[Code of Federal Regulations]
[Title 21, Volume 4]
[Revised as of April 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR201.301]

[Page 59]
 
                        TITLE 21--FOOD AND DRUGS
 
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN 
                                SERVICES
 
PART 201--LABELING--Table of Contents
 
  Subpart G--Specific Labeling Requirements for Specific Drug Products
 
Sec. 201.301  Notice to manufacturers, packers, and distributors of estrogenic hormone preparations.

    Some drug preparations fabricated wholly or in part from estradiol 
and labeled as to potency in terms of international units or in terms of 
international units of estrone activity have been marketed. The 
international unit of the estrus-producing hormone was established by 
the International Conference on the Standardization of Sex Hormones at 
London, England, on August 1, 1932. This unit was defined as ``the 
specific estrus-producing activity contained in 0.1 gamma (=0.0001 mg.) 
of the standard'' hydroxyketonic hormone found in urine (estrone). The 
International Conference declared that it did not recommend the 
determination of the activity of nonhydroxyketonic forms of estrogenic 
hormones in units of estrone because of the varying ratios between the 
activity of such nonhydroxyketonic estrogenic hormones and estrone, when 
measured by different methods on test animals. There is no international 
unit for measuring the activity of estradiol and no accepted 
relationship between its activity and that of estrone, either in test 
animals or in humans. The declaration of potency of estradiol in terms 
of international units or in terms of international units of estrone 
activity is therefore considered misleading, within the meaning of 21 
U.S.C. 352(a). The declaration of the estradiol content of an estrogenic 
hormone preparation in terms of weight is considered appropriate.