Estradiol-intranasal: a review of its use in the management of menopause

Intranasal 17β-Estradiol Modulates Spatial Learning and Memory in a Rat Model of Surgical Menopause

Exogenously administered 17β-estradiol (E2) can improve spatial learning and memory, although E2 also exerts undesired effects on peripheral organs. Clinically, E2 has been solubilized in cyclodextrin for intranasal administration, which enhances brain-specific delivery. Prior work shows that the cyclodextrin structure impacts region-specific brain distribution of intranasally administered small molecules. Here, we investigated (1) cyclodextrin type-specific modulation of intranasal E2 brain distribution, and (2) cognitive and peripheral tissue effects of intranasal E2 in middle-aged ovariectomized rats. First, brain and peripheral organ distribution of intranasally administered, tritiated E2 was measured for E2 solubilized freely or in one of four cyclodextrin formulations. The E2-cyclodextrin formulation with greatest E2 uptake in cognitive brain regions versus uterine horns was then compared to free E2 on learning, memory, and uterine measures. Free E2 improved spatial reference memory, whereas E2-cyclodextrin impaired spatial working memory compared to their respective controls. Both E2 formulations increased uterine horn weights relative to controls, with E2-cyclodextrin resulting in the greatest uterine horn weight, suggesting increased uterine stimulation. Thus, intranasal administration of freely solubilized E2 is a strategic delivery tool that can yield a cognitively beneficial impact of the hormone alongside decreased peripheral effects compared to intranasal administration of cyclodextrin solubilized E2.

Activity of Multidrug Resistance-Associated Proteins 1-5 (MRP1-5) in the RPMI 2650 Cell Line and Explants of Human Nasal Turbinate

The profound influence of ATP-binding cassette (ABC) transporters on the disposition of numerous drugs has led to increased interest in characterizing their expression profiles in various epithelial and endothelial barriers. The present work examined the presence and functional activity of five ABC efflux proteins, i.e., MRP 1-5, in freshly isolated human nasal epithelial cells and two in vitro models based on the human RPMI 2650 cell line. To evaluate the expression patterns of MRP1, MRP2, MRP3, MRP4, and MRP5 at the mRNA and protein levels in the ex vivo model and the differently cultured RPMI 2650 cells, reverse transcriptase polymerase chain reaction (RT-PCR), Western blot analysis, and indirect immunofluorescence staining were used. The functionality of the MRP transporters in the three models was assessed using efflux experiments and accumulation assays with the respective substrates and inhibitors. The mRNA and protein expression of all selected ABC transporters was detected in excised human nasal mucosa as well as in the corresponding cell culture models. Moreover, the functional expression of the MRP transport proteins was demonstrated in the three models for the first time. Therefore, the potential impact of multidrug resistance-associated proteins 1-5 on drug disposition after intranasal administration may be taken into consideration for future developments. The specimens of human nasal turbinate exhibited slightly lower efflux capacities of MRP1, MRP3, and MRP5 in relation to the submerged and ALI-cultured RPMI 2650 cells, but showed a promising comparability to both in vitro models concerning the activity of MRP2 and MRP4. In this regard, the different RPMI 2650 cell culture models will be able to provide useful experimental data in the preclinical phase to estimate the interaction of particular efflux transporters with drug candidates for nasal application.

Use of vascular Doppler ultrasound to detect acute estradiol vascular effect in postmenopausal women

OBJECTIVES

To report on a simple practical test for assessing acute estradiol vascular effects on healthy and unhealthy postmenopausal women.

INTRODUCTION

Estradiol acts in the endothelium to promote vasodilatation through genomic and non-genomic mechanisms, but its vascular action may be impaired in diabetes mellitus, hypertension, smoking and obesity.

METHODS

Nineteen postmenopausal women (nine healthy and 10 with two or more of the above factors) of similar age and time since menopause were examined with vascular Doppler ultrasound. Resistance indexes and systolic and diastolic flow velocities were determined for the brachial and internal carotid arteries at baseline and 20 minutes after administration of a nasal estradiol formulation, available on the market, which reaches 1,200-1,500 pg/ml in the serum in 10-30 minutes. Estradiol blood levels were measured at 30 minutes.

