Birth Control Medications (Contraceptives) (cont.)
Francisco Talavera, PharmD, PhD
Drug and Food Interactions and Side Effects of Birth Control Medications
Drug or Food Interactions
Contraceptive effectiveness may be reduced by antibiotics, antifungals, anticonvulsants, HIV-fighting drugs, St. John’s Wort, and other drugs that speed the body’s breakdown and use of contraceptive hormones, which could result in unintended pregnancy or breakthrough bleeding. Examples of such drugs include barbiturates (amobarbital [Amytal], phenobarbital [Barbita, Luminal]), griseofulvin (Grifulvin V, Gris-PEG), rifampin (Rifadin, Rimactane), phenylbutazone (Butazolidin), phenytoin (Dilantin), carbamazepine (Carbatrol, Tegretol), felbamate (Felbatol), oxcarbazepine (Trileptal), topiramate (Topamax), and, possibly, ampicillin (Marcillin, Omnipen).
Birth control may cause a change in vision, necessitating a change in prescription, or an inability to wear contact lens. Birth control pills do not provide protection from sexually transmitted diseases (STDs). The pills must be taken daily and consistently (at the same time every day). If a woman stops taking birth control pills, it may take a few months for her normal ovulatory cycle to return; however, once stopped, a woman can become pregnant even if her cycle has not returned to normal. The following general side effects apply to all the hormonal birth control medications, regardless of how they are taken (for example, pills, topical patch, injection): nausea, breast tenderness, fluid retention, weight gain, acne, breakthrough bleeding, missed periods, headaches, depression, anxiety, other mood changes, and lower sexual desire. Additionally, the following more serious side effects may occur:
- Thromboembolism (blood clots): Women who use estrogen-containing birth control pills are at a 3- to 6-fold increased risk of developing blood clots. Blood clots may lead to deep vein thrombosis, heart attack, or stroke. Additional causes of blood clots include advanced age, obesity, family history, recent surgery, and pregnancy. Low-dose (less than 50 mcg of ethinyl estradiol) oral contraceptives pose less risk than older, higher-dose formulations. Cigarette smoking increases the risk of blood clots in women using combination contraceptives, particularly for women older than 35 years and those who smoke more than 15 cigarettes per day.
- Breast cancer: The association of birth control pill use and breast cancer in young women is controversial. The Collaborative Group on Hormonal Factors in Breast Cancer performed the most comprehensive study in 1996. The results demonstrated that current pill users and those who had used birth control pills within the past 1-4 years had a slightly increased risk of breast cancer. Although these observations support the possibility of a marginally elevated risk, the group noted that pill users had more breast examinations and breast imaging studies than nonusers. Thus, although the consensus states that birth control pills can lead to breast cancer, the risk is small, and the resulting tumors spread less aggressively than usual. Most doctors currently believe that birth control pill use might interact with another primary cause to stimulate breast cancer.
- Cervical cancer: The relationship between birth control pill use and cervical cancer is also quite controversial. The risk is not related to the contraceptive agent itself but to how it leaves a woman unprotected from STDs. Early sexual intercourse, numerous lifetime sexual partners, and exposure to human papillomavirus are all important risk factors. Most authorities now believe that, if birth control pills increase the risk of cervical cancer at all, the risk is small.
- Benign liver tumors: Hormones are metabolized by the liver. A small increase in the frequency of benign liver tumors may exist, particularly after 4-8 years of birth control pill use.
- Diabetes: Progesterone and high estrogen doses may alter blood glucose (sugar) levels in diabetic women.
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Patient Comments & Reviews
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