Medical brain notes 42

  Contraception and Sterilization   In the past 15 years several new contraceptive op- I  tions have been introduced in the United States,and several that were available have left the mar-ket for various reasons. Many methods are very reliable,  although no method is effective if it is not used correctly.  The goal of all contraception is obviously to prevent the sperm and oocyte from uniting.  This goal is accomplished by severalmechanisms of action: (1) inhibiting the development and release of the egg (via oral contraceptives, long-acting pro-gesterone injection, or contraceptive patch and ring), or imposing a mechanical, chemical, or temporal barrier between sperm and egg (via condom, diaphragm, sper-micide, natural family planning, and intrauterine contracep-tion). As a secondary mechanism, some methods also alter the ability of the fertilized egg to implant and grow (e.g., intrauterine contraception and postcoital oral contracep-tives). Each approach ...

  FACTORS AFFECTING CHOICE  OF CONTRACEPTIVE METHOD   Although efficacy is important in the choice of contracep-tive methods, other factors to be considered include safety, availability, cost, and personal acceptability to patient and partner. Although we tend to think of safety in terms of sig-nificant health risks, for many patients this also includes the possibility of side effects. For a couple to use a method, it must be accessible and affordable for the patient. How and when the method is used also can determine accept-ability. Options vary from methods that are coitus-depen-dent (barriers) to methods that are placed by a healthcare provider and last for up to 10 years (intrauterine contracep-tion). Some women prefer methods they control. They can choose an oral daily preparation, while others consider the weekly transdermal (contraceptive patch) or the monthly transvaginal (contraceptive ring) forms easier to use suc-cessfully. Other women elect to use a method adm...

  HORMONAL CONTRACEPTIVES   For many women, “birth control” is synonymous with oral contraceptives (OCs) or hormonal contraception. Hormone-dependent choices now also include injectable hormonal preparations, an implantable hormonal rod, con-traceptive patches, hormone-containing intrauterine sys-tems, and contraceptive rings.   Oral Contraceptives   About one-third of all sexually active women in the United States use oral contraceptives, with over one half of young women 20 to 24 years old using these contraceptives.   Hormonal contraceptives have many health benefits, including decreasing a woman’s risk of ovarian and uterine cancer. Although hormonal contraceptive methods are associated with risks, for most women the use of one of these agents is safer than pregnancy.   Hormone-based contraceptives provide the most ef-fective reversible pregnancy prevention available. Method (theoretical) failure rates for oral, transdermal, and trans-vaginal contracept...

  Ring and Patch   The  transdermal contraceptive patch  contains synthetic estrogen and progestin and remains effective for an entire week (Fig. 24.2). The patient should start the patch on the first day of her menstrual period and replace it weekly for 3 weeks. The fourth week is patch-free to allow a with-drawal bleed. Placement on clean, dry skin located on the buttocks, upper outer arm, or lower abdomen is recom-mended. Because of its ease of application and improved compliance, the “method failure” and “patient failure” of the patch are almost identical. Caution should be used when prescribing the patch for women weighing more than 90 kg (198 pounds) because of its decreased efficacy. Side effects and contraindications are similar to the OCs. A complaint specific to the patch, however, includes skin irritation from adhesive residue at the application site.   The  contraceptive vaginal ring  releases a sustained amount of synthetic estrogen and pr...

  Injectable and Implantable Hormonal Contraceptives   Depo medroxyprogesterone acetate  (DMPA) is an in-jectable progestin given in intramuscular or subcutaneous injections every 3 months. It maintains a contraceptive level of progestin for at least 14 weeks, providing a useful “safety” margin in case an injection is not administered within precisely 3 months. The injection should be given within the first 5 days of the current menstrual period, and, if not, a back-up method of contraception is necessary for 2 weeks. DMPA is not a sustained-release preparation, re-lying instead on higher peaks and sustained levels of prog-estin. In addition to thickening of the cervical mucus and decidualization of the endometrium, DMPA also acts by maintaining a circulating level of progestin high enough to block the luteinizing hormone surge and, thus, ovulation. FSH suppression does not occur with DMPA as it does with combination oral contraceptives.   Recently, concerns have bee...

  BARRIER CONTRACEPTIVES   Among the oldest and most widely used contraceptive methods are those that provide a barrier between sperm and egg. These barriers include condoms, diaphragms, and cervical caps.  Each of these methods depends on proper usebefore or at the time of intercourse and, as such, is subject to a higher failure rate than noncoitus-dependent methods.  This isthe result of inconsistent or incorrect use as well as actual damage to the barrier material itself. For example, the latex in condoms, diaphragm, and cervical cap can be damaged by the application of oil-based lubricants. Despite this, these methods provide relatively good protection from unwanted pregnancy, are inexpensive, and most require    little or no medical consultation.   In addition, condoms and diaphragms provide some protection against the trans-mission of STDs, including gonorrhea, herpes, chlamydia, human immunodeficiency virus (HIV), and human papil-lomavirus infec...

  INTRAUTERINE CONTRACEPTION   Intrauterine contraceptives,  also known as  intrauterine devices (IUDs),  are among the most commonly usedand safe methods of interval contraception worldwide (Fig. 24.8). Two types of IUDs are available in the United  States. Both are T-shaped. One releases a small amount of levonorgestrel into the uterus, and the other releases a small amount of copper into the uterus.   The Lippe loop is an unmedicated IUD available throughout the world except in the United States. The levonorgestrel-containing device primarily works by pre-venting the sperm and egg from meeting. It also thick-ens the cervical mucus and creates an unfavorable uterine environment. The copper in the copper-containing device can prevent the egg from being fertilized or from attach-ing to the wall of the uterus. It also prevents sperm from going into the uterus and the fallopian tube, reducing the sperm’s ability to fertilize an egg. The copper-containing...