Biphasic and triphasic oral contraceptives vary the dosage of progestin, and sometimes of estrogen, in two or three phases and are theoretically less likely to disrupt normal metabolic patterns. But no clinical advantage has been demonstrated unambiguously for multiphasic preparations. Progestin-only oral contraceptives have a higher failure rate and a higher incidence of ectopic pregnancy, and they may cause irregular bleeding. They are principally recommended for smokers older than 35 or women who cannot take estrogen.
Whats new
Two new progestins, desogestrel and norgestimate, are now available. These new synthetic progestins are formulated in monophasic and triphasic packages with ethinyl estradiol. A third progestin, gestodene, will be available in the very near future.
These new progestins have been used in Europe for many years and have accumulated an excellent database. They offer the possibility of fewer androgenic effects, including less acne, and a more favorable impact on the cholesterol and lipid profile. The new progestins have a longer half-life, so they are more forgiving if the patient forgets to take a pill. And their minimal metabolic effects make them a good choice for women with diabetes mellitus or an elevated risk of cardiovascular disease.
Efficacy and safety
Pregnancy rates are very low with all oral contraceptives. They offer essentially 100 protection--as long as the pills are taken regularly--and are relatively safe for long-term use.
Advantages
Although oral contraceptives have many benefits, the most important is probably protection against ovarian and endometrial cancers. A woman who takes birth control pills for at least 10 years reduces her risk of ovarian cancer by as much as 80. Given the high mortality rate for ovarian cancer, this is a major advantage. Oral contraceptives also decrease the incidence of fibrocystic breast disease.
Oral contraceptives can regularize the menstrual cycle--an advantage for premenopausal women--correct heavy bleeding, and diminish menstrual cramps. They can increase bone mass, decrease anemia among women with a heavy menstrual flow, and reduce the risk of pelvic inflammatory disease. The pill may also be used as a backup contraceptive for couples using nonhormonal methods of birth control.
Disadvantages
Spotting may occur with oral contraceptives. Occasional nausea, other hormonal side effects, and the need to take a daily pill are also perceived disadvantages. Thromboembolic disease occurs in 1 of every 100,000 patients who use oral contraceptives.
(Hassle-free methods of contraception Luigi Mastroianni Jr. and J. Courtland Robinson Patient Care 1995-03-15295, 46(11))
The injection
Contraceptive injections contain the hormone progestogen. There are two types of injection--Depo-Provera which is effective for 12 weeks and Noristerat which is effective for eight weeks. Given as a deep intramuscular injection, progestogen is released slowly into the body and works by inhibiting ovulation, thickening the cervical mucus and thinning the endometrium preventing implantation.
Advantages Both are over 99 per cent effective. Depo-Provera is the most commonly used injection in the UK. Fertility may take up to a year to return to normal on stopping Depo-Provera.
Disadvantages Periods can stop, be irregular or prolonged. Irregular bleeding can also continue for some months after stopping Depo-Provera. Side-effects include headaches, acne, breast tenderness, changes in mood and libido. Some women put on weight with Depo-Provera. Women need aware that any side-effects they experience may continue for sometime after the injection is stopped.
Using Depo-Provera can cause a loss of bone mineral density (BMD) in young women under 19 years of age who have not reached their peak bone mass and long-term users (defined as two years or more). This is not normally a problem as the bone replaces itself once the injection is stopped.
(National Collaborating Centre for Womens and Childrens Health 2005).
However, women who are already at risk of developing osteoporosis are normally advised to use another method of contraception and young women should consider all other suitable methods first.
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