Contraceptive transdermal delivery of hormones

1. A method of preventing pregnancy in a woman that comprises, during a treatment cycle based on a calendar month:

(A) transdermally administering a contraceptively effective amount of a progestin and an estrogen during a three-week treatment interval by successive applications of transdermal hormone delivery devices; and

(B) transdermally administering low dose progestin and low dose estrogen throughout rest interval that is the balance of the calendar month by application of a transermal hormone delivery device,

wherein

the progestin is levonorgestrel;

the amount of the progestin delivered during the treatment interval results in an average levonorgestrel serum concentration of at least 750 pg/ml;

the amount of the progestin delivered during the rest interval results in an average levonorgestrel serum concentration that is 25% to 75% the amount of the progestin delivered during the treatment interval;

the estrogen is ethinyl estradiol;

the amount of the estrogen delivered during the treatment interval results in an average ethinyl estradiol serum concentration of at least 15pg/ml; and

the amount of the estrogen delivered during the rest interval results in an average ethinyl estradiol serum concentration that is 25% to 75% the amount of the estrogen delivered during the treatment interval;

whereby the woman experiences menstruation with attenuated symptoms of menstruation during the rest interval.

2. The method of claim 1 , comprising:

(A) transdermally administering the contraceptively effective amounts of the progestin and the estrogen during the treatment interval by successive weekly applications of three transdermal hormone delivery devices, one for each week of each treatment interval; and

(B) transdermally administering the low dose progestin and low dose estrogen throughout the rest interval by application of a transdermal hormone delivery device during the rest interval.

3. The method of claim 2 , wherein each device worn during the treatment interval provides a peak serum hormone concentration level after the patch is applied and a trough serum concentration level at the time the patch is removed, the peak levels being at least about 1.25 times trough levels.

4. The method of claim 2 , wherein the rest interval device has the same hormone concentrations as the treatment interval device but is a fraction of the size of the treatment interval device.

5. The method of claim 2 , wherein the rest interval device is the same size as the treatment interval device but comprises reduced hormone amounts compared to the treatment interval device.

6. The method of claim 2 , wherein: (a) the amount of levonorgestrel delivered during the rest interval is ¼, ⅓, ½, 2/3 or 3/4 of the amount delivered from each treatment interval device during the treatment interval; and (b) the amount of ethinyl estradiol delivered during the rest interval is ¼, ⅓, ½, 2/3 or 3/4 of the amount delivered from each treatment interval device during the treatment interval.

7. The method of claim 6 , wherein the rest interval device is worn during all of the rest interval.