Are even longer cycles feasible?
Given the success of 84-7I and 84-7EE regimens, investigators have studied the clinical effects of 168- and 365-day cycles.
Recently, a randomized clinical trial compared the reproductive endocrine effects of six cycles of a classic 21-7 formulation against a 168-day continuous active pill regimen.3 Sixty-two women were randomized to treatment for six cycles with either the 21-7 regimen with 7 days of inert pills at the end of each cycle or 168 consecutive days of estrogen–progestin pills (ethinyl estradiol, 20 mcg, plus norethindrone acetate, 1 mg).
Vaginal bleeding was the primary outcome measured; secondary outcomes were endogenous hormone production, pelvic ultrasonographic (US) measures of the ovary, and quality-of-life measures. Days of vaginal bleeding were similar in both groups. Over the 168 days of the study, the mean number of reported days of bleeding was 35 in the 28-day cyclic regimen group and 32 in the 168-day continuous regimen group. Reported days of moderate and heavy bleeding were greater in the cyclic regimen group (11 days) than in the continuous regimen group (5 days) (P < .005). Breakthrough bleeding was reported by more women in the continuous treatment group (13%) than in the cyclic group (7%) (P=.03).
Other findings are also noteworthy:
- Overall, subjects on continuous therapy reported less severe menstrual pain
- A decrease in the urinary estrone glucuronide level with continuous treatment was, overall, 51% greater than it was with cyclic treatment
- Pelvic US demonstrated that continuous treatment was associated with fewer ovarian follicles and a smaller ovarian volume
- Pregnanediol glucuronide measurements indicated that “escape” ovulation occurred more often in the 21-7 cyclic group.
Taken together, these findings indicate that continuous therapy produced more pronounced ovarian suppression than 21-7 cyclic therapy.
Leave the work of Rock and Pincus behind?
One of the acknowledged great inventions of the 20th century isn’t making the leap into the 21st century. The time has come to ask: “Why do we continue to prescribe 21-7 OCs?” For women who desire a monthly withdrawal bleed, it’s likely preferable to have our prescribing practices evolve to make greater use of 24-4 formulations. For all others, consider an extended-cycle regimen.