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Recommendations for Contraceptive Use |
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Progestin-Only Injectables |
Q.8. How much grace period is there
for subsequent progestin-only injections?
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a) For DMPA (150 mg), on a
3-month schedule, it is acceptable to give the next injection:
- up to 2 weeks late and possibly up to 4 weeks late
depending on the population, or
- up to 4 weeks early though not ideal.
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a) DMPA blood levels
consistently remain high enough to maintain contraceptive effect through 3 months
post-injection and the pregnancy risk at 4 months post-injection is extremely
low (and DMPA has no known teratogenic effects, although one study has suggested in
utero DMPA exposure may possibly increase risk of low birth weight babies).
- Mishell DR. Long-acting contraceptive
steroids: Postcoital contraceptives and antiprogestins, in Mishell DR, Davajan V, Lobo RA
(eds). Infertility, Contraception, and Reproductive Endocrinology, 3rd edition.
Boston, Blackwell Scientific Publications, 1991, pp 872-894.
- Bracken MB. Oral contraceptives and
congenital malformations in offspring: A review and meta-analysis of the prospective
studies. Obstetrics and Gynecology 1990;76:552-557.
- Pardthaisong T, Gray RH. In utero
exposure to steroid contraceptives and outcome of pregnancy. American Journal of
Epidemiology 1991;134(8):795-803.
- Schwallie PC, Assenzo JR. The effect
of Depo-medroxyprogesterone acetate on pituitary and ovarian function, and the return of
fertility following its discontinuation: A review. Contraception
1974;10(4):181-202.
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b) For NET-EN, on a 2-month
schedule, it is acceptable to give the next injection:
- up to 1 week late and possibly up to 2 weeks late depending
on the population, or
- up to 2 weeks early though not ideal.
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b) For NET-EN, blood levels
remain high enough to maintain contraceptive effect through 74 days (2 months plus 2
weeks).
- Hall PE. Long-acting injectable
formulations, in Diczfalusy E, Bygdeman M (eds). Fertility, Regulation Today and
Tomorrow. New York, Raven Press, 1987, p 119.
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| c) If a client comes in after
the grace period, advise her that delays in obtaining progestin-only injections increase
the risk of pregnancy and in utero exposure to the progestin-only injectable. It is
acceptable to give the progestin-only injection if you can be
reasonably sure she is not pregnant. Although there is good reason to believe the
effect on cervical mucus will promptly provide contraceptive protection within 24 hours,
it may be prudent to consider a back-up method for up to 7 days. Reschedule the next
injection (for 3 months with DMPA or 2 months with NET-EN). |
c) It has been shown that the
time it takes for progestin levels to be insufficient for contraception may vary somewhat
from population to population. Studies show that Thai women seem to metabolize DMPA
rapidly. Additionally, weight has also been shown to have an independent influence on
progestin levels (in heavier women the contraceptive effects last longer).
- Garza-Flores J, Hall PE,
Perez-Palacios G. Long-acting hormonal contraceptives for women. Journal of Steroid
Biochemistry and Molecular Biology 1991;40(4-6):697-704.
- Fotherby K, Koetsawang S, Mathrubutham
M. Pharmacokinetic study of different doses of Depo Provera. Contraception
1980;22(5):528-536.
- Bassol S, Garza-Flores J, Cravioto MC,
Diaz-Sanchez V, Fotherby K, Lichtenberg R, Perez-Palacios G. Ovarian function following a
single administration of Depo-medroxyprogesterone acetate (DMPA) at different doses. Fertility
and Sterility 1984;42(2):216-222.
- World Health Organization. A
multicentered phase III comparative clinical trial of depot-medroxyprogesterone acetate
given three-monthly at doses of 100 mg or 150 mg: I. Contraceptive efficacy and side
effects. Contraception 1986;34(3):223-235.
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