Pharmacokinetics and pharmacodynamics of three dosages of oestriol after continuous vaginal ring administration for 21 days in healthy, postmenopausal women

Impact of vaginal estriol on serum hormone levels: a systematic review

The genitourinary syndrome of menopause (GSM) affects up to 84% of postmenopausal women and may significantly reduce the quality of life in some. For symptom relief, there are several non-hormonal and hormonal vaginal products available. In Europe, vaginal estriol (E3) is the most frequently chosen estrogen for GSM treatment. The aim of this systematic review was to assess the impact of vaginal E3 on serum sex hormone levels, an outcome that has been previously used to assess safety in similar products. In our review, we did not find any alterations in serum estrone, estradiol, testosterone, progesterone and sex hormone binding globulin levels after vaginal E3 application. In contrast, some studies showed a minimal and transient decrease in serum gonadotropin levels, which however remained within the postmenopausal range. Similarly, only a few studies reported a minimal and transient increase of serum E3 levels, with the rest reporting no changes. The lack of clinically relevant long-term changes in serum sex hormone levels supports the current literature providing evidence about the safety of vaginal E3 products.

Oestrogen-based therapies for menopausal symptoms

PURPOSE

To summarise the dosing options, regimens, pharmacokinetics, risks and benefits of oestrogen-based therapies for the treatment of menopausal symptoms.

METHODS

A review of the literature was undertaken using multiple databases. Randomised trials, observational studies, meta-analyses and review papers were included.

RESULTS

Multiple systemic preparations of oestrogen exist and all appear comparable in terms of efficacy. They differ by pharmacokinetics and those preparations that avoid hepatic metabolism have a lower risk profile in general although their use can be limited by skin barriers or patient acceptability. All vaginal oestrogen treatments are comparable in efficacy and have not been associated with any health risks. Side-effects between all preparations differ.

CONCLUSIONS

With regards to oestrogen treatments there is not a one size fits all. Multiple treatments are available and a clinician's role is to guide and help women make evidence based, unbiased and informed choices.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Single-dose pharmacokinetics and pharmacodynamics assessment of oestriol and trimegestone containing vaginal rings in healthy women with childbearing potential

PURPOSE

To evaluate the pharmacokinetics and pharmacodynamics of oestriol (E3) and trimegestone (TMG) in healthy women after application of three different vaginal rings over 21 days. The vaginal rings had a nominal delivery rate of 0.413/0.050 mg/day (Test 1), 0.311/0.090 mg/day (Test 2) and 0.209/0.137 mg/day (Test 3) E3/TMG.

METHODS

Thirty-five healthy women were randomised to receive a single application of Test 1, 2 or 3 (Clinical Trial NCT03343912). The E3 and TMG plasma concentration was determined by LC-MS/MS. Oestradiol (E2) and progesterone (PG) serum concentrations, and bleeding patern were determined as pharmacodynamic parameters. Safety was assessed by evaluation of adverse events and local tolerability.

RESULTS

The total and maximum exposure of E3 and TMG increased in a proportional ratio to dose. However, not in a magnitude which was expected from the dose differences for E3. During Test 2 and 3 treatment all E2 and PG values remained on a well suppressed level until end of treatment. E2 and PG serum levels increased distinctly earlier after ring removal with Test 1 compared to Test 2 and 3. Test 3 achieved 95.24% of "no bleeding" days under treatment followed by Test 1 (91.67%), and Test 2 (86.15%).

CONCLUSIONS

The Test 3 formulation presented the best dose combination of E3/TMG for contraception. Moreover, all vaginal rings were well tolerated.

Serum concentrations of estriol vary widely after application of vaginal oestriol cream

AIMS

The aim of this study was to establish the pharmacokinetic profile of serum oestriol (E₃ ) concentrations over 24 h following application of vaginal E₃ in chronic users (>12 weeks of E₃ use). The interindividual and intraindividual differences before and after E₃ were examined.

METHODS

Ten women participated. Vaginal cream was omitted for ≥36 h prior to the study days. Blood sampling was performed for E₃ , oestradiol and oestrone concentrations prior to cream application and at 1, 2, 3, 5, 8, 10, 12 and 24 h afterwards. In five women, all samples were repeated on a separate day.

RESULTS

E₃ was absorbed rapidly in most women. Peak serum E₃ concentration occurred around 2 h (range 1-5 h). The decline in E₃ concentrations was also rapid: falling <100 pmol L^-1 in six out of ten women within 8 h and returning to ≤ 10 pmol L^-1 at 24 h in nine out of the ten patients. Interindividual variability for peak concentrations was considerable (mean 546 pmol L^-1 ; 95% CI 349-743). Area under the concentration-time curve (AUC) values over a dosage interval also varied widely: mean 2145 pmol.h L^-1 ; 95% CI 1422-3233. However, repeated measurements in the same woman were highly (peaks: ρ = 0.94) or moderately (AUC: P = 0.74) correlated.

CONCLUSIONS

Postmenopausal E₃ concentrations are negligible. Serum E₃ concentrations of chronic users of E₃ cream varied greatly; however, concentrations declined rapidly within 8 h, generally reaching 'postmenopausal' levels by 24 h. The basis for the variation between subjects needs further elucidation. Additional research is required to establish the safety of topical E₃ .