Bleeding patterns with low-dose, monophasic oral contraceptives.
Cycle control over 12 months with low-dose oral contraceptives (OCs) was analyzed using calendars of bleeding on pill-taking days 1 through 21 (intermenstrual bleeding; IMB). One preparation contained 0.5 mg norethindrone and 0.035 mg ethinyl estradiol (NET + EE), the other 0.3 mg norgestrel and 0.03 mg ethinyl estradiol (Ng + EE). Half the subjects had previously used OCs containing greater than or equal to 0.05 mg estrogen (switch-over); the others had not previously used OCs for 2 months or more (fresh). Fresh subjects reported more IMB than switch-over subjects, especially during the first three cycles; IMB decreased over time for both groups. Ng + EE subjects had fewer IMB episodes during the early cycles than NET + EE subjects. Daily incidence of IMB formed a characteristic W-shaped curve in the NET + EE subjects that was most apparent in early cycles.
Edgren
R A
RA
Syntex Laboratories, Inc., Palo Alto, California 94303.
Nelson
J H
JH
Gordon
R T
RT
Keifer
W S
WS
D000293:Adolescent; D000328:Adult; D003278:Contraceptives, Oral, Hormonal / Q000008:administration & dosage / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006801:Humans; D008598:Menstruation / Q000187:drug effects*; D015337:Multicenter Studies as Topic; D009640:Norethindrone / Q000008:administration & dosage / Q000494:pharmacology; D009644:Norgestrel / Q000008:administration & dosage / Q000494:pharmacology; D011897:Random Allocation; D013997:Time Factors
D003278:Contraceptives, Oral, Hormonal; D009644:Norgestrel; D004997:Ethinyl Estradiol; D009640:Norethindrone