Letter to the editor
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CORRESPONDENCE
© 2005 Adis Data Information BV. All rights reserved.
Letter to the Editor In a recent issue of the American Journal of Drug Delivery (Am J Drug Deliv 2005; 3 [1]: 7–16), percutaneous estradiol gel formulations were one of the delivery options reviewed in the publication entitled “Advances in Menopausal Hormonal Therapy Delivery Systems: A Comparative Review”.[1] The article stated that there are currently no estradiol gel formulations approved for use in the US. However, Unimed Pharmaceuticals, Inc. (a wholly owned subsidiary of Solvay Pharmaceuticals, Inc.) received US FDA approval for marketing EstroGel® 1 (estradiol gel) 0.06% in February 2004, and the product has been available for use by prescription since 19 July 2004.[2] Currently, EstroGel® is the only FDA-approved estradiol gel formulation for the treatment of moderate to severe vasomotor symptoms and for moderate to severe symptoms of vulvar and vaginal atrophy associated with the menopause.[3] Also in the publication, the authors state that the rubbing intensity may influence the variability of absorption and patient response. The approved dose for EstroGel® is 1.25g of gel (containing 0.75mg of estradiol) applied once daily (in a thin layer from wrist to shoulder) on one arm. It is not necessary to massage or rub in EstroGel® as it dries quickly – within 2–5 minutes. EstroGel® is available in a metered-dose pump designed to deliver an accurate dose per compression equal to 1.25g of gel, and each container is capable of delivering a total of 64 metered doses.[3] The following pharmacokinetic information is being provided to further supplement the information provided in table II of the
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publication. In a pharmacokinetic study, EstroGel® 1.25g was administered to 24 postmenopausal women once daily on the posterior surface of one arm from wrist to shoulder for 14 consecutive days. Mean maximal serum concentrations of estradiol and estrone on day 14 were 46.4 pg/mL and 64.2 pg/mL, respectively. The time-averaged serum estradiol and estrone concentration over the 24-hour dose interval after administration of EstroGel® 1.25g on day 14 were 28.3 pg/mL and 48.6 pg/mL, respectively.[3] In a previous study, the metabolic clearance rate for estradiol was evaluated in 57 postmenopausal women and found to be 1240 L/ day.[4] Based on the observed average concentration (28.3 pg/mL) and the reported clearance rate for estradiol (1240 L/day), the average estradiol delivery rate per day for EstroGel® given as 1.25g of gel containing estradiol 0.75mg would be 35μg or 0.035 mg/day. Christi Cawood Marsh, Pharm D1 and John J. Brennan, PhD2 1
Medical Information Specialist, Solvay Pharmaceuticals, Inc., Marietta, Georgia, USA 2 Clinical Development and Medical Affairs, Solvay Pharmaceuticals, Inc., Marietta, Georgia, USA
References 1. Moghadam KK, Williams DB. Advances in menopausal hormonal therapy delivery systems: a comparative review. Am J Drug Deliv 2005; 3 (1): 7-16 2. U.S. Food and Drug Administration. CDER Drug and Biologic Approvals for Calenda
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