The Medicines and Healthcare Products Regulatory Agency (MHRA) in the United Kingdom has issued a new warning to women using the emergency contraceptive drugs levonorgestrel and ulipristal, saying that they may not work if they take some other medications.
Medications that can affect levonorgestrel and ulipristal, which are commonly called the "morning after pill," include those for:
The warning also covers the herbal remedy St John's wort.
When asking for emergency contraceptive pills, the physician, nurse, or pharmacist needs to know if these medications have been used over the last 4 weeks.
A double dose of the emergency contraceptive pills may be needed for them to be effective. This means getting two packs.
Sarah Branch, MD, from the MHRA, said in a statement: "This is important new advice for women who want to use the emergency contraceptive pill. It will help to protect women who are taking certain medicines against unwanted pregnancies.
"Our new patient information sheet provides information on what types of medicines could interfere with how the emergency contraceptive works. It tells women what steps they need to take to ensure they receive the correct dose.
"The earlier that emergency contraception is taken after unprotected intercourse, the better it works."
If a patient has used the emergency contraceptive pill before this new guidance was issued, and is concerned about other medications taken, seek medical advice, the MHRA notes.
Should the MHRA action prompt a similar warning in the United States?
Medscape Medical News asked Dana Stone, MD, who is in private practice in Oklahoma City, Oklahoma, and has held various positions with the American Congress of Obstetricians and Gynecologists (ACOG), to comment.
"It makes sense," she said, "that this is something we should all start looking at [because] the medications work the same here as they do there. ACOG puts out guidelines intermittently but we haven't put anything out about emergency contraception recently…. It's probably something we should look at if we want our emergency contraception to be effective for women.
"We've known for a long time that women should be cautious when taking birth control pills with some of these medications because they induce liver enzymes to process those hormones faster and so you have a lower level in your bloodstream than you need. So it makes sense to look at the emergency contraception in the same way," Dr Stone said.
"The interesting thing," she noted, "and we seem to always forget about it, is that the copper IUD is the most effective emergency contraception out there and it wouldn't be affected by [hepatic enzyme-inducing drugs]. That would be another reason to encourage doctors and patients to think about that as more of a first-line as opposed to Plan B."
Additional reporting by Megan Brooks.
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Cite this: Emergency Contraceptives Affected by Other Medications, UK Warns - Medscape - Sep 21, 2016.