Long-term contraception by steroid-releasing implants. II. A preliminary report on long-term contraception by a single silastic implant containing norethindrone acetate (ENTA) in women
Bhatnagar, S.; Srivastava, U.K.; Takkar, D.; Chandra, V.L.; Hingorani, V.; Laumas, K.R.
Contraception 11(5): 505-521
1975
ISSN/ISBN: 0010-7824 PMID: 1139938 DOI: 10.1016/0010-7824(75)90105-5Document Number: 342014
A preliminary report on the long-term contraceptive effectiveness and acceptability of a single subdermal silastic implant containing norethindrone acetate (ENTA) is presented. The 4 types of implants used varied in length, wall thickness, and amount of ENTA; implant A contained 20-25 mg ENTA, implant B contained 30-35 mg ENTA, implant C contained 45-50 mg ENTA as was longer than all the other implants, and implant D contained 40 mg ENTA and had a greater wall thickness than all the other implants. 213 women volunteers received a single implant and were followed for a total of 909 cycles. 2 of 13 women receiving implant A, 2 of 39 women receiving implant B, 3 of 76 women receiving implant C, and none of the 85 women receiving implant D became pregnant. Implant D had the longest expected life-span (10 months). Menstrual irregularities were fewest with implants A (23%) and D (20%), and greatest with implant C (42%). there were no complaints of nausea, insomnia, tender breasts, or loss of libido. 4 patients with implant B and 6 patients with implant C had the capsules removed for medical reasons. More detailed studies of implant D are in progress.