this review is to provide a background overview of vaginal development, anatomy, and physiology and the effect this has on the use of this route for both local and systemic drug delivery, with special reference to OAB management. Vaginal therapy continues to be an underused route of drug delivery. Vaginal administration allows nondaily, low, continuous dosing, which results in stable drug levels and may, in turn, achieve a lower incidence of side effects and improve patient compliance. These benefits must be balanced against inherent patient or physician bias against using this route and the need to overcome cultural, personal, and hygiene-related barriers to this form of therapy. More sophisticated and programmable vaginal rings are being developed for systemic delivery of therapeutically important macromolecules, such as antimuscarinic therapy in OAB management.

PEGylation of a proprotein convertase peptide inhibitor for vaginal route of drug delivery: in vitro bioactivity, stability and in vivo pharmacokinetics

Uterine proprotein convertase (PC) 6 is critical for embryo implantation in mice and women. It is also one of the PC family members that play a vital role in HIV infectivity. We hypothesized that inhibiting PC6 in the female reproductive tract (vagina, cervix and uterus), may protect women from both pregnancy and HIV infection. One key requirement to prove this concept in an animal model is a vaginally deliverable PC6 inhibitor. Nona-D-arginine (Poly R) is a potent peptide PC inhibitor and is able to inhibit HIV in cell culture. We modified Poly R by PEGylation with different strategies and determined their biochemical properties in vitro and in vivo. PEGylation at the C-terminus, regardless of the PEG size (30 kDa or 1239 Da) did not compromise the inhibitory potency of Poly R. In contrast, PEGylation at both termini (1239 Da) dramatically reduced its inhibitory activity. Poly R and C-PEGylated Poly Rs also showed equal potency in inhibiting a PC6-dependent cellular process critical for embryo implantation. Poly R and the equipotent C-PEGylated Poly Rs were further tested for their serum stability in vitro and pharmacokinetics in vivo following vaginal administration in mice. All Poly Rs were equally stable in mouse serum in vitro for 24h; C-PEGylated Poly Rs showed enhanced vaginal absorption and penetration across the vaginal mucosa/epithelium. This is the first report that C-terminal PEGylation significantly enhances the therapeutic properties of Poly R for vaginal drug delivery. Our findings also provide important insights into future design of Poly R derivatives.

Inhibition of proprotein convertase 5/6 activity: potential for nonhormonal women-centered contraception

BACKGROUND

Proprotein convertase 5/6 (PC6) is critical for endometrial epithelial receptivity and stromal cell decidualization for embryo implantation in women. We hypothesized that inhibiting PC6 could block implantation for contraception. The aim of this study was to prove this concept using human cell models and rabbits.

STUDY DESIGN

A potential PC6 inhibitor, C1239-PEG-Poly R, was biochemically confirmed to be a potent PC6 inhibitor. The potential contraceptive action of the inhibitor was then tested in decidualization of primary human endometrial stromal cells in a human trophoblast spheroid attachment model and in vivo in rabbits.

RESULTS

The PC6 inhibitor C1239-PEG-Poly R inhibited in a dose-dependent manner both decidualization and spheroid attachment. Vaginal delivery of 200 μL of the inhibitor at a final concentration of 5 mM to rabbits over a 3-day period starting 6 days after mating resulted in a 60% decrease in implantation and, hence, pregnancy.

CONCLUSIONS

This study presents proof of concept that PC6 inhibition has the potential to block embryo implantation, providing nonhormonal contraception for women.

What agent should be used to prevent recurrent preterm birth: 17-P or natural progesterone?

Preterm birth has increased over the last decade. In 2006, 12.5% of all births in the United States occurred at fewer than 37 weeks gestation. This is associated with significant health care costs as well as related neonatal morbidity and mortality. In 2003, costs related to care for infants with preterm-birth or low-birth weight exceeded 11 billion dollars. This article reviews the literature on 17 alpha-hydroxyprogesterone caproate (17-P) and natural progesterone and concludes that 17-P is indicated for prevention of preterm birth in women with a documented history of a preterm birth before 37 weeks.

