Depo Provera

Depo-Provera Birth Control Injection (medroxyprogesterone acetate) is the U.S. brand name of a birth control product manufactured by Pfizer Inc. It is a hormonal birth control method containing the pregnane (17α-hydroxyprogesterone derivative) progestin medroxyprogesterone acetate, without oestrogen, and is administered to women in the form of an intramuscular injection once every 11 to 13 weeks. Depo-Provera causes the ovaries to stop releasing eggs.

Mechanism of action

The mechanism of action of progestin-only contraceptives depends on the progestin activity and dose. High dose progestin-only contraceptives, such as the injectable Depo-Provera, completely inhibit follicular development and ovulation. Like all progestin-only contraceptives, Depo-Provera also has a progestogenic effect of increasing cervical mucus viscosity, thereby inhibiting sperm penetration. In anovulatory cycles using progestin-only contraceptives, the endometrium is thin and atrophic. If the endometrium was also thin and atrophic during an ovulatory cycle, this could theoretically interfere with implantation of a blastocyst (embryo).

Benefits

   

  • Extremely effective at preventing pregnancy.

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  • Unlike many other birth control methods, Depo does not require daily action. The only continuing action is to book subsequent follow-up injections every twelve weeks, and to monitor side effects to insure that they do not require medical attention.

       

  • Depo-Provera reduces the risk of endometrial cancer by 80%.  The reduced risk of endometrial cancer in Depo-Provera users is thought to be due to both the direct anti-proliferative effect of progestogen on the endometrium and the indirect reduction of oestrogen levels by suppression of ovarian follicular development.

       

  • Use of Depo may offer more privacy to some users than other forms of contraception, such as pills, condoms, and diaphragms, as there are no material objects which must be kept at home to continuously provide contraceptive protection.

    Depo and Menstruation

    Most women using Depo Provera experience disruption of menstrual bleeding patterns, something which has been called "menstrual chaos." Altered menstrual bleeding patterns include irregular or unpredictable bleeding or spotting, or rarely, heavy or continuous bleeding. After continuous use, fewer experience irregular bleeding and more experience amenorrhea. By month 12 amenorrhea was reported by 55% of women, and by month 24 amenorrhea was reported by 68%. Some women may prefer amenorrhea. (But it is not a guaranteed effect of Depo.) Amenorrhea induced by birth control products has not been studied. According to Jerilynn Prior, M.D., professor of endocrinology and metabolism at the University of British Columbia in Vancouver, and board member for the Society for Menstrual Cycle Research,"the most important thing to emphasize about menstrual suppression is that the long-term effects are simply unknown," and "allowing the one vital sign unique to women to go unmonitored...could ultimately lead to an enormous uncontrolled experiment with a woman's health."

    Depo and Pregnancy/Breastfeeding

    Depo Provera may be used by breast-feeding mothers. Heavy bleeding is possible if given in the immediate postpartum time and is best delayed until six weeks after birth. It may be used within five days if not breast feeding. While a small study "showed no significant difference in birth weights or incidence of birth defects" and "no significant alternation of immunity to infectious disease caused by breast milk containing DMPA", a possible subgroup of babies with 75% higher incidence of infectious disease was seen in mothers who started Depo Provera at 2 days postpartum. A larger study with longer follow-up concluded that "use of DMPA during pregnancy or breastfeeding does not adversely affect the long-term growth and development of children". This study also noted that "children with DMPA exposure during pregnancy and lactation had an increased risk of suboptimal growth in height," but that "after adjustment for socioeconomic factors by multiple logistic regression, there was no increased risk of impaired growth among the DMPA-exposed children." "Unfavorable socioeconomic factors" may therefore result in suboptimal height for DMPA-exposed children. The study also noted that effects of DMPA exposure on puberty require further study, as so few children over the age of 10 were observed.

    Disadvantages & side effects

       

  • Recent research has shown that Depo-Provera significantly decreases bone density in women, as compared with others in the same age group (see below). The manufacturer of Depo Provera does not advise prolonged use (longer than two years). This loss of BMD is of particular concern during adolescence and early adulthood, a critical period of bone accretion. It is unknown if use of Depo Provera by younger women will reduce peak bone mass and increase the risk for osteoporotic fracture in later life.

       

  • Depo Provera is associated with increased risk of breast cancer, particularly in women under 35, and current or recent users.

       

  • For some women, Depo-Provera may have a number of potentially intolerable side effects, including loss of interest in sexual activity, infertility, severe headaches, constant bleeding (metrorrhagia), weight gain, panic attacks, muscle pain, heart palpitations, pain during sex, acne, irregular menstrual bleeding, abdominal cramps, dizziness, weakness or fatigue, leg cramps, nausea, vaginal discharge or irritation, breast swelling and tenderness, bloating, swelling of the hands or feet, backache, depression,insomnia, pelvic pain, no hair growth or excessive hair loss, rash, hot flashes,joint pain, convulsions, jaundice, urinary tract infections, allergic reactions, fainting, paralysis, deep vein thrombosis, and pulmonary embolus.

       

  • Return to fertility may be slow. Fifty percent of women may be able to conceive in about 10 months from the last injection, but fertility may be totally suppressed in some women for up to 18 months or more.

       

  • Depo is not immediately reversible. In the case of intolerable side effects, they must be endured for three months or more.

       

  • Infants born to women exposed to Depo during pregnancy in one study had an 80% greater chance of dying in the first year of life.

       

  • A study of 819 women in one city found an association between using Depo-Provera and higher incidence of chlamydia and gonorrhea.

       

  • Depo Provera may simultaneously increase susceptibility to the herpesvirus and decrease immune response to the herpesvirus.

       

  • Depo Provera exacerbates glutamate excitotoxicity, which may render users more vulnerable to "neurodegenerative insult"--a greater likelihood of such diseases as fibromyalgia.

       

  • One reason for people not choosing this method of contraception is hypodermic needle phobia.

    B

    lack box warning

    While it has long been known that Depo-Provera causes bone loss, it has recently been discovered that the osteoporotic effects of the injection grow worse the longer Depo-Provera is administered, last long after the injections are stopped, and may be irreversible. For this reason, on November 17, 2004 the United States Food and Drug Administration and Pfizer agreed to put a "black box warning" on Depo-Provera's label.

    However, the WHO (World Health organisation)-- which provided Depo-Provera to developing countries when the US FDA refused to approve it for safety reasons pertaining to breast cancer--advises that the use of Depo Provera should not be restricted. One cohort study has shown that BMD loss may be reversible within 30 months of discontinuation of DMPA. At least one of the authors of the study, AZ Lacroix, is a consultant for Pfizer. The School of Public Health at the University of Washington, where the study was conducted, receives financial support from Pfizer. And Pfizer continues to advise in the Depo product insert that bone loss caused by Depo Provera may not be reversible.

    Contraindications

    Women with the following conditions should not use Depo Provera:

       

  • stroke

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  • currently pregnant

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  • current or past breast cancer

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  • liver problems or liver disease

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  • blood clots

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