A contraceptive subdermal implant releasing the progestin ST-1435: ovarian function, bleeding patterns, and side effects.

OBJECTIVE

To study ovarian function, bleeding patterns, and side effects during the 1-year use of a new modified contraceptive subdermal implant releasing the progestin ST-1435 with a lifetime of 2 years.

DESIGN, PATIENTS: The effect on ovarian function and bleeding patterns of one contraceptive implant releasing the progestin ST-1435 was studied in 26 healthy women who volunteered. Side effects were recorded.

SETTING

The outpatient clinic of the City Maternity Hospital, Helsinki, Finland.

INTERVENTION

One ST-1435 contraceptive implant was inserted subcutaneously into the ventral aspect of left upper arm.

MAIN OUTCOME MEASURES

The women attended the clinic at half-year intervals. Records of bleeding were kept. Blood samples were collected from 5 women before insertion of an implant, from 12 women during the first 5 to 6 weeks of use, and from 10 women during the 6th and 12th month of use. Serum concentrations of ST-1435, progesterone, and estradiol were determined. Side effects were reported.

RESULTS

The study covered 302 woman-months. The implant gave serum concentrations of ST-1435 high enough to inhibit ovulation in all of the 37 analyzed cycles. No pregnancies occurred. Irregular bleeding or spotting was the main event observed, especially during the 1st year of use. One half of the users had irregular cycles. None of the women's implants was removed during 1 year of use because of irregular bleeding. The implant was well accepted and tolerated by the women; no hormonal side effects were reported.

CONCLUSIONS

One single 4-cm subdermal ST-1435 implant with a lifetime of 2 years showed good contraceptive efficacy and led to suppression of ovulation. No hormonal side effects were reported. Irregular bleeding patterns were common but well-tolerated, and the implant had a high continuation rate.