Comparative trials of low-dose combined oral contraceptives
Edelman, D.A.; Kothenbeutel, R.; Levinski, M.J.; Kelly, S.E.
Journal of Reproductive Medicine 28(3): 195-200
1983
ISSN/ISBN: 0024-7758 PMID: 6854550 Document Number: 510776
2 studies were conducted to assess the rate of side effects among women using combined oral contraceptives (OCs). In the 1st study, women were randomly assigned to Norinyl, Norlestrin, or Ovral for 3 cycles and then switched to 1 of the other 2 OCs or stayed on the same OC. For all 3 OCs, the rates of most side effects declined significantly with the increasing duration of OC use. Cycle control appeared best for women using Ovral. There were some adverse effects due to switching from 1 OC to another. Generally, women who switched to Ovral experienced a decrease in the rate of breakthrough bleeding and those who switched from Ovral experienced an increase in the rate of breakthrough bleeding. Discontinuation rates were similar for users of all 3 OCs. In the 2nd study, women who had used Norinyl or Ovral for at least 3 cycles were randomly assigned to either Brevicon or Lo-Ovral for 6 cycles. The most noticeable effect was a large increase in the proportions of women with breakthrough bleeding; this rate remained above the preswitchover rate even after 6 cycles of either drug. In the initial cycle after crossover, there was an increase in the rate of some side effects. By the completion of the 6th cycle, the rates of side effects were generally lower than those before crossover, with the exception of breakthrough bleeding. Discontinuation rates were similar for users of Brevicon and Lo-Ovral. The results of the study indicate that although women on low-dose OCs report lower rates of certain side effects, breakthrough bleeding occurs more frequently and might adversely affect continuation rates.