The use of contraception has increased tremendously worldwide. Birth control methods that can be injected may contain two hormones, a progestin and an oestrogen. The use of combined injectable contraceptives (CICs) is a highly efficient, reversible method for preventing pregnancy. One main advantage is that it can be stopped when a woman wants to be pregnant.
The most preferred contraceptives in low-income countries are those that do not change the rhythm of the menstrual cycle. Absence or suppression of normal menstrual flow, i.e. amenorrhoea raises a suspicion of pregnancy or induction of menopause; excessive bleeding may interfere with sexual relations. Thus a contraceptive that causes either of these loses acceptability. Compliance with the requirement of taking a birth control pill daily is low in under-resourced settings where many women lack formal education, this is where CICs score. CICs offer the advantage of preserving a regular bleeding pattern and there is no need to remember to take the pill daily.
Progestin-only contraceptives have troublesome side-effects. They produce a thin endometrium (lining of the uterus) that can bleed. With an oestrogen added to the contraceptive, this gets corrected as it builds up endometrium and thus normal bleeding patterns can be attained. When CICs are taken in a cyclical manner, bleeding occurs when the oestrogen is withdrawn, and this mimics a typical menstrual period. Monthly doses produce withdrawal bleeding as they allow serum oestrogen levels to fall. Bleeding normally occurs when serum oestrogen and progesterone levels fall and the endometrium is shed.CICs feature a rapid return to fertility and also offer confidentiality (unlike pills).
Unfortunately authentic studies that evaluated the contraceptive efficacy, bleeding patterns, discontinuation,user preferences, and side effects of combination injectable contraceptives were scanty. Computerized databases for randomized controlled trials were hence searched for. Nine combination injectable formulations were studied. The results were published in the Cochrane Database of Systematic Reviews.
Two notable CICs include:
• Depot medroxyprogesterone acetate (DMPA) 25 mg plus estradiol cypionate (E2C) 5mg
• Norethisterone enanthate (NET-EN) 50 mg plus estradiol valerate (E2V) 5 mg.
Among the two, NET-EN 50 mg plus E2V 5 mg resulted in less overall early discontinuation and less discontinuation due to amenorrhea or prolonged bleeding. This CIC also had more cyclical (regular) bleeding.
Discontinuation can indeed be viewed as a measure of acceptability of the method. But the results should be treated with caution. Acceptability depends on many factors. CICs definitely offer advantages over other hormonal contraceptive measures as we have already seen. Future researches should target interventions to improve compliance. Reference:
Gallo MF, Grimes DA, Schulz KF, d'Arcangues C, Lopez LM. Combination injectable contraceptives for contraception.Cochrane Database of Systematic Reviews
2005, Issue 3. Art. No.: CD004568. DOI: 10.1002/14651858.CD004568.pub2.