Tamoxifen for the Treatment of Unfavorable Bleeding in Contraceptive Implant Users

Nearly all of the 3 million unintended pregnancies in the United States each year result
from inconsistent or non-use of contraception. Increasing use of the most effective methods
of contraception will reduce unintended pregnancies and their social, medical and economic
consequences. The contraceptive etonogestrel implant (ENG implant) is 20 times more
effective at pregnancy prevention than oral contraceptive pills, but it has bleeding side
effects that make it unappealing for many women. Tamoxifen, a selective estrogen receptor
modulator (SERM) used most commonly for adjuvant treatment of breast cancer, has previously
been shown to dramatically reduce bleeding in users of an older levonorgestrel-based
contraceptive implant (Norplant tm). It has not been studied in newer progestin-based
methods such as the ENG implant. If tamoxifen could stop bleeding in users of the ENG
implant, it would give patients and physicians a valuable option for management of
progestin-induced irregular bleeding. This research project will test the effectiveness of
tamoxifen taken on an as-needed basis to treat abnormal bleeding in ENG implant users. If
tamoxifen can be established as an effective treatment for frequent or prolonged bleeding,
it will increase the acceptability of the ENG implant, increase its use and reduce
unintended pregnancies. This is the first project to evaluate tamoxifen for treatment of
unfavorable bleeding in users of the ENG contraceptive implant.

Inclusion Criteria:

- Current user of the etonogestrel implant (Nexplanon, Implanon) for at least one month

- Experiencing bleeding episodes more frequently than every 24 days, or a single
episode of bleeding lasting longer than 14 days

- English or Spanish speaking

- Planning to continue implant use for six months

- Access to a cell phone that can accept and send text messages

Exclusion Criteria:

- Postpartum within six months

- Post-abortion within six weeks

- Pregnant

- Breast-feeding

- Undiagnosed abnormal uterine bleeding pre-dating placement of contraceptive implant

- Bleeding dyscrasia

- Anticoagulation use

- Active cervicitis

- Allergy to tamoxifen

- History of venous thromboembolism

- Current or past breast or uterine malignancy

- Use of medication contraindicated with tamoxifen (coumadin, letrozole, bromocriptine,
rifampicin, aminoglutethimide, phenobarbital)