Progestin treatment for the prevention of preterm birth

Progestin supplementation appears to be a promising approach to both preventing initiation of preterm labor and treating it once it is already established, given the role of progesterone in maintaining pregnancy, as well as support from basic and clinical research. Progesterone and 17α-hydroxyprogesterone acetate slow the process of cervical ripening, and this is the rationale for prophylactic long-term progestin supplementation mostly studied so far. However, progesterone (but not 17α-hydroxyprogesterone acetate) also inhibits myometrial activity even after the cervix has already ripened. Moreover, these effects depend greatly on the vehicle used and the route of administration. Understanding different mechanisms of action, as well as the importance of progestin formulation, vehicle and route of administration, is the key to finding the optimal progestin treatment for prevention of preterm birth.

Vaginally administered PEGylated LIF antagonist blocked embryo implantation and eliminated non-target effects on bone in mice

Female-controlled contraception/HIV prevention is critical to address health issues associated with gender inequality. Therefore, a contraceptive which can be administered in tandem with a microbicide to inhibit sexually transmitted infections, is desirable. Uterine leukemia inhibitory factor (LIF) is obligatory for blastocyst implantation in mice and associated with infertility in women. We aimed to determine whether a PEGylated LIF inhibitor (PEGLA) was an effective contraceptive following vaginal delivery and to identify non-uterine targets of PEGLA in mice.

Vaginally-applied ¹²⁵I-PEGLA accumulated in blood more slowly (30 min vs 10 min) and showed reduced tissue and blood retention (24 h vs 96 h) compared to intraperitoneal injection in mice. Vaginally-applied PEGLA blocked implantation. PEGLA administered by intraperitoneal injection inhibited bone remodelling whereas vaginally-applied PEGLA had no effect on bone. Further, PEGLA had no effect in an animal model of multiple sclerosis, experimental auto-immune encephalomyelitis, suggesting PEGLA cannot target the central nervous system.

Vaginally-administered PEGLA is a promising non-hormonal contraceptive, one which could be delivered alone, or in tandem with a microbicide. Vaginal application reduced the total dose of PEGLA required to block implantation and eliminated the systemic effect on bone, showing the vagina is a promising site of administration for larger drugs which target organs within the reproductive tract.

Pharmacologic actions of progestins to inhibit cervical ripening and prevent delivery depend on their properties, the route of administration, and the vehicle

OBJECTIVE

The purpose of this study was to evaluate cervical changes and delivery at term during pregnancy in rats after various progestin treatments.

STUDY DESIGN

Pregnant rats were treated by various routes and vehicles with progesterone, 17-alpha-hydroxyprogesterone caproate (17P), R5020, and RU-486. Delivery time was determined and cervical ripening was assessed in vivo by collagen light-induced fluorescence.

RESULTS

The cervix is rigid in the progesterone injection, 17P, and vaginal R5020 groups vs controls. Vaginal progesterone had no effect. RU-486 treatment softened the cervix during preterm delivery. Only subcutaneous injected progesterone, R5020 (subcutaneous and vaginal), and topical progesterone in sesame and fish oil inhibits delivery. Delivery is not changed by subcutaneous injection of 17P, vaginal progesterone, oral progesterone, and topical progesterone in Replens (Crinone; Columbia Labs, Livingston, NJ).

CONCLUSION

Inhibition of cervical ripening and delivery by progestins depends on many factors that include their properties, the route of administration, and the vehicle. This study suggests reasons that the present treatments for preterm labor are not efficacious.

Uterine dynamics: impact on the human reproduction process

This review assesses data on the possible relationship between the contractility of the non-pregnant uterus and the human reproduction process. The possibility of assessing non-invasively uterine contractility using ultrasound scans has improved understanding of hormone regulation and the influence of uterine contractility on the human embryo implantation process in both natural and ovarian stimulation cycles. Contractions of the non-pregnant uterus are influenced by ovarian hormones and, presumably, partake in the in-vivo fertilization and embryo implantation processes in humans. Approaches aimed at either stimulating or inhibiting uterine contractions could be instrumental in improving pregnancy rates after the use of assisted reproductive technologies.

