***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Three hundred thirteen women participated in an open , multicenter comparison of the incidence of intermenstrual bleeding ( breakthrough bleeding and or spotting )  associated with the use of three triphasic oral contraceptives . Triphasil ( n = 107 ) , containing levonorgestrel and ethinyl estradiol , and Ortho-Novum 7/7/7 ( n = 97 ) and Tri-Norinyl ( n = 109 ) , both of which contain norethindrone and ethinyl estradiol , were administered over four cycles for a total of 1141 cycles . The total incidence of intermenstrual bleeding was significantly lower with Triphasil ( 17.2 % ) than with Ortho-Novum 7/7/7 ( 39.5 % ) or Tri-Norinyl ( 49.0 % ) . The pattern remained the same when findings were analyzed cycle by cycle and for breakthrough bleeding and spotting separately . The incidence of other side effects was comparable for all regimens . Results of this study demonstrate superior cycle control with Triphasil compared with Ortho-Novum 7/7/7 and Tri-Norinyl during the first four cycles of use Oral contraceptives have the highest theoretic efficacy of all reversible forms of contraception , yet in practice they have an actual failure rate equivalent to that of some barrier methods . The efficacy of oral contraceptives depends primarily on patient compliance . So-called " nuisance " side effects , such as intermenstrual bleeding ( breakthrough bleeding or spotting ) , play a major role in their discontinuation . The Triphasic R and omized Clinical Trial compared the incidence of these side effects in three groups of subjects taking NET ( A ) ( Ortho-Novum 7/7/7 ) , LNG ( Tri-Levlen ) , or NET ( B ) ( Tri-Norinyl ) .  Subjects taking NET ( A ) had the highest incidence of intermenstrual bleeding ( 63 % ) followed by NET ( B ) ( 44 % ) and LNG ( 33 % ) . Only the difference between NET ( A ) and LNG attained statistical significance ( p less than 0.030 ) . Control subjects had no breakthrough bleeding and a 4 % incidence of spotting . Further research is warranted to establish the cause of the disparity in the incidence of intermenstrual bleeding among patient groups assigned to the three oral triphasic contraceptives Cycle control was studied comparing the  monophasic oral contraceptive Loestrin with three low-dose phasic preparations ( Triphasil , Ortho 10/11 and Ortho 7/7/7 )  in 391 women of whom 300 completed 6 cycles . Loestrin  subjects had a rate of occurrence ( 31 % of cycles ) for intermenstrual bleeding ( IMB ) comparable to the rates for subjects on the phasic preparations ( 36 % , 37 % and 37 % , respectively ) . Triphasil subjects had lower rates than the Ortho 10/11 and Ortho 7/7/7 subjects ( p less than 0.01 ) in cycle one when all subjects were analyzed and in pre- study users when continuing menstrual flow ( CMF ) episodes were not included as IMB . IMB was a cause for dropping out of the study in 7 % of subjects who were evenly distributed between groups . There were no differences between groups for BTB when perceived by subjects as a side effect . Spotting was perceived as a side effect more often with Ortho 10/11 and Ortho 7/7/7 use than with Triphasil ( p less than 0.01 ) . Loestrin , Ortho 10/11 and Ortho 7/7/7 subjects were more likely to report amenorrhea ( p less than 0.001 ) and less likely to report leg cramps ( p less than 0.01 ) compared to those on Triphasil . Triphasil subjects were less likely to report acne than subjects on Ortho 7/7/7 ( p less than 0.01 ) Four hundred and fifty-eight women were followed for 3,586 cycles in a controlled , r and omized , open trial design ed to compare two biphasic and one triphasic norgestrel/ethinyl estradiol ( ee ) regimens . The three regimens are effective and no pregnancies were reported . Cycle control was good with all three regimens but the incidence of intermenstrual bleeding was higher with the triphasic . With this regimen , total hormonal ingestion is well below the lowest fixed dose norgestrel/ethinyl estradiol preparation ( 300 mcg norgestrel and 30 mcg ee ) in the original 10:1 ratio . It is concluded that the staggering of hormonal doses opens the possibility of contraception with less hormone intake than is possible when a fixed dose regimen is used 
    Output:
    
No important differences emerged , and the frequency of discontinuation due to medical problems was similar with all three pills .
Given that caveat , the biphasic pill containing norethindrone was associated with inferior cycle control compared with the triphasic pill containing levonorgestrel .