RESULTS

The carotid resistance index increased 14.2% (vasoconstriction) in the unhealthy group after estradiol, from a mean +/- S.E. of 0.56 +/- 0.016 at baseline to 0.64 +/- 0.05 (p=0.033), and remained unchanged in healthy women. Brachial diastolic flow velocity increased 19.7% (vasodilatation) in healthy women, from 16.2 +/- 1.93 to 19.4 +/- 0.64 cm/s (p=0.046), and did not change in the unhealthy subjects. Estradiol levels were similar in both groups.

DISCUSSION

Healthy postmenopausal women showed brachial vasodilatation while unhealthy postmenopausal women displayed vasoconstriction at the carotid artery. Vascular responses to estradiol were divergent between the groups.

CONCLUSIONS

The acute estradiol test, coupled with Doppler ultrasound, seemed to be able to differentiate women with normal and abnormal endothelial function in a simple, non-invasive manner.

Drug delivery systems for hormone therapy

Various types of formulations and delivery devices have been developed for hormone therapy (HT) and their modes of hormone action and patient responses have been evaluated. Although the Women's Health Initiative (WHI) reported the controversial results on estrogen/progestin combination therapy, HT still remains a primary therapeutic option for the treatment of menopausal symptoms and osteoporosis. As a novel alternative to HT may not be probable in clinical use for the next decade, the currently available formulations containing estrogen and progestogen should be properly optimized for HT. The extensive reviews and comparisons on the characteristics of various types of HT could lead to the development of an efficient delivery formulation which maximizes patient compliance and minimizes adverse effects for individual users.

Uptake of estradiol or progesterone into the CSF following intranasal and intravenous delivery in rats

The uptake of estradiol and progesterone into the cerebrospinal fluid (CSF) after intranasal and intravenous administration in rats was investigated. Each animal received estradiol intranasally (40 microg/rat) and by intravenous infusion (10 microg/rat) into the jugular vein using a vascular access port. Hereafter, the same set of rats was treated with progesterone intranasally (200 microg/rat) and by intravenous infusion (104 microg/rat). Following nasal delivery, both steroid hormones reach Cmax values in plasma and CSF at 15 min after administration. Intravenous infusion of estradiol and progesterone shows comparable plasma and CSF concentration-time profiles compared to the nasal route. For both hormones the AUCCSF/AUCplasma ratios (mean +/- SD) after intranasal delivery (estradiol 2.3 +/- 1.1%; progesterone 1.9 +/- 0.7%) do not differ significantly from the ratios shown after intravenous infusion (estradiol 2.0 +/- 0.6%; progesterone 2.2 +/- 0.8%). These results indicate that after nasal delivery estradiol and progesterone are rapidly absorbed into the systemic circulation, from where the non-protein bound hormones probably enter the CSF by crossing the blood-brain barrier. No extra direct nose-CSF transport could be demonstrated.

Permeability of porcine nasal mucosa correlated with human nasal absorption

The Ussing chamber diffusion system was used as a model to study the apparent permeability across porcine nasal mucosa of eight drugs and molecules with different physicochemical characteristics, namely insulin, lidocaine, nicotine, PEG 4000, propranolol, sumatriptan, melagatran and an amino diether. A weak correlation was found between the apparent permeability coefficients and the corresponding literature data on the fraction absorbed after nasal administration in humans. In the case of passively transported drugs, a closer correlation was found than for the substances where other mechanisms such as carrier-mediated transport or possible efflux were involved. Factors influencing the correlation between in vitro and in vivo data are discussed and the importance of electrophysiological control of the viability status of the excised mucosa is emphasised. Although caution has to be exercised in view of the limitations of the in vitro system, it seems to be a useful tool when evaluating different factors influencing permeability of nasal mucosa.