(( VaginaPagina ))

A recent post & the comments to it suggested that there is a lot of confusion about this issue.  (Hell-- even pharmacies are confused; in Michigan they never put interaction stickers on my NuvaRing, while in Florida they do.)

""This absence of interaction with amoxicillin and doxycycline adds further to the convenience of NuvaRing," said Prof. Dr. Cosima Brucker, gynecologist, Nurnberg, Germany. "Furthermore, this along with the fact that vomiting does not affect the contraceptive efficacy of NuvaRing and its once-a -month action reduces the chances of unplanned pregnancy in real-life as a result of user error....Amoxicillin and doxycycline are among the most commonly used of the penicillin and tetracycline groups of antibiotics respectively."
http://www.medicalnewstoday.com/medicalnews.php?newsid=22397
http://www.contraceptiononline.org/slides/slide01.cfm?q=doxycycline&dpg=3 (a pretty picture)
(This information is also in the paper insert that comes with the Ring, so it's definitely true.)

So many websites about the NuvaRing just copy over the same interacton possibilities as other contraceptives.  They start out with, "As with any contraceptive, there can be interactions with...." - but there is a difference between ORAL contraceptives and vaginal ones!

Definitely check legitimate drug interaction websites or ask your pharmacist before combining other antibiotics & the NuvaRing.  The NP's I've talked to have said that NuvaRing doesn't interact with any antibiotics except ones that are used primarily in the treatment of TB.  (But I don't have proof for that, so check first!)


FURTHERMORE: The NP's I've talked to have said that most combined ORAL contraceptives actually don't interact with most antibiotics, as was previously thought.  Here is some proof of that:

http://www.contraceptiononline.org/slides/slide01.cfm?q=doxycycline&dpg=1

Although there are many anecdotal reports of OC failure in women taking concomitant oral antibiotics, pharmacokinetic evidence of lower serum steroid levels exists only for rifampin and griseofulvin. Women who take rifampin or griseofulvin should use nonhormonal methods of birth control. Many oral anti-infective agents prescribed for acne treatment or for other reasons do not decrease hormonal steroid levels in women taking OCs. These include tetracycline, doxycycline, ampicillin, metronidazole, and quinolone antibiotics. Because the product information sheets accompanying many OCs suggest some antibiotics may be associated with reduced efficacy, acne patients who are prescribed antibiotics (other than rifampin or griseofulvin) should be forewarned and reassured that no large-scale prospective epidemiologic study has shown an association between oral antibiotics prescribed for acne and reduced OC effectiveness. Patient education should include information that regular use of an OC is one of the most effective methods of birth control, but-like all other birth control methods, excluding abstinence-is not effective 100% of the time; in particular, strict compliance is an issue.

By the way - rifampin is commonly used to treat TB and leprosy.  Griseofulvin is used to treat fungal infections like ringworm, jock itch, etc.


This article, of which you can only read one page without paying for the rest, seems to suggest that some caution is still necessary because the large scale population studies just haven't been done.  He states that women who have breakthrough bleeding while using antibiotics & COC's need to use back up (this makes sense; BTB suggests that the hormone level in your blood went down & you may not be protected), and that any women who get antibiotics should be warned that there is a possible interaction with their COC's, just because the consequences of an unintended pregnancy are so huge.  


What do I personally conclude?  
-Ring users are safe when using antibiotics from the penicillin and tetracycline families
-COC (pill) users are PROBABLY safe when using most oral antibiotics other than rifampin & griseofulvin.  The interaction sticker is merely cautionary and is based on anecdotal evidence, rather than science. However, if there's any BTB during your antibiotic use it could be caused by low hormone levels in your blood, meaning you need to use a backup method to be completely protected.