Effect of dose on the absorption of estradiol from a transdermal gel

Assessment of estrogen exposure from transdermal estradiol gel therapy with a dried urine assay

Transdermal estradiol gel is a commonly used menopausal hormone therapy. In research studies investigating the pharmacokinetics and clinical utility of transdermal estradiol gels, serum is often used to measure estradiol levels. Serum results only represent a moment in time during phlebotomy and thus provide little information and allow for limited inference unless serial measurements are performed. In contrast, dried urine may provide a representation of serum estradiol levels over a longer period of time, while also being non-invasive and easier to collect. The primary aim of this study was to evaluate a dried urine method to determine if it may be a viable option for evaluating estrogen exposure resulting from transdermal estradiol gel use. A secondary aim was to explore differences in the urinary estrogen profiles of premenopausal women on no therapy and postmenopausal women who were either on transdermal estradiol gel therapy or no therapy at all. The results of this study demonstrated that the expected dose-proportional changes in estrogen exposure can be observed in the urinary estrogen profile using a GC-MS/MS dried urine assay. The GC-MS/MS assay also showed the differences in the urinary estrogen profiles of premenopausal women, postmenopausal women on estrogen replacement therapy, and postmenopausal women on no therapy.

Hormone replacement therapy in menopausal women: Past problems and future possibilities

Oral administration of conjugated equine estrogens (CEE) with and without the synthetic progestin medroxyprogesterone acetate (MPA) in postmenopausal women is associated with side-effects that include increased risk of stroke and breast cancer. The current evidence that transdermal administration of estradiol may provide a safer alternative to orally administered CEE is reviewed. Transdermally administered estradiol has been shown to be an efficacious treatment for hot flushes possibly without the increase in blood clotting that is associated with administration of oral CEE. Further, natural progesterone may have a more beneficial spectrum of physiological effects than synthetic progestins. The substantial differences between CEE compared with estradiol and estriol, as well as the differences between synthetic MPA and natural progesterone, are detailed. Estriol is an increasingly popular alternative hormone therapy used for menopausal symptoms. There is evidence that estriol, by binding preferentially to estrogen receptor-beta, may inhibit some of the unwanted effects of estradiol. New clinical trials are needed to evaluate the safety and efficacy of topically or transdermally administered combinations of estradiol, estriol and progesterone. Future studies should focus on relatively young women who begin estrogen supplement use near the start of menopause.

Evaluation of brain-targeting for the nasal delivery of estradiol by the microdialysis method

The uptake of estradiol into the cerebrospinal fluid (CSF) after intranasal and intravenous administration in rats was investigated to study whether direct nose-CSF transport of estradiol exits or not. Animals received 0.48 mg kg(-1) estradiol randomly methylated beta-cyclodextrin (RAMEB) inclusion complex intranasally and intravenously. Following nasal delivery, estradiol reached a C(max) value (mean+/-S.D.) in plasma (26.70+/-11.37 ng ml(-1)) and CSF (54.76+/-32.84 ng ml(-1)) after 20 min in each case, while after intravenous infusion, estradiol reached a C(max) value in plasma (170.08+/-64.67 ng ml(-1)) and CSF (26.48+/-11.34 ng ml(-1)) at 5 min and 60 min, respectively. The AUC(CSF)/AUC(plasma) ratio (1.60+/-0.67) after intranasal delivery differed significantly from the ratio (0.61+/-0.16) observed after intravenous infusion (P<0.05). All these results indicate that estradiol is transported into CSF via olfactory neurons, and, hence, there is a direct transport route from the nasal cavity into the CSF for estradiol.

The effects of transdermal estrogen therapy on bone mass and turnover in early postmenopausal smokers: A prospective, controlled study

OBJECTIVE

The purpose of this study was to investigate whether smoking reduces the effects of transdermal estrogen replacement therapy on bone.

STUDY DESIGN

One hundred forty-eight women (0.5-5 years after menopause, aged 46-58 years) completed the study. Smokers were assigned randomly to receive either 1.0 mg (n=32 women) or 1.5 mg (n=31 women) of transdermal estradiol in gel daily, and nonsmokers (n=46 women) were assigned to receive 1.0 mg of transdermal estradiol for 2 years. The control group consisted of 17 smokers and 22 nonsmokers. Bone mineral density was measured by dual-energy x-ray absorptiometry. Bone turnover was assessed by measurements of urinary aminoterminal telopeptide of type I collagen and serum aminoterminal propeptide of type I procollagen.

RESULTS

Lumbar spine bone mineral density increased similarly in smoking (+3.6%) and nonsmoking (+2.6%) estrogen users (P<.0001 to a decrease of 2.5% in the control group). Femoral neck bone mineral density increased 2.2% to 2.4% in smoking and nonsmoking estrogen users but decreased 0.2% in control subjects (P<.05). Urinary aminoterminal telopeptide of type I collagen decreased similarly in all estrogen-using groups (P<.05 to control group), but serum aminoterminal propeptide of type I procollagen decreased more in smoking than in nonsmoking estrogen users (P=.006). Serum 25-hydroxyvitamin D was 20% lower (P=.004) in smokers than in nonsmokers.

CONCLUSION

Transdermal estrogen treatment protects smoking women as effectively as nonsmokers from osteoporosis. Smoking worsens the vitamin D state of postmenopausal women.

Active influx transport is mediated by members of the organic anion transporting polypeptide family in human epidermal keratinocytes

Normal human epidermal keratinocytes have been shown to express a cell-type-specific pattern of extrahepatic cytochrome P450 enzymes and efflux transport proteins showing that these cells metabolize and excrete a variety of xenobiotics. Recently transport proteins involved in the uptake of xenobiotics have been detected and here we analyzed the mRNA and protein expression profiles and functional activities of these proteins in human keratinocytes in comparison to primary liver cells. The transporters studied included the subtypes A, B, C, D, and E of the organic anion transporting polypeptide (OATP) family, which are responsible for the uptake of various anionic and neutral molecules and especially organic cations - including drugs. Constitutive expression of OATP-B, OATP-D, and OATP-E was shown for the first time in normal human epidermal keratinocytes on a molecular level using reverse transcription polymerase chain reaction and northern blot analysis, as well as in human skin tissue shown by tissue blot hybridization and immunohistochemistry. Expression of OATP-A and OATP-C was not detected in any of the keratinocyte samples. In contrast, liver tissue showed a significant expression of OATP-A and OATP-B as well as OATP-C, a weak expression of OATP-D, and no expression of OATP-E. These data revealed that normal human epidermal keratinocytes express a specific profile of transporters involved in drug influx. Using a newly developed uptake-transport assay, uptake of known and well-characterized OATP substrates like estradiol-17beta-glucuronide and estrone sulfate was inhibited in normal human epidermal keratinocytes by specific inhibitors such as taurocholate, verifying the functional capacity of the expressed OATPs. Human dermal fibroblasts seem to have a lower influx transport activity for estradiol-17beta-glucuronide, which correlates with the immunohistologic data. Even though the substrate specificity of the OATP isoforms is only partially known until now, our findings support the concept that uptake of large organic cations like drugs in keratinocytes is an active transport process mediated by members of the OATP family.