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Recommendations for Contraceptive Use |
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NORPLANT® Implants |
Q.10. Are NORPLANT®
Implants less effective in heavier women? Is there a weight limit for the use of NORPLANT®
Implants?
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| Increased weight does not appear
to substantially diminish the effectiveness of soft tubing NORPLANT® Implants.
In contrast, NORPLANT® Implants made with older hard tubing are less effective
in women weighing more than 60 kg. However, hard tubing NORPLANT® Implants
have not been manufactured since 1992. |
There is not a significant
effect of user's weight on the contraceptive effectiveness of soft tubing NORPLANT®
Implants, the only kind of implants now being manufactured. Heavy women using hard tubing
NORPLANT® Implants experience a higher pregnancy risk than women using soft
tubing because less hormone diffuses out through the hard tubing. NORPLANT®
Implants made with hard tubing demonstrated a cumulative five year failure rate of 4.5% in
women who weighed 60 to 69 kg. In contrast, NORPLANT® Implants made with soft
tubing demonstrated a cumulative five year failure rate of 1.5% in women who weighed 60 to
69 kg. This difference between hard and soft tubing is more pronounced for heavier women.
Women who weighed more than 70 kg had a five year cumulative failure rate of 9.3% for hard
tubing NORPLANT® Implants and 2.4% for soft tubing use. Although recent data from China reported cumulative five year
failure rates for hard tubing use which were lower than the failure rates reported above,
an increased number of pregnancies was still associated with increasing weight - 1.46
pregnancies (over five years) per 100 women weighing 50 to 59 kg, 2.08 pregnancies (over
five years) per 100 women weighing 60 to 69 kg, and 4.58 pregnancies (over five years) for
women weighing 70 kg or more. |
Cumulative Five Year Failure Rate for NORPLANT® Implants
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Pooled Data from Clinical
Trials, 19881 |
Data from China, 19952 |
| User's Weight |
Soft Tubing |
Hard Tubing |
Hard Tubing |
| 60 to 69 kg |
1.5% |
4.5% |
2.08% |
| 70 kg or more |
2.4% |
9.3% |
4.58% |
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- Sivin I. International experience with
NORPLANT and NORPLANT-2 contraceptives. Studies in Family Planning 1988;19(2):81-94.
- Gu S, Sivin I, Du M, Zhang L, Ying L,
Meng F, et al. Effectiveness of Norplant Implants through seven years: a large-scale study
in China. Contraception 1995;52(2):99-103.
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| b) There are no known weight
limits for NORPLANT® Implants use. |
b) Previous concerns about a 70
kg weight limit apply only to the older, harder tubing. Currently, only the new softer
tubing is in use. |
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