Local Effects of Vaginally Administered Estrogen Therapy: A Review

The results of the Women's Health Initiative (WHI) led to a distinct decline in the routine use of estrogen as preventive therapy for vasomotor symptoms, osteoporosis, and cardiovascular disease in postmenopausal women. Without estrogen replacement, one third of women experience symptoms of atrophic vaginitis including dryness, irritation, itching and or dyspareunia. Local application of estrogen has been shown to relieve these symptoms and improve quality of life for these women. In addition, local estrogen therapy may have a favorable effect on sexuality, urinary tract infections, vaginal surgery, and incontinence. This review examines the effects of vaginally applied estrogen on the vaginal epithelium, urethra and endometrium. An accompanying review examines the systemic effects of vaginally applied estrogen.

Intravaginal oestrogen and progestin administration: advantages and disadvantages

The vagina provides a local and a systemic route for delivering hormones for systemic effects and uterine targeting. Due to the 'uterine first-pass effect', hormones concentrate in the uterus and nearby tissues with low systemic exposure. Vaginal oestrogens, progesterone/progestins and danazol are currently used to obtain local (vagina and urethra), regional (uterus, pelvic structures) and systemic effects or contraception. Very low dosages of transvaginal oestrogens in the forms of creams, tablets and rings are effective for vaginal atrophy and urinary incontinence. To avoid endometrial stimulation, no deep vaginal application of low dosages for less than 6 months is recommended. For postmenopausal hormonal therapy by the vaginal route, progesterone is delivered directly to the uterus; the target organ for which it is designed. Worldwide, vaginal progesterone is employed for luteal phase support. Contraceptive vaginal rings offer the advantages of non-oral administration and sustained release. Vaginal administration of steroids is a promising option for the treatment of endometriosis.

Progesterone vaginal gel for the reduction of recurrent preterm birth: primary results from a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Preterm birth is the leading cause of perinatal morbidity and mortality worldwide. Treatment of preterm labor with tocolysis has not been successful in improving infant outcome. The administration of progesterone and related compounds has been proposed as a strategy to prevent preterm birth. The objective of this trial was to determine whether prophylactic administration of vaginal progesterone reduces the risk of preterm birth in women with a history of spontaneous preterm birth.

METHODS

This randomized, double-blind, placebo- controlled, multinational trial enrolled and randomized 659 pregnant women with a history of spontaneous preterm birth. Between 18 + 0 and 22 + 6 weeks of gestation, patients were assigned randomly to once-daily treatment with either progesterone vaginal gel or placebo until either delivery, 37 weeks' gestation or development of preterm rupture of membranes. The primary outcome was preterm birth at </= 32 weeks of gestation. The trial was analyzed using an intent-to-treat strategy.

RESULTS

Baseline characteristics were similar in the two treatment groups. Progesterone did not decrease the frequency of preterm birth at </= 32 weeks. There was no difference between the groups with respect to the mean gestational age at delivery, infant morbidity or mortality or other maternal or neonatal outcome measures. Adverse events during the course of treatment were similar for the two groups.

CONCLUSION

Prophylactic treatment with vaginal progesterone did not reduce the frequency of recurrent preterm birth (</= 32 weeks) in women with a history of spontaneous preterm birth. The effect of progesterone administration in patients at high risk for preterm delivery as determined by methods other than history alone (e.g. sonographic cervical length) requires further investigation.

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.

Mifepristone vaginally in an early medical abortion regimen: a pilot study

OBJECTIVE

This prospective observational pilot study was undertaken to assess the efficacy of mifepristone and misoprostol, both administered vaginally. The ultimate goal is to investigate alternative means of reducing the time interval between the two treatments involved. The efficacy of the early medical abortion regimen utilizing mifepristone and misoprostol is beyond doubt. The regimen usually involves administering misoprostol 36 h following oral administration of mifepristone. The interval between the two treatment components might affect a woman's choice of the medical method.

METHODS

Eighteen women undergoing abortion for nonmedical reasons were recruited.

RESULTS

Seven women required further intervention to achieve complete abortion. Median induction-to-abortion interval was 7.66 h in the 11 women with complete abortion.

CONCLUSION

The complete abortion rate of 61% in this study was lower than that with the standard medical regimen.

Comparison of uterine concentrations of ethinyl estradiol and etonogestrel after use of a contraceptive vaginal ring and an oral contraceptive

OBJECTIVE

To compare uterine tissue concentrations of ethinyl estradiol (EE) and etonogestrel (ENG) after one cycle of use of a contraceptive vaginal ring (NuvaRing; NV Organon, Oss, The Netherlands) or a combined oral contraceptive (COC).

DESIGN

Randomized, open-label, pharmacokinetic study.

SETTING

Obstetrics and gynecology unit.

PATIENT(S)

Eight premenopausal women about to undergo hysterectomy but otherwise healthy.

INTERVENTION(S)

One cycle (17-21 days) of NuvaRing or COC treatment that ended with surgical hysterectomy.

MAIN OUTCOME MEASURE(S)

Tissue concentrations of EE and ENG in uterine tissue samples taken from the upper myometrium and mid-myometrium, the cervical region, and the endometrium.

RESULT(S)

In both groups, concentrations of EE and ENG were similar in uterine tissue taken from the upper myometrium and mid-myometrium and the cervical region. However, compared with the COC group, concentrations of both hormones were markedly lower in tissue samples from the endometrium of women who had been treated with NuvaRing.

CONCLUSION(S)

Vaginal administration of hormones with NuvaRing did not produce elevated uterine concentrations of EE and ENG, compared with an oral contraceptive.

Vaginal delivery of contraceptives

Although a steady increase in contraceptive use has been observed both in developed and less-developed countries, the large number of unplanned pregnancies may indicate that the contraceptive needs of a significant percentage of couples have so far not been met. Several new contraceptive products have reached the market during the last 2 years. Among these is a new contraceptive vaginal ring, which has become available for prescription. This new female method has been developed to expand the contraceptive choices available to couples. This review will address the specifics of the vaginal route for delivering contraceptive steroids and describe the various systems available or under evaluation.

Comparison of vaginal and oral administration of emergency contraception

OBJECTIVE

To compare the physiologic effects of vaginally and orally administered emergency contraception.

DESIGN

Prospective, open-label, crossover study.

SETTING

University research center.

PATIENT(S)

Nine regularly menstruating volunteers.

INTERVENTION(S)

Five subjects received 1,000 microg of levonorgestrel with 200 microg of ethinyl E2 (twice the standard Yuzpe regimen dose) vaginally, and the standard Yuzpe regimen dose orally 1 week later. Four subjects received 1,500 microg of levonorgestrel (twice the standard Plan B regimen dose) vaginally and received the standard Plan B dose orally 1 week later. Serum samples were obtained at baseline and at frequent intervals after each dose.

MAIN OUTCOME MEASURE(S)

Serum gonadotropin, hepatic globulin, and androgen levels measured at baseline, at the time of peak levonorgestrel, and 24 hours later.

RESULT(S)

Gonadotropin, hepatic globulin, and androgen levels were suppressed to a similar degree among the four regimens, with a return to baseline levels after 24 hours.

CONCLUSION(S)

We conclude that high doses of levonorgestrel found in emergency contraception regimens lead to a transient direct suppression of gonadotropin, hepatic globulin, and androgen levels. This effect is similar after vaginal and oral administration of emergency contraception. Therefore, the vaginal route of administration of emergency contraception regimens may be as efficacious as the oral route.

Inhibiting Uterine PC6 Blocks Embryo Implantation: An Obligatory Role for a Proprotein Convertase in Fertility1

Successful embryo implantation involves complex interactions between the embryo and the uterus and is critical in establishing pregnancy. Proprotein convertase (PC) 6 (PC6) is one of the PC endoproteases regulating protein function through posttranslational activation of precursor proteins, including growth and differentiation factors. Here we show that PC6 protein is induced in the uterine stromal cells specifically at the site of embryo attachment during early pregnancy in mice. In vivo blocking of uterine production of PC6 protein using morpholino antisense oligonucleotides in mice resulted in total inhibition of implantation, revealing a vital role for PC6 in modulating the uterus for embryo implantation. Studies in primates (rhesus monkey and human) showed a dramatic upregulation of endometrial PC6 during the phase of uterine receptivity and at implantation, particularly during a critical uterine cell differentiation process termed decidualization. Thus, the current studies have demonstrated that PC6 is an essential molecule in modulating uterine function to support the establishment of embryo implantation. Interestingly, PC6 is one of the PCs identified to be important in processing the coat protein of HIV; inhibition of PCs has been suggested to be an effective approach to reduce HIV transmission. We therefore propose the novel concept that PC6 could be a potential nonhormonal target in the female reproductive tract for dual protection for women, both in preventing pregnancy and reducing HIV infection.

Identification of novel endometrial targets for contraception

Successful embryo implantation is a critical step in establishing pregnancy and requires appropriate preparation of the endometrium to provide a transient state of "uterine receptivity." The most essential of the molecular events determining receptivity may therefore provide potential targets for postcoital contraception. Using the mouse as a model, we identified molecules specifically regulated in the endometrium at very early implantation: these were monoclonal nonspecific suppressor factor beta (MNSFbeta), splicing factor SC35, a novel protease of the HtrA family, termed HtrA3, calcium-binding protein (CaBP)-d9k (calbindin d9k) and proprotein convertase 6 (PC6). All of these molecules were also expressed in human endometrium, with the exception of CaBP-d9k, which was represented by the functionally similar CaBP-d28k. Appropriate spatial and temporal expressions of mRNA and protein were demonstrated for all five candidate molecules in mouse and primate (human and rhesus monkey) endometrium during the menstrual cycle and early pregnancy. Functional studies in mice established that blocking production of the CaBPs and PC6 within the endometrium completely prevented implantation and thus provided proof of principle that these molecules are potential contraceptive targets.

Why consider vaginal drug administration?

OBJECTIVE

To review the anatomy and physiology of the vagina, the merits of vaginal drug administration, and the currently available vaginal drug-administration systems.

DESIGN

Review of basic and clinical research.

RESULT(S)

Although clinicians commonly use topically administered drugs in the vagina, this route for systemic drug administration is somewhat novel. Experience with a variety of products demonstrates that the vagina is a highly effective site for drug delivery, particularly in women's health. The vagina is often an ideal route for drug administration because it allows for the administration of lower doses, steady drug levels, and less frequent administration than the oral route. With vaginal drug administration, absorption is unaffected by gastrointestinal disturbances, there is no first-pass effect, and use is discreet. Knowledge of anatomy, physiology, histology, and immunology of the vagina should allow clinicians to reassure their patients concerning this mode of delivery. Greater understanding and experience by clinicians should lead to increased use and acceptance of the vagina as a route for drug administration.

CONCLUSION(S)

The safety and efficacy of vaginal administration have been well established. The vaginal route of drug delivery is acceptable and may even be a preferable route of administration for many drugs, particularly hormones, whether for contraception or postmenopausal estrogen therapy.

Luteal phase support using either Crinone 8% or Utrogest: results of a prospective, randomized study

The Crinone 8% preparation makes it possible to administer natural progesterone (90 mg) vaginally once daily for luteal phase support (LPS). Until now, no prospective, randomized studies have directly compared this new preparation with widely used Utrogest capsules, which were originally designed for oral administration but are used routinely as a vaginal preparation. A prospective, randomized study investigated 126 patients undergoing cycles of in vitro fertilization (IVF) and IVF/intracytoplasmic sperm injection (ICSI). Patients received either Crinone 8% (n = 73) vaginally once daily or two Utrogest capsules (n=53) vaginally three times daily (600 mg). Clinical pregnancy rates were comparable (28.8 versus 18.9%), as were clinical abortion rates until 12 weeks of gestation (14.3 versus 10.0%) and clinical ongoing pregnancy rates (24.7 versus 17.0%) in the Crinone 8% and Utrogest groups, respectively. Forty-seven non-pregnant patients were randomly selected to answer questions regarding comfort during LPS. Crinone 8% had a clear advantage over Utrogest as it resulted in less vaginal discharge (P < 0.01) and fewer application difficulties (P<0.05). Twenty patients familiar with the alternative preparation from a previous cycle also noted that Crinone 8% was easier to apply (P < 0.01) and less time consuming (P < 0.05) to use than Utrogest.

Is there evidence for preferential delivery of ovarian estradiol to the endometrium?

OBJECTIVE

To determine the direction of delivery of E(2) in the female pelvis by assessing the ratio of endometrial to serum E(2) in women whose ovaries were stimulated to produce E(2) with women who received exogenous E(2).

DESIGN

Prospective comparative study.

SETTING

University-based ART program.

PATIENT(S)

Oocyte donors and recipients of donor oocytes.

INTERVENTION(S)

Micronized E(2) administered by the oral or vaginal route and oocyte donation.

MAIN OUTCOME MEASURE(S)

Serum and endometrial levels of E(2).

RESULT(S)

Serum E(2) levels were significantly higher in women who underwent controlled ovarian hyperstimulation (COH) and women receiving exogenous E(2) by the vaginal route than in those who received oral E(2). Levels of E(2) in endometrial tissue were similar in women who underwent COH and those receiving oral E(2). Endometrial E(2) levels in women who underwent vaginal administration were significantly higher than those in the oral E(2) or COH groups. The ratio of endometrial to serum E(2) was highest in women who underwent vaginal E(2) and lowest in those undergoing COH.

CONCLUSION(S)

Vaginal administration of micronized E(2) results in preferential absorption of E(2) into the endometrium, consistent with a "uterine first pass" effect. Since endogenous E(2) produced the smallest ratio of E(2) between the endometrium and serum, E(2) produced by the ovaries is not preferentially delivered to the uterus.

The scope and potential of vaginal drug delivery

The vagina, in addition to being a genital organ with functions related to conception, serves as a potential route for drug administration. Mainly used for local action in the cervico-vaginal region, it has the potential of delivering drugs for systemic effects and uterine targeting. Currently available vaginal dosage forms have several limitations, necessitating the need to develop novel drug delivery systems. In addition, consideration of the regulatory aspects and consumer preferences for vaginal formulations is also required in the early stages of development.

Serum and tissue hormone levels of vaginally and orally administered estradiol

OBJECTIVE

Our purpose was to determine serum and endometrial estradiol levels when micronized estradiol is administered vaginally and orally.

STUDY DESIGN

Five subjects were given oral estradiol (2 mg twice daily), during an artificial luteal phase, and another group of 5 subjects were given the same dose of estradiol by the vaginal route. Endometrial biopsies and blood samples were obtained on day 21 of the cycle, 2 hours after the last dose was administered. Tissue and blood samples were assayed for estradiol.

RESULTS

Serum estradiol levels were significantly higher with vaginally administered estradiol than with orally administered estradiol (2344 +/- 398 vs 279 +/- 76 pg/mL, P <.005). Endometrial estradiol concentrations were also significantly higher with vaginally administered estradiol than with the oral preparation (918 +/- 412 vs 13 +/- 2 pg/mg protein, P <.05).

CONCLUSIONS

Vaginal administration of estradiol is more effective in increasing serum and endometrial levels of estradiol than the oral route and may represent the optimal route of administration for recipients of egg donation. If the vaginal route of estradiol administration is considered for menopausal replacement therapy, much lower doses of the standard oral quantities should be used. Furthermore, if the uterus is present, a progestin must be used to compensate for the high tissue levels of estradiol.