By: Ellen Whipple Guthrie, Pharm.D.
Oral contraceptives – birth control pills – are considered one of the safest and most effective means of preventing pregnancy. However, oral contraceptives are not for all women. If you are over the age of 35 and smoke cigarettes, the pill increases your risk for medical problems, including heart attacks, blood clots, and stroke. In fact, a study recently published in the Lancet found that women who smoke are 25% more likely to die from any cause if they also take oral contraceptives.
Because oral contraceptives are metabolized in the liver, they can interact with many medications, including some of the more common ones prescribed to women with MS. Let’s take a look at some of those medications, along with what you can do to protect yourself.
Different Drugs, Different Interactions
Various types of drug interactions can occur between oral contraceptives and prescription, over-the-counter, and herbal products.
- Some medications can reduce the effectiveness of oral contraceptives (see table 1). Clearly, women taking both oral contraceptives and any of these medications should talk with both their MS specialist and gynecologist. It is generally a good idea to use a second method of birth control as a backup. Barrier methods (including condoms, diaphragms, and new-generation intrauterine devices) are considered good options.
- Oral contraceptives may decrease the effectiveness of some medications (see table 2). An increased dose of the medication may be needed in order to obtain maximum benefits.
- Oral contraceptives can increase the effectiveness of some medications (see table 3). In many cases, a decreased dose of the medication is needed in order to avoid too much active drug.
What About the Disease-Modifying Drugs?
There is no evidence indicating that oral contraceptives interfere with any of the commercially available disease-modifying drugs – Avonex®, Betaseron®, Copaxone®, Novantrone®, Tysabri®, or Rebif®. However, it is recommended for women in their childbearing years to use some form of birth-control while taking these drugs, since they have not been extensively studied in pregnancy.
Table 1: Medications that can reduce the effectiveness of oral contraceptives:
- All antibiotics
- Anti-seizure medications, including carbamazepine (Tegretol®), phenytoin (Dilantin®), phenobarbital, and primidone (Mysoline®)
- Modafinil (Provigil®)
- St. John’s Wort
Table 2: Oral contraceptives may decrease the effectiveness of these medications:
- Salicylates (over-the-counter or prescription pain and fever reducers)
- Benzodiazepines—such as lorazepam (Ativan®), oxazepam (Serax®), and temazepam (Restoril®)
Table 3: Oral contraceptives may increase the effectiveness of these medications:
- Benzodiazepines—such as diazepam (Valium®)
- Beta blockers—including propranolol (Inderal®)
- Corticosteroids—including prednisone or methylprednisolone
- Tricyclic antidepressants—including amitriptyline (Elavil®)
If you have any questions about the interactions between any of your medications, always talk to your doctor and/or pharmacist.
(Last reviewed 7/